turbine

[facetoface]

Please, what is by summary the main diference between reaction turbine and impulse turbine ,and how the pressure transferred to torque for both

 

[rmw]

http://www.gepower.com/prod_serv/products/tech_docs/en/steam_turbines.htm

What you ask is answered in several of the papers listed.

rmw

 

[facetoface]

taht is means the impulse turbine trsfer the flow or speed to torque and reaction transfer pressure to torque , and what is the diference between nozzle and blade and where is position ro place of nozzle in both type of turbine

 

[gtsim]

In an impulse turbine all the expansion takes place in the stator or nozzle guide vane. In 100% reaction turbine all the expansion takes place in the rotor. For a 50% reaction turbine the expansion is equal between the stator and rotor. This condition gives the maximum efficiency. However, cooled turbines (gas turbines) tend to have a higher than 50% reaction as this increases the stage loading and therefore reduces the number of stages. This eases the cooling requirements.

 

[facetoface]

what about for the steam turbine which is the first stage is imoulse and other is reaction , how the pressure transfer to torq

 

[gtsim]

In impulse stages the torque is produced by the change in momentum of the fluid (e.g. steam or gas) in the rotor (i.e. there is no change in static pressure in the rotor – all the expansion occurs in the stator thus increasing the velocity). In a 100% reaction stage the torque is produced by velocity increase as the steam/gas expands in the rotor - no expansion or velocity increase occurs the stators. In a 50% reaction stage the torque is produced partly by impulse (i.e. momentum changes) and partly by reaction (velocity increase in the rotor due to expansion in the rotor).

Best regards,

 

[facetoface]

thanks for good info, I need the difference between Nozzle and blade and where there blade , nozzle sould be exist

 

[facetoface]

Please, the diff between stator and rotor for both type

 

[gtsim]

An axial turbine stage consists of a stator and then a rotor. Turbine section has many such turbine stages. The stator, which is fixed, deflects the steam/gas to enter the rotor at a suitable angle of incidence to minimise losses. All the work done or power developed occurs in the rotor, which drives the load such as a generator. If the stage is impulse then the geometry of the stator is convergent so that there is a static pressure drop or expansion across the stator. The rotor geometry does not allow a static pressure drop or expansion. In a 100 % reaction stage the geometry of the stator does not allow a static pressure drop and convergent geometry of the rotor now produces the entire static pressure drop.

 

[facetoface]

thanks , what abour for before question of Nozzel and blade,shroud ,bouket all term required clear please

 

[gtsim]

The stator is also known as the nozzle. In the UK and Europe they are also know as Nozzle Guide Vanes or NGVs. In North America a bucket is a term used for the rotor. In the UK and Europe it is known as a rotor or rotor blades. Shrouds are positioned at the tip of the rotors or buckets to minimise over tip leakage.

You could refer to text, which give schematic and cutaways of turbines describing turbine design configurations. I trust this helps.

Best regards,
GTSIM

 

[facetoface]

Yhanks,but we about of fxed and movable nozzel and this is placed only on the stator

 

[rmw]

I believe bucket is a term referring to what might otherwise be called a blade by some. GE uses the term bucket and rotor while Westinghouse (now Siemens-Westinghouse) called them blades and spindles.

Buckets connote impulse where the pressure drop, hence the velocity increase, takes place in the stationary parts (diaphram) and the buckets 'catch' or try to 'stop' the kinetic energy of the high velocity steam, imparting torque to the moving parts (rotor).

In the USA, GE historically went the impulse route while Westinghouse turbines were principally reaction turbines. Reaction turbines tend to have more stages. Reading some of the GER's referred to in my first reply imply that GE has seen the light and is now advocating more reaction stages.

Also recognize that pure impulse and/or pure reaction stages are impractical, so each type of turbine contains some of the other. My comments only imply that the 'majority' of a stage ends up being impulse or reaction.

To my way of thinking, sakram seems to be mixing up some combustion turbine terminology and steam turbine terminology.

Sakram; lots of the questions you are asking are available in the GER's link that I referred you to in the beginning of this thread. Do you have the capability to open and read them?

rmw

 

[facetoface]

rmw , thanks it is good to see your openion and other

 

[facetoface]

again please ,fixed nozle is placed stator and move nozle in rotor , and is the area betwee blade called also nozle

 

[rmw]

In an impulse type turbine, the nozzle is fixed onto the stator. The stator nozzle changes the pressure energy to kinetic energy, and the bucket attached to the rotor catches and changes that kinetic energy to torque.

Imagine a stationary steam hose (nozzle) directed at a rotor with some water buckets attached to it.

In a reaction turbine, the stator parts are for not much more than to change the direction of the steam and redirect it into the next row of turbine blades which are essentially rotating nozzles.

Imagine a rotor with two jet engines mounted opposite each other, each producing thrust making the rotor rotate. Now change the jets to steam nozzles.

Most turbines use a combination of both, impulse and reaction, with one or the other being the predominant type. Some larger diameter stages are impulse at one part of the blade, and reaction at another part. As it changes, you can see the blades twist. The machines I have experience with have impulse at the root of the blade, changing to reaction at the tips. The first stage, however was typically pure impulse.

This is because of the relative velocities of various parts of the blade with respect to the stationary parts. The root area rotates at a slower rotational speed than does the tip. Since the 'impulse' on the bucket is dependent upon the relative difference between the speed of the rotating bucket and the nozzle exit velocity, at the higher tip speeds, the bucket may be moving away from the nozzle so that there is very little relative difference. Here the blade profile changes to reaction, since all that is important here is to get the steam into the blades so that it can expand and turn the rotor by the velocity 'reaction.'

rmw

 

[gtsim]

rmw, I think sakram was referring to variable geometry nozzles. The nozzles (stators) can rotate on their axis and therefore change flow area and thus the flow capacity of the turbine. Such variable geometry turbines are used for turn down or in gas turbines for better matching other engine components (e.g. RR WR21). Variable geometry rotors are uncommon. Variable geometry stators are applicable to both impulse and reaction turbines.

 

[rmw]

gtsim,

Any remarks I made in recent posts above except the one where I noted that I thought sakram was mixing steam and gas turbine terminology were limited to steam turbines only. I didn't even put my gas turbine hat on just because of what you point out. Gas paths in CT's are a whole different discussion for just the reason you point out.

rmw

 

[gtsim]

No problem rmw, Thanks for the clarification.

Best wishes,
gtsim

 

[facetoface]

Thanks. now the turbine consiste of from stages ,and each stage contain nozzel and movable blade in impulse turbine and fixed balde and movable blade in reaction turbine , but that mean the nozzle is exist in any stage as well as the stator exist for any stage ,please specify the location for fixed plade , nozzle,movable blade