Steam and Gas Turbines Questions and Answers – Relationship between Velocity Ratios

This set of Steam and Gas Turbines Multiple Choice Questions & Answers (MCQs) focuses on “Relationship between Velocity Ratios”.

1. Velocity ratio is represented by ___________
a) Alpha
b) Beta
c) Sigma
d) None of the mentioned

Explanation: Velocity ratio is represented by sigma.

2. For single stage impulse turbine optimum sigma value lies between ____________
a) 0.4 and 0.6
b) 0.2 and 0.4
c) 0.1 and 0.3
d) none of the mentioned

Explanation: 0.4 and 0.6 are the boundary values for sigma in single stage impulse turbine which can be found from graph plotted between sigma and efficiency.

3. For two stage impulse turbine optimum sigma value lies between __________
a) 0.3 and 0.5
b) 0.2 and 0.4
c) 0.1 and 0.5
d) none of the mentioned

Explanation: For two stage impulse turbine sigma value lies in between 0.2 and 0.4 which can be found out from graph plotted between sigma value and efficiency.

4. For reaction turbines the optimum sigma value lies between _____________
a) 0.8 and 1.0
b) 0.6 and 1.0
c) 0.4 and 0.8
d) none of the mentioned

Explanation: For reaction turbines sigma value lies between 0.8 and 1.0 which can be found out from graph plotted between sigma and efficiency.

5. Speed of the blade to speed of the gas ratio can be denoted by ___________
a) Alpha
b) Sigma
c) Gamma
d) None of the mentioned

Explanation: Blade to gas speed ratio is known as velocity ratio and it can be represented by sigma.
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6. Best velocity ratio for four row impulse turbine is ________
a) one seventh
b) one sixth
c) half
d) none of the mentioned

Explanation: The best velocity ratio for four row impulse turbine is one seventh.

6. Efficiency of the four row impulse turbine with a velocity ratio of one seventh is ______
a) 55%
b) 44%
c) 34%
d) 77%

Explanation: Efficiency of four row impulse turbine with a velocity of one seventh is 44% which was found from graph plotted against efficiency and velocity ratio.

7. Velocity ratio is the integral of ________ of the velocity in each row.
a) fourth power
b) cube
c) square
d) none of the mentioned

Explanation: Velocity ratio is the integral of square of velocity in each row.

8. Velocity ratio is directly proportional to square of velocity.
a) True
b) False

Explanation: Velocity ratio is directly proportional to integral of square of velocity in each row.

9. When velocity in each row increases its velocity ratio __________
a) decreases
b) remains constant
c) increases
d) none

Explanation: When velocity in each row increases its velocity ratio also increases.

10. Velocity ratio is directly proportional to velocity in each row.
a) True
b) False

Explanation: Velocity in each row is inversely proportional to velocity ratio.

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