multi row choke flow in axial turbine

[hosein]

Hi.



I'm trying to write a meanline code for axial turbine that can solve an axial turbine and give its maps. There is no problem until I reach to choke condition. I search a lot about choke and still can't find a simple explain for what happening in turbine after choking and when we increases PR more than critical PR. In fact I read in some paper That choke start in first row and eventually reach to the last row when maximum power is available in this condition but I can't understand why. and can't find an algorithm to solve turbine. can anyone please help me or introduce some text book.



Thank you very much

[racket]

Hi

I always look for old Papers on a subject, maybe try this one to start with naca.central.cranfield.ac.uk/reports/arc/rm/2974.pdf

Cheers
John

[finiteparts]

Choking in multi-stage turbines is definitely a possibility. The reason for multistage choke is that it takes a given PR across a single turbine stage to choke the flow. So as you increase the turbine inlet pressure, the residual pressure after choking across the first stage also increases. If the residual pressure, which is the inlet pressure for the next stage, gets high enough, you can now have a sufficient pressure ratio across the second stage and thus choke in the second stage also. And this goes on similarly in any other stage downstream. Actually, this assumes that the second stage has an effective area that is larger than that of the first stage, but smaller than any other flow station downstream of the first stage. This may not necessarily be the case...you can choke anywhere else in the flowpath if it has the next minimum effective area. A simple way to think of it is similar to orifices in series.

A really good reference for building your own meanline program is Ronald Aungier's "Turbine Aerodynamics, Axial-Flow and Radial-Inflow Turbine Design and Analysis" from ASME Press.

Good luck!

Chris

[hosein]

Mar 30, 2021 20:10:56 GMT -5 racket said:

Hi

I always look for old Papers on a subject, maybe try this one to start with naca.central.cranfield.ac.uk/reports/arc/rm/2974.pdf

Cheers
John

Hi John.

 I have seen this paper already. Indeed I read some other papers too. but It's not clear how they solve multi-row choking.

Thanks for your suggestion. I would search more in old papers.

[hosein]

Mar 30, 2021 22:16:56 GMT -5 finiteparts said:

Choking in multi-stage turbines is definitely a possibility. The reason for multistage choke is that it takes a given PR across a single turbine stage to choke the flow. So as you increase the turbine inlet pressure, the residual pressure after choking across the first stage also increases. If the residual pressure, which is the inlet pressure for the next stage, gets high enough, you can now have a sufficient pressure ratio across the second stage and thus choke in the second stage also. And this goes on similarly in any other stage downstream. Actually, this assumes that the second stage has an effective area that is larger than that of the first stage, but smaller than any other flow station downstream of the first stage. This may not necessarily be the case...you can choke anywhere else in the flowpath if it has the next minimum effective area. A simple way to think of it is similar to orifices in series.

A really good reference for building your own meanline program is Ronald Aungier's "Turbine Aerodynamics, Axial-Flow and Radial-Inflow Turbine Design and Analysis" from ASME Press.

Good luck!

Chris

Hi Chris.

Thanks for your answer.
I it seems that Aungier explain choke algorithm for stream-line analysis. But I will study that part and try to understand.

Thanks.
Hosein