Roll No.

MECHANICAL ENGINEERINGB.Tech (Semester-V)

1st Sessional Examination 2015-16 IC Engines and Compressors (NME505)

Paper Id: Time: 2Hr Total Marks: 50 Note: Attempt all questions

1. Attempt ALL parts of the following: (provide solution in each case) 2x10=20a. Why is a float chamber vented to the atmosphere?b. What is carburetor depression?c. What does it mean by applying the choke in a bike?d. What is the effect of cut off ratio on air standard efficiency in a Diesel cycle.e. Draw the valve timing diagram for a 4-stroke Otto cycle.f. Draw the Otto cycle on p-T diagram.g. What are the disadvantages of a simple carburetor?h. Draw the Stirling cycle on p-v and T-s diagram.i. Give four differences between a SI and CI engines.j. Draw the pressure-crank angle (p-θ) diagram for normal and abnormal combustion.

2. Attempt any THREE parts of the following: 5x3=15a. In an Otto cycle the upper and lower temperature of T3 and T1 respectively and the temperature at

the end of compression is T2 and at the end of expansion T4. Show that for maximum work per kg of air:

T 2=T 4=√T 1T 3

b. Describe the phenomenon of detonation in SI engines. On what factors does detonation depend?

c. With the help of suitable diagram compare the Diesel and Otto cycle for:i) Same compression ratio and heat addition.ii) Same compression ratio and heat rejection.iii) Same maximum temperature and heat rejection.

.d. What are the fuel air requirements of a carburetor at different operating conditions?

e. Explain the working and construction of a simple carburetor in detail.

3. Attempt any TWO parts of the following: 7.5x2=15

a. An engine is working on Diesel cycle. The inlet pressure and temperature are 1 bar and 17 oC. The pressure at the end of compression is 35 bar and the expansion ratio is 5. Calculate heat addition, heat rejection and efficiency of cycle. Take Cp=1.004 kJ/kg.K, Cv=0.717 kJ/kg.K and γ =1.4.

b. A simple jet carburetor is required to supply 5 kg of air per minute and 0.4 kg of fuel per minute. Density of fuel is 780 kg/m3. The air is initially at 1.013 bar and 27 oC. Calculate the throat diameter of the choke for an air flow velocity of 90 m/sec. Take the velocity coefficient for the venture to be 0.80 and co-efficient of discharge of the main fuel jet to be 0.6. Assume isentropic flow and the flow to be compressible. If the pressure drop, across the fuel metering orifice is 0.75 of that of the choke, Calculate orifice diameter.

c. Discuss diesel cycle with the help of p-v and T-s diagrams. Also obtain relationship for the air standard efficiency