Compressors

101. Standard air is the air at

1. atmospheric conditions at any specific location
2. 20°C and 1 kg/cm2 and relative humidity 36%
3. 0°C and standard atmospheric conditions
4. 15°C and 1 kg/cm2
5. 25°C, 1 kg/cm2 and RH of 60%.

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102. Surging is the phenomenon of

1. air stream blocking the passage
2. motion of air at sonic velocity
3. unsteady, periodic and reversed flow
4. air stream not able to follow the blade contour
5. production of no air pressure.

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103. Temperature of gases at end of compression as compared to exhaust gases in a gas turbine is

1. higher
2. lower
3. equal
4. can’t be compared
5. unpredictable.

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104. tercooling in gas turbine results in

1. increase in net output but decrease in thermal efficiency
2. increase in thermal efficiency but decrease in net output
3. increase in both thermal efficiency and net output
4. decrease in both thermal efficiency and net output
5. none of the above.

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105. The advantage of multistage compression over single stage compression is

1. lower power consumption per unit of air delivered
2. higher volumetric efficiency
3. decreased discharge temperature
4. moisture free air
5. all of the above.

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106. The air entry velocity m a rocket as compared to aircraft is

1. same
2. more
3. less
4. zero
5. dependent on power and speed.

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107. The air-fuel ratio in gas turbines is of the order of

1. 07:01
2. 15:01
3. 30:01:00
4. 40:01:00
5. 50:01:00

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108. The area of actual indicator diagram on an air compressor as compared to area of ideal indicator diagram is

1. less
2. more
3. same
4. more/less depending on compressor capacity
5. unpredictable.

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109. The blades of gas turbine are made of

1. mild steel
2. stainless steel
3. carbon steel
4. high alloy seel
5. high nicket alloy (neimonic).

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110. The capacity of a compressor is 5 m /mih. 5 m /min refers to

1. standard air
2. free air
3. compressed air
4. compressed air at delivery pressure
5. air sucked.

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