Compressors, Gas Turbines and Jet Engines - Set 10

Practice Test: Question Set - 10

1. With the decrease in compression ratio, the volumetric efficiency
    (A) Does not change
    (B) Increases
    (C) Decreases
    (D) First decrease and then increase

2. Pick up wrong statement. Surging phenomenon in centrifugal compressor depends on
    (A) Mass flow rate
    (B) Pressure ratio
    (C) Change in load
    (D) Stagnation pressure at the outlet

3. In air compressors, free air delivery means the
    (A) Actual volume of the air delivered by the compressor when reduced to normal temperature and pressure conditions
    (B) Volume of air delivered by the compressor
    (C) Volume of air sucked by the compressor during its suction stroke
    (D) None of the above

4. The ratio of the increase in pressure in rotor blades to total increase in pressure in the stage is called
    (A) Pressure ratio
    (B) Pressure coefficient
    (C) Degree of reaction
    (D) Slip factor

5. A turboprop is preferred to turbojet because
    (A) It has high propulsive efficiency at high speeds
    (B) It can fly at supersonic speeds
    (C) It can fly at high elevations
    (D) It has high power for take off

6. Axial flow compressor resembles
    (A) Centrifugal pump
    (B) Reciprocating pump
    (C) Turbine
    (D) Sliding vane compressor

7. The efficiency of roots blower ________ with the increase in pressure ratio.
    (A) Decreases
    (B) Increases
    (C) Does not change
    (D) None of these

8. Axial flow compressor has the following advantage over centrifugal compressor
    (A) Larger air handling ability per unit frontal area
    (B) Higher pressure ratio per stage
    (C) Aerofoil blades are used
    (D) Higher average velocities

9. The maximum temperature in a gas turbine is
    (A) 200°C
    (B) 500°C
    (C) 700°C
    (D) 1000°C

10. Actual compression curve is
    (A) Same as isothermal
    (B) Same as adiabatic
    (C) Better than isothermal and adiabatic
    (D) In between isothermal and adiabatic

11. In a centrifugal compressor, an increase in speed at a given pressure ratio causes
    (A) Increase in flow
    (B) Decrease in flow
    (C) Increase in efficiency
    (D) Increase in flow and decrease in efficiency

12. Atmospheric pressure is 1.03 kg/cm and vapour pressure is 0.03 kg/cm. The air pressure will be
    (A) 1.03 kg/cm²
    (B) 1.06 kg/cm²
    (C) 1.00 kg/cm²
    (D) 0.53 kg/cm²

13. For maximum work, the reheating should be done to an intermediate pressure of
      (Where p₁ = Maximum pressure, and p₂ = Minimum pressure)
    (A) (p₁ - p₂)/2
    (B) (p₁ + p₂)/2
    (C) p₁/p₂
    (D) p₁ p₂

14. The pressure ratio of an ideal vaned compressor with increase in mass flow rate
    (A) Increases
    (B) Decreases
    (C) Remain constant
    (D) First decreases and then increases

15. If the flow of air through the compressor is parallel to its axis, then the compressor is
    (A) Reciprocating compressor
    (B) Centrifugal compressor
    (C) Axial flow compressor
    (D) Turbo compressor

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