Compressors, Gas Turbines and Jet Engines - Set 05

Practice Test: Question Set - 05

1. In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in
    (A) Exit nozzle, which is a constant volume process
    (B) Exit nozzle, which is essentially an isentropic process
    (C) Turbine blades, which is a constant volume process
    (D) Turbine blades, which is essentially an isentropic process

2. 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

3. The overall efficiency of the compressed air system is the
    (A) Ratio of shaft output of the air motor to the shaft input to the compressor
    (B) Ratio of shaft input to the compressor to the shaft output of air motor
    (C) Product of shaft output of air motor and shaft input to the compressor
    (D) None of the above

4. Adiabatic compression is one in which
    (A) Temperature during compression remains constant
    (B) No heat leaves or enters the compressor cylinder during compression
    (C) Temperature rise follows a linear relationship
    (D) Work done is maximum

5. A machine used to raise the pressure of air is called
    (A) Gas turbine
    (B) I.C engine
    (C) Compressor
    (D) Air motor

6. The capacity of a compressor is 5 m/min refers to
    (A) Standard air
    (B) Free air
    (C) Compressed air
    (D) Compressed air at delivery pressure

7. The process, which causes the air to enter the impeller blades of a centrifugal compressor at ________ velocity (without effecting the mass of air to flow and velocity of flow) is known as prewhirl.
    (A) Reduced
    (B) Increased
    (C) Zero
    (D) None of these

8. The overall isothermal efficiency 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

9. In a centrifugal compressor, the ratio of the ________ to the blade velocity is called slip factor.
    (A) Inlet whirl velocity
    (B) Outlet whirl velocity
    (C) Inlet velocity of flow
    (D) Outlet velocity of flow

10. The most efficient method of compressing air is to compress it
    (A) Isothermally
    (B) Adiabatically
    (C) Isentropically
    (D) Isochronically

11. The performance of air compressor at high altitudes will be ________ as compared to that at sea level.
    (A) Same
    (B) Lower
    (C) Higher
    (D) None of these

12. 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 less than atmospheric and temperature slightly more than atmospheric

13. Which of the following statement is correct as regard to centrifugal compressors?
    (A) The flow of air is parallel to the axis of the compressor
    (B) The static pressure of air in the impeller increases in order to provide centripetal force on the air
    (C) The impeller rotates at high speeds
    (D) The maximum efficiency is higher than multistage axial flow compressors

14. Isothermal compression efficiency 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

15. Gas turbine as compared to internal combustion engine
    (A) Can be driven at a very high speed
    (B) Produces uniform torque
    (C) Has more efficiency
    (D) All of these

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