Compressors

171. Volumetric efficiency of a compressor with clearance volume

1. increases with increase in compression ratio
2. decreases with increase in compression ratio
3. in not dependent upon compression ratio
4. may increase/decrease depending on compressor capacity
5. unpredictable.

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172. Volumetric efficiency of a compressor without clearance volume

1. increases with increase in compression ratio
2. decreases with increase in compression ratio
3. is not dependent upon compressin ratio
4. may increase/decrease depending on compressor capacity
5. unpredictable.

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173. Volumetric efficiency of air compressors is of the order of

1. 20-30%
2. 40-50%
3. 60-70%
4. 70-90%
5. 90-100%.

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174. Water gas is produced by

1. carbonisation of coal
2. passing steam over incandescent coke
3. passing air and a large amount of steam over waste coal at about 65°C
4. partial combustion of caol, eke, anthractie coal or charcoal in a mixed air steam blast
5. same way as the natural gas.

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175. Water is injected in gas turbine cycle to

1. control temperature
2. control output of turbine
3. control fire hazards
4. increase efficiency
5. it is never done.

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176. What will be the volume of air at 327°C if its volume at 27°C is 1.5 m3/mt

1. 3 m3/mt .
2. 1.5 m3/mt
3. 18 m3/mt’
4. 6 m3/mt
5. 0.75 m3/mt.

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177. Which is false statement about advantages of multistage compressor in comparison to single stage compressor

1. less power requirement
2. better mechanical balance
3. less loss of air due to leakage past the cylinder
4. more effective lubrication
5. lower volumetric efficiency.

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178. Which is false statement about air receivers

1. These are used to dampen pulsations ,
2. These act as reservoir to- take care of sudden demands
3. These increase compressor efficiency
4. These knock out some oil and moisture
5. These reduce frequent on/off operation of compressors.

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179. Which is false statement about multistage compression .

1. Power consumption per unit of air delivered is low
2. Volumetric efficiency is high
3. It is best suited for compression ratios around 7:1
4. The moisture in air is condensed in the intercooler
5. Outlet temperature is reduced.

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180. Which of the following fuels can be used in turbojet engines

1. liquid hydrogne
2. high speed diesel oil
3. kerosene
4. demethylated spirit
5. methyl alcohol

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