# Compressors, Gas Turbines and Jet Engines MCQ Practice Test – Set 10 :: Mechanical Engineering

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(A) 7: 1
(B) 15: 1
(C) 30: 1
(D) 50: 1.

## Q2. It is not possible to use closed gas turbine cycle in aeronautical engines because

(A) It is inefficient
(B) It is bulky
(C) It requires cooling water for its operation
(D) None of the above

Answer: (C) It requires cooling water for its operation

## Q3. Choose the correct statement

(A) Gas turbine requires lot of cooling water
(C) Gas turbines has flat efficiency at part loads
(D) Gas turbines have high standby losses and require lot of maintenance

(A) 3.5 : 1
(B) 5 : 1
(C) 8 : 1
(D) 12 : 1

## Q5. An air compressor may be controlled by

(A) Throttle control
(B) Clearance control
(C) Blow off control
(D) Any one of the above

Answer: (D) Any one of the above

## Q6. The stagnation pressure rise in a centrifugal compressor takes place

(A) In the diffuser only
(B) In the impeller only
(C) In the diffuser and impeller
(D) In the inlet guide vanes only

Answer:(C) In the diffuser and impeller

## Q7. If the clearance ratio for a reciprocating air compressor is ‘K’, then its volumetric efficiency is given by

(A) 1 – k + k (p₁/p₂)1/n
(B) 1 + k – k (p₂/p₁)1/n
(C) 1 – k + k (p₁/p₂) n- 1/n
(D) 1 + k – k (p₂/p₁) n-1/n

Answer: (B) 1 + k – k (p₂/p₁)1/n

## Q8. 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

(A) 10: 1
(B) 15: 1
(C) 20: 1
(D) 60: 1

## Q10. Euler’s equation can be used for

(B) Axial flow compressors
(C) Pumps
(D) All of these

## Q11. Inter-cooling in multistage compressors is done

(A) To cool the air during compression
(B) To cool the air at delivery
(C) To enable compression in two stages
(D) To minimize the work of compression

Answer: (D) To minimize the work of compression

(A) 75%
(B) 85%
(C) 90%
(D) 99%

## Q13. In the cross compounding of the gas turbine plant

(A) H.P. compressor is connected to H.P. turbine and L.P. compressor to L.P. turbine
(B) H.P. compressor is connected to L.P. turbine and L.P. compressor is connected to H.P. turbine
(C) Both the arrangements can be employed
(D) All are connected in series

Answer: (B) H.P. compressor is connected to L.P. turbine and L.P. compressor is connected to H.P. turbine

## Q14. Reheating in multistage expansion gas turbine results in

(A) High thermal efficiency
(B) Reduction in compressor work
(C) Decrease of heat loss in exhaust
(D) Maximum work output

(A) Equal to
(B) Double
(C) Three times
(D) Six times

(A) 3 m³/ mt.
(B) 1.5 m³/ mt.
(C) 18 m³/ mt.
(D) 6 m³/ mt.

## Q12. The criterion of the thermodynamic efficiency for rotary compressor is

(A) Isentropic compression
(B) Isothermal compression
(C) Polytropic compression
(D) None of the above

(A) 1: 1
(B) 2: 1
(C) 4: 1
(D) 1: 6

## Q13. In which case the air-fuel ratio is likely to be maximum?

(A) Gas turbine
(B) 4-stroke petrol engine
(C) 4-stroke diesel engine
(D) Multi cylinder engine

## Q14. Gas turbine works on

(A) Brayton or Atkinson cycle
(B) Carnot cycle
(C) Rankine cycle
(D) Ericsson cycle

Answer: (A) Brayton or Atkinson cycle

(A) 2: 1
(B) 4:1
(C) 61: 1
(D) 9: 1

## Q16. For an irreversible gas turbine cycle, the efficiency and work ratio both depend on

(A) Pressure ratio alone
(B) Maximum cycle temperature alone
(C) Minimum cycle temperature alone
(D) Both pressure ratio and maximum cycle temperature

Answer: (D) Both pressure ratio and maximum cycle temperature

## Q17. A jet engine works on the principle of conservation of

(A) Mass
(B) Energy
(C) Flow
(D) Linear momentum

## Q18. The main purpose of reheating in gas turbine is to

(A) Increase temperature
(B) Reduce turbine size
(C) Increase power output
(D) Increase speed

## Q19. The air power of the compressor is also known as

(A) Indicated power
(B) Brake power
(C) Frictional power
(D) None of these