Test: Gas Turbine - 2 - Mechanical Engineering MCQ

Optimum pressure ratio for maximum specific output for ideal gas turbine plant operating at initial temperature of 300 k and maximum temperature of 1000 k is closer to   

In a single-stage open-cycle gas turbine, the mass flow through the turbine is higher than the mass flow through compressor, because    

The given figure shows the effect of the substitution of an isothermal compression process for the isentropic compression process onthe gas turbine cycle. The shadedare (1-5-2-1) in the p-v diagramr epresents

Which one of the following statements is correct ? Increasing the number of reheating stages a gas turbine to infinity, makesthe expansion tending: 

Which one of the following is correct ? In a gas turbine cycle with regeneration, 

The efficiency of a simple gas turbine can be improved by using are generator, because the 

A gas turbine plant working on Joule cycle produces 4000 kW of power. Ifits work ratio is 40%, what is the power consumed by the compressor? 

A gas turbine develops 120 kJ of work while the compressor absorbed 60kJ of work and the heat supplied is 100 kJ. If a regenerator which wouldrecover 40% of the heat in the exhaust was used, then the increase in theoverall thermal efficiency would be: 

The use of regenerator in a gas turbine cycle 

Consider the following statements in respect of gas turbines: A gas turbine plant with reheater leads to a1. Considerable improvement in the work output2. Considerable improvement in the thermal efficiency. 

Assertion (A): In a gas turbine, reheating is preferred over regeneration to yield ahigher thermal efficiency.

Reason (R): The thermal efficiency given by the ratio of the difference of work doneby turbine (W_t) and work required by compressor (W_c) to heat added (Q_A) isimproved by increasing the W_t keeping W_c and Q_A constant in reheating, whereas inregeneration Q_A is reduced keeping W_t and W_c constant. 

Reheating in a gas turbine 

Inter-cooling in gas turbines 

Consider the following statements:

1. Inter-cooling is effective only at lower pressure ratios and high turbineinlet temperatures

2. There is very little gain in thermal efficiency when inter-cooling is usedwithout the benefit of regeneration

3. With high values of 'γ' and c_p of the working fluid, the net power outputof Brayton cycle will increase.  

Consider the following statements: When air is to be compressed to reasonably high pressure, it is usually carried out by a multistage compressor with an intercooler between thestages because

1. Work supplied is saved.

2. Weight of compressor is reduced.

3. More uniform torque is obtained leading to the reduction in the size offlywheel.

4. Volumetric efficiency is increased.Of the four statements listed above correct is/are? 

Consider the following statements: Which of the following increase the work ratio in a simple gas turbine plant ?

1. Heat exchanger

2. Inter cooling

3. Reheating Select the correct answer using the code given below: 

Assertion (A): In gas turbines, regenerative heating always improves the efficiency unlike that in the case of reheating.

Reason (R): Regenerative heating is isentropic. 

Consider the following statements about modification in a gas turbinepower plant working on a simple Brayton cycle:

1. Incorporation of regeneration process increases specific work outputas well as thermal efficiency.

2. Incorporation of regeneration process increases thermal efficiency butspecific work output remains unchanged.

3. Incorporation of inter cooling process in a multi-stage compressionincreases specific work output but the heat input also increases

4. Incorporation of intercooling process in a multi-stage compressionsystem increases specific work output, the heat addition remainsunchanged.Which of the above statements are correct? 

Consider the following features for a gas turbine plant:

1. Intercooling

2. Regeneration

3. Reheat

Which of the above features in a simple gas turbine cycle increase the work ratio? 

In a simple single stage gas turbine plant, if T₁ is the minimum temperature and T₃ is the maximum temperature then what is the work ratio in terms of r_p?

Consider the toll owing statements:Steam turbines are suitable for use as prime movers for large steam power plants because

1. A single steam turbine can be designed for a capacity of 1000 MW or more

2. Much higher speed may be possible as compared to a reciprocating engine

3. They are more compact when compared to a gas turbine power plant

4. The maintenance cost and running cost may not increase with years of service Which of these statements are correct? 

Assertion (A): A gas turbine power plant is very sensitive to turbine and compressor inefficiencies.

Reason(R): In a gas turbine power plant, a large portion of the turbine work is consumed by the compressor. 

Which cycle is represented inthe diagram given above?

Assertion (A): Brayton cycle is not suitable for reciprocating engines.

Reason (R): A reciprocating engine cannot have complete expansion. 

For air standard Brayton cycle, increase in the maximum temperature of the cycle, while keeping the pressure ratio the same would result in 

In a simple gas turbine power plant operating on standard Brayton cycle power needed to drive the compressor is 175 kW, rate of heat supplied during constant pressure heat addition process is 675 kW. Turbine output obtained during expansion is 425 kW. What is the rate of heat rejection during constant pressure heat rejection? 

The given figure shows an open-cycle gas turbine employing reheating, on T-splane. Assuming that the specific heats are same for both air and gas, and neglecting the increase in mass flow due to addition of fuel, the efficiency is