B.E (Fifth Semester) Examination,
Apr.-May., 2008
(Mechanical Branch)
INTERNAL COMBUSTION ENGINES-I
Time allowed : THREE Hours
Maximum Marks : 80
Minimum Pass Marks : 28
Note :- Attempt all five questions as per choice provided in each question. All
questions carry equal marks. Explain your answer by means of neat sketches. Answer all parts of one place as far as possible.
1. (a) Define I.C. Engine. 2
Attempt any two of the following :
(b) Explain the working of two stroke petrol engine.Discuss its merits & demetris. 7
(c) Draw a typical valve timing diagram of a four stroke C.I. engine & give the resons for opening the valves after dead centres.
(d) What is meant by burning time loss ? Explain with the help of P-V diagram.
2. (a) Define stiochiometric (chemically correct) air fuel ratio .
Attempt any two parts of the following :
(b) What are the requirements of petrol engine fuel and disel engine fuel ?
(c) Explain the stages of combustion in C.I. engine with the help of pressure crank angle (p - 0(thita)) diagram.
(d) What is Octane number & how is it found ? What is the difference between preignition and knocking ?
3. Attempt any one part of the following :
(a) (i) What are the mixture requirement for idiling and normal power range ? Describe with suitable sketches idiling system and main metering system.
(ii) Describe acceleration pump system and choke of a modern carburettor.
(b) The venturi of a simple carborettor has a throat diameter of 20mm and the coefficient of air flow is 0.85. The fuel orifice has a diameter of 1.25 mm and the coefficient of fuel is 0.66. The petrol surface is 5 mm below the throat. Find :
(i) the air fuel for a pressure drop of 0.07 bar when the nozzle lip is neglected ;
(ii) the air fuel ratio when the nozzle lip is taken into account.
(iii) the minimum velocity of air or critical air velocity required to start the fuel flow when nozzle lip is provided.
4. Write notes on any three of the followings :
(a) Battery ignition system
(b) Wet sump lubrication system
(c) various methods od governing of I.C. engines
(d) Necessity of engine cooling
(e) Fuel injector & its construction
(f) Liquid cooling of automobile engines
5. Solve any two parts of the followings:
(a) Draw the following performance curves of C.I. engine and comment on the nature of curve :
(i) Brake power Vs. Engine speed
(ii) Specific fuel consumption vs. Engine speed
(b) Describe "Morse Test". What is the assumption made in this test ?
(c) A four stroke, four cylinder gasoline engine has a bore of 60 mm and a stroke of 100mm. On test it develops a torque of 66.5 Nm when running at 3000 rpm. If the clearance volume in each cylinder is 60 cc and the relative efficiency with respect to brake thermal efficiency is 50%, calculate the brake power and brake thermal efficiency.
