Hello guy’s ! How are you?… I know you are also fine. Today we want to discuss different topics. I know you are an engineer, so the information that I am going to give you is about compounding to steam turbine.
The mechanical engineering have lot’s of branches and here we will explain with you all detailed knowledge of mechanical engineering with the help of smart notes.
Compounding to steam turbine :-
The arrangement to reduce pressure from boiler pressure to condenser pressure by use of multiple system of rotors in series, keyed to common shaft or by increasing number of stages and the steam pressure or the steam velocity flows over moving blades absorbed in stages . This can be called as compounding.
*Necessity of compounding of steam turbines:–
*Generally, in steam power plants, Steam temp and pressure are very highly, the high in order to maintain high thermal efficiency.
*The turbine, entire pressure dropped from the boiler pressure to the condenser pressure is carried out in single stage, the velocity of steam becomes very highly entering the turbine.
*The speed of turbine rotational result in very high which is not useful / desirable from practical point of view. this could even lead to failure of blades results to centrifugal stresses.
*To overcome this difficulty, multiple systems of rotors is keyed to a common shaft in the series and the steam pressure or jet velocity is flows over rotor blades a absorbed in a stages . Is also knows as compounding.
*Methods of compounding :-
*Pressure compounding.
*Velocity compounding.
*Pressure – Velocity compounding.
*Pressure compounding :-
- Pressure compounding is the method of in which pressure is made of steam turbine to drop in a number of stages very single nozzle.
- In pressure compounded turbine, moving blades and fixed nozzles are shown in fig. It consists of a number of fixed nozzles which are placed between the moving blades.
- The moving blades keyed on a same shaft in series.
- Now, The steam of boiler pressure the first set of nozzle enters but the total pressure doesn’t drop in one set of nozzles. Only small amount of pressure is drop here by which it increases its velocity.
- The total steam pressure by number of stages is dropped and each stage consists of a ring of moving blades and a set of nozzles.
Velocity compounding :-
*The velocity compounding turbine, a set of nozzle, fixed blades and some moving blades are shown in figure.
*In velocity compounded of the impulse turbine has moving and fixed blade.
*The moving blades are keyed to turbine fixed blades and shaft are fitted to casing.
*High pressure steam from boiler is expanded in nozzle where pressure energy is converted into kinetic energy.
*The high velocity steam enters the first ring of moving blades at a high velocity. A portion of high velocity is absorbed by this blade ring & remaining is passed on to the next ring of fixed blades.
*The fixed blades change the direction of steam & direct it to the second ring of moving blades, without altering the velocity appreciably.
*The steam then go to next set of moving blades and this process is a repeated until all the steam energy is absorbed.All pressure drops occurs in the nozzles.
*Pressure – Velocity compounding :-
- This method is the combination of both pressure and velocity compounding .
- Here the set of nozzle rings is fixed at the beginning of each stage and pressure remaining constant during each stage.
- The steam coming from the boiler is passed to the first ring of fixed nozzles, where it gets partially expanded. The pressure partially the velocity rises and decreases correspondingly.
*It then passes over rings of moving blades with fixed blades between them where nearly all of its velocity is absorbed.
*From the last ring of the stage, steam exhausts into the next nozzle ring and is again partially expanded.
*The change in pressure & velocity as shown in figure.
Regenerative feed heating system / Bleeding of steam :-
- The process of draining steam from certain section of turbine during its expansion and this using of steam for heating feed water supplied by the boiler is called as bleeding. This process of heating feed water is also known as regenerative feed heating.
- Regenerative feed water heating uses bleed steam from the turbine heat the feed water or condensed water.
- By heating the boiler feed water before it enters into the boiler, we are reducing the heat overall the input to the cycle doesn’t hampering the efficiency of the turbine and pump.
- Advantages of feed heating :-
- The thermal efficiency of boiler increases as heat input decreases.
- The reduced capacity of condenser.
- Reduce by the fuel consumption.
- Thermal stress in the boiler reduces as hot feed water is supplied.
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