Compressors

81. Pick up the false statement

  1. gas turbine is a self-starting unit
  2. gas turbine does not require huge quantity of water like steam plant
  3. exhaust losses in gas turbine are high due to large mass flow rate
  4. overall efficiency of gas turbine plant is lower than that of a reciprocating engine
  5. gas turbine can be easily started and stopped and thus is best suited for peaking demands.

Correct answer: (A)
gas turbine is a self-starting unit

82. Pick up the wrong statement

  1. centrifugal compressors deliver prac-tically constant pressure over a considerable range of capacities
  2. Axial flow compressors have a sub-stantially constant delivery at variable pressures
  3. centrifugal compressors have a wider stable operating range than axial flow compressors
  4. axial flow compressors are bigger in diameter compared to centrifugal type
  5. axial flow compressors apt to be longer as compared to centrifugal type.

Correct answer: (D)
axial flow compressors are bigger in diameter compared to centrifugal type

83. Pick up the wrong statement about advantages of multistage compression

  1. better lubrication is possible advantages of multistage
  2. more loss of air due to leakage past the cylinder
  3. mechanical balance is better
  4. air can be cooled perfectly in between
  5. more uniform torque, light cylinder and saving in work.

Correct answer: (B)
more loss of air due to leakage past the cylinder

84. Pick up wrong statement. Surging phenomenon in centrifugal com-pressor depends on

  1. mass flow rate
  2. pressure ratio
  3. change in load
  4. stagnation pressure at the outlet
  5. all of the above.

Correct answer: (D)
all of the above.

85. Pressure ratio in gas turbines is the ratio of

  1. compressor pressure ratio
  2. highest pressure to exhaust pressure
  3. inlet pressure to exhaust pressure
  4. pressures across the turbine
  5. none of the above.

Correct answer: (B)
highest pressure to exhaust pressure

86. Producer 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 coal, coke, anthracite coal or charcoal in a mixed air steam blast
  5. same way as the natural gas.

Correct answer: (D)
partial combustion of coal, coke, anthracite coal or charcoal in a mixed air steam blast

87. Propulsion efficiency of the following order-is obtained in practice

  1. 34%
  2. 50%
  3. 60%
  4. 72%
  5. 85%.

Correct answer: (C)
60%

88. Propulsive efficiency is defined as ratio of

  1. thrust power and fuel energy
  2. engine output and propulsive power
  3. propulsive power and fuel input
  4. thrust power and propulsive power
  5. none of the above.

Correct answer: (D)
thrust power and propulsive power

89. Ram compression in turbojet involves

  1. reduction of speed of incoming air and conversion of part of it into pressure energy
  2. compression of inlet air
  3. increasing speed of incoming air
  4. lost work
  5. leakage losses.

Correct answer: (A)
reduction of speed of incoming air and conversion of part of it into pressure energy

90. Ram-jet engine

  1. is self-operating at zero flight speed
  2. is not self-operating at zero^flight speed
  3. requires no air for its operation
  4. produces a jet consisting of plasma
  5. none of the above.

Correct answer: (B)
is not self-operating at zero^flight speed

Previous
Page 9 of 19
Next
Copyright © EngineeringMCQ.com