Steam Nozzles and Turbines – Section 2

1. A single stage impulse turbine with a diameter of 1.2 m runs at 3000 r.p.m. If the blade speed ratio is 0.42, then the inlet velocity of steam will be

A. 79 m/s
B. 188 m/s
C. 450 m/s
D. 900 m/s

Correct Answer: C. 450 m/s

2. In a De-Laval impulse turbine, the nozzle is kept very close to the blades.

A. Yes
B. No

Correct Answer: A. Yes

3. The flow of steam is super-sonic

A. at the entrance to the nozzle
B. at the throat of the nozzle
C. in the convergent portion of the nozzle
D. in the divergent portion of the nozzle

Correct Answer: D. in the divergent portion of the nozzle

4. The pressure of steam at throat of a steam nozzle is called critical pressure.

A. Agree
B. Disagree

Correct Answer: A. Agree

5. For maximum efficiency of an impulse turbine, the steam should leave the blades at right angles to their motion.

A. Correct
B. Incorrect

Correct Answer: A. Correct

6. De-Laval turbine is a

A. simple impulse turbine
B. simple reaction turbine
C. impulse-reaction turbine
D. none of these

Correct Answer: A. simple impulse turbine

7. The impulse turbine rotor efficiency will have a maximum value of 0.5 cos2 α, where α is the nozzle exit flow angle if the

A. blades are equiangular
B. blade velocity coefficient is unity
C. blades are equiangular and frictionless
D. blade solidity is 0.65

Correct Answer: C. blades are equiangular and frictionless

8. When the cross-section of a nozzle increases continuously from entrance to exit, it is called a

A. divergent nozzle
B. convergent nozzle
C. convergent-divergent nozzle
D. none of these

Correct Answer: A. divergent nozzle

9. Rateau turbine is

A. simple reaction turbine
B. velocity compounded turbine
C. pressure compounded turbine
D. pressure-velocity compounded turbine

Correct Answer: C. pressure compounded turbine

10. The ratio of the work delivered at the turbine shaft to the heat supplied is called overall thermal efficiency of turbine.

A. True
B. False

Correct Answer: A. True

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