Basically governing of a turbine is controlling the speed of the turbine as the load keeps varying. The turbine needs to rotate at a constant speed. The governing of an impulse turbine is done by varying the jet of water that hits the buckets of the runner. This is done by using a spear arrangement in the pen stock. A pen stock is a type of pipe that provides the jet of water.
Basically governing of a turbine is controlling the speed of the turbine as the load keeps varying. The turbine needs to rotate at a constant speed. The governing of an impulse turbine is done by varying the jet of water that hits the buckets of the runner. This is done by using a spear arrangement in the pen stock. A pen stock is a type of pipe that provides the jet of water.
A diagram of an impulse turbine is in related links.
1) Impulse turbine 2) reaction turbine
A two stage impulse contains 2 stages. One stage is a stator and rotor, therefore a 2 stage impulse turbine contains a stator-rotor-stator-rotor.
Water is blasted at the buckets one by one or more jets mounted in the surroundings casing. Momentum is transferred from water to buckets and a torque is created, causing the wheel to rotate. That's why it is an impulse turbine.
In an impulse turbine, the stage is a set of moving blades behind the nozzle. In a reaction turbine, each row of blades is called a "stage." A single Curtis stage may consist of two or more rows of moving blades.
The device which control the speed of Turbine is Governor. The Governing system sense the speed of shaft & regulate the Fuel/ Motive fluid flow to the Turbine to maintain the set shaft speed.
That is how fast the steam is actually moving in the turbine. For impulse turbines it is twice as fast as the turbine blades. In reaction turbines it is the same speed as the blades. Because the blades of a turbine cannot move faster than 4500 feet per second without self destructing as it overcomes the centripetal force of the turbine wheels, the steam turbine is designed such that no turbine will exceed more than ~1150 feet per second on its tip speed. Thus the steam velocity through the turbine will be less than ~1150 fps for a reaction turbine and less than ~2300 fps for an impulse turbine, or about ~1570 mph, more than twice the speed of sound.
The difference between impulse and reaction turbine goes here...... 1) In case of an impulse turbine the pressure remains same in the rotor or runners, but in case of reaction turbine the pressure decreases in runners as well as stators also. 2) In case of impulse turbine the pressure drop happens only in the nozzle part by means of its kinetic energy. In case of Reaction one the stators those are fixed to the diaphragm act as a nozzle.
in the case of impule turbine total energy at inlet is kinetic energy and in case reaction turbine energy at inlet is kinetic and pressure......
in reaction turbine pressure compounding is employed as every stage has a set of nozzle ring nozzle control is not feasible.
It sends hot gases from the combustion chamber to the 1st stage turbine blades at the correct angle and speed