Answer true or false.

For same maximum pressure and temperature, the efficiency of Diesel cycle is less than that of Dual and Otto cycles.

For minimum heat loss, the outer radius of insulation should be more than the critical radius of insulation.

In mist lubrication, 2 to lubricating oil is added to the fuel.

Fill in the blanks.

In a four-stroke engine, the exhaust valve opens before BDC to reduce the work required to exhaust gases.

Brake power Indicated power


No-load running of an engine is called

Volumetric efficiency is the ratio of to swept volume.

2. Explain the physical significance of mean effective pressure and specific fuel consumption.

3. Compression ratio of an air standard Diesel cycle is 15. Pressure and temperature at inlet to isentropic compression are 25°C and 0·1 MPa, respectively. Heat is added at constant pressure till the temperature reaches 1500°C. Calculate the

cut-off ratio

heat supplied per kg of air

cycle efficiency

network.

Assume Cv and Cp as 1.005 kJ/kg K and 0·72 kJ/kg °K and y =0.4.

4. Analyse the performance of propulsion system in terms of specific thrust, propulsive efficiency and thermal efficiency.

5. With the help of p-8 diagram, discuss the combustion process in C.I. engines. Also show the stages of combustion.

6. A two-stroke engine delivers 6000 kW while using 1500 kW to overcome frictional losses. It consumes 2400 kg of fuel per hour at an air-fuel ratio of 18: 1. The heating value of fuel is 43000 kJ/kg. Find the

indicated power

mechanical efficiency,

air consumption per hour

indicated thermal efficiency, and

brake thermal efficiency.

7. Explain in brief about the ignition system used in an aircraft's S.I. engine.

8. The walls of a room are made of brick outside, wood inside and plastic foam in the middle. The thickness of each is 0·25 2 cm and 10 cm, respectively. The inside and outside convective heat transfer coefficients are 30 and 15 and thermal conductivities of brick, foam and wood are 0·1 0·02 and 0·18 respectively. The outside and inside temperatures of the room are 25°C and respectively. Determine the rate of heat removal by refrigeration system, if total wall area is 100 m^2 and also determine the inside temperature of the brick surface.

9. Derive the expression for heat transfer by natural convection from a heated vertical flat plate.

10. With a neat sketch, discuss the construction and working of a simple carburettor.

11. Explain splash lubrication system. Also mention its merits and demerits.

12. Explain the engine performance test keeping the speed of engine constant.