## Monday, February 18, 2019

### 228 TOP Compressors, Gas Turbines and Jet Engines (Objective Questions With Answers)

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1. Free air is the air at
(a) atmospheric conditions at any specific location
(b) 20°C and 1 kg/cm2 and relative humidity of 36%
(c) 0°C and standard atmospheric conditions
(d) 15°C and 1 kg/cm2
(e) 25°C, 1 kg/cm2 and relative humidity of 50%.
Ans: a

2. Standard air is the air at
(a) atmospheric conditions at any specific location
(b) 20°C and 1 kg/cm2 and relative humidity 36%
(c) 0°C and standard atmospheric conditions
(d) 15°C and 1 kg/cm2
(e) 25°C, 1 kg/cm2 and RH of 60%.
Ans: b

3. 1 m of air at atmospheric condition weighs approximately
(a) 0.5 kg
(b) 1.0 kg
(c) 1.3 kg
(d) 2.2 kg
(e) 3.2 kg.
Ans: c

4. Adiabatic compression is one in which
(a) temperature during compression remains constant
(b) no heat leaves or enters the compressor cylinder during cornpression
(c) temperature rise follows a linear relationship
(d) work done is maximum
(e) entropy decreases.
Ans: b

5. The capacity of a compressor is 5 m /mih. 5 m /min refers to
(a) standard air
(b) free air
(c) compressed air
(d) compressed air at delivery pressure
(e) air sucked.
Ans: b

6. The overall isothermal eiffciency of compressor is defined as the ratio of
(a) isothermal h.p. to the BHP of motor
(b) isothermal h.p. to adiabatic h.p.
(c) power to drive compressor to isothermal h.p.
(d) work to compress air isothermally to work for actual compression
(e) isothermal work to ideal work.
Ans: a

7. The- most efficient method of compressing air is to compress it
(a) isothermally
(c) isentropically
(d) isochronically
(e) as per law pV
Ans: a

8. Maximum work is done in compressing air when the compression is
(a) isothermal
(c) polytropic
(d) any one of the above
(e) none of the above.
Ans: b

9. The pressure and temperature conditions of air at the suction of compressor are
(a) atmospheric
(b) slightly more than atmospheric
(c) slightly less than atmospheric
(d) pressure slightly more than atmospheric and temperature slightly less than atmospheric
(e) pressure sightly less than atmospheric and temperature slightly more than atmospheric.
Ans: e

10. Isothermal compression effeicency can be attained by running the compressor
(a) at very high speed
(b) at very slow speed
(c) at average speed
(d) at zero speed
(e) isothermally.
Ans: b