turbo-expander performance curves

[Iradah]

Hello all,

I am trying to predict a new turbo-expander performance using supplier performance curves.
expander curve showed a certian power produced for a given flow rate and speed. using the same speed and power on the compressor curve to see what flow rate is needed, I found that the flow rate on the curve is higher than what actually will going to the compressor. for the actual flow rate and power produced from the expander, the point will be above the speed used for the expander.If the power produced by the expander is more than what is needed by the compressor to compress to certain discharge pressure what will happen?
I have attached the performance curves. thanks.

 

[Pinga]

Those graphs are for standard cubic feets per minute, but for an expander or compressor it is about actual cubic feets per minute, and actual molecular weights, and actual pressure ratios.

Presumably those graphs were supplied for the original design specification of the turbo-expander. That is: for certain in- and outlet pressures of both expander and compressor, certain inlet temperatures of both, and certain molecular weights of both feeds. They are not useful to predict performance under different conditions.

If the power produced by the expander is more than what is needed by the compressor to compress to certain discharge pressure what will happen?

I expect the inlet pressure of the compressor, and outlet pressure of expander, will change to the extent that both powers adjust and become equal.

 

[chicopee]

Examining both the expander and compressor curves that you supplied, I am noting that at 17000 rpm and 2900 HP the mass flow rates for both units is 120MMSCFD or am I missing something in your OP.