Compressors

121. The degree of reaction of an axial flow turbine is the ratio of isentropic temperature drop in a blade row to the

  1. adiabatic temperature drop in the stage
  2. total temperature drop
  3. total temperature drop in the stage
  4. total adiabaitc temperature drop
  5. difference of maximum and minimum temperature in the cycle.

Correct answer: (C)
total temperature drop in the stage

122. The effective power of gas turbines is increased by adding the following in compressor

  1. ammonia and water vapour
  2. carbon dioxide
  3. nitrogen
  4. hydrogen
  5. none of the above.

Correct answer: (A)
ammonia and water vapour

123. The efficiency and work ratio of a gas turbine plant can be increased by

  1. using mulit-stage compressor with mfercooler
  2. adding heat exchanger
  3. injecting water in/around combustion chamber
  4. reheating the air after partial expansion in the turbine
  5. all of the above.

Correct answer: (E)
all of the above.

124. The efficiency of jet engine is

  1. higher at ground
  2. higher at high altitudes
  3. same at all altitudes
  4. higher at high speed
  5. lower at low speed.

Correct answer: (B)
higher at high altitudes

125. The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is

  1. heated
  2. compressed air before entering the combustion chamber is heated
  3. bled gas from turbine is heated and readmitted for complete expansion
  4. exhaust gases drive the compressor
  5. part of exhaust gases are heated and mixed up with atmospheric air to utilise exhaust heat.

Correct answer: (B)
compressed air before entering the combustion chamber is heated

126. The following property is most important for material used for gas turbine blade

  1. toughness
  2. fatigue
  3. creep
  4. corrosion resistance
  5. bulk modulus.

Correct answer: (C)
creep

127. The fuel consumption in gas turbines is accounted for by

  1. low.er heating value
  2. higher heating value
  3. heating value
  4. higher calorific value
  5. highest calorific value.

Correct answer: (A)
lower heating value

128. The hottest point in a gas turbine is

  1. at the base
  2. at the tip
  3. in the center
  4. between ~ to i of the blade height
  5. uniformly heated.

Correct answer: (D)
between ~ to i of the blade height

129. The ideal efficiency of simple gas turbine cycle depends on

  1. pressure ratio
  2. maximum cycle temperature
  3. minimum cycle temperature
  4. all of the above
  5. none of the above.

Correct answer: (A)
pressure ratio

130. The indicated work per unit mass of air delivered is

  1. directly proportional to clearance volume
  2. greatly affected by clearance volume
  3. not affected by clearance volume
  4. inversely proportional to clearance volume
  5. none of the above.

Correct answer: (C)
not affected by clearance volume

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