Steam Turbine Performance Curve 1

[qazx]

I have a performance curve(steam rate vs. horsepower) for a single stage turbine (back pressure type)at a certain inlet/outlet steam conditions (temperature and pressure). How can I modify this curve for the other steam inlet/outlet conditions (such as different inlet pressure or temperature or different outlet pressure)?

 

[paragmpatel]

Hi,
Each machine has it's individual operation cheq. curve.It is depended on the inlet condotion, outletcondition of steam.It means temp,& pressure, Purity of steam, Vacuum in condenser ,if condensing turbine. For the back pressure turbine efficiency depend upon the backpressure, inlet pressure, stage efficiency, Bearing efficinecy, Electrical Generater efficiency, Governor throlling pressure loss.
If u modified the operating curve ucan condisider the above things.

Thanks,

 

[poetix99]

I described some of the considerations involved in predicting off-design performane in thread666-26115. I suggest that you review this thread.

Other related threads are
thread666-27491
thread391-35162
thread605-47965

In brief, without the original manufacturer's prediction program based on the actual turbine details, performance predictions may be adjusted based on ratios of available energy; "DESIGN A.E." vs. "ACTUAL A.E."

The corrections are generally made to one variable at a time. The accumulated corrections are more uncertain as the number of off-design parameters increases.

 

[qazx]

Thank you "poetix99" for your good comments.In other words, in my case that the steam rate vs. power output is a stright line with a slope, for the new operating conditions(for example higher inlet pressure) there would be another line with different slope. Am I right?

 

[poetix99]

The fact that the "curve" is a straight line is a simplification in the first place.

A steam turbine is a volume flow device. Corrections for different operating conditions, if based solely upon changes in the available energy at design conditions vs. off-design conditions, will not include the changes in aerodynamic behavior due to differing volume flow at different loads and/or different steam conditions. Changes in load cause more significant changes (i.e. errors) in correction factors than (small) changes in steam conditions.

Consult a good text on turbomachinery design, or a text more specifically concerned with turbine performance (K.C.Cotton, Salisbury, Horlock, Balje, Stodola, D.G.Wilson,...) Don't be put off by the age of some of these books; there are also more recent texts, but the fundamentals of this subject are not new, and you are interested in the fundamentals.