Compressors, Gas Turbines and Jet Engines Objective Questions with Answers - Set 18

Practice Test: Question Set - 18


1. Which is false statement about advantages of multistage compressor in comparison to single stage compressor?
    (A) Less power requirement
    (B) Better mechanical balance
    (C) Less loss of air due to leakage past the cylinder
    (D) Lower volumetric efficiency

2. In a jet propulsion
    (A) The propulsive matter is ejected from within the propelled body
    (B) The propulsive matter is caused to flow around the propelled body
    (C) Its functioning does not depend upon presence of air
    (D) None of the above

3. The ratio of isentropic work to Euler work is known as
    (A) Pressure coefficient
    (B) Work coefficient
    (C) Polytropic reaction
    (D) Slip factor

4. 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

5. The criterion of the thermodynamic efficiency for rotary compressor is
    (A) Isentropic compression
    (B) Isothermal compression
    (C) Polytropic compression
    (D) None of the above

6. The maximum compression ratio in an actual single stage axial flow compressor is of the order of
    (A) 1 : 1.2
    (B) 1 : 2
    (C) 1 : 5
    (D) 1 : 10

7. Volumetric efficiency of a compressor decreases with ________ in compression ratio.
    (A) Decrease
    (B) Increase
    (C) Remain same
    (D) Does not change

8. Maximum delivery pressure is a rotary air compressor is of the order of
    (A) 6 kg/cm²
    (B) 10 kg/cm²
    (C) 16 kg/cm²
    (D) 25 kg/cm²

9. The efficiency of the vane blower is (where W₁ = Workdone due to compression, and W₂ = Workdone due to back flow)
    (A) W₁/(W₁ + W₂)
    (B) W₂/(W₁ + W₂)
    (C) (W₁ + W₂)/W₁
    (D) (W₁ + W₂)/W₂

10. Surging is the phenomenon of
    (A) Air stream blocking the passage
    (B) Motion of air at sonic velocity
    (C) Unsteady, periodic and reversed flow
    (D) Air stream not able to follow the blade contour

11. Rotary compressors are suitable for
    (A) Large discharge at high pressure
    (B) Low discharge at high pressure
    (C) Large discharge at low pressure
    (D) Low discharge at low pressure

12. For perfect intercooling in a two stage compressor
    (A) p₂/p₁ = p₃/p₂
    (B) p₁/p₃ = p₂/p₁
    (C) p₁ = p3
    (D) p₁ = p₂ p3

13. The volumetric efficiency of compressor with increase in compression ratio will
    (A) Increase
    (B) Decrease
    (C) Remain same
    (D) May increase or decrease depending on clearance volume

14. The propulsive power of the rocket is (where v₁ = Jet velocity, and v₂ = Aircraft velocity)
    (A) (v₁² -v₂²)/2g
    (B) (v₁ - v₂)²/2g
    (C) (v₁² -v₂²)/g
    (D) (v₁ - v₂)²/g

15. Stalling of blades in axial flow compressor is the phenomenon of
    (A) Air stream blocking the passage
    (B) Motion of air at sonic velocity
    (C) Unsteady periodic and reversed flow
    (D) Air stream not able to follow the blade contour

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