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Stators

Old 20th Oct 2005, 11:54
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GTP
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Stators

Are Stators in jet engines divergent or convergent? any one know?
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Old 20th Oct 2005, 12:31
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I think they are divergent. The rotor adds energy by accelerating the air, the stators slow it again, thus raising the pressure & temperature. Then the next row of rotor blades can re-accelerate the air, adding energy without getting the velocity up to untenable values. And so on through as many stages as the designer requires to achieve the compression he needs.

Sven
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Old 20th Oct 2005, 20:11
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If you're talking compressor stators, Sven is right.

But turbine stators (a.k.a. nozzle guide vanes) are convergent, to accelerate gas flow into the turbine rotor blades.
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Old 20th Oct 2005, 22:55
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Most compressors are designed around 0.5 Degree of reaction ratio, meaning half of the static enthalpy rise (and thus pressure) occured in the rotor and half at the stator. The stages can be esigned with 0 degree of reaction, meaning no pressure rise occurs in the rotor, (rotor blades are thus of an "Impulse" type). They can alternately be designed with a factor of 1, meaning all pressure rises occur in the rotor. thus the stator is of the "impulse" type.

In reality, the degree of reaction varies along the length of the blade, ie the level of convergence/divergence of the stator varies. This is in order to take into account of supersonic flow patterns (remember, supersonic flow accelerates in a diverging passageway). hope that helps!
 
Old 21st Oct 2005, 12:02
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mbga9pgf

Thanks for that explanation.

Great fodder for a pub fight some day )


Will you be available for referee
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Old 21st Oct 2005, 19:12
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GTP

See mbga9pgf's post.

I over-simplified.

I will go away and re-read "Fundamentals of Thermodynamics" as a penance.

Expect to hear from me again in 2013.

Sven
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Old 22nd Oct 2005, 09:18
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thank you. people. very helpfull
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