Compressors, Gas Turbines and Jet Engines Objective Questions with Answers - Set 19 - ObjectiveBooks

# Practice Test: Question Set - 19

1. Gas turbines for power generation are normally used
(A) To supply base load requirements
(B) To supply peak load requirements
(C) To enable start thermal power plant
(D) In emergency

2. A closed cycle gas turbine works on
(A) Carnot cycle
(B) Rankine cycle
(C) Ericsson cycle
(D) Joule cycle

3. Mechanical efficiency of gas turbines as compared to I.C engines is
(A) Higher
(B) Lower
(C) Same
(D) None of the above

4. In a single stage, single acting reciprocating air compressor, without clearance volume, the work-done is minimum during
(A) Isothermal compression
(B) Isentropic compression
(C) Polytropic compression
(D) None of these

5. The ratio of specific weight/h.p. of gas turbine and I.C engines may be typically of the order of
(A) 1: 1
(B) 2: 1
(C) 4: 1
(D) 1: 6

6. The ideal efficiency of simple gas turbine cycle depends on
(A) Pressure ratio
(B) Maximum cycle temperature
(C) Minimum cycle temperature
(D) All of the above

7. The thermal efficiency of a simple gas turbine for a given turbine inlet temperature with increase in pressure ratio
(A) Increases
(B) Decreases
(C) First increases and then decreases
(D) First decreases and then increases

8. The pressure of air at the beginning of the compression stroke is ________ the atmospheric pressure.
(A) Equal to
(B) Less than
(C) More than
(D) None of these

9. As the turbine inlet temperature increases, the thermal efficiency of gas turbine for the optimum pressure ratio
(A) Increases
(B) Decreases
(C) Remain same
(D) First increases and then decreases

10. There is a certain pressure ratio (optimum) for a gas turbine at which its thermal efficiency is maximum. With increase in turbine temperature, the value of pressure ratio for the peak efficiency would
(A) Remain same
(B) Decrease
(C) Increase
(D) None of the above

11. A closed cycle gas turbine gives ________ efficiency as compared to an open cycle gas turbine.
(A) Same
(B) Lower
(C) Higher
(D) None of these

12. If infinite number of heaters be used in a gas turbine, then expansion process in turbine approaches
(A) Isothermal
(B) Isentropic
(D) Isochoric

13. Pick up the correct statement
(A) Gas turbine uses low air-fuel ratio to economise on fuel
(B) Gas turbine uses high air-fuel ratio to reduce outgoing temperature
(C) Gas turbine uses low air-fuel ratio to develop the high thrust required
(D) All of the above

14. Inter-cooling in gas turbine results in
(A) Increase in net output but decrease in thermal efficiency
(B) Increase in thermal efficiency but decrease in net output
(C) Increase in both thermal efficiency and net output
(D) Decrease in both thermal efficiency and net output

15. If V, U and Vr represent the absolute velocity of fluid, velocity of blade, and relative velocity of fluid, and suffix ‘I’ and ‘o’ stand for entry and exit conditions, then in a rotary machine whose degree of reaction is unity
(A) Vi = Vo
(B) Vt  >  Vo
(C) U < Vo
(D) V = Uo

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