Jadavpur University 2006 B.E Mechanical Engineering IC Engine and Turbine - Question Paper

Ref. No Ex/ML 32A/69/2006
B.M.E. PART-I EXAMINATION, 2006
(2nd Semester)
Internal Combustion Engines and Gas Turbines
Time: 3 hours Full Marks 100
ans any 5 ques.
All parts of the identical ques. must be answered together
Data, consistent with the issue may be presumed if necessary
Q:1(a) discuss the air-fuel ratio requirement for a spark-ignition engine at
idling and power regimes. (10)
(b) A simple jet carburetor is needed to supply 4.5 kg of air and 0.5 kg
of fuel per minute. The fuel specific gravity is 0.8. The air is
initially at one bar and 300 K. compute the throat diameter of the
choke for a flow velocity of 110m/s. The coefficient of discharge
for venturi is 0.8. If the pressure drop across the fuel metering
orifice is 0.85 of that of the choke, compute the orifice diameter
assuming coefficient of discharge for fuel orifice to be 0.6 and ?
= 1.4. 10
Q:2(a) elaborate the functional requirements of a fuel injection system in a
C.I. engine? 5
(b) Distinguish ranging from air injection and solid injection systems. 4
(c) compute the diameter of a fuel orifice of a four-stroke engine,
which develops 25 kW per cylinder at 2500 rpm. The specific fuel
consumption is 0.3kg/kW-hr and fuel specific gravity is 0.8762.
The fuel is injected at a pressure of 150 bar over a crank travel of
25°. The pressure in the combustion chamber is 40 bar. Coefficient
of discharge is 0.875. 12
Q:3(a) Draw a tagged sketch of a battery ignition system. define the 8+4
function of the capacitor in the circuit.
(b) discuss why a definite firing order is necessary for a multicylinder
S.I. engine. 5
(c) State the disadvantage of a magneto ignition system. 3
Q:4(a) discuss the working principle of a two-stroke engine. 10
Compare 2 stroke and 4 stroke engines. 5
(b) discuss why inlet and exhaust valves close after dead centers
respectively. 5
Ref. No Ex/ML 32A/69/2006
Q:5(a) What is flame speed? How does turbulence and equivalence ratio of
fuel-air mixture affect the flame speed? 8
(b) explain the measures adopted in the design of S.I. engine
combustion chambers to decrease the possibility of knocking. 7
(c) Draw p-? diagrams, showing normal and abnormal combustion of
an S.I. engine. 5
Q:6(a) Draw a p-? diagram, showing the various stages of normal
combustion of a C.I. engine. 4
(b) discuss the occurrence of rapid combustion and controlled
combustion in a C.I. engine. 6
(c) How is knocking in S.I. engines various from that in C.I. engines? 10
Q:7(a) discuss Morse test method of determination of frictional power of a
multicylinder engine. 8
(b) How do you determine the frictional power of a single cylinder 5
engine?
(c) A four-cylinder four-stroke engine has a bore of 100 mm and a
stroke of 120 mm. The speed of the engine is 1600 rpm. The fuel
consumption is 0.2 kg/min and calorific value of the fuel is 44000
kJ/kg. The dynamometer arm is 300 cm and the dynamometer scale
studying is 40 kgf. If the mechanical efficiency is 80%, compute (i)
brake thermal efficiency (ii) indicated thermal efficiency (iii)
indicated mean effective pressure (iv) brake specific fuel
consumption. 7
Q:8 Write short notes on
(a) Disadvantages of carburetion over fuel injection system.
(b) Common rail systems in a C.I. engine.
(c) Magneto ignition system 8+6+6

Earning:   Approval pending.