Thermodynamics (Gas Power Cycles)

1. The air standard Otto cycle comprises
(a) two constant pressure processes and two constant volume processes
(b) two constant pressure and two constant entropy processes
(c) two constant volume processes and two constant entropy processes
(d) none of the above.

2. Greater the difference between jet velocity and aeroplane velocity
(a) greater the propulsive efficiency
(b) less the propulsive efficiency
(c) unaffected is the propulsive efficiency
(d) none of the above.

3. The thermal efficiency of theoretical Otto cycle
(a) increases with increase in compression ratio
(b) increases with increase in isentropic index γ
(c) does not depend upon the pressure ratio
(d) follows all the above.

4. The work output of theoretical Otto cycle
(a) increases with increase in compression ratio
(b) increases with increase in pressure ratio
(c) increases with increase in adiabatic index γ
(d) follows all the above.

5. For same compression ratio
(a) thermal efficiency of Otto cycle is greater than that of Diesel cycle
(b) thermal efficiency of Otto cycle is less than that of Diesel cycle
(c) thermal efficiency of Otto cycle is same as that for Diesel cycle
(d) thermal efficiency of Otto cycle cannot be predicted.

6. In air standard Diesel cycle, at fixed compression ratio and fixed value of adiabatic index (γ)
(a) thermal efficiency increases with increase in heat addition cut-off ratio
(b) thermal efficiency decreases with increase in heat addition cut-off ratio
(c) thermal efficiency remains same with increase in heat addition cut-off ratio
(d) none of the above.

7. Thermal efficiency of a gas turbine plant as compared to Diesel engine plant is
(a) higher
(b) lower
(c) same
(d) may be higher or lower.

8. Mechanical efficiency of a gas turbine as compared to internal combustion reciprocating engine is
(a) higher
(b) lower
(c) same
(d) un-predictable.

9. For a gas turbine the pressure ratio may be in the range
(a) 2 to 3
(b) 3 to 5
(c) 16 to 18
(d) 18 to 22.

10. For a jet propulsion unit, ideally the compressor work and turbine work are
(a) equal
(b) unequal
(c) not related to each other
(d) unpredictable.


11. The work ratio of closed cycle gas turbine plant depends upon
(a) pressure ratio of the cycle and specific heat ratio
(b) temperature ratio of the cycle and specific heat ratio
(c) pressure ratio, temperature ratio and specific heat ratio
(d) only on pressure ratio.

12. Thermal efficiency of closed cycle gas turbine plant increases by
(a) reheating
(b) intercooling
(c) regenerator
(d) all of the above.

13. With the increase in pressure ratio thermal efficiency of a simple gas turbine plant with fixed turbine inlet
temperature
(a) decreases
(b) increases
(c) first increases and then decreases
(d) first decreases and then increases.

14. The thermal efficiency of a gas turbine cycle with ideal regenerative heat exchanger is
(a) equal to work ratio
(b) is less than work ratio
(c) is more than work ratio
(d) unpredictable.

15. In a two stage gas turbine plant reheating after first stage
(a) decreases thermal efficiency
(b) increases thermal efficiency
(c) does not effect thermal efficiency
(d) none of the above.

16. In a two stage gas turbine plant, reheating after first stage
(a) increases work ratio
(b) decreases work ratio
(c) does not affect work ratio
(d) none of the above.

17. In a two stage gas turbine plant, with intercooling and reheating
(a) both work ratio and thermal efficiency improve
(b) work ratio improves but thermal efficiency decreases
(c) thermal efficiency improves but work ratio decreases
(d) both work ratio and thermal efficiency decrease.

Answers
1. (c) 2. (c) 3. (d) 4. (d) 5. (a) 6. (b) 7. (b) 8. (b) 9. (d) 10. (a) 11. (a) 12. (b) 13. (b) 14. (b) 15. (d) 16. (d) 17. (a) 18. (a)

Comments

  1. I think the 1st que ans is not 'b' , it is 'c'. Because otto cycle consist is the 2 const volume and 2 isentropic process

    ReplyDelete
  2. 1st answer wrong hai,,,,,,,,,, its answer is 'b'..

    ReplyDelete

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