Mechanical Engineering - Power Engineering - Gas Turbine

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Question - 1

Thermal efficiency of a standard Otto cycle for compression ratio 6 is

  • A 60%
  • B 68%
  • C 71%
  • D 65%

Question - 2

Air standard efficiency of an IC engine depends on

  • A fuel
  • B compression ratio
  • C speed
  • D All of these

Question - 3

If engine produces 10 kW brake power while working with a brake thermal efficiency of 30%. If the calorific value of the fuel used is 40000 kJ/kg. Then, what is the fuel consumption?

  • A 1.5 kg/h
  • B 3.0 kg/h
  • C 0.3 kg/h
  • D 1.0 kg/h

Question - 4

An Otto cycle operates with volumes of 40 cm3 and 400 cm3 at Top Dead Centre (TOG) and Bottom Dead Centre (BDC) respectively. If the power output is 100 kW, what is heat input in kJ/s? Assume \(\gamma\) = 1.4.

  • A 166
  • B 145
  • C 110
  • D 9.3

Question - 5

In a gas turbine cycle with regeneration

  • A pressure ratio increases
  • B work output decreases
  • C thermal efficiency increases
  • D heat input increases

Question - 6

An open cycle constant pressure gas turbine uses a fuel of calorific value 40000 kJ/kg with air fuel ratio of 80 : 1 and develops a net output of 80 kJ/kg of air. The thermal efficiency of the cycle is

  • A 61%
  • B 16%
  • C 18%
  • D None of these

Question - 7

In a Morse test for a 2-cylinder, 2-stroke, spark ignition engine, the brake power was 9 kW whereas the brake powers of individual cylinders with spark cut-off were 4.25 kW and 3.75 kW respectively. The mechanical efficiency of the engine is

  • A 90%
  • B 80%
  • C 45.5%
  • D 52.5%

Question - 8

In a Brayton cycle, the value of optimum pressure ratio for maximum net work done between temperatures T1 and T3' where T3 is the maximum temperature and T1 is the minimum temperature is

  • A \({ r }_{ p }=\left( \frac { { T }_{ 3 } }{ { T }_{ 1 } } \right) ^{ \frac { \gamma }{ \gamma -1 } }\)
  • B \({ r }_{ p }=\left( \frac { { T }_{ 3 } }{ { T }_{ 1 } } \right) ^{ \frac { \gamma -1 }{ 2\gamma } }\)
  • C \({ r }_{ p }=\left( \frac { { T }_{ 3 } }{ { T }_{ 1 } } \right) ^{ \frac { \gamma }{ 2\left( \gamma -1 \right) } }\)
  • D \({ r }_{ p }=\left( \frac { { T }_{ 3 } }{ { T }_{ 1 } } \right) ^{ \frac { 2\left( \gamma -1 \right) }{ \gamma } }\)

Question - 9

The thermal efficiency of a gas turbine cycle with regeneration in terms of T3 (maximum temperature), T1 (maximum temperature), rp (pressure ratio) and k\(\left( =\frac { { C }_{ P } }{ { C }_{ V } } \right) \) IS given by

  • A \(1-\frac { { T }_{ 1 } }{ { T }_{ 3 } } { r }_{ p }=\left( \frac { K }{ K-1 } \right) \)
  • B \(1-\frac { { T }_{ 3 } }{ { T }_{ 1 } } { r }_{ p }=\left( \frac { K }{ K-1 } \right) \)
  • C \(1-\frac { { T }_{ 3 } }{ { T }_{ 1 } } { r }_{ p }=\left( \frac { K-1 }{ K } \right) \)
  • D \(1-\frac { { T }_{ 1 } }{ { T }_{ 3 } } { r }_{ p }=\left( \frac { K-1 }{ K } \right) \)

Question - 10

In an ideal air-standard gas turbine cycle the minimum and maximum temperatures are respectively 300 K and 1200 K. Then, optimal pressure ratio of cycle for maximum work output is (for air \(\gamma\) = 1.4)

  • A 2.1
  • B 1.3
  • C 1.2
  • D 3.5
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