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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