Compressors, Gas Dynamics and Gas Turbines problems
- 1. The pressure of air at the beginning of the compression stroke is __________ the atmospheric pressure.
Options- A. equal to
- B. less than
- C. more than Discuss
Correct Answer: less than
- 2. 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.
Options- A. reduced
- B. increased Discuss
Correct Answer: reduced
- 3. The axial flow compressor is preferred in air-craft gas turbines because of
Options- A. low frontal area
- B. higher thrust
- C. high pressure rise
- D. none of these Discuss
Correct Answer: low frontal area
- 4. Which of the following statement is correct as regard to centrifugal compressors?
Options- 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 multi-stage axial flow compressors. Discuss
Correct Answer: The static pressure of air in the impeller increases in order to provide centripetal force on the air.
- 5. The mass of gas turbine per kW developed is about __________ as that of an I.C. engine.
Options- A. same
- B. one-half
- C. one-fourth
- D. one-sixth Discuss
Correct Answer: one-sixth
- 6. In a turbo jet engine, subsequent to heat addition to compressed air, to get the power output, the working substance is expanded in
Options- 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 Discuss
Correct Answer: turbine blades, which is essentially an isentropic process
- 7. The performance of air compressor at high altitudes will be __________ as compared to that at sea level.
Options- A. same
- B. lower
- C. higher Discuss
Correct Answer: lower
- 8. The intercooler pressure, for minimum work required, for a two stage reciprocating air compressor, is given by (where p1 = Intake pressure of air, p2 = Intercooler pressure, and p3 = Delivery pressure of air)
Options- A. p2 = p1 x p3
- B. p2 = p1/p3
- C. p2 = p1 x p3
- D. p2 = p3/p1 Discuss
Correct Answer: p2 = p1 x p3
- 9. In a centrifugal compressor, the air enters the impeller axially and leaves the vane radially.
Options- A. Yes
- B. No Discuss
Correct Answer: No
- 10. Reheating in a gas turbine
Options- A. increases the thermal efficiency
- B. increases the compressor work
- C. increases the turbine work
- D. decreases the thermal efficiency Discuss
Correct Answer: increases the thermal efficiency
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