SECTION -3 
COMPRESSORS, GAS TURBINES AND JET ENGINES MCQ
 
 
Q51. For delivering small quantities of air at high pressure

(a) rotary compressor are used 
(b) reciprocating air compressor are used 
(c) air engines are used 
(d) none of the above. 

Ans:(b) reciprocating air compressor are used

 

Q52. For delivering large quantities of air at low pressure

(a) rotary compressors are used 
(b) reciprocating air compressors are used 
(c) air engines are used 
(d) none of the above. 

Ans:(a) rotary compressors are used

 

Q53. The suction pressure and delivery pressure of a two-stage reciprocating compressors are 1 kgf/cm2 and 16 kgf/cm2. If the cooling is perfect, then intermediate pressure is equal to

(a) 8 kgf/cm2 
(b) 4 kgf/cm2 
(c) 2 kgf/cm2 
(d) 8.5 kgf/cm2.

Ans:(b) 4 kgf/cm2

 

Q54. In a rotary air compressor, the maximum delivery pressure is limited to

(a) 100 kgf/cm2 
(b) 50 kgf/cm2 
(c) 25 kgf/cm2 
(d) 10 kgf/cm2

Ans:(d) 10 kgf/cm2.

 

Q55. The efficiency of a rotary air compressor as compared to that of reciprocating air compressor is

(a) more 
(b) less 
(c) nearly the same 
(d) none of the above. 

Ans:(c) nearly the same

 

Q56. Choose the wrong statement

(a) The rotary compressors are used for delivering large quantity of air at low pressure. 
(b) The speed of rotary compressor is high as compared to reciprocating air compressor. 
(c) For a single stage compressor, the safe delivery pressure is 6 to 8 kgf/cm2. 
(d) A compressor at high altitude will required more power.

Ans:(d) A compressor at high altitude will required more power.

 

Q57. In case of centrifugal compressor, the work done per kg by an ideal radial vaned impeller (with no heat transfer and having slip factor equal to one) is given by

(a) CpJ (T1 – T2
(b) CpJ(T01 + T02
(c) CpJ (T01 – T02
(d) CpJ (T1– T02). 
where T1 and T2 = Static temperatures at inlet and outlet, and T01 and T02 = Stagnation temperatures at inlet and outlet.

Ans:(c) CpJ (T01 – T02)

 

Q58. For a centrifugal compressor, when the impeller has backward curved vanes, then with an increase in flow rate the Euler head H will be

(a) unaffected 
(b) decreasing 
(c) increasing 
(d) none of the above. 

Ans:(b) decreasing

 

Q59. For a centrifugal compressor, when the impeller has radial vanes, then with an increase in flow rate the Euler head H will be

(a) unaffected 
(b) decreasing 
(c) increasing 
(d) none of the above.

Ans:(a) unaffected

 

Q60. The efficiency of a roots blower is defined as

(a) the ratio of work required for ideal isentropic compressor to the work done by the roots blower on the air during the same interval of time. 
(b) the ratio of work done by the roots blower to the work required for ideal isentropic compressor per minute. 
(c) product of the ideal work required for isentropic compressor to the work done by the roots blower
(d) none of the above.

Ans:(a) the ratio of work required for ideal isentropic compressor to the work done by the roots blower on the air during the same interval of time.

 

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Compressors, Gas turbines and Jet Engines – Section-1
 
Compressors, Gas turbines and Jet Engines – Section-2
 
Compressors, Gas turbines and Jet Engines – Section-3
 

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