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Chapter 4 – Gas Turbine

Total questions: 72

Worksheet time: 36mins

Name
Class
Date
1.

Brayton cycle has _______.

a)

two isentropic and two constant volume processes

b)

two isentropic and two constant pressure processes

c)

one constant pressure, one constant volume, and two adiabatic processes

d)

two isothermals, one constant volume and a constant pressure process

2.

Brayton cycle cannot be used in reciprocating engines even for same adiabatic compression ratio and work output because _______.

a)

Otto cycle is highly efficient

b)

Brayton cycle is less efficient

c)

Brayton cycle is for slow speed engines only

d)

large volume of low pressure air cannot be efficiently handled in reciprocating engines

3.

Which cycle is generally used for gas turbine?

a)

Otto cycle

b)

Dual cycle

c)

Carnot cycle

d)

Brayton cycle

4.

When r is the compression ratio, the efficiency of Brayton cycle is given by:

a)

1 − 1/r(k−1)/k1/r^{(k−1)/k}

b)

1−1rk1 - \frac{1}{r^k}

c)

1−1rk1 - \frac{1}{r^k}

d)

1 − 1/r

5.

A regenerator in a gas turbine _______.

a)

reduces heat loss during exhaust

b)

allows use of higher compression ratio

c)

improves thermal efficiency

d)

allows use of fuels of inferior quality

6.

Which of the following compressors is generally used for gas turbines?

a)

lobe type

b)

centrifugal type

c)

axial flow type

d)

reciprocating type

7.

The constant pressure gas turbine works on the principle of _______.

a)

Carnot cycle

b)

Bell–Coleman cycle

c)

Rankine cycle

d)

Brayton cycle

8.

What type of gas turbine is used in aircraft?

a)

Open cycle type

b)

Closed cycle type with reheating

c)

Closed type with reheating and regeneration

d)

Open cycle type with reheating, regeneration and intercooling

9.

For multi-stage compression of an ideal Brayton cycle, the back work ratio will _______.

a)

increase

b)

remains the same

c)

decrease

d)

none of these

10.

In most common designs of gas turbine, the pressure ratio ranges from _______.

a)

10 to 12

b)

11 to 16

c)

12 to 18

d)

15 to 20

11.

Overall efficiency of a gas turbine is _______.

a)

equal to Carnot cycle efficiency

b)

equal to Rankine cycle efficiency

c)

less than Diesel cycle efficiency

d)

more than Otto or Diesel cycle efficiency

12.

Which of the following turbine has least weight per bhp developed?

a)

Simple open cycle gas turbine

b)

Open cycle gas turbine with inter-cooling and reheating

c)

Open cycle gas turbine, with inter-cooling, reheating and regenerating

d)

Closed cycle gas turbine

13.

Which of the following is/are advantage(s) of closed cycle gas turbine over open cycle gas turbine?

a)

no containing of working substance with combustion gases

b)

inferior quality fuel can be used

c)

low maintenance costs

d)

all of these

14.

The range of compression ratio in a gas turbine is _______.

a)

3 to 5

b)

8 to 12

c)

5 to 8

d)

12 to 20

15.

In Brayton cycle, the heat is transformed during which process?

a)

Constant temperature

b)

Isobaric process

c)

Isentropic process

d)

Isochoric process

16.

In Brayton cycle, the ______ during constant pressure process.

a)

work is added

b)

heat is transferred

c)

pressure is rejected

d)

energy is added

17.

What are the two major application areas of gas turbine engines?

a)

driving automotive engine and locomotives

b)

heating and generation

c)

aircraft propulsion and electric power generation

18.

The use of regenerator is recommended only when the turbine exhaust temperature is higher than the compressor _______.

a)

exit temperature

b)

mean temperature

c)

inlet temperature

d)

absolute temperature

19.

Aircraft gas turbines operate at higher pressure ratio, typically between _______.

a)

6 to 8

b)

10 to 18

c)

12 to 24

d)

10 to 25

20.

A constant volume combustion gas turbine operates on _______.

a)

Ericsson cycle

b)

Brayton cycle

c)

Joule cycle

d)

Atkinson cycle

21.

The heat exchanger used to provide heat transfer between the exhaust gases and the air prior to its entrance to the combustor _______.

a)

Evaporator

b)

Regenerator

c)

Combustion chamber

d)

Heater

22.

How does the value for work per unit mass flow of air in the compressor and turbine influenced by the addition of a regenerator?

a)

Slightly increased

b)

Greatly decreased

c)

Unchanged

d)

Greatly increased

23.

What is the ideal cycle for gas turbine work?

a)

Brayton cycle

b)

Stag combined cycle

c)

Bottom cycle

d)

Ericsson cycle

24.

Brayton cycle cannot be used in reciprocating engines even for same adiabatic compression ratio and work output because _______.

a)

Brayton cycle is highly efficient

b)

Brayton cycle is for low speed engines only

c)

Brayton cycle needs large air–fuel ratio

d)

large volume of low pressure air cannot be efficient handled in reciprocating engines

25.

In order to increase the gas velocity gas turbines generally have fixed nozzles. This is to allow the _______.

a)

compression of gases

b)

condensation of gases

c)

expansion of gases

d)

evaporation of gases

26.

Combustion turbines or gas turbines are the preferred combustion engines in application much above _______.

a)

8 MW

b)

9 MW

c)

10 MW

d)

7 MW

27.

Large units gas turbine regularly operate _______.

a)

in 100 to 200 MW range

b)

in 50 to 100 MW range

c)

over 150 MW

d)

below 150 MW

28.

Small units gas turbine operate below _______.

a)

20 MW

b)

30 MW

c)

12 MW

d)

24 MW

29.

Heavy duty gas turbines typically have _______.

a)

double shafts

b)

single shaft

c)

triple shafts

d)

quadruple shafts

30.

Which of the following is basically a jet engine that exhausts into a turbine generator?

a)

aeroderivative gas turbine

b)

industrial gas turbine

c)

Brayton engine

d)

Joule turbine

31.

Most aeroderivative combustion turbine produce less than _______.

a)

20 MW

b)

30 MW

c)

40 MW

d)

50 MW

32.

The compression ratio based on pressures in the compression stage in a gas turbine is typically _______.

a)

11 to 16

b)

5 to 8

c)

12 to 18

d)

8 to 14

33.

The compression ratio based on pressures of heavy duty gas turbine is in the range of

a)

14 to 15

b)

19 to 21

c)

11 to 16

d)

16 to 18

34.

Aeroderivative combustion turbine have higher compression ratios typically

a)

14 to 15

b)

19 to 21

c)

11 to 16

d)

16 to 18

35.

Most heavy duty combustion turbines have how many compression stages?

a)

14 to 16

b)

18 to 20

c)

10 to 12

d)

16 to 18

36.

The temperature of the gas entering the expander section is typically

a)

1200 C to 1290 C

b)

1000 C to 1200 C

c)

1500 C to 1490 C

d)

1300 C to 1390 C

37.

The exhaust temperature which makes the exhaust an ideal heat source for combined cycles is typically

a)

540 C to 590 C

b)

600 C to 650 C

c)

300 C to 350 C

d)

440 C to 490 C

38.

Most combustion turbines have

a)

2 to 3 expander stages

b)

3 to 4 expander stages

c)

4 to 5 expander stages

d)

1 to 2 expander stages

39.

The exhaust flow rate in modern heavy duty turbines per 100 MW is approximately

a)

240 to 250 kg/s

b)

140 to 150 kg/s

c)

340 to 350 kg/s

d)

440 to 450 kg/s

40.

The Brayton gas turbine cycle is also known as

a)

Joule cycle

b)

Stirling cycle

c)

Ericsson cycle

d)

Atkinson cycle

41.

Approximately how many percent of the turbine power is used to drive the high efficiency compressor?

a)

50 to 75 %

b)

60 to 85 %

c)

45 to 70 %

d)

30 to 55 %

42.

Depending on the turbine construction details, the temperature of the air entering the turbine will be between

a)

650 C to 1000 C

b)

750 C to 1100 C

c)

550 C to 950 C

d)

850 C to 1200 C

43.

Which of the following engines are typically used by Turbojet and turboprop?

a)

open combustors

b)

closed combustors

c)

turbo combustors

d)

high combustors

44.

The full load thermal efficiency of existing heavy duty combustion turbines in simple cycles is approximately

a)

34 to 36 %

b)

30 to 32 %

c)

40 to 42 %

d)

26 to 28 %

45.

New combustion turbines on the cutting edge of technology (Advanced turbine systems) are able to achieve

a)

38 to 38.5 %

b)

36 to 36.5 %

c)

40 to 40.5 %

d)

34 to 34.5 %

46.

Aeroderivative turbines commonly achieve efficiencies up to

a)

42 %

b)

38 %

c)

45 %

d)

35 %

47.

Which of the following is the typical back-work ratio of gas turbines?

a)

50 to 75 %

b)

40 to 65 %

c)

30 to 55 %

d)

35 to 60 %

48.

Which of the following is an example of a regenerator?

a)

a counterflow heat exchanger

b)

a cross flow heat exchanger

c)

a mixed flow heat exchanger

d)

a parallel flow heat exchanger

49.

Which of the following is an effect of having a regenerator?

a)

less heat is added

b)

compressor work is reduced

c)

turbine work is increased

d)

compressor work is increased

50.

A regenerator in a gas turbine has no effect in

a)

compressor and turbine work

b)

heat added

c)

thermal efficiency

d)

Combustor

51.

In a Brayton cycle multiple stages of compression and expansion will

a)

increase thermal efficiency

b)

decrease thermal efficiency

c)

limit thermal efficiency

d)

control efficiency

52.

The first commercial high-pass ratio engines has a bypass ratio of

a)

1

b)

5

c)

3

d)

7

53.

The single-stage expansion process of an ideal Brayton cycle without regeneration is replaced by a multistage expansion process with reheating between the same pressure limits. As a result of modification, what will happen to the thermal efficiency?

a)

Increases

b)

Remains constant

c)

Decreases

d)

None of these

54.

Which of the following is/are the application of Brayton cycle?

a)

Propulsion system

b)

Automotive Turbine Engines

c)

Aircraft Turbine engines

d)

All of these

55.

Brayton cycle is also known as

a)

Carnot cycle

b)

Diesel cycle

c)

Joule cycle

d)

Rankine cycle

56.

This is applied to propulsion of vehicles because of certain practical characteristics.

a)

Diesel cycle

b)

Carnot cycle

c)

Otto cycle

d)

Brayton cycle

57.

In a Brayton cycle, reheating and intercooling will

a)

increase thermal efficiency

b)

decrease thermal efficiency

c)

limit thermal efficiency

d)

control efficiency

58.

In a Brayton cycle, reheating has no effect in

a)

heat added

b)

backwork ratio

c)

thermal efficiency

d)

Network

59.

In a Brayton cycle, intercooling has no effect in

a)

turbine work

b)

thermal efficiency

c)

Back-work ratio

d)

network

60.

If Wt is the turbine power and Wc is the compressor power then the back-work ratio is

a)

Wt/WcW_t / W_c

b)

Wc/WtW_c / W_t

c)

(Wt−Wc)/Wt(W_t - W_c)/W_t

d)

(Wt−Wc)/Wc(W_t - W_c)/W_c

61.

The first commercial high pass ratio engines has a bypass ratio of

a)

1

b)

5

c)

3

d)

7

62.

Reheating process in Brayton cycle, the turbine work will

a)

increase

b)

remains the same

c)

decrease

d)

none of these

63.

If Wt is the turbine power and Wc is the compressor power then the network is

a)

Wt×WcW_t \times W_c

b)

Wc/WtW_c / W_t

c)

Wt−WcW_t - W_c

d)

Wt+WcW_t + W_c

64.

Physical limitations usually preclude more than how many stages of intercooling and reheating?

a)

2

b)

3

c)

4

d)

5

65.

New combustion turbines on the cutting edge of technology (Advanced turbine systems) are able to achieve

a)

38 to 38.5 %

b)

40 to 40.5 %

c)

36 to 36.5 %

d)

34 to 34.5 %

66.

It is the ratio of the maximum pressure in the cycle to the atmospheric pressure.

a)

cycle pressure ratio

b)

cycle pressure level

c)

regenerator effectiveness

d)

thermal efficiency

67.

The quantity of working medium entering the first stage of compression per unit of output energy.

a)

Air rate

b)

work ratio

c)

thermal efficiency

d)

regenerator effectiveness

68.

The quantity of a specified fuel consumed per unit of output energy

a)

air rate

b)

fuel rate

c)

work ratio

d)

thermal efficiency

69.

Past Board Question: It is the ratio of the actual heat transfer in a regenerator to that theoretically possible if the heated fluid were to reach the temperature of the entering hot gas.

a)

back-work ratio

b)

thermal efficiency

c)

regenerator effectiveness

d)

pressure ratio

70.

Past Board Question: It is the ratio of output power to the total installed turbine power.

a)

work ratio

b)

thermal efficiency

c)

cycle pressure level

d)

regenerator effectiveness

71.

Which of the following does not use ambient air for propulsion?

a)

Turbo jet

b)

Pulse jet

c)

Turbo-prop

d)

Rocket

72.

In a gas turbine combined cycle plant, a waste heat boiler is used to _____.

a)

heat air from intercooler

b)

gases from regenerator

c)

recover heat from exhaust gases

d)

none of these

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