What is the compounding steam turbine?

Answer 1

Velosity compounding:This is a combination of pressure-velocity compounding.

Lets say you have superheated steam coming out of the boiler at 70 bar, which is suppose to drive a steam turbine. How many stages of blading required to reduce the pressure to acceptable exhaust pressure so that it does not overheat the condenser?Remember, when you reduce the pressure the kinetic energy increases so is the steam speed. In order to reduce the pessure you must have pressure compounded arrangement. In order to reduce speed you must have velocity compounded. So what is pressure componded?This is an array of nozzles and impulse blades laid out accordingly to mainly reduce the steam pressure as it pass through the respected stages.Notice the pressure drop gradually as it pass through a fixed blade stage, but the speed increases as it pass the same stage. The velocity compounded which is arranged so that you have nozzles,moving and fixed blades laid accordingly. As it enters the nozzle the pressure is dropped, steam velocity inctreased.Then it pass through moving blades which reduces the steam velocity but maintain steam pressure.Then the steam is pass through guide blades or fixed blades where further reduction in velocity but none in pressure.Last stage is moving blades where velocity is reduced but pressure is maintained.

How is pressure-velocity compounding accomplished?

Answers:

It is a combination of pressure compounding and velocity compounding.

Steam is expanded partially in a row of nozzles whereupon its velocity gets increased. This high velocity steam then enters a few rows of velocity compounding whereupon its velocity gets successively reduced.

The velocity of the steam is again increased in the subsequent row of nozzles and then again it is allowed to pass onto another set of velocity compounding that brings about a stage-wise reduction of velocity of the steam.

This system is continued.