Practice Test: Question Set - 08
1. Rotary compressors are used for delivering
- (A) Small
quantities of air at high pressures
- (B) Large
quantities of air at high pressures
- (C) Small
quantities of air at low pressures
- (D) Large
quantities of air at low pressures
2. More than one stage will be preferred for reciprocating compressor if the delivery pressure is more than
- (A) 2 kg/cm²
- (B) 6 kg/cm²
- (C) 10 kg/cm²
- (D) 14.7 kg/cm²
3. Only rocket engines can be propelled to space because
- (A) They
can generate very high thrust
- (B) They
have high propulsion efficiency
- (C) These
engines can work on several fuels
- (D) They
are not air breathing engines
4. The advantage of multistage compression over single stage compression is
- (A) Lower power
consumption per unit of air delivered
- (B) Higher volumetric
efficiency
- (C) Decreased discharge
temperature
- (D) All of the above
5. Reheating in a gas turbine
- (A) Increases
the thermal efficiency
- (B) Increases
the compressor work
- (C) Increases
the turbine work
- (D) Decreases
the thermal efficiency
6. Pick up the wrong statement about advantages of multistage compression
- (A) Better lubrication is
possible advantages of multistage
- (B) More loss of air due
to leakage past the cylinder
- (C) Mechanical balance is better
- (D) Air can be cooled
perfectly in between
7. For perfect intercooling in a three stage compressor
- (A) p₂/p₁ =
p₃/p₂ = p₄/p₃
- (B) p₃/p₁ =
p₄/p₂
- (C) p₁ p₂
= p₃ p₄
- (D) p₁ p₃
= p₂ p₄
8. The ratio of outlet whirl velocity to blade velocity in case of centrifugal compressor is called
- (A) Slip factor
- (B) Velocity factor
- (C) Velocity coefficient
- (D) None of the above
9. When the temperature of air leaving the inter-cooler, in a two stage compression with inter-cooler, is ________ the original atmospheric air temperature, then the intercooling is known as perfect or complete intercooling.
- (A) Equal to
- (B) Less than
- (C) More
than
- (D) None
of these
10. Losses in a centrifugal compressor are due to
- (A) Inlet losses
- (B) Impeller channel
losses
- (C) Diffuser losses
- (D) All of the above
11. The axial flow compressor is preferred in aircraft gas turbines because of
- (A) Low
frontal area
- (B) Higher
thrust
- (C) High
pressure rise
- (D) None of
these
12. The volumetric efficiency of a compressor falls roughly as follows for every 5°C increase in atmospheric temperature
- (A) 0.1%
- (B) 0.5%
- (C) 1%
- (D) 5%
13. If p₁, is the pressure of air entering the L.P. cylinder and p₂ is the pressure of air leaving the L.P. cylinder (or inter-cooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D₁ = Dia. of L.P. cylinder, and D₂ = Dia. of H.P. cylinder)
- (A) D₁/D₂
= p₁ p₂
- (B) D₁/D₂
= p₁/p₂
- (C) D₁/D₂
= p₂/p₁
- (D) None of
these
14. The indicated work per unit mass of air delivered is
- (A) Directly proportional to clearance volume
- (B) Greatly affected by clearance volume
- (C) Not affected by clearance volume
- (D) Inversely proportional to clearance volume
15. Which of the following statement is correct?
- (A) The
ratio of the discharge pressure to the inlet pressure of air is called
compressor efficiency
- (B) The
compression ratio for the compressor is always greater than unity
- (C) The
compressor capacity is the ratio of work-done per cycle to the stroke volume
- (D) During
isothermal compression of air, the work-done in a compressor is maximum
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