Steam Cycle Performance Model

[mfdoom]

Hi,

I have designed a performance model for a steam cycle that has 7 bleeds and 3 turbines, using EES. I have reflected the changes in pressure at different bleed pts in the turbines using Stodola's Ellipse Law i.e. p_new = p_reference*(m_new/m_reference), where p is pressure and m is mass flow rate.

However I am now confused as to how I can 1) have the pressure at these bleeds change if I decide to change the HP turbine inlet pressure, 2) if I decide to change condenser vacuum pressure, by either changing inlet CW temp or changing CW flow rate.

Thanks,

mfdoom

 

[davefitz]

I am not sure of your model's config, but the turbine's inlet may have a throttle valve . If the turbine is a constant speed machine, then the pressure downstream of the throttle valve ( and also at the inlet of each end every stage of the turbine) will follow the same Ellipse law, with a different P_reference . I had often seen it written differently , as W,i = K,i*SQRT ( P,i/ sv,i), where W,i is the mass flowrate into the i'th row of blades, K,i is the "flow factor " for the i'th row of blades, and sv,i is the specific volume entering the i'th row of blades.

The basis of the relationship is compressible flow theory assuming the relative velocity between the steam and rotating blade open area is roughly 50% of soundspeed.

"...when logic, and proportion, have fallen, sloppy dead..." Grace Slick