15 Questions
What is the function of the governor in a steam turbine?
It controls the speed and power output of the turbine at various load conditions
How does the governor respond when the turbine load increases?
By admitting more steam to the turbine nozzles
What method do most turbine governors use to sense turbine shaft speed?
Mechanical means
In which type of governing system do flyweights move in accordance with changes in turbine speed?
Flyweight governing system
What is the role of flyweights in a purely mechanical governing system?
Apply force to the steam governor valve directly or indirectly
How does the governor respond when the turbine load decreases?
By decreasing the amount of steam admitted to the turbine nozzles
What is the primary purpose of adjusting the steam control valve in a steam turbine?
To control the steam flow through the turbine
What causes the flyweights of a mechanical hydraulic governor to move outwards?
Increase in speed
How does the flyweight-operated oil relay governing system respond to an increase in turbine speed?
Moves the governor sleeve to the 'fast' position
In a hydraulic turbine governing system, what varies with turbine speed to supply hydraulic oil through two passages to the pressure relay?
Oil pump output pressure
What prevents the force on the operating cylinder bellows from varying in a hydraulic turbine governing system?
Bled oil replenishment rate
How does an overspeed trip mechanism protect a turbine against excessive speed?
By releasing a catch and closing the steam supply valve
What happens when a sudden loss of load occurs in a turbine without adequate protection?
The blades tear from the blade wheels due to centrifugal forces
What is the primary element that senses overspeed in a typical overspeed trip mechanism of a small mechanical drive steam turbine?
Unbalanced weight mounted in the turbine shaft
What does an increase in turbine load cause in a hydraulic oil relay governing system?
Immediate pressure decrease on top of the pressure relay
Study Notes
Governor Function and Response
- The governor in a steam turbine controls the steam flow to maintain a constant speed, regardless of changes in turbine load.
- When the turbine load increases, the governor responds by reducing the steam flow to the turbine, decreasing its speed.
- Conversely, when the turbine load decreases, the governor increases the steam flow, increasing the turbine speed.
Turbine Speed Sensing
- Most turbine governors sense turbine shaft speed using a mechanical or hydraulic system.
Mechanical Governing System
- In a purely mechanical governing system, flyweights move in accordance with changes in turbine speed, regulating the steam flow.
- The flyweights play a crucial role in the mechanical governing system, as they directly control the steam flow valve.
Hydraulic Governing System
- In a hydraulic governing system, the flyweights move outwards due to an increase in turbine speed, causing hydraulic oil to flow through two passages to the pressure relay.
- The pressure relay then adjusts the steam control valve to maintain a constant turbine speed.
Overspeed Protection
- An overspeed trip mechanism protects the turbine against excessive speed by rapidly closing the steam valve and applying a braking mechanism.
- A sudden loss of load without adequate protection can cause the turbine to overspeed, leading to catastrophic failure.
Overspeed Trip Mechanism
- The primary element that senses overspeed in a typical overspeed trip mechanism is a flyweight, which triggers the trip mechanism when the turbine speed exceeds a set limit.
Load Changes and Response
- An increase in turbine load causes the hydraulic oil relay governing system to decrease the steam flow to the turbine, reducing its speed.
- The primary purpose of adjusting the steam control valve is to maintain a constant turbine speed, regardless of changes in load.
Test your knowledge about the governor, a crucial component of a steam turbine that automatically regulates its speed and power output at different load conditions by controlling the steam flow through the turbine. This quiz covers the principles and mechanisms of turbine governing.
Make Your Own Quizzes and Flashcards
Convert your notes into interactive study material.
Get started for free
