Compressors, Gas Dynamics and Gas Turbines problems
- 1. When the temperature of air leaving the intercooler, in a two stage compression with intercooler, is __________ the original atmospheric air temperature, then the intercooling is known as perfect or complete intercooling.
Options- A. equal to
- B. less than
- C. more than Discuss
Correct Answer: equal to
- 2. The increase in pressure in a vane blower takes place first due to compression and then due to back flow of air.
Options- A. Correct
- B. Incorrect Discuss
Correct Answer: Correct
- 3. Intercooling in multi-stage compressors is done
Options- A. to cool the air during compression
- B. to cool the air at delivery
- C. to enable compression in two stages
- D. to minimise the work of compression Discuss
Correct Answer: to minimise the work of compression
- 4. The stagnation pressure rise in a centrifugal compressor takes place
Options- A. in the diffuser only
- B. in the impeller only
- C. in the diffuser and impeller
- D. in the inlet guide vanes only Discuss
Correct Answer: in the diffuser and impeller
- 5. The type of rotary compressor used in aeroplanes, is of
Options- A. centrifugal type
- B. axial flow type
- C. radial flow type
- D. none of these Discuss
Correct Answer: axial flow type
- 6. In a centrifugal compressor, an increase in speed at a given pressure ratio causes
Options- A. increase in flow
- B. decrease in flow
- C. increase in efficiency
- D. increase in flow and decrease in efficiency Discuss
Correct Answer: increase in flow and decrease in efficiency
- 7. The total heat rejected in a reciprocating air compressor is equal to the sum of the heat rejected during polytropic compression per kg of air and heat rejected in the intercooler per kg of air.
Options- A. True
- B. False Discuss
Correct Answer: True
- 8. High air-fuel ratio in gas turbines
Options- A. increases power output
- B. improves thermal efficiency
- C. reduces exhaust temperature
- D. do not damage turbine blades Discuss
Correct Answer: reduces exhaust temperature
- 9. If p1, is the pressure of air entering the L.P. cylinder and p2 is the pressure of air leaving the L.P. cylinder (or intercooler pressure), then the ratio of cylinder diameters for a single acting, two stage reciprocating air compressor with complete intercooling is given by (where D1 = Dia. of L.P. cylinder, and D2 = Dia. of H.P. cylinder)
Options- A. D1/D2 = p1p2
- B. D1/D2 = p1/p2
- C. D1/D2 = p2/p1
- D. none of these Discuss
Correct Answer: D1/D2 = p2/p1
- 10. In a four stage compressor, if the pressure at the first and third stage are 1 bar and 16 bar, then the delivery pressure at the fourth stage will be
Options- A. 1 bar
- B. 16 bar
- C. 64 bar
- D. 256 bar Discuss
Correct Answer: 64 bar
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