Power Plant Engineering

61. The amount of air which is supplied for complete combustion is called

1. primary air
2. secondary air
3. tertiary air
4. all above

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62. The artificial draught normally is designed to produce

1. less smoke
2. more draught
3. less chimney gas temperature
4. all of the above

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63. The average ash content in Indian co als is about

1. 5%
2. 10%
3. 15%
4. 20%

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64. The capacity of large turbo-generators varies from

1. 20 to 100 MW
2. 50 to 300 MW
3. 70 to 400 MW
4. 100 to 650 MW

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65. The commercial sources of energy are

1. solar, wind and biomass
2. fossil fuels, hydropower and nuclear energy
3. wood, animal wastes and agriculture wastes
4. none of the above

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66. The cooling section in the surface condenser

1. increases the quantity of vapour extracted along with air
2. reduces the quantity of vapour extracted along with air
3. does not affect vapour quantity extracted but reduces pump capacity of air extraction pump
4. none of the above

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67. The critical pressure ratio of a convergent nozzle is defined as

1. the ratio of outlet pressure to inlet pressure of nozzle
2. the ratio of inlet pressure to outlet pressure of nozzle
3. the ratio of outlet pressure to inlet pressure only when mass flow rate per unit area is minimum
4. the ratio of outlet pressure to inlet pressure only when mass flow rate = c

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68. The draught in locomotive boilers is produced by

1. forced fan
2. chimney
3. steam jet
4. only motion of locomotive

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69. The draught produced by chimney of given height at given outside temperature

1. decreases if the chimney gas temperature increases
2. increases if the chimney gas temperature increases
3. remains same irrespective of chimney gas temperature
4. may increase or decrease

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70. The draught produced by steel chimney as compared to that produced by brick chimney for the same height is

1. less
2. more
3. same
4. may be more or less

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