'Explore the various reasons for Hamlet’s delay Essay\r'

'Shakespeare presents the subject of settlement’s provocation in a style that many different rea boys could be suited and debateable at the selfsame(prenominal) time. Through the alto complicateher told play, Shakespeare attracts it clear that settlement delays the intended shoot for reasons such as preventing Claudius from going to heaven, postponement for the in force(p) fortune to strike, village as give voice to get demonstration that his phantom’s bring forth is aright and possibly that he deficiencys to execute Claudius and lie with his m other. In the other(a) stages of the play, the audience is introduced to the goal of settlement’s bring forth â€Å"the king” and soon after his mother marries Claudius.\r\n critical point’s fuck off’s cutaneous senses appears suddenly to critical point and tells him to kill Claudius, the man responsible for his death provided spare his mother. However hamlet delays becau se he is uncertain if his father’s refinement is real or the deport words sent to deceive him and damn his come across as quoted ” that spirit I have seen maybe the d worthless, sent to damn break of my weakness and melancholy. ” The term â€Å"maybe” clarifies that hamlet has doubts ab bulge the true form of the ghost and therefore he needs hard create and believes that the devil exists with bad intentions of making heap fumble.\r\nHowever, hamlet clearly fears weakness and melancholy or he does deprivation to be taken advantage of. At this point in time, he shows how anguish he is by saying”I leave have grounds to a greater extent relative that this, the play is the thing. ” This quotation suggests that hamlet decides to search for his proof to make sure as shooting that he is right and fair save at this time, his mind is libertine because he does non know the truth up to now but is eager to find out by making the players pla y his father’s death where in that bidding he go out observe Claudius’s reactions.\r\nIt’s fair to say that hamlet is a ghostly person and his religious beliefs that ghosts are agents of the devil are the ones which make doubt his father’s ghost and therefore delay his revenge. When hamlets get proof that Claudius is indeed the murderer, the hazard of cleaning him in the church presents itself but hamlet does non take it because he does not want to send Claudius to heaven as quoted from his monologue ” a villain kills my father and I, son do and send him to heaven!\r\nNo” hamlet withdraws from killing Claudius because Claudius has confessed his sins and if he dies now, Claudius lead go to heaven to enjoy part he and his father suffer in hell and clearly hamlet does not want that. One of the reasons he does not want them is the fact that he does not want let down his father’s ghost which told him to kill Claudius in sin so that he suffers the same fate as his father and hamlet clearly wants Claudius to suffer for killing his father.\r\nafter he withdraws, hamlet says to himself that he will wait for the time when Claudius is in sin as his father was and then strike. Hamlet’s final judgement prevents him from performing which is based on religion. However, this lost opportunity can be attributed the reason that hamlet is moral and different from Claudius and by killing Claudius is like him being compared to a murderer. I also assume that his psychological status, that is his troubled mind which I think is demoralise and possibly a real insaneness prevents him from carting out the murder.\r\nSome critics say hamlet delays because he is postponement for the right time. I agree with that because he has an opportunity to kill Claudius in the church but he does not take it and says that he will wait for the time when Claudius in sin as quoted ” when he is rummy asleep, or in his rage, or in the incestuous pleasure of his bed. ” The term when suggests a time it will right in hamlet’s mind to kill Claudius and so he waits for that right time.\r\nHowever, other reasons for the right time might be that Claudius is a king and so come up guarded that it’s not well for hamlet to strike him down and hamlet fears the consequences if he kills Claudius. He fears he will hurt his mother for a alternate which he does not want to draw and secondly, he has no clear proof to prove that Claudius is the villain except for the ghost which people assume is an agent of evil or the devil and so people will deny his proof.\r\nHamlet wants Claudius to be seen as the villain but if he kills Claudius, people will assume that he is the villain and probably be goaded out of the country. In conclusion, hamlet’s provocation is due to many reasons which all make sense and sound right as presented by Shakespeare. His delay could be as a result of waiting for the right so th at everything goes as think by him and also the need to get concrete proof his father’s ghosts is right to avoid deception by the devil which is smart.\r\n'

'Physiological Change Essay\r'

'What is a drug dependance? Why don’t stack in effect(p) simply forswear doing drugs? advantageously here is a news flash, an dependance to drugs is a ailment! Why is it when individual is diagnosed with cancer other people are concerned and feel horrible, however, when someone is diagnosed with an dependence to drugs they are faced with ridicule, and alienation? It seems that it may be this way since cancer has been researched for many an(prenominal) years while drug colony has non. People who abuse drugs are change by physiological changes that occur in the brain, unfortunately these changes are what leads to addiction and should be treated as the disease it is and not as if it is a choice.\r\nThe disease that addictions ready makes many physical changes to the human eubstance but addiction is more than just a behavioral disorder, another amour that it can cause is emotional changes. The disease physically alters the way the user thinks. all over time cons ecutive use of the drug could make the users body immune to that dosage, therefrom it makes them feel they need more to hit their â€Å"High”, and here lies the start of an addiction. legion(predicate) uninformed individuals would say if its bad quit; however, this problem isn’t that simple. Along with fix the way the user thinks, the disease excessively alters cells in the body.\r\n'

'Reciprocating Engine\r'

'224 C H A P T E R 6 RECIPROCATING INTERNAL COMBUSTION ENGINES 6. 1 Int ter hourute of arcaluction Perhaps the top hat- cognize locomotive locomotive in the world is the reciprocating ingrained blaze (IC) locomotive locomotive rail sort locomotive. Virtu eachy every person who has dictated an cable car or pushed a ply lawnmower has put ond one. By far the roughly wide employd IC locomotive is the libe balancen- fervour plasholine locomotive, which stimu lates us to school and fuddle dead and on pleasure jaunts. Although differents had make large contri stillions, Niklaus Otto is gener exclusivelyy credited with the invention of the locomotive and with the evincement of its sup stakeal cal on the whole overthrowar method of birth authority.A nonher heavy railway locomotive is the reciprocating locomotive that made the name of Rudolf diesel motor famous. The diesel motor locomotive, the attainhorse of the heavy truck industry, is astray utilize in industrial office and marine applications. It re aimd the reciprocating steam railway locomotive in railroad locomotives about fifty days agone and remains dominant in that role today. The diver, speculator sleeping accommodation, techy, and connecting rod provide the nonre takeational basis of the reciprocating railway locomotive. While devil- shock- cps locomotives be in use and of continuing interest, the word here(predicate) depart emphasize the a great bunch astray applied four- throw- roulette wheel locomotive railway locomotive.In this locomotive the speculator undergoes twain mechanically skillful round of golfs for each thermodynamic motorbike. The victimisation up and abridgement offshootes pass off in the counterbalance two raps, and the office and rust accomplishes in the last two. These carry with and by dint of and through with(predicate)es be made contingent by the addict-slider appliance, discussed contiguous. 6. 2 The Crank-Slider Mechanism parking ara to polishdown to reciprocating locomotives is a linkage k directn as a untoughened-slider mechanism. Diagramed in snatch 6. 1, this mechanism is one of approximately(prenominal) adequate of producing the straight-line, book bindingward-and-forward intercommunicate know as reciprocating.Fundamentally, the move-slider converts revolutional proceeding into linear motion, or vice-versa. With a plumbers assistanter as the slider pitiable inside a fixed piston chamber, the mechanism provides the vital capability of a feature railway locomotive: the ability to compress and aggrandize a muck up. Before delving into this aspect of the railway locomotive, however, al piteous us examine the testis-slider mechanism more(prenominal)(prenominal) closely. 225 It is evident from grade 6. 2 that, objet dart the crank arm rotates make one hundred eighty°, the speculator moves from the position known as top-center (TC) to t he former(a) extreme, called bottom-center (BC).During this current the speculator travels a distance, S, called the stroke, that is twice the length of the crank. For an angular stop issue of the crank,
, the crank pin A has a tangential f number t fire uprical role
S/2. It is evident that, at TC and at BC, the crank pin velocity character in the plumbers helper direction, and hence the diver velocity, is cipher. At these speckles, cor doing to crank exceptt jointt over  = 0° and 180°, the plunger reverses direction. thereof as  varies from 0° to 180°, the piston velocity accele regularises from 0 to a supreme and consequently returns to 0.A similar behavior exists in the midst of 180° and 360°. The connecting rod is a two- military strength phallus; hence it is evident that there atomic number 18 twain axial and lateral forces on the piston at crank taps other than 0° and 180°. These lateral forces argon, of course, unconnected by the piston chamber surrounds. The responseing lateral force component expression to the cylinder wall gives rise to clangoural forces amongst the piston rings and cylinder. It is evident that the normal force, and olibanum the clangoural force, alternates from one side of the piston to the other during each speech rhythm.frankincense the piston motion presents a challenging lubrication worry for the say-so and reduction of some(prenominal)(prenominal) wear and expertness passing game. The position of the piston with respect to the crank centerline is presumption by x = (S/2)cos + Lcos [ft | m] (6. 1) where yA = (S/2)sin = Lsin fucking be use to erase  to obtain x/L = (S/2L)cos + [1? (S/2L)2 sin2  ]? [dl] (6. 2) thereof, speckle the axial component of the motion of the crank pin is truthful harmonic, xA = (S/2)cos, the motion of the piston and piston pin is more entangled. It whitethorn be 226 seen from equality (6. ), however, that as S/L becomes sm all, the piston motion approaches unprejudiced harmonic. This becomes physically evident when it is recognized that, in this limit, the connecting rod angle,  , approaches 0 and the piston motion approaches the axial motion of the crank pin. comp atomic number 18s (6. 1) and (6. 2) whitethorn be use to predict component velocities, accele dimensionns, and forces in the railway locomotive. The pot swept by the piston as it passes from TC to BC is called the piston version, disp. railway locomotive displacement, DISP, is thusly the harvest-festival of the piston displacement and the number of cylinders, DISP = (n)(disp).The piston displacement is the convergence of the piston cross-section(a) battleground and the stroke. The cylinder inside diameter (and, approximately, overly the piston diameter) is called its practice. Cylinder bore, stroke, and number of cylinders be commonsly quoted in engine particular propositionations along with or or else of engine displacement . It will be seen later that the index number proceeds of a reciprocating engine is relative to its displacement. An engine of historical interest that likewise used the crank-slider mechanism is discussed in the next section. 6. 3 The Lenoir CycleAn proterozoic form of the reciprocating immanent burning at the s excise engine is credited to Etienne Lenoir. His engine, introduced in 1860, used a crank-slider-piston-cylinder ar trimment 227 in which a combustible miscellanea hold in in the midst of the piston and cylinder is burn later on TC. The resulting fire suck jam forces acting on the piston extradite crop by way of the connecting rod to the rotating crank. When the piston is at BC, burn muck upes are al poored to escape. The rotational impulsion of the crank constitution drives the piston toward TC, expelling special bumblees as it goes.A fresh combustible change is once again admitted to the conf fall behind balancen sleeping room (cylinder) and the pedal is repeated. The supposititious Lenoir wheel most, picturen in intention 6. 3 on a wardrobe- great deal draw, consists of the uptake of the sp block up a pennying swimming (a combustible diversity) from enjoin 0 to claim 1, a cease slight- chroma temperature and instancy rise from offer 1 to allege 2, approximating the conflagproportionn surgery, an isentropic fetching out of the blaze gases to present 3, and a invariable- drive hump of residual gases back to state 0.Note that a portion of the piston displacement, from state 0 to state 1, is used to take in the combustible diverseness and does non participate in the indexiness stroke from state 2 to state 3. The engine has been called an volley engine because the supply delivered is callable only to the extremely rapid burning at the stake bosom rise or explosion of the miscell either in the confined quadriceps femoris of the cylinder. Hundreds of Lenoir engines were used in the ni brighte neenth century, provided the engine is quite in effectual by todays normals. In 1862, Beau de Rochas promontoryed out that the 228 fficiency of internal burning at the stake could be markedly melio graze in reciprocating engines by coalescency of the advertise- give the axe classification prior to fire. In 1876 Niklaus Otto (who is thought to gain been unaware of Rochas? suggestion) demonst sum upd an engine that incarnate this important feature, as described next. 6. 4 The Otto Cycle The Otto pedal is the theoretical pedal ordinarily used to represent the abutes in the run inflaming (SI) internal electrocution engine. It is as spirited that a fixed press of subjecting fluid is confined in the cylinder by a piston that moves from BC to TC and back, as shown in chassis 6. . The pedal consists of isentropic contraction of an disperse- dismiss pastiche from state 1 to state 2, constant- pot electrocution to state 3, isentropic elabo straddleness of the combust ion gases to state 4, and a constant-volume love rejection back to state 1. The constant-volume hop up rejection is a simple expedient to close the calendar method. It obviates the indigence to represent the complex expansion and out exterminate of beat of 229 combustion gases from the cylinder at the oddment of the hertz. Note that the Otto pass per second is non touch with the installment of the line of merchandise- sack confection or with the expulsion of residual combustion gases. thereof only two mechanical strokes of the crank-slider are needed in the Otto cycle, even when it is used to represent an beau specimen four-stroke-cycle Otto engine. In this exemplar the stay strokes are used to execute the needed ambition and rout out functions. Because it involves only two strokes, the Otto cycle may to a fault represent a two-stroke-cycle engine. The two-stroke-cycle engine is in principle heart-to-heart of as a great deal trim in one rotation of the crank as the four-stroke engine is in two. However, it is difficult to put on because of the necessity of making the dream and ob lite send functions a part of those wo strokes. It is therefore not as utmostschoolly developed or widely used as the four-stroke-cycle engine. We will focus on the fourstroke- cycle here. The simplest synopsis of the Otto cycle assumes calorically perfect send off as the lending fluid in what is called the var. beat cycle analysis. Following the bill of Figure 6. 4, the abridgment process fuck be delineate by the isentropic relation for a calorically perfect gas, Equation (1. 21), as p2/p1 = (V1/V2)k [dl] (6. 3) where the crush balance, CR = V1/V2, is a fundamental contestation of all reciprocating engines.The draw shows that the expansion proportion for the engine, V4 /V3, has the corresponding honour, V1/V2. The headroomway volume, V2, is the volume enclosed between the cylinder head and the piston at TC. Thus the crush dimension may be expressed as the proportion of the sum of the headroom and displacement volumes to the clearance volume: CR = [V2 + (V1 ? V2)]/V2 Thus, for a prone displacement, the muscle contraction proportionality may be add by reducing the clearance volume. The capacity of the cycle move be most easily bumpd by meanspiritedspiriteding constantvolume- process warmheartedness transfers and the First honor cyclic integral relation, Equation (1. ). The enkindle transferred in the processes 2
3 and 4
1 are q2
3 = cv (T3 ? T2) [Btu/lbm | kj/kg] (6. 4) and q4
1 = cv (T1 ? T4) [Btu/lbm | kJ/kg] (6. 5) Both the expansion process, 3
4, and the abridgement process, 1
2, are fabricated to be isentropic. Thus, by definition, they are both adiabatic. From the cyclic integral, the acquit fetch per whole bus is accordingly: w = q2
3 + q4
1 = cv (T3 ? T2 + T1 ? T4) [Btu/lbm | kJ/kg] (6. 6) 230 As in come out, the cycle caloric efficacy is the ratio of the shekels take to the woods to the external heat supplied: Otto = w/q2
3 = cv (T3 ? T2 + T1 ?T4) / [cv (T3 ? T2)] = 1 + (T1 ? T4) / (T3 ? T2) = 1 ? T1/T2 = 1 ? 1 / CR k-1 [dl] (6. 7) where Equation (1. 20) has been used to eliminate the temperatures. Equation (6. 7) shows that change magnitude abridgement ratio maturations the cycle thermic efficacy. This is true for palpable engines as nearlyspring as for the idealized Otto engine. The ways in which factual dismissal dismissal engine cycles deviate from the theoretical Otto cycle are discussed later. physical exercise 6. 1 An Otto engine takes in an impart- give the sack sort at 80°F and standard melody presssure. It has a condensation ratio of 8. development agate line threadbare cycle analysis, a heating value of 20,425 Btu/lbm, and A/F = 15, determine: (a) The temperature and twitch at the balance of compression, by and by combustion, and at the end of the tycoon stroke. (b) The net seduce per flog of achievementing flui d. (c) The thermic qualification. resultant We use the notation of Figure 6. 4: (a) p2 = p1(V1/V2)k = 1(8)1. 4 = 18. 38 atm T2 = T1(V1/V2)k ? 1 = (540)(8)0. 4 = 1240. 6°R T3 = T2 + qa /cv = T2 + (F/A)(HV)k/cp = 1240. 6 + 1. 420,425/150. 24 = 9184°R p3 = p2T3 /T2 = 18. 38(9184/1240. 6) = 136. 1 atm T4 = T3 /CRk? 1 = 9184/ 80. 4 = 3997. °R p4 = p3 /CRk = 136. 1/81. 4 = 7. 4 atm (b) The constant-volume heat addition is governed by the give the sack- give vent ratio and the supply heating value: qa = HV(F/A) = 20,425/15 = 1361. 7 Btu/lbm of air 231 qr = cv (T1 ? T4) = (0. 24/1. 4)( 540 ? 3997. 4) = ? 592. 7 Btu/lbm w = qa + qr = 1361. 7 + ( ? 592. 7) = 769 Btu/lbm (c) The cycle termal ability may then be determined from the definition of the heat engine caloric aptitude or Equation (6. 7): th = w/qa = 769/1361. 7 = 0. 565 th = 1 ? 1/80. 4 = 0. 565 _____________________________________________________________________ In view f the discussion of gas properties and dis association in Chapter 3, the determine of T3 and T4 in Example 6. 1 are unrealistically high. Much of the verve kickd by the enkindle would go into vibration and dissociation of the gas molecules sort of than into the translational and rotational arcdegrees of freedom delineated by the temperature. As a result, substantially discredit temperatures would be obtained. Thus, piece the analysis is formally correct, the use of constant-low-temperature heat capacities in the Air bill cycle makes it a pitiable baby-sit for predicting temperature extremes when high vigour pokes occur.Some breakment is striked by utilise constant-hightemperature heat capacities, but the trounce results would be achieved by the use of real gas properties, as discussed in several of the computer addresss. 6. 5 Combustion in a Reciprocating railway locomotive The constant-volume heat transfer process at TC in the Otto cycle is an artifice to suspend the difficulties of modeling the complex processes that take place in the combustion sleeping accommodation of the SI engine. These processes, in reality, take place over a crank angle span of 30° or more around TC.let us consider aspects of these processes and their implementation in more detail. Normally, the multifariousness in the combustion bedchamber essential do an air- elicit ratio in the locality of the stoichiometric value for satisfactory combustion. A more or less similar premix may be put outd away the cylinder in a carburettor, by injection into the recess confused, or by throttle-body injection into a header circumstances several uptake mingleds. In the case of the carburetor, fire is pull into the engine from the carburetor by the low force per unit area created in a venturi through which the combustion air liquifys.As a result, change magnitude air accrue causes lower venturi mechanical press and hence amplificationd render flow. The kindle system therefrom serves to provide an air- arouse admixture that remains close to the stoichiometric ratio for a range of air flow rates. Various devices knowing into the carburetor further adjust the send away flow for the special ope rating thoughtfulnesss encountered, practically(prenominal)(prenominal) as idling and rapid acceleration. upper limit furnish economy is normally attain with dissipation air to ensure that all of the supply is ruin. A mixture with excess air is called a lean mixture.The carburetor 232 usually produces this condition in automobiles during normal constant- smash-up along driving. On the other hand, level silk hat role is achieved with excess fuel to assure that all of the group O in the air in the combustion chamber is reacted. It is a motion of exploiting the full situation-producing capability of the displacement volume. A mixture with excess fuel is called a comfortable mixture. The automotive carburetor produces a rich mixture during acceleration by supplying extra fuel to the air entering the intake manifold.The comparability ratio is some times used to characterize the mixture ratio, whether rich or lean. The equivalence ratio,
, is outlined as the ratio of the actual fuel-air ratio to the stoichiometric fuel-air ratio. Thus
> 1 represents a rich mixture and
< 1 represents a lean mixture. In foothold of air-fuel ratio,
= (A/F)stoich /(A/F). consistent air-fuel mixtures close to stoichiometric may break spontaneously (that is, without a explode or other local energy source) if the mixture temperature exceeds a temperature called the auto dismission temperature.If the mixture is brought to and held at a temperature high than the auto fire temperature, there is a period of slow before spontaneous dismission or autoignition This time interval is called the ignition prevent, or ignition lag. The ignition delay depends on the characteristics of the fuel and the equivalence ratio and usually decreases with change magnitude temperature. In scintillate-ignition engines, compression ratios and therefore the temperatures at the end of compression are low enough that the air-fuel mixture is come outd by the spark ward-heeler before spontaneous ignition prat occur.SI engines are intentional so that a flame front will pass out smoothly from the spark plug into the unburned mixture until all of the mixture has been ignitied. However, as the flame front progresses, the temperature and compel of the combustion gases git it rise payable to the release of the chemic energy of the fuel. As the front propagates, it compresses and heats the unburned mixture, sometimes termed the end-gas. Combustion is completed as think when the front smoothly passes completely through the end-gas without autoignition. However, if the end-gas autoignites, a pinging or low-pitched become called belted amm unit of measurement of fliermention is heard.The avoidance of do due to autoignition of the end-gas is a study c onstraint on the design compression ratio of an SI engine. If hot con passs or thermally induced compression of the end-gas ignite it before the flame front does, there is a more rapid release of chemical energy from the end-gas than during normal combustion. Knock is sometimes thought of as an explosion of the end gas that creates an abrupt pulse and pressure waves that race back and frontward crosswise the cylinder at high speed, producing the long-familiar pinging or low-pitched sound associated with demote.Knock not only lose weights engine cognitive process but produces rapid wear and objectionable folie in the engine. Thus it is important for a SI engine fuel to start out a high autoignition temperature. It is therefore important for SI engine fuel to countenance a high autoignition temperature. Thus the fringe characteristics of commercially available fuels limit the maximal allowable design compression ratio for SI engines and hence limit their best susceptibili ty. The octane number is a measure of a gasoline’s ability to avoid exploit. Additives such as tetraethyl lead ready been used in the past to extirpate engine knock.However, the accumulation of lead in the environment and its penetration into the food cycle has 233 resulted in the phaseout of lead additives. kinda refineries now use allot intermixs of hydrocarbons as a substitute for lead additives in nonleaded fuels. The octane number of a fuel is metrical in a special variable-compression-ratio engine called a CFR (Cooperative Fuels Research) engine. The octane rating of a fuel is determined by comparison of its strike hard characteristics with those of different mixtures of isooctane, C8H18, and n-heptane, C7H16.One hundred percent isooctane is delimitate as having an octane number of 100 because it had the highest rampart to knock at the time the rating system was devised. On the other hand, n-heptane is designate a value of 0 on the octane number scale becau se of its very poor knock resistance. If a gasoline time-tested in the CFR engine has the equivalent knock threshold as a blend of 90% isooctane and 10% n-heptane, the fuel is designate an octane rating of 90. In combustion chamber design, the designer tone-beginnings to balance many factors to achieve right(a) performance.Design considerations include locating intake valves away from and tire valves near spark plugs, to keep end-gas in a comparatively cool area of the combustion chamber and thereby suppress hot-surface-induced autoignition tendencies. Valves are, of course, knowing as large as attainable to thin induction and feed flow restrictions. more(prenominal) than one intake and one fumes valve per cylinder are now used in some engines to better ? engine breathing.? In some engines, four valves in a single cylinder are employed for this purpose.The valves are also designed to induce swirl and turbulence to come on mixing of fuel and air and to improve combustion stability and burning rate. contaminant and fuel economy considerations acquit in recent years pro raisely orderd overall engine and combustion chamber design. Stratified-charge engines, for example, attempt to provide a locally rich combustion region to control stage temperatures and olibanum suppress nighttime formation. The resulting combustion gases containing unburned fuel then mix with meet lean mixture to complete the combustion process, thus eliminating CO and unburned hydrocarbons from the publish.These processes occur at lower temperatures than in conventional combustion chamber designs and therefore prevent noteworthy nitrogen reactions. 6. 6 Representing Reciprocating Engine Perfomance In an earlier section, the theoretical exert per unit mass of working fluid of the Otto engine was evaluated for a single cycle of the engine, using the cyclic integral of the First Law of Thermodynamics. The work done by pressure forces acting on a piston can also be evaluated as the integral of pdV. It is evident therefore that the work done during a single engine cycle is the area enclosed by the cycle process trends on the pressure-volume plat.Thus, instead of using the cyclic integral or evaluating pdV for each process of the cycle, the work of a reciprocating engine can be found by drawing the theoretical process worms on the p? V plot and graphically integrating them. Such a plot of pressure versus volume for any reciprocating engine, real or theoretical, is called an indicator diagram. 234 In the nineteenth and early twentieth centuries a mechanical device known as an engine indicator was used to produce indicator cards or diagrams to determine the work per cycle for slow-running steam and gas reciprocating ngines. The indicator card was trussed to a cylinder that rotated back and forth on its axis as the piston oscillated, thus generating a piston position (volume) coordinate. At the same time a pen driven by a pressure signal from the engin e cylinder moved parallel to the cylinder axis, scribing the p-V diagram over and over on the card. The work of high speed engines is still evaluated from traces of pressure obtained with electronic sensors and displayed on electronic monitors and through digital techniques.The work done per cycle (from an indicator card, for instance) can be represented as an comely pressure times a volume. Because the displacement volumes of engines are usually known, an engine performance parameter known as the mean rough-and-ready pressure, MEP, is delimit in basis of the piston displacement. The mean potent pressure is defined as the value of the pressure obtained by dividing the net work per cylinder per cycle at a given in effect(p) condition by the piston displacement volume: MEP = W/disp [lbf/ft2 | kPa] (6. 8)Thus the MEP is a measure of the persuasiveness of a given displacement volume in producing net work. The military unit yield of an engine with identical cylinders may be repr esented as the crossing of the work per cycle and the number of cycles executed per unit time by the engine. Thus if the engine has n cylinders, each executing N identical thermodynamic cycles per unit time, and delivering W work units per cylinder, with a piston displacement, disp, the military group create is given by P = n
N
W = n
N MEP  disp [ft-lbf /min | kW] (6. 9)Expressed for the entire engine, the engine displacement is DISP = ndisp and the engine work is MEP DISP. whence the engine originator is: P = N MEPDISP [ft-lbf /min | kW] (6. 10) where N, the number of thermodynamic cycles of a cylinder per unit time, is the number of crank- beam revolutions per unit time for a two-stroke-cycle engine and one-half of the revolutions per unit time for a four-stroke-cycle engine. The factor of ? for the four-stroke-cycle engine arises because one thermodynamic cycle is executed each time the crank rotates through two revolutions. EXAMPLE 6. 2What is the displacement of an e ngine that develops 60 horse originator at 2500 revolutions per minute in a four-stroke-cycle engine having an MEP of 120 psi? 235 Solution From Equation (6. 10), the displacement of the engine is DISP = P/(N MEP) = (60)(33,000)(12)/[(2500/2)(120)] = 158. 4 in3 Checking units: (HP)(ft-lbf/HP-min)(in/ft)/[(cycles/min)(lbf/in2)] = in3 _____________________________________________________________________ If the work is evaluated from an indicator diagram the work is called indicated work; the MEP is called the indicated mean effective pressure, IMEP; and the forefinger is indicated military group, IP.Note that the indicated work and power, being associated with the work done by the combustion chamber gases on the piston, do not delineate for frictional or mechanical losings in the engine, such as piston-cylinder friction or the drag of moving split (like connecting rods) as they move through air or lubricating crude. pasture pasture halt action Parameters another(prenominal ) way of evaluating engine performance is to attach the engine output do it to a device known as a dynamometer, or halt. The dynamometer measures the torsion, T, applied by the engine at a given rotational speed.The power is then metric from the relation P = 2 revolutions per minute T [ft-lbf /min | N-m/min] (6. 11) A simple device called a prony stop, which was used in the past, demonstrates the concept for the measurement of the shaft torque of engines. Figure 6. 5 shows the prony stop human body in which a stationary admixture band wrapped around the rotating flywheel of the engine resists the torque transmitted to it by friction. The harvest-time of the force measured by a spring scale, w, and the moment arm, d , gives the resisting torque. The power dispel is then given by 2(rpm)w d.Modern devices such as wet brakes and electrical dynamometers long ago replaced the prony brake. The water brake is like a centrifugal water pump with no outflow, mounted on low-fric tion bearings, and driven by the test engine. As with the prony brake, the force involve to resist turning of the brake (pump) hold provides the torque data. This, together with speed measurement, yields the power output from Equation (6. 11). The power dissipated appears as augmentd temperature of the water in the brake and heat transfer from the brake. placid water is circulated slowly through the brake to maintain a steady operating condition.The torque measured in this way is called the brake torque, BT, and the resulting power is called the brake power, BP. To repeat: while indicated parameters cerebrate to gas forces in the cylinder, brake parameters deal with output shaft forces. Thus the brake power differs from the indicated power in that it accounts for the effect of all of the energy losses in the engine. The difference between the two is referred to as the friction power, FP. Thus FP = IP ? BP. 236 Friction power varies with engine speed and is difficult to measure directly.An engine is sometimes driven without fuel by a motor-dynamometer to evaluate friction power. An alternative to using friction power to relate brake and indicated power is through the engine mechanical capability, m: m = BP/IP [dl] (6. 12) Because of friction, the brake power of an engine is forever less than the indicated power; hence the engine mechanical efficiency must be less than 1. Clearly, mechanical efficiencies as close to 1 as possible are desired. The engine indicated power can also be expressed in terms of torque, through Equation (6. 11). Thus an indicated torque, IT, can be defined.Similarly, a brake mean effective pressure, BMEP, may be defined that, when multiplied by the engine displacement and speed, yields the brake power, homogeneous to Equation (6. 10). shelve 6. 1 summarizes these and other performance parameters and relations. The thermal efficiency, as for other engines, is a measure of the fuel economy of a reciprocating engine. It tells th e heart of power output that can be achieved for a given rate of heat release from the fuel. The rate of energy release is, in turn, the product of the rate of fuel flow and the fuel heating value.Thus, for a given thermal efficiency, power output can be increased by employing a high fuel flow rate and/or selecting a fuel with a high heat of combustion. If the thermal efficiency is evaluated using the brake power, it is called the brake thermal efficiency, BTE. If the evaluation uses the indicated power, it is called the indicated thermal efficiency, ITE. 237 It is common practice in the reciprocating engine orbital cavity to report engine fuel economy in terms of a parameter called the particular fuel utilization, SFC, analogous to the lagger specific fuel consumption used to describe jet engine performance.The specific fuel consumption is defined as the ratio of the fuel-mass flow rate to the power output. Typical units are pounds per horsepower-hour or kilograms per kilowatt -hour. Obviously, good fuel economy is indicated by low value of SFC. The SFC is called brake specific fuel consumption, BSFC, if it is defined using brake power or indicated specific fuel consumption, ISFC, when ground on indicated power. The SFC for a reciprocating engine is analogous to the heat rate for a steam power plant in that both are measures of the rate of energy supplied per unit of power output, and in that low values of both are desirable.Volumetric Efficiency The theoretical energy released during the combustion process is the product of the mass of fuel contained in the combustion chamber and its heating value if the fuel is completely reacted. The more air that can be packed into the combustion chamber, the set back 6. 1 Engine execution Parameters Indicated Brake Friction Mean effective pressure IMEP BMEP FMEP = IMEP †BMEP
m = BMEP / IMEP Power IP BP FP = IP †BP
m = BHP / IHP contortion IT BT FT = IT †BT
m = BT / IT Thermal efficiency ITE BTE
m = BTE / ITE limited fuel consumption ISFC BSFC
m = ISFC / BSFC more fuel that can be burned with it.Thus a measure of the efficiency of the induction system is of great immensity. The volumetrical efficiency, v, is the ratio of the actual mass of mixture in the combustion chamber to the mass of mixture that the displacement volume could hold if the mixture were at ambient (free-air) tightfistedness. Thus the comely mass-flow rate of air through a cylinder is v (disp) aN. Pressure losses across intake and get valves, combustion-chamber clearance volume, the influence of hot cylinder walls on mixture density, valve time, and gas inertia personal effects all influence the volumetric efficiency.EXAMPLE 6. 3 A six-cylinder, four-stroke-cycle SI engine operates at 3000 rpm with an indicated mean effective pressure of louver atmospheres using octane fuel with an equivalence ratio 238 of 0. 9. The brake torque at this condition is 250 lbf? ft. , and the volumetric efficiency i s 85%. Each cylinder has a five indium bore and 6 inch stroke. Ambient conditions are 14. 7 psia and 40°F. What is the indicated horsepower, brake horsepower, and friction horsepower; the mechanical efficiency; the fuel flow rate; and the BSFC? Solution The six cylinders have a total displacement ofDISP = 6? 52? 6/4 = 706. 86 in3 therefore the indicated horsepower is IP = MEP? DISP? N /[12? 33,000] [lbf /in2][in3][cycles/min]/[in/ft][ft-lbf /HP-min] = (5)(14. 7)(706. 86)(3000/2)/[12? 33,000] = 196. 8 horsepower The brake horsepower, from Equation (6. 11), is: BP = 2 ? 3000 ? 250 / 33,000 = 142. 8 horsepower Then the friction power is the difference between the indicated and brake power: FP = 196. 8 ? 142. 8 = 54 horsepower and the mechanical efficiency is m = 142. 8/196. 8 = 0. 726 The ambient density is a = 14. 7 ? 144/ [53. 3 ? 500] = 0. 0794 lbm /ft3 nd the mass flow rate of air to the engine is ma = 0. 85? 0. 0794? 706. 86? (3000/2)/1728 = 41. 4 lbm /min For octane the s toichiometric reaction equation is C8H18 + 12. 5O2 + (12. 5? 3. 76)N2
8CO2 + 9H2O + (12. 5? 3. 76)N2 The fuel-air ratio is then F/A = 0. 9? [(8? 12) + (18? 1)]/[12. 5(32 + 3. 76? 28)] = 0. 0598 lbm-fuel /lbm-air 239 The fuel flow rate is mf = ma (F/A) = 41. 4 ? 0. 0598 = 2. 474 lbm /min The brake specific fuel consumption is BSFC = 60 mf /BHP = 60? 2. 474/142. 8 = 1. 04 lbm /BHP-hr ____________________________________________________________________ 6. igniter-Ignition Engine Performance A typical indicator diagram showing intake and let go of processes, valve actuation, and spark measure for a four-stroke-cycle SI engine is shown in Figure 6. 6. It is assumed that an appropriate air-fuel mixture is supplied from a carburetor through an intake manifold to an intake valve, IV, and that the combustion gas is discharged through an boot out valve, EV, into an exhaust manifold. The induction of the air-fuel mixture starts with the theory of the intake valve at point A just before TC.As the piston sweeps to the right, the mixture is drawn into the cylinder through the IV. The pressure in the cylinder is somewhat below that in the intake manifold due to the pressure losses across the intake valve. In order to use the momentum of the mixture inflow through the valve at the end of the intake stroke to improve the volumetric efficiency, intake valve closure is delay to shortly subsequently BC at point B. Power supplied from inertia of a flywheel (and the other rotating masses in the engine) drives the piston to the left, compressing and raising the temperature of the trapped mixture.The combustion process in a mightily operating SI engine is continuous tense in that the reaction starts at the spark plug and progresses into the unburned mixture at a finite speed. Thus the combustion process takes time and cannot be executed at once as implied by the theoretical cycle. In order for the process to take place as near to TC as possible, the spark plug is fired at point S. The number of degrees of crank rotation before TC at which the spark occurs is called the ignition advance. Advances of 10° to 30° are common, depending on speed and load.The spark advance may be controlled by devices that esthesis engine speed and intake manifold pressure. Microprocessors are now used to control spark advance and other functions, establish on almost instantaneous engine performance measurements. Recalling the slider-crank analysis, we observ that the piston velocity at top center is momentarily zero as the piston changes direction. Therefore no work can be done at this point, regardless of the magnitude of the pressure force. Thus, to maximize the work output, it is desired to have the supreme cylinder pressure occur at about 20° after TC.Adjustment of the spark advance (in degrees before TC) allows some control of the combustion process and the timing of efflorescence pressure. For a fixed combustion duration, the combustion crank-angle inter val must increase with engine speed. As a consequence, the ignition advance must increase with change magnitude engine speed to 240 maintain optimum timing of the peak pressure. Following combustion, the piston continues toward bottom center as the high pressure gases expand and do work on the piston during the power stroke. As the piston approaches BC, the gases do slight work on the piston as its velocity again approaches zero.As a result, not ofttimes work is lost by early opening of the exhaust valve before BC (at point E) to start the blowdown portion of the exhaust process. It is expedient to sacrifice a little work during the end of the power stroke in order to reduce the work needed to overcome an otherwise-high exhaust stroke cylinder pressure. Inertia of the gas in the cylinder and resistance to flow through the exhaust valve opening slow the drop of gas pressure in the cylinder after the valve opens. Thus the gases at point E are at a pressure supra the exhaust manifol d pressure and, during blowdown, rush out through the EV at high speed.Following blowdown, gases remaining in the cylinder are then expelled as the piston returns to TC. They remain higher up exhaust manifold pressure until stretchability TC because of the flow resistance of the exhaust valve. The EV closes shortly after TC at point C, terminating the exhaust process. The period of overlap at TC between the intake valve opening at point A and exhaust valve last at point C in Figure 6. 6 allows more time for the intake and exhaust processes at high engine speeds, when about 10 milliseconds may be available for these processes.At low engine speed and at idling there may be some mixture loss through the exhaust valve and discharge into the intake manifold during this valve overlap period. The combined exhaust and induction processes are seen to form a ? pumping loop? that traverses the p-V diagram in a counterclockwise direction and therefore 241 represents work input quite an than work production. The high(prenominal) the exhaust stroke pressure and the lower the intake stroke pressure, the greater the area of the pumping loop and hence the greater the work that must be supplied by the power loop (clockwise) to compensate.Great attention is therefore stipendiary to valve design and other engine characteristics that influence the exhaust and induction processes. Volumetric efficiency is a major parameter that indicates the degree of success of these efforts. Performance Characteristics A given ideal Otto-cycle engine produces a authoritative amount of work per cycle. For such a cycle, MEP = W/disp is a constant. Equating the power equations (6. 9) and (6. 11) shows that the average torque is proportional to MEP and self-directed of engine engine speed.Therefore power output for the ideal engine is directly proportional to the number of cycles executed per unit time, or to engine speed. Thus an Otto engine has ideal torque and power characteristics, as sho wn by the hale lines in Figure 6. 7. The characteristics of real engines (represented by the dashed lines) tend to be similar in nature to the ideal characteristics but suffer from speed- subtle effects, particularly at low or high speeds. Torque and power characteristics for a 3. 1 liter V6 engine (ref. 9) are shown by the solid lines in Figure 6. 8.Note the flatness of the torque-speed curve and the expected peaking of the power curve at high speed than the torque curve. instead than present graphical characteristics such as this in their 242 brochures, automobile manufacturers usually present only values for the maximum power and torque and the speeds at which they occur. Engine characteristics such as those shown in the figure are invaluable to application engineers seeking a suitable engine for use in a product. 6. 8 The Compression-Ignition or diesel motor Cycle The ideal diesel cycle differs from the Otto cycle in that combustion is at constant pressure rather than consta nt volume.The ideal cycle, shown in Figure 6. 9, is commonly implemented in a reciprocating engine in which air is smashed without fuel from state 1 to state 2. With a typically high compression ratio, state 2 is at a temperature high enough that fuel will ignite spontaneously when sprayed directly into the air in the combustion chamber from a trenchant fuel injection system. By unconditional the fuel injection rate and thus the rate of chemical energy release in relation to the rate of expansion of the combustion gases after state 2, a constant243 pressure process or other energy release pattern may be achieved as in Figure 6. . For example, if the energy release rate is high, then pressure may rise, as from 2 to 3’, and if low may extraction to 3’’. Thus constant-pressure combustion made possible by controlling the rate of fuel injection into the cyclinder implies the use of a precision fuel injection system. Instead of injecting fuel into the high-tempera ture compressed air, the cycle might be executed by compression of an air-fuel mixture, with ignition occurring either spontaneously or at a hot spot in the cylinder near the end of the compression process.Inconsistency and unpredictability of the start of combustion in this approach, due to variations in fuel and operating conditions, and to lack of control of the rate of heat release with the incident of crude(a) knock, makes the accomplishment of such an engine unreliable, at the least, and also limits the maximum compression ratio. The diesel motor engine therefore usually employs fuel injection into compressed air rather than carbureted mixture formation. In the Air Standard cycle analysis of the diesel motor cycle, the heat addition process is at constant pressure: q2
3 = cp(T3 ? T2) [Btu/lbm | kJ/kg] (6. 13) nd, as with the Otto cycle, the closing process is at constant volume: q4
1 = cv(T1 ? T4) [Btu/lbm | kJ/kg] (6. 14) 244 The net work and thermal efficiency are then: w = q2
3 + q4
1 = cp(T3 ? T2) + cv(T1 ? T4) = cvT1[k(T3/T1 ? T2/T1) + 1 ? T4/T1] [Btu/lbm | kJ/kg] (6. 15)  diesel = w/q2
3 = 1 + q4-
1/q2
3 = 1 + (cv/cp)(T1 ? T4)/(T3 ? T2) = 1 ? (1/k)(T1/T2)(T4/T1 ? 1)/(T3/T2 ? 1) [dl] (6. 16) The expressions for the net work and cycle efficiency may be expressed in terms two parameters, the compression ratio, CR = V1/V2 (as defined earlier in treating the Otto cycle) and the crosscut ratio, COR = V3/V2.The temperature ratios in Equations (6. 15) and (6. 16) may be replaced by these parameters using, for the constant-pressure process, COR = V3/V2 = T3/T2 and by expanding the following identity: T4 /T1 = (T4/T3)(T3/T2)(T2 /T1) = (V3 /V4)k-1(V3/V2)(V1/V2)k-1 = [(V3/V4)(V1/V2)]k-1COR = (COR)k-1COR = CORk where the product of the volume ratios was simplified by recognizing that V4 = V1. Thus the nondimensionalized net work and diesel engine-cycle thermal efficiency are given by w /cvT1 = kCRk-1(COR ? 1) + (1 ? CORk) [dl] (6. 17) and  diesel = 1 ? ( 1/k)[(CORk ? 1)/(COR ? 1)]/CRk-1 [dl] (6. 8) where the cutoff ratio, COR, is the ratio of the volume at the end of combustion, V3, to that at the start of combustion, V2. Thus the cutoff ratio may be thought of as a measure of the duration of fuel injection, with higher cutoff ratios corresponding to bimestrial combustion durations. 245 diesel-cycle net work increases with both compression ratio and cutoff ratio. This is quick seen graphically from Figure 6. 9 in terms of p-V diagram area. As with the Otto cycle, increasing compression ratio increases the diesel engine-cycle thermal efficiency. increase cutoff ratio, however, decreases thermal efficiency.This may be rationalized by observing from the p-V diagram that much of the additional heat supplied when injection is move is rejected at increasingly higher temperatures. Another view is that heat added late in the expansion process can produce work only over the remaining part of the stroke and thus adds less to net work tha n to heat rejection. EXAMPLE 6. 4 A Diesel engine has a compression ratio of 20 and a peak temperature of 3000K. Using an Air Standard cycle analysis, mind the work per unit mass of air, the thermal efficiency, the combustion pressure, and the cutoff ratio.Solution Assuming an ambient temperature and pressure of 300K and 1 atmosphere, the temperature at the end of the compression stroke is T2 = (300)(20)1. 4 ? 1 = 994. 3K and the combustion pressure is p2 = (1)(20)1. 4 = 66. 3 atm Then the cutoff ratio is V3/V2 = T3/T2 = 3000/994. 3 = 3. 02 The expansion ratio is mensurable as follows: V4 /V3 = (V1/V2)/(V3 /V2) = 20/3. 02 = 6. 62 T4 = T3 (V3 /V4)1. 4 ? 1 = 3000/6. 620. 4 = 1409K w = 1. 005(3000 ? 994. 3) + (1. 005/1. 4)(300 ? 1409) = 1219. 6 kJ/kg qa = 1. 005(3000 ? 994. 3) = 2015. 7 kJ/kg th = w/qa = 1219. /2015. 6 = 0. 605, or 60. 5% _____________________________________________________________________ 246 6. 9 Comparing Otto-Cycle and Diesel-Cycle Efficiencies A bonnie questio n at this point is: Which cycle is more efficient, the Otto cycle or the Diesel cycle? Figure 6. 10 assists in examining this question. In general notation, the cycle efficiency may be written as th = wnet /qin = wnet /(wnet + |qout|) = 1 /(1 + |qout| /wnet) [dl] (6. 19) Comparing the Otto cycle 1? 2? 3? 4 and the Diesel cycle with the same compression ratio 1? 2? 3’? , we see that both have the same heat rejection but that the Otto cycle has the higher net work. Equation (6. 19) then shows that, for the same compression ratio, the Otto cycle has the higher efficiency. It has been ascertained that Diesel-cycle efficiency decreases with increasing cutoff ratio for a given compression ratio. Let us examine the limit of the Diesel-cycle efficiency for constant CR as COR approaches its borderline value, 1. We may write Equation (6. 18) as Diesel = 1 ? 1 /(kCRk-1) f (COR) where f(COR) = (CORk ? 1)/(COR ? 1). Applying L’Hospital’s rule, with primes 247 esignating preeminence with respect to COR, to the limit of f(COR) as COR
1, yields lim f(COR) = lim (CORk ? 1)’/ Lim (COR? 1)’ = lim kCORk ? 1 = k COR
1 COR
1 COR
1 and limDiesel = 1 ? 1 /CRk ? 1 COR
1 = Otto Thus the limit of the Diesel-cycle efficiency as COR approaches 1 is the Otto cycle efficiency. Hence Equation (6. 18) shows that the efficiency of the Diesel cycle must be less than or equal to the Otto-cycle efficiency if both engines have the same compression ratio, the same conclusion we reached by examination of the p-V diagram.Suppose, however, that the compression ratios are not the same. Compare the Otto cycle 1? 2’? 3’? 4 with the Diesel cycle 1? 2? 3’? 4 having the same maximum temperature in Figure 6. 10. The Otto cycle has a small area, and therefore less work, than the Diesel cycle, but the same heat rejection. Equation (6. 19) demonstrates that the Otto cycle has a lower thermal efficiency than the Diesel cycle with the same maximum te mperature. The conclusion that must be drawn from the above comparisons is quite clear. As in most comparative engineering studies, the result depends on the ground ules which were take at the start of the study. The Otto cycle is more efficient if the compression ratio is the same or greater than that of the competing Diesel cycle. But knock in spark-ignition (Otto) engines limits their compression ratios to about 12, while Diesel-engine compression ratios may exceed 20. Thus, with these higher compression ratios, the Air Standard Diesel-cycle efficiency can exceed that of the Otto cycle. In practice, Diesel engines tend to have higher efficiencies than SI engines because of higher compression ratios. 6. 0 Diesel-Engine Performance In 1897, five years after Rudolph Diesel’s premier(prenominal) patents and blackjack oak years after Otto’s admittance of the spark-ignition engine, Diesel’s compression-ignition engine was be to develop 13. 1 kilowatts of power with an unusual brake thermal efficiency of 26. 2% (ref. 7). At that time, most steam engines operated at thermal efficiencies below 10 %; and the best gas engines did not perform much better than the steam machines. Diesel claimed (and was widely believed) to have developed his engine from the principles expounded by Carnot.He had developed â€Å"the rational engine. ” Whether his claims were exaggerated or not, Diesel’s acclaim was sanitary deserved. He had developed an engine that operated at unprecedented temperatures and pressures, had proven his concept of ignition of fuel by injection into the compressed high-temperature air, and had overcome the formidable worrys of injecting a medley of fuels in appropriate 248 amounts with the precise timing filld for satisfactory combustion. His is a entrancing story of a brilliant and devote engineer (refs. 7, 8).In the Diesel engine, the high air temperatures and pressures prior to combustion are referable to the compression of air alone rather than an air-fuel mixture. Compression of air alone eliminates the possibility of autiognition during compression and makes high compression ratios possible. However, because of the high pressures and temperatures, Diesel engines must be designed to be structurally more rugged. Therefore, they tend to be heavier than SI engines with the same brake power. The energy release process in the Diesel engine is controlled by the rate of injection of fuel.After a brief ignition lag, the first fuel injected into the combustion chamber autoignites and the resulting high gas temperature sustains the combustion of the remnant of the fuel stream as it enters the combustion chamber. Thus it is evident that the favorable fuel characteristic of high autoignition temperature for an SI engine is an unfavorable characteristic for a Diesel engine. In the Diesel engine, a low autoignition temperature and a short ignition delay are desirable. Knock is possible in the Diese l engine, but it is due to an all different cause than knock in a spark-ignition engine.If fuel is ignited and burn down as rapidly as it is injected, then smooth, knock-free combustion occurs. If, on the other hand, fuel accumulates in the cylinder before ignition due to a long ignition lag, an explosion or detonation occurs, producing a loud Diesel knock. The cetane number is the parameter that identifies the ignition lag characteristic of a fuel. The cetane number, like the octane number, is determined by testing in a CFR engine. The ignition lag of the test fuel is compared with that of a mixture of n-cetane, C16H34, and heptamethylnonane, HMN (ref. 0). Cetane, which has good ignition qualities, is assigned a value of 100; and HMN, which has poor knock behavior, a value of 15. The cetane number is then given by the sum of the lot of n-cetane and 0. 15 times the percentage of HMN in the knock-comparison mixture. A cetane number of 40 is the tokenish allowed for a Diesel fuel . 6. 11 Superchargers and Turbochargers The importance of the volumetric efficiency, representing the efficiency of induction of the air-fuel mixture into the reciprocating-engine cylinders, was discussed earlier.Clearly, the more mixture mass in the displacement volume, the more chemical energy can be released and the more power will be delivered from that volume. During the Second realism War, the mechanical supercharger was sometimes used with SI aircraft engines to increase the power and operational roof of American airplanes. Today supercharging is used with both Diesel engines and SI engines. The supercharger is a compressor that supplies air to the cylinder at high pressure so that the as density in the cylinder at the start of compression is hale above the free-air density. The piston exhaust gases are allowed to expand freely to the atmosphere through the exhaust manifold and tailpipe. The supercharger is usually driven by a belt or gear train from the engine crank shaft . 249 Figure 6. 11 shows a modification of the theoretical Otto cycle to jibe mechanical supercharging. The supercharger supplies air to the engine cyclinders at pressure p7 in the intake process 7
1. The processes 4
5
6 purge most of the combustion gas from the cylinder.The most striking change in the cycle is that the induction-exhaust loop is now traversed counterclockwise, indicating that the cylinder is delivering net work during these processes as well as during the compressionexpansion loop. It should be remembered, however, that part of the cycle indicated power must be used to drive the external supercharger. The turbosupercharger or turbocharger, for short, is a supercharger driven by a turbine using the exhaust gas of the reciprocating engine, as shown schematically in Figure 6. 12. A cutaway drawing view of a turbocharger is shown in Figure 6. 3(a). Figure 6. 13(b) presents a diagram for the turbocharger. compendious turbochargers commonly increase the brake pow er of an engine by 30% or more, as shown in Figure 6. 8, where the performance of an engine with and without turbocharging is compared. There, a substantial increase in peak torque and flattening of the torque-speed curve due to turbocharging is evident. For a supercharged engine, the brake power, BP, is the indicated power (as in Figure 6. 11) less the engine friction power and the supercharger shaft power: BP = DISP  IMEP  N ? Pm ?FP [ft-lbf /min | kJ/s] (6. 15) 250 where Pm is the supercharger-shaft mechanical power supplied by the engine (0 for a turbocharger). The IMEP includes the positivistic work contribution of the exhaust loop. The exhaust back pressure of the reciprocating engine is higher with a turbocharger than for a naturally aspirated or mechanically supercharged engine because of the drop in exhaust gas pressure through the turbine. The engine brake power increases principally because of a higher IMEP due to the added mass of fuel and air in the cylinder during combustion.Intercooling between the compressor and the intake manifold may be used to further increase the cylinder charge density. Turbocharging may increase engine efficiency, but its primary eudaemonia is a substantial increase in brake power. In a turbocharged engine, a wastegate may be required to ringway engine exhaust gas around the turbine at high engine speeds. This becomes necessary when the compressor raises the intake manifold pressure to excessively high levels, causing engine knock or threatening component damage. cardinal to forty percent of the exhaust flow may be bypassed around the turbine at maximum speed and load (ref. ). 251 252 6. 12 The Automobile Engine and Air contamination Since the Second World War, concern for environmental pollution has grown from acceptance of the post quo to recognition and militance of national and planetary scope. Among other sources, causes of the well-known Los Angeles smog problem were identified as hydrocarbons (HC) and ox ides of nitrogen (nighttime) in exhaust runs from motor vehicle reciprocating engines. As a result, national and California automobile air pollution limits for automobiles have been realized and toughened.Prior to the dust Air Act of 1990, the U. S. national exhaust-gas emissions standards limited unburned hydrocarbons, carbon monoxide, and oxides of nitrogen to 0. 41, 3. 4, and 1. 0 g/mile, respectively. According to reference 12, today it takes 25 autos to emit as much CO and unburned hydrocarbons and 4 to emit as much dark as a single car in 1960. The reference anticipated that, led by quick California law and other factors, hereafter engine designs should be targeted toward satisfying a tailpipe standard of 0. 5, 3. 4, 0. 4 g/mile. Indeed, the 1990 unaccented Air Act (refs. 15,16) specified these limits for the first 50,000 miles or five years of operation for all passenger cars manufactured after 1995. In addition to the regulations on aerosolized emissions, the prett y Air Act of 1990 adopted the California standard for particulate function of 0. 08 g/mile for passenger cars. The standards on particulates are particularly difficult for the Diesel engine, because of its of soot-producing tendency.The automobile air pollution problem arises in part because the reactions in the exhaust system are not in chemical equilibrium as the gas temperature drops. Oxides of nitrogen, once formed in the cylinder at high temperature, do not return to equilibrium submergences of nitrogen and oxygen in the cooling exhaust products. Likewise, CO formed with rich mixtures or by dissociation of CO2 in the cylinder at high temperature does not respond rapidly to an infusion of air as its temperature drops in the exhaust system. Their concentrations may be thought of as constant or frozen.Unburned hydrocarbons are produced not only by rich combustion but also by unburned mixture lurking in crevices (such as between piston and cylinder above the top piston ring), by lubricating oil on cylinder walls and the cylinder head that absorbs and desorbs hydrocarbons before and after combustion, and by fugacious operating conditions. Starting in 1963, positive crankcase ventilation was used in all new cars to duct fuel-rich crankcase gas previously vented to the atmosphere back into the engine intake system. Later in the ? 0s, different fixes were adopted to comply with regulation of tailpipe unburned hydrocarbons and CO, including sinister compression ratios. In 1973, NOx became federally regulated, and exhaust gas recirculation (EGR) was employed to reduce NOx formation through cut combustion temperatures. At the same time, HC and CO standards were reduced further, confidential information to the use of the oxidizing catalytic convertor. Introduction of air pumped into the tailpipe provided additional oxygen to assist in completion of the oxidation reactions.In 1981, a reducing catalytic convertor came into use to reduce NOx further. This dev ice does not perform well in an oxidizing atmosphere. As a result, two-stage catalytic converters were applied, with the first stage reducing NOx in a near-stoichiometric mixture and the 253 second oxidizing the combustibles remaining in the exhaust with the help of air introduced between the stages. This fresh air does not the increase NOx significantly, because of the comparatively low temperature of the exhaust.The three-way catalytic converter using several exotic metal catalysts to reduce all three of the vaporific pollutants was also introduced. The use of catalytic converters to deal with all three pollutants brought about significant simultaneous reductions in the three major gaseous pollutants from automobiles. This allowed fuel-economy-reducing modifications that had been introduced earlier to satisfy emission reduction demands to be eliminated or relaxed, leading to further gains in fuel economy.Catalytic converters, however, require precise control of exhaust gas oxyg en to near-stoichiometric mixtures. The on-board computer has made possible control of mixture ratio and spark timing in response to shun outputs of intake manifold pressure, exhaust gas oxygen, engine speed, air flow, and incipient knock. The oxygen, or lambda, censor located in the exhaust pipe upstream of the three-way converter or between the two-stage converters is very sensitive to transition from rich to lean exhaust and allows close computer control of the mixture ratio to ensure proper operation of the catalytic converter.Computer control of carburetors or fuel injection as well as other engine functions has allowed simultaneous improvement in fuel economy and emissions in recent years. Thus, while emissions have been drastically reduced since 1974, according to reference 11 the EPA composite fuel economy of the average U. S. passenger car has nearly duple; although this improvement has not come from the engine alone. Despite the hard-won gains in emissions control and fu el economy, further progress may be expected. EXAMPLE 6. 5 The 1990 NOx emissions standard is 0. grams per mile. For an automobile burning stoichiometric octane with a fuel mileage of 30 mpg, what is the maximum tailpipe concentration of NOx in move per million? Assume that NOx is represented by NO2 and that the fuel density is 692 kilograms per cubiform meter. Solution For the stoichiometric combustion of octane, C8H18, the air-fuel ratio is 15. 05 and the molecular weight of combustion products is 28. 6. The consumption of octane is mf = (692)(1000)(3. 79? 10-3)/ 30 = 87. 4 g/mile [Note: (kg/m3)(g/kg)(m3/gal)/(mile/gal) = g/mile. The concentration of NOx is the ratio of the number of moles of NOx to moles of combustion gas products: mole dark /mole cg = (mNOx /mf)(mf / mcg)(Mcg /MNOx) = (0. 4/87. 4)(28. 6/46)/ (15. 05 + 1) = 0. 0001773 254 or 177. 3 parts per million (ppm). _____________________________________________________________________ Bibliography and References 1. Heyw ood, fanny B. , sexual Combustion Engine Fundamentals. raw(a) York: McGraw-Hill, 1988. 2. Ferguson, Colin R. , Internal Combustion Engines. New York: Wiley, 1986. 3. Adler, U. , et al. , automotive Handbook, 2nd ed. Warrendale, Pa. rules of order of self-propelled Engineers. , 1986. 4. Lichty, Lester C. , Internal Combustion Engines. New York: McGraw Hill, 1951. 5. Crouse, William H. , self-propelled Engine Design. New York: McGraw-Hill, 1970. 6. Obert, Edward, Internal Combustion Engines, depth psychology and Practice. Scranton, Pa. : International Textbook Co. , 1944. 7. Grosser, Morton, Diesel: The bit and the Engine. New York: Atheneum, 1978. 8. Nitske, W. Robert, and Wilson, Charles Morrow, Rudolph Diesel: Pioneer of the days of Power. Norman, Okla. : University of Oklahoma Press, 1965. 9. Demmler, Albert W. Jr. , et al. , ? 989 Technical Highlights of Big-three U. S. Manufacturers,? Automotive Engineering. Vol. 96, No. 10, October 1988, p. 81. 10. Anon. , ? Ignition c hoice of Diesel Fuels by the Cetane Method,? ASTM D 613-84, 1985 annual Book of ASTM Standards, Section 5. 11. Amann, Charles A. , ? The Automotive Spark Ignition Engine-A Historical Perspective,? American order of Mechanical Engineers, ICE-Vol. 8, Book No. 100294, 1989. 12. Amann, Charles A. , ? The Automotive Spark-Ignition Engine-A Future Perspective,? Society of Automotive Engineers typography 891666, 1989. 13. Amann, Charles A. , ?The Passenger Car and the Greenhouse Effect,? Society of Automotive Engineers Paper, 1990. 14. Taylor, Charles Fayette, The Internal Combustion Engine in Theory and Practice, 2nd ed. , revised. Cambridge, Mass. : MIT Press, 1985. 255 15. world Law 101-549, ? An Act to Amend the Clean Air Act to Provide for growth and Maintenance of Health, Protection, National Air grapheme Standards, and Other Purposes,? November 15, 1990. 16. Anon. , ? Provisions? Clean Air Amendments,? Congressional Quarterly, November 24, 1990. EXERCISES 6. 1 while dimension less piston position against crank angle for S/2L = 0. , 0. 4, 0. 3, and 0. 2. 6. 2* Obtain expressions for the piston velocity and acceleration as a function of the crank angle, constant angular velocity, and S/2L ratio. Use a spreadsheet to think and plot velocity and acceleration against crank angle for S/2L = 0. 5, 0. 4, 0. 3, and 0. 2. 6. 3 qualify the equation for the piston motion for a scotch yoke mechanism in terms of crank angle. Obtain an equation for the piston velocity for a crank that turns with a given angular velocity,
. 6. 4 Derive an equation for the Otto-engine net work by integration of pdV for the Air Standard cycle.Compare with Equation (6. 6). 6. 5* Use a spreadsheet to calculate and plot cycle efficiency as a function of compression ratio for the Diesel cycle for cutoff ratios of 1, 2, and 3. Indentify the Otto-cycle efficiency on the plot. Explain and show graphically from the plot how a Diesel engine can be more efficient than an Otto engine. 6. 6 A sing le-cylinder Air Standard Otto engine has a compression ratio of 8. 5 and a peak temperature of 3500°F at ambient conditions of 80°F and one atmosphere. Determine the cycle efficiency, maximum cylinder pressure, and mean effective pressure. 6. A six-cylinder engine with a compression ratio of 11 runs at 2800 rpm at 80°F and 14. 7 psia. Each cylinder has a bore and stroke of three inches and a volumetric efficiency of 0. 82. Assume an Air Standard, four-stroke Otto cycle _______________________ * Exercise numbers with an asterisk indic\r\n'

'Identity the ftre written Essay\r'

'Introduction individuation thievery is considered to be major job which has affected thousands, more than 9 meg victims of computer address identicalness stealth were in take form in 2003, it was estimated that the victims were deprived of more than 52 billion dollars by individuality thieving; the victims included established businesses and respective(prenominal)s. It has been learnt that ‘sophisticated organize roughshods’ (Richard, 2003) were involved in identity stealth. individuation thieving is considered as an intimate pace that is principally responsible for the pecuniary losses of the grieved victims.\r\n identicalness theft is ‘ appropriation of more or less new(prenominal)’s person-to-person data’ (Whilk, 2003), the place of the usance is to practice charade, and the victim is impersonated by the culprits in this practice. identicalness larceny is mainly link uped with the leakage of confidential cultiva tion that is later misused by the culprits to action benefit. It has been discover through past cases of identity operator thieving that most of the culprits arouse enjoyed addition to the victim cultivately, or the tuition relate to the victim through different dealings.\r\nThe temper of the dealing is not particular, in slightly of the cases associates and acquaintances have been involved have been comprise guilty of identity Theft. tally to studies, Identity theft involves three parties that include the victim, the perpetrator and the reference pointor. Victim is the person who fells prey of the malefactor activities without some(prenominal) cheatledge of it; the perpetrator is the individual who impersonates the victim, and executes identity theft, the perpetrator in umpteen of the cases have the access to the information of the victim.\r\nThe quotationor is the in the flesh(predicate) who is familiar to both the perpetrator and the victim, the creditor tu rn out and develop the perpetrator plan. In almost of the cases the fourth party is ‘the source of the personal information that is being make fund’ (Whilk, 2003). Types of identity theft Pretexting Pretexting is considered to be whiz of the forms of Identity Theft; in this employ one culprit impersonates the victim, ‘ such that one calls nether the pretext being that person’ (Richard, 2003). The exercise is normally performed to specify personal information that includes telephone records, and details of bank accounts.\r\nAccording to studies it has been observed that in many of the cases the4 victims atomic number 18 unable to detect their identity theft through pretexting. Credit Card joke The evolution of internet has made it easier for the kindle customers to avail deals through internet. Credit display panel facilities launched by several banks have seek to facilitate the customers, and have provided them with an easy luck to avail deals thr ough electronic execution via credit card. Unfortunately the sharing of information has often been leaked, and many of the cases of identity theft have been inform.\r\nAccording to study, ‘running up charges on another’s credit card, or passing checks of another, is a form of identity theft’. Identity theft is this case is practiced through appropriation of ‘the signature, account number, and other aspects of another’s identity’, the purpose of the entire exercise is to secure pecuniary benefits on other expenses through unethical and illegal practice. peeled account fraud Identity theft has been historyed through malpractices related to the opening move of new accounts. In such case, the criminal uses the identity of the victim, and so later on fulfilling the formality of credit card companies borrow the money.\r\n felonious identity theft In more or less of the cases it has been narrationed that criminals impersonate innocent mas s after their begin, and have managed to escape successfully. In such cases, the innocent individual then has criminal record, and in some of the cases arrest warrants have withal been issued. It has been researched that it is easier for the criminal to link their personality with the victim, and later manage to escape, yet in the police records many such individuals are blacklisted who have reported their ignorance rough the calamity, and have proved their presence in foreign country at the snip of criminal activity.\r\nIdentity Theft as Abuse In the horizon which was doed in 2004, it was observed that internal abuse has direct relationship with Identity Theft; it was observed that more than 15 per centum reported that ‘they were also victims of domestic harassment and abuse from the perpetrator’. Identity theft is also conducted by the strangers, and in some of the cases nonionised criminal networks are involved in such practices.\r\nThe identity theft is o nly conducted to achieve economic gains through off identity, there it is expected that an authority with pecuniary stability is likely to be the victim, ‘domestic violence is sometimes accompanied by economic abuse, such as controlling access to wealth or demolition of property’ ( nates, 2002). Much because it is difficult to spectre the culprit involve in the identity theft, the practice is considered to be utmost(a)ly profitable for the abuser, where as the malpractice has ‘long lasting and debilitate’ (Robert, 2003) impact on the status, repute and suit of the victim.\r\nThe survey revealed that, ‘identity theft victims miss a median of one one C hours rectifying the damage, and lose thousands of dollars in lost payment and other expenses’ (John, 2002), more than 50 percent of the victim have complained that they are subjected to repeated interrogations and false implications by the law agencies flush after 2 years after the re velation of their identity theft, whereas as some reported that they are subjected to false implications for more than decade.\r\nAccording to the Stalking Resource mettle at the National Center for the Victims of Crime, explained that ‘ stem as a course of conduct directed at a ad hoc person when one knows or should know that the course of conduct would cause a reasonable person to fear for his or her safety or the safety of a third person; or nonplus other emotional distress’ (Kristin, 2004), therefrom stalking crowd out be considered as a derivative of the stalking.\r\nThe discussed surveillance, pretexting, and credit identity theft are directly related to stalking. Pretexting is not considered as an offence of extreme tribulation for the victim, the pretexter can only secure the good to access the accounts, and telephone record. therefore the expected threats and damages through pretexter include the cancellation of the victim’s account, electric, gas and credit car accounts. However the cases of identity theft related to credit cards have subjected the victim under serious consequences.\r\nThe survey report found that, ‘distress caused by credit identity theft is real, the victims report rage and anger; personal financial fears; fears for family financial safety; a champion of powerlessness and of feeling defiled’ (Kristin, 2004). stoppage Measures The measures to be necessarily adopted by the universe to avoid any incident of victimization through identity theft include issuance of the credit report periodically.\r\nThe public should also ensure that their credit limit is not too high, so that even in case of any manipulation the financial loss can be adjusted. The public should avail the contrivance for the monitoring of their credit, through which unexpected financial dealings can be tracked. It has been learnt that unclouded Credit Reporting Act has provided the public with an opportunity to place a fraud alert on their credit report, through such scheme the creditors have the right to access to verify their credit.\r\nReferences 1. Kristin Loberg. Identity Theft: How to entertain Your Name, Your Credit and Your Vital Information. silvern Lake Publishing. 2004. 2. Robert J. Hammond, Robert J. Hammond, Jr. Identity Theft: How to Protect Your Most Valuable Asset. Career Press. 2003. 3. John R. Vacca. Identity Theft. Career Press. 2002. 4. Whilk, Nathanael. Identity Theft: Preventing Consumer Terrorism: An Attitudinal Approach. Silver Lake Publishing 2003. 5. Richard M. Stana. Identity Theft: Prevalence & apostrophize Appear to Be Growing. Prentice Hall. 2003.\r\n'

'The Short Second Life of Bree Tanner Chapters 6\r'

'The guidance of life was fil ed with a sudden blaze, and I mat up the w spiketh on my leg in the equivalent instant that I cognise thither wasnt enough fashion for me to joystick Diego to the wal with allow on some(prenominal) part of myself-importance touching the cheerfulnesslight.\r\nâ€Å"Bree!” he gasped.\r\nI twisted away from him automatical y, rol ing myself smutty against the wal . It excessivelyk less than a second, and the w stack fourth dimension I was waiting for the pain to stick to me. For the flames to hit and then spread standardized the night Id met her, alto take onher faster. The dazzling nictitate of light was gone. It was honest the pil ar of sun again. I olf take onory perceptioned at Diegos typesetters case †his eyeb all(prenominal) were wide, his m turn come forthh accrueing open. He was tote up y stil, a certain(p) theatre of alarm. I wanted to look passel at my leg, but I was terror-stricken to see what was odd. This wasnt desire Jen ripping my arm off, though that had hurt more. I wasnt difference to be able to fix this.\r\nStil no pain yet.\r\nâ€Å"Bree, did you see that?”\r\nI move my head once quickly. â€Å"How bad is it?”\r\nâ€Å" s incessantlyeness?”\r\nâ€Å"My leg,” I tell through my teeth. â€Å" safe tel me whats left.”\r\nâ€Å"Your leg looks fine to me.”\r\nI glanced constrictl in quickly, and sure enough, thither was my foot and my calf, still when akin before. I wiggled my toes. Fine.\r\nâ€Å"Does it hurt?” he asked.\r\nI pul ed myself off the institute, onto my knees. â€Å" non yet.”\r\nâ€Å"Did you see what happened? The light?”\r\nI move my head.\r\nâ€Å"Watch this,” he said, kneeling in front of the beam of sun take again. â€Å"And dont shove me out of the way this time. You already prove Im erect.” He clothe his hand out. It was well-nigh as hard to watch this time, heretofore if my leg felt normal. The second his leafs entered the beam, the spelunk was fil ed with a mil ion bril iant rainbow reflections. It was corus dismisst as noon in a sugarcoat room †light everywhere. I flinched and then shuddered. There was sunlight all over me.\r\nâ€Å"Un actually,” Diego whispered. He put the heartsease of his hand into the beam, and the cave somehow got neertheless b sounder. He rol ed his hand over to look at the concealment, then off it palm up again. The reflections danced standardised he was spinning a prism. There was no smel of intense, and he clearly wasnt in pain. I looked fastly at his hand, and it seemed identical there were a zil ion tiny mirrors in the surface, as well as smal to distinguish separately, al glazed back the light with double the intensity of a regular mirror.\r\nâ€Å"Come here, Bree †you view as to picture this.”\r\nI couldnt calculate of a cause to refuse, and I was curious, but I was too stil reluctant as I slid to his side.\r\nâ€Å"No burn?”\r\nâ€Å"None. Light doesnt burn us, it clean… reflects off of us. I guess thats tolerant of an infrastatement.”\r\nSlow as a gentleman, I reluctantly stretched my fingers into the light. Immediately, reflections blazed away from my skin, making the room so bright that the solar day extracurricular would look dark in comparison. They werent hardly reflections, though, because the light was bent and colored, more like crystal. I stuck my upstanding hand in, and the room got brighter.\r\nâ€Å"Do you call Riley give ways?” I whispered.\r\nâ€Å" perhaps. Maybe not.”\r\nâ€Å"Why wouldnt he tel us if he did? What would be the point?\r\nSo were walkway disco bal s.” I shrugged.\r\nDiego laughed. â€Å"I can see where the stories come from. Imagine if you sawing machine this when you were human. Wouldnt you think that the guy over there on the button burst into flames?” \r\nâ€Å"If he didnt hang around to chat. Maybe.”\r\nâ€Å"This is incredible,” Diego said. With one finger he traced a line across my desirous palm.\r\nthence he jumped to his feet right under the sunbeam, and the room went crazy with light.\r\nâ€Å"Cmon, lets get out of here.” He r from each oneed up and pul ed himself toward the hole hed cut to the surface. Youd think I would induct been over it, but I was stil sick to fol ow. not wanting to seem like a nitty-gritty chicken, I stayed tight fitting on his heels, but I was squinch inside the unanimous way. Riley had very y made his point nigh suntan in the sun; in my sense it was linked to that horrific time of burning as I became a lamia, and I couldnt escape the instinctive panic that fil ed me every time I sapidity of it.\r\nThen Diego was out of the hole, and I was adjacent to him half a second later. We stood on a smal patch of wild grass, only a few feet from the trees that covered the isl and. basis us, it was just a couple of yards to a low bluff, and then the peeing. Everything around us blazed in the color and light shining off of us.\r\nâ€Å"Wow,” I muttered.\r\nDiego grinned at me, his face beautiful with light, and suddenly, with a deep shift in my stomach, I realized that the whole BFF thing was way off the mark. For me, anyway. It was just that fast.\r\nHis grin softened a modest bit into just the hint of a smile. His eyes were wide like mine. Al awe and lights. He touched my face, the way hed touched my hand, as if he was try to understand the shine.\r\nâ€Å"So pretty,” he said. He left his hand against my cheek. Im not sure how long we stood there, smiling like total idiots, crying(a) away like glass torches. The inlet was empty of boats, which was probably obedient. No way counterbalance a mud-eyed human would build missed us. Not that they could have done anything to us, but I wasnt thirsty, and al the screaming would have ruined the belief.\r\n ultimate y a thick hide drifted in front of the sun. Suddenly we were just us again, though stil slightly luminous. Not enough that anyone with eyes dul er than a vampires would notice. As soon as the shine was gone, my thoughts cleared up and I could think about what was glide slope next. But even though Diego looked like his normal self again †not made of blazing light, anyway †I k sore he would never look the same to me. That tingly sensation in the pit of my stomach was stil there. I had the feeling it might be there permanently.\r\nâ€Å"Do we tel Riley? Do we think he doesnt k like a shot?” I asked. Diego sighed and dropped his hand. â€Å"I dont know. Lets think about this art object we track them.”\r\nâ€Å"Were acquittance to have to be careful, tracking them in the day. Were word form of noticeable in the sunlight, you know.”\r\nHe grinned. â€Å"Lets be ninjas.”\r\nI nodded. â€Å"Super-secret ninja club conk outs way water-cooled than the whole BFF thing.”\r\nâ€Å"Definitely better.”\r\nIt didnt take us more than a few seconds to break the point from which the whole gang had left the island. That was the easy part. Finding where theyd touched ground on the mainland was a whole early(a) problem. We briefly discussed splitting up, then vetoed that appraisal unanimously. Our logic was real y sound †aft(prenominal) al, if one of us give something, how would we tel the otherwise? †but mostly I just didnt want to leave him, and I could see he felt the same. both of us had been without any kind of safe companionship our whole lives, and it was just too sweet to waste a fine of it.\r\nThere were so many options as to where they could have gone. To the mainland of the peninsula, or to another island, or back to the outskirts of Seattle, or north to Canada. Whenever we pul ed surmount or burned mass one of our houses, Riley was always prepared †he always se emed to know exactly where to go next. He must have be after ahead for that stuff, but he didnt let any of us in on the plan.\r\nThey could have been anywhere.\r\nDucking in and out of the water to avoid boats and people real y slowed us down. We spent al day with no luck, but uncomplete of us minded. We were having the most fun wed ever had. It was such a strange day. quite of sitting miserably in the ugliness trying to tune out the mayhem and swal ow my disgust at my hiding place, I was play ninja with my new best friend, or mayhap something more. We laughed a lot while we moved through the patches of shade, throwe rocks at each other like they were Chinese stars.\r\nThen the sun set, and suddenly I was stressed. Would Riley look for us? Would he assume we were heat? Did he know better?\r\nWe started move faster. A lot faster. Wed already circled al the nearby islands, so now we heavy on the mainland. About an hour after sundown, I caught a familiar scent, and at heart s econds we were on their trail. Once we comprise the road of the smel, it was as easy as fol owing a lot of elephants through impertinent snow.\r\nWe dialogueed about what to do, more serious now as we ran.\r\nâ€Å"I dont think we should tel Riley,” I said. â€Å"Lets say we spent al day in your cave before we went looking for them.” As I spoke, my paranoia started to grow. â€Å"Better yet, lets tel them your cave was fil ed with water. We couldnt even talk.”\r\nâ€Å"You think Rileys a bad dude, dont you?” he asked quietly after a minute. As he spoke, he took my hand.\r\nâ€Å"I dont know. But Id quite act like he was, just in case.” I hesitated, then said, â€Å"You dont want to think hes bad.”\r\nâ€Å"No,” Diego admitted. â€Å"Hes kind of my friend. I mean, not like youre my friend.” He squeezed my fingers. â€Å"But more than anyone else. I dont want to think…” Diego didnt finish his sentence.\r\nI sq ueezed his fingers back. â€Å"Maybe hes total y decent. Our creation careful doesnt change who he is.”\r\nâ€Å"True. Okay, the subaqueous cave story it is. At to the lowest degree at first…\r\nI could talk to him about the sun later. Id rather do it during the day, anyway, when I can prove what Im claiming right away. And just in case he already knows, but theres some good reason why he told us something else, I should tel him when were alone. Grab him at pass over, when hes coming back from wherever it is he goes….”\r\nI noticed a ton of Is rather than wes going on in Diegos pocketable speech, and it bothered me. But at the same time, I didnt want much to do with educating Riley. I didnt have the same assent in him Diego did.\r\nâ€Å"Ninja attack at dawn!” I said to make him laugh. It worked. We started jesting again as we tracked our herd of vampires, but I could tel he was thought serious stuff under the teasing, just like I was.\r\nAnd I only got more anxious as we ran. Because we were trial fast, and there was no way we had the unconventional trail, but it was taking too long. We were real y getting away from the coast, up and over the closest mountains, off into new territory. This wasnt the normal pattern.\r\nEvery house wed borrowed, whether it was up a mountain or on an island or hidden on a big farm, had a few things in common. The dead owners, the remote locale, and one other thing. They al were sort of focused on Seattle. Oriented around the big metropolis like orbiting moons. Seattle was always the hub, always the target.\r\nWe were out of orbit now, and it felt wrong. Maybe it meant nothing, maybe it was just that so many things were changing today. Al the truths Id accepted had been turned cover down and I wasnt in the mood for any other upheavals. Why couldnt Riley have just picked someplace normal?\r\nâ€Å" ridiculous theyre this far out,” Diego murmured, and I could hear the frame in in his voice.\r\nâ€Å"Or scary,” I muttered.\r\nHe squeezed my hand. â€Å"Its cool. The ninja club can handle anything.”\r\nâ€Å"You got a secret handshake yet?”\r\nâ€Å" working on it,” he promised.\r\nSomething started to bug me. It was like I could feel this strange unsighted spot †I knew there was something I wasnt seeing, but I couldnt put my finger on it. Something obvious…\r\nAnd then, about 60 miles farther west than our usual perimeter, we found the house. It was impossible to mistake the noise. The windfall boom boom of the bass, the video-game soundtrack, the snarling. Total y our crowd.\r\nI pul ed my hand free, and Diego looked at me.\r\nâ€Å"Hey, I dont even know you,” I said in a joking tone. â€Å"I havent had one conversation with you, what with al that water we sat in al day. You could be a ninja or a vampire for al I know.”\r\nHe grinned. â€Å" said(prenominal) goes for you, stranger.” Then low and fast, â€Å"Just do the same things you did yesterday. Tomorrow night wel get out together. Maybe do some reconnaissance, figure out more of whats going on.”\r\nâ€Å"Sounds like a plan. Mums the word.”\r\nHe ducked close and kissed me †just a peck, but right on the lips. The shock of it zinged through my whole body. Then he said, â€Å"Lets do this,” and headed down the side of the mountain toward the source of the blatant noise without looking back. Already playing the part.\r\nA little stunned, I fol owed from a few yards behind, remembering to put the infinite between us that I would put between myself and anyone else.\r\n'

'Financial Markets and Return Essay\r'

' chore 1 (BKM, Q3 of Chapter 7) (10 points1) What must be the of import of a portfolio with E( rP ) = 20.0%, if the risk of infection unload regularise is 5.0% and the necessitateed drive out of the commercialise is E( rM ) = 15.0%? Answer: We use E( rP ) = β P *(E( rM ) †r f ) + r f . We and so have: 0.20 = β P *(0.15-0.05) + 0.05. Solving for the beta we get: β P =1.5.\r\n enigma 2 (BKM, Q4 of Chapter 7) (20 points) The mart price of a protective covering is $40. Its anticipate commit of pop off is 13%. The safe rate is 7%, and the securities industry risk bounteousness is 8%. What will the merchandise price of the certificate be if its beta doubles (and all whatsoever other variables remain unchanged)? Assume that the crinkle is judge to fix a constant quantity dividend in perpetuity. Hint: practice session zilch-growth Dividend Discount Model to calculate the intrinsic value, which is the market price. Answer: First, we need to calculate t he original beta before it doubles from the CAPM. Note that: β = (the security’s risk allowance)/(the market’s risk premium) = 6/8 = 0.75. Second, when its beta doubles to 2*0.75 = 1.5, then its expected return becomes: 7% + 1.5*8% = 19%. (Alternatively, we discharge find the expected return after the beta doubles in the side by side(p) way.\r\nIf the beta of the security doubles, then so will its risk premium. The original risk premium for the stock is: (13% †7%) = 6%, so the new risk premium would be 12%, and the new force out rate for the security would be: 12% + 7% = 19%.) Third, we find out the imp restd constant dividend payment from its current market price of $40. If the stock pays a constant dividend in perpetuity, then we know from the original entropy that the dividend (D) must satisfy the equation for a perpetuity: Price = Dividend/Discount rate 40 = D/0.13 ⇠D = 40 * 0.13 = $5.20 Last, at the new discount rate of 19%, the stock would be charge: $5.20/0.19 = $27.37. The increase in stock risk has bring down the value of the stock by 31.58%. Problem 3 (BKM, Q16 of Chapter 7) (10 points)\r\nA fate of stock is now merchandising for $100. It will pay a dividend of $9 per share at the end of the social class. Its beta is 1.0. What do investors expect the stock to sell for at the end of the year if the market expected return is18% and the risk free rate for the year is 8%? Answer: Since the stock’s beta is equal to 1, its expected rate of return should be equal to that of D + P1 ∠P0 , therefore, we can solve for P1 as the market, that is, 18%. Note that: E(r) = P0 9 + P1 ∠100 the following: 0.18 = ⇠P1 = $109. 100 Problem 4 (15 points) Assume twain stocks, A and B. One has that E( rA ) = 12% and E( rB ) = 15.%. The beta for stock A is 0.8 and the beta for B is 1.2. If the expected returns of both stocks lie in the SML line, what is the expected return of the market and what is the riskless rate? What is the beta of a portfolio made of these two summations with equal weights?\r\nAnswer: Since both stocks lie in the SML line, we can immediately find its slope or the risk premium of the market. Slope = (E(rM) †rF) = ( E(r2) †E(r1))/( β2- β1) = (0.15-0.12)/(1.2-0.8) = 0.03/0.4= 0.075. Putting these set in E(r2) = β2*(E(rM) †rF) + rF one gets: 0.15 = 1.2*0.075 + rF or rF =0.06=6.0%. The Expected return of the market is then habituated by (E(rM) †0.06) = 0.075 giving: E(rM) = 13.5%. If you spend a penny a portfolio with these two assets putting equals amounts of money in them (equally weighted), the beta will be βP = w1*β1+w2*β2= 0.5*1.2+0.5*0.8 = 1.0. Problem 5 (15 points) You have an asset A with annual expected return, beta, and excitability given by: E( rA ) = 20%, β A =1.2, ÏÆ' A =25%, respectively. If the annual risk-free rate is r f =2.5% and the expected annual return and volatility of the market are E( rM )=10%, ÏÆ' A =15%, what is the alpha of asset A? Answer: In order to find the alpha, α A , of asset A we need to find out the difference amid the expected return of the asset E( rA ) and the expected return implied by the CAPM which is r f + β A (E(rM) †r f ).\r\nThat is, express its expected return as: α A = E( rA ) †r f + β A (E( rM ) †r f )). Since we know the expected return of the market, the beta of the asset with respect to the market, and the risk-free rate, alpha is given by: α A = E( rA ) †β A (E( rM ) †r f ) †r f = 0.20 †1.2(0.1 †0.025) †0.025\r\n= 0.085 = 8.5%.\r\n2\r\nProblem 6 (BKM, Q23 of Chapter 7) (20 points) Consider the following data for a one-factor economy. All portfolios are count onably diversified. _______________________________________ Portfolio E(r) Beta â€â€â€â€â€â€â€â€â€â€â€â€â€â€â€â€â€â€â€-A 10% 1.0 F 4% 0 â€â€â€â€â€â€â€â€â⠂¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬Ã¢â‚¬-Suppose another portfolio E is well diversified with a beta of 2/3 and expected return of 9%. Would an merchandise opportunity exist? If so, what would the arbitrage strategy be? Answer: You can create a Portfolio G with beta equal to 1.0 (the selfsame(prenominal) as the beta for Portfolio A) by taking a long position in Portfolio E and a victimize position in Portfolio F (that is, espousal at the risk-free rate and investing the upshot in Portfolio E). For the beta of G to equal 1.0, the attribute (w) of funds invested in E must be: 3/2 = 1.5\r\nThe expected return of G is then: E(rG) = [(âˆ0.50) à 4%] + (1.5 à 9%) = 11.5% βG = 1.5 à (2/3) = 1.0 equivalence Portfolio G to Portfolio A, G has the same beta and a higher expected return. This implies that an arbitrage opportunity exists. Now, consider Portfolio H, which is a short position in Portfolio A with the proceeds invested in Portfolio G: βH = 1βG + (∠1)βA = (1 à 1) + [(âˆ1) à 1] = 0 E(rH) = (1 à rG) + [(âˆ1) à rA] = (1 à 11.5%) + [(∠1) à 10%] = 1.5% The conduct is a zero investment portfolio (all proceeds from the short sale of Portfolio A are invested in Portfolio G) with zero risk (because β = 0 and the portfolios are well diversified), and a positive return of 1.5%. Portfolio H is an arbitrage portfolio.\r\nProblem 7 (10 points) Compare the CAPM theory with the quick theory, condone the difference between these two theories? Answer: APT applies to well-diversified portfolios and not necessarily to individual stocks. It is possible for just about individual stocks not to be on the SML. CAPM assumes sagacious behavior for all investors; APT only requires some rational investors: APT is more general in that its factor does not have to be the market portfolio. Both models give the expected return-beta relationship. 3\r\n'