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Total No. of Questions-l2] [Total No. of Printed Pages-4+2' 137621-27S.E. (MECH.) (Second Semester) 'EXAMINAIION, 2010

I.C. ENGINES AND AI.,]"TOMOBILE ENGINEERING(2003couRsE)

Time : Three Hours Maximum Marks : 100N.B. :- (i) Answer 3 questions from Section I and 3 questions

from Section II.(il) Answers to the two sectionsshould be written in separate

answer-books.(iii) Neat diagrams must be drawn wherever necessary.(lu) Figures to the right indicate full marks.(u) Use of logarithmic ables,slide rule, Mollier charts, electronic

. pocket calculator and steam tables is allowed.(ul) Assumesuitabledata, iI necessary.

SECTION IUnit Il. (a) Why the actual cycle effrciency s much lower than the air

standard cycle efficiency? List the major lossesand differencesin actual engine cycle and air-standard cycle. t8l

(b) A four-cylinder,our-strokeS.I.Enginehasa displacernentolurne' o1 300 CC per cylinder.The compressionatio of the engineis 10 and operatesat a speedof 3000r.p.rn.The enginedevelopsan out-put of 40 kW at this speed.

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Calculate :(i), The air standard efEciency(ii) Rate of Heat addition(iii) The mean effective pressure(lu) The maximum temperature of the cycle.Assume the pressure and temperature atare 1 bar and 27"C respectively. Take C, =v = 1.4.

initial conditions0.717 kJ/kgK and

t10lOr

Explain with neat sketches, the valve timing diagrams for low, (a)

(b). and high speed petrol engine. t41

Compareair standardOtto, dieseland duelcycleson the followingbasis with P*V,and T-S diagram. t6j(l) Same compressionRatio and heat rejection(ii) Same maximum pressure and heat input.

(c) The air-fuel ratio of a Diesel engine s 31 : 1,. f the cornpressionratio is 15 : 1 and temperature at the end of compressronis 1000 K. Find at what percentage f stroke is the combustioncomplete f the combustionbegins at TDC and continuousatconstant pressure. Calorific val.ueof the fuel is 40000 kJ/kg.Assume the variable specifrc heat Cp = o + bT, whereo = 1 a n d b = 0 . 2 8 x 1 # . t81

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q. @)Unit I I

Explain common ail diesel njection system with a neat sketch.t8l

(b) A sinple jet carburretor is required to supply 4.6 kg of airper minute. The pressure and ternperature of air are 1.013bar and 25'C respectively.Assuming flow to be isentropicandcompressible nd velocitycoe{ficientas 0.8, calculate he throatdiametelof the choke for air flow velocity of 80 m/s. TakeCp 1.005 kJ/kgK, t, = 1.4. t8l

4. (a) State the needof petrol injection system.Explain MPFI systemwith a neat sketch. I8lWhat are functional requirements of a fuel injectionsystem ? Explain any four types of nozzle with merits anddemerits. tSl

List the method used for governing of IC engines. Explainthe governing,system generally used in SI engine. t6lWhat is function of radiator and thermostate ? Explain withneat sketch in cooling system. l4l

(b)

o.Unit III

( Why spark advances requiredn SI engine? Explarnanyoze spark advancemechanism. t6l

(b)

\c)

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6. \q)

SECTION IIUnit IV

(o) A 4-cylinder,4-strokepetrol enginehas a compressionatio.g observationswere recordedduringa trial:Net brake loadEffective armimepSpeedFuel consumPtionC.V. of fuelDiameter of cYlinder boreEngine .stroke

U .* = t.4 forUDCalcul4te :(i) Mechanical eltrcrency(li) Brake thermal efEciencY' (iii) Indicated thermal effrciency(iu Air standartl efficiencY(u) Relative efficiencY on BP basis'

iszaa-zt 4

OrWhat are the functions ofsurnp lubrication sYstem'Explain firing order of ICExplain evaPorative coolingadvaltages.

lubrication system ? ExPlain dryt81onoine l4l

.systemfor I.C. engines.Stateitst4l

= 2 0 k s" = 1 m

= 15x10-5N/m2= 2200r'P.m.= 12 kglht= 45000kJ/ks= 9 0 m m= 110 mmanr

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If, the compression ratio is increased to g, what will be theeffecton relative efficiency Assumeall the otherdata remainingthe same. f-i2]What is the .necessity of I.C. engine testing ? What arethe basic merasurementsj carrietl out for I.C. enginetesting ? t6l

Or8. (a) Why single clinder engines are generally not supercharged?What are the advantagesand limitations of turbo_charging? [6]

(b) During a test on a 4-strokecycleoil engind the following dataand results lvere obtained : tlzlMean height of indicator diagrarn = 21 mm,C.V. of l'uel = 44000 kJ/kC

.Indicator spring number = 22 kN/m2lmm.Cooling water circulation = 0.15 kds.Swept volume of cylinders = 14 litres, cooling water inlettemperature = BB.C.Speed of engine = 6.6 rev/s' Cooling v.ater outlet temperature = Z1.CEffective brake load = 77 kC.Specific heat capacity water = 4.18 kJ/kCKEffective brake radius = 0.2 m,Ener.gy of exhaust gases = 38.6 kJ/s.Fuel consurnption = 0.002 kg/s.

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9.

10, (ct)

(b)

11. (o)

(b)

Determineefficiency.aTo.

What are theapplications ?Write a short

(a)

(6)

Unit VDescribe with the help of a neat dia6pam the combustionphenomenon n SI engines. t8lExplain the phenomenon f Dieselknock? Comparedieselknockwith detonation in SI engines.

OrWhat is igrrition delay ? Whataffect delay period ?

t8l

List the combustion chambers usedany one with a neat sketch,

Unit VIvalious requirementsof engine for automotive

the indicated and brake outputs andDraw up an overall energ'y balance

the mechanicalin kJ/s and as

are the engine variables thatt8l

for S.I. engines. Explainl8l

t81t8l12. (a)

137621.27

(b)

note on hybrid vehicles.UT

What are the major pollutants found in the CI engineemissions ? I81State PUC norms in India for different types ofvehicles. t8l

o