APPLIED THERMODYNAMICS 2 PAPER 3

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APPLIED THERMODYNAMICS II ME 208 4th Sem May 2k5
Max Marks 60

Note: Section A is compulsory. Attempt any Four questions from Section B and two from Section C.

Section A Marks 2 each

1.
(a) Enlist the variables which effect the knock in S.I. engine.
(b) What is “SUPERCHARGING”?
(c) What is ‘PREIGNITION”?
(d) What do you understand by ‘PREWHIRL” in dynamic compressors?
(e) Explain the term “SURGING” in centrifugal and axial flow compressor.
(f) Give principle of working of centrifugal compressor.
(g) What is “Diffuser Efficiency”?
(h) On a Temperature- entropy diagram show open cycle gas turbine cycle tieh “INTERCOOLING, REHEATING and REGENERATION”
(i) State merits of closed cycle gas turbine.
(j) Define “PROPULSIVE POWER”.

Section B Marks 5 each

2. Describe in detail KNOCK RATING of S.I. fuel.

3. With a neat sketch explain the construction and working of LYSHOLM compressor.

4. A centrifugal air compressor delivers 20.5 kg/s of air with a total head pressure ratio of 4 to 1. The speed of compressor is 20,000 rpm. Inlet total head temperature is 15 oC, slip factor 0.85, power input factor 1.05 and 65% isentropic efficiency. Calculate the power input and overall diameter.

5. What is “Degree of Reaction”? Establish the relation for degree of reaction for axial flow compressor.

6. With a neat sketch explain the working of turbo-prop engine.

Section C Marks 10 each

7. (a) Give industrial applications of compressed air.
(b) A single stage, single sides centrifugal compressor delivers 18 kg/s of air with a pressure ratio 4 when running at 15,000 rpm. The inlet conditions are 1 bar and 20 oC. The slip factor is 0.9. The power input factor is 1.04 and the isentropic efficiency of compressor is 75% . Calculate:
(i) The final temperature of air
(ii) power required
(iii) the tip diameter of impeller
(iv) the blade angles at impeller eye which has root and tip diameter 15 cm and 20 cm. 2,8

8. A multistage axial compressor is required for compressing air at 293 K through a pressure ratio of 5 to 1.Each stage is to be 50% reaction and the mean blade sped is 275 m/s, flow coefficient 0,5 and stage loading factor 0.3 are taken for simplicity as constant for all stages. Determine the flow angles and number of stages required if the stage efficiency is 88.8 %. Assume Cp=1.005 kJ/kg K and ?=1.4 for air.

9. A gas turbine is designed to operate under the following conditions: Max Temp. : 650 oC, Pressure ratio = 5, inlet pressure and temp. = 1.05 bar and 15 oC, turbine isentropic efficiency = 86%, compressor isentropic efficiency = 82%, mechanical efficiency of compressor and turbine = 99%, efficiency of combustion = 98%.

Determine the improvement inplant thermal efficiency that would result from addition of heat exchanger of 65% effectiveness. Allow a pressure loss of 0.905 bar in the heat exchanger.

For air Cp=1.005 kJ/kg K, for gas Cp= 1.13 kJ/kg K. Assume that in the heat exchanger the mean specific heat of exhaust products and air is same.