Thermal Engineering Multiple Choice Questions on “Steam Turbine Governing and Control”.
1. What is the objective of steam turbine governing?
a) To keep turbine load constant irrespective of the turbine speed
b) To keep turbine speed constant irrespective of the load
c) To enhance the output of the turbine
d) To reduce the losses in the turbine
Answer: b
Clarification: The objective of steam turbine governing is to keep turbine speed constant irrespective of the load on the turbine shaft. The performance of a steam turbine is affected when the load changes. Turbine governing is important because in practical conditions the load frequently varies.
2. Which of the following is NOT a method of steam turbine governing?
a) By-pass governing
b) Throttle governing
c) Steam governing
d) Nozzle governing
Answer: c
Clarification: Throttle governing, by-pass governing and nozzle governing are all different methods of steam turbine governing while there is no method called steam governing. The mentioned three methods are used to keep the turbine speed constant at varying load condition.
3. Which of the following statements about throttle governing is wrong?
a) It cannot be used in small turbines
b) It has a relatively simpler mechanism
c) Steam is throttled whenever the load falls below the design load
d) Its initial cost is less
Answer: a
Clarification: Throttle governing is used particularly for small turbines. Its cost is less and it has a simple mechanism. In throttle governing the steam is throttled whenever the load falls below the design load to maintain turbine speed constant.
4. In case of throttle governing, the beat valve is operated using oil supply. The oil is supplies using a _____
a) centrifugal pump
b) servomotor
c) reciprocatory pump
d) diaphragm pump
Answer: b
Clarification: The double beat valve in the throttle governing mechanism is operated by supply of oil. This supply of oil is carried out by an oil servomotor. When the steam turbine gains speed this valve is closed and supply to the nozzle is reduced.
5. The oil servomotor in case of throttle governing mechanism is controlled by a _____ governor.
a) centrifugal
b) reciprocatory
c) diaphragm
d) gear
Answer: a
Clarification: In throttle governing mechanism, the oil servomotor is controlled by a centrifugal governor. The servomotor supplies oil for operating the double beat valve. The closing of the valve reduces the supply to the nozzle.
6. The relationship between steam consumption and load in throttle governing is given by _____
a) Wilson’s line
b) Wilkinson’s line
c) Willan’s line
d) Wilber’s line
Answer: c
Clarification: Willan’s line gives the relationship between the steam consumption and load in throttle governing. In throttle governing the steam is throttled whenever the load falls below the design load. It is used mostly in small turbines.
7. Which of the following is the correct equation for Willan’s line?
a) ms0=KM+ms
b) ms0=M/K+ms
c) ms=KM+ms0
d) ms=M/K+ms0
Answer: c
Clarification: Willan’s line gives the relationship between steam consumption and load in case of throttle governing. It’s given by –
ms=KM+ ms0
where, ms – Steam consumption at any load M (kg/h)
ms0 – Steam consumption at no load (kg/h)
M – Any load (kW)
K – Constant.
8. Carrying out throttle governing at low loads reduces the turbine efficiency.
a) True
b) False