Engineering Questions with Answers - Multiple Choice Questions
Thermal Engineering MCQ’s – Brayton Cycle
1 - Question
Gas turbine works on _____
a) Dual cycle
b) Otto cycle
c) Brayton cycle
d) Diesel cycle
View Answer
Explanation: Brayton cycle is used in gas power plant. It is used in open system that is gas turbine.
2 - Question
The compression ratio (r) of dual cycle is equal to _________
a) r = volume of the cylinder at the beginning of the compression/volume of the cylinder at the end of the compression
b) r = volume of the cylinder at the end of the compression/ volume of the cylinder at the beginning of the compression
c) r = clearance volume/ volume of the cylinder at the beginning of the compression
d) r = volume of the cylinder at the end of the compression/clearance volume
View Answer
Explanation: compression ratio of dual cycle (r)=sweptvolume+clearancevolumeclearancevolume r=volume of the cylinder at the beginning of the compression/volume of the cylinder at the end of the compression
3 - Question
For same maximum pressure and heat input, most efficient cycle is _________
a) Dual cycle
b) Rankine cycle
c) Brayton cycle
d) Diesel cycle
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Explanation: Efficiency of brayton cycle is directly proportional to pressure ratio. Therefore for maximum pressure and heat input brayton cycle is most efficient.
4 - Question
Which of the following methods cannot be used to increase the efficiency of brayton cycle?
a) Decreasing pressure ratio
b) Increasing pressure ratio
c) Regeneration
d) Heat exchanger
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Explanation: Heat exchanger and regeneration is used to increase the efficiency of brayton cycle. Also, efficiency of brayton cycle is directly proportional to pressure ratio.
5 - Question
In a brayton cycle heat addition takes place __________
a) At constant volume process
b) At constant pressure process
c) First at constant volume then at constant pressure process
d) First at constant pressure then at constant volume process
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Explanation: The sequence of processes in brayton cycle is isentropic compression, isobaric heat addition, isentropic expansion and isobaric heat rejection. Therefore heat addition takes place at constant pressure process
6 - Question
In a brayton cycle heat rejection takes place ____
a) At constant volume process
b) At constant pressure process
c) First at constant volume then at constant pressure process
d) First at constant pressure then at constant volume process
View Answer
Explanation: The sequence of processes in brayton cycle is isentropic compression, isobaric heat addition, isentropic expansion and isobaric heat rejection. Therefore heat rejection takes place at constant pressure process.
7 - Question
In brayton cycle regenerator is placed between __________
a) Turbine and heat exchanger
b) Turbine and intercooler
c) Compressor and intercooler
d) Compressor and heat exchanger
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Explanation: In regenerative brayton cycle a regenerator is placed between compressor and heat exchanger. The exhaust from turbine before entering in heat exchanger and then compressed in compressor.
8 - Question
Reheating will _______ the efficiency of brayton cycle.
a) Decreases
b) Increases
c) Zero
d) Remain same
View Answer
Explanation: Reheating increases the net work output. Reheating necessarily decreases the efficiency.
9 - Question
If regeneration is also used along with reheating the efficiency will _____
a) Decreases
b) Increases
c) Zero
d) Remain same
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Explanation: Regeneration in the brayton cycle increases efficiency by recovery of waste heat. Hence if regeneration is also used along with reheating the efficiency will increase.
10 - Question
What is the effect of regeneration in brayton cycle work output?
a) Work output increases
b) Work output decreases
c) Work output becomes zero
d) Work output doesn’t change
View Answer
Explanation: Regeneration in the brayton cycle increases efficiency by recovery of waste heat. It doesn’t change the net work output.
11 - Question
In how many stages the compression process is divided in intercooling?
a) One
b) Two
c) Three
d) Five
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Explanation: In intercooling the compression process is divided into two stages. Air is compressed in first stage is cooled then further compressed in second stage.
12 - Question
Reheat and regeneration in combination used to increases ________
a) Net work output
b) Efficiency
c) Both net work output and efficiency
d) Doesn’t change net work output and efficiency
View Answer
Explanation: Reheating increases the net work output. Reheating necessarily decreases the efficiency. Regeneration in the brayton cycle increases efficiency by recovery of waste heat. It doesn’t change the net work output.
13 - Question
Intercooling and regeneration in combination used to increases _________
a) Net work output
b) Efficiency
c) Doesn’t change net work output and efficiency
d) Both net work output and efficiency
View Answer
Explanation: Intercooling mainly increases the net work output by decreasing compression work. Reheating necessarily decreases the efficiency. Regeneration in the brayton cycle increases efficiency by recovery of waste heat. It doesn’t change the net work output.