Compressors

51. In a compressor, free air delivered is the actual volume delivered at the stated pressure reduced to

1. N.T.P. conditions
2. intake temperature and pressure conditions
3. 0°C and 1 kg/cm2
4. 20°C and 1 kg/cm2
5. none of the above.

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52. In air breathing jet engine, the jet is formed by expading

1. gases
2. solids
3. liquid
4. plasma
5. highly heated atmospheric air.

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53. In gas turbines^ high thermal efficiency is obtained in

1. closed cycle
2. open cycle
3. both of the above
4. closed/open depending on other con-siderations
5. unpredictable.

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54. In jet engines the compression ratio

1. varies as square root of the speed
2. Varies linearly to the speed
3. varies as square of the speed
4. varies as cube of the speed
5. is constant irrespective of variation in speed.

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55. In jet engines the products of combustion after passing through the gas lurbine are discharged into

1. atmosphere
2. back to the compressor
3. discharge nozzle
4. vacuum
5. none of the above.

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56. In jet engines, for the efficient production of large power, fuel is burnt in an atmosphere of

1. vacuum
2. atmospheric air
3. compressed air
4. oxygen alone
5. liquid hydrogen.

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57. In jet engines, paraffin is usually used as the fuel because of its

1. high calorific value
2. ease of atomisation
3. low freezing point
4. (a) and (c) above
5. none of the above.

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58. In jet propulsion power unit, the inlet duct of diverging shape is used in order to

1. collect more air
2. convert kinetic energy of air into pres-sure energy
3. provide robust structure
4. beautify the shape
5. none of the above

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59. In multistage compressor, the isothermal compression is achieved by

1. employing intercooler
2. by constantly cooling the cylinder
3. by running compressor at very slow speed
4. by insulating the cylinder
5. none of the above.

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60. In the aircraft propellers

1. the propulsive matter is caused to flow around the propelled body
2. propulsive matter is ejected from within the propelled body
3. its functioning does not depend on presence of air
4. all of the above
5. none of the above.

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