Stall in axial compressor

csmistry · September 28, 2011, 09:21

Dear sir,

what will be the best way to predict stalling mass flow rate?
While doing simulation at low mass flow rate convergence is a issue and even expert parameter say total pressure also fluctuates!!!

Guide me for the same.

Far · September 28, 2011, 14:19

your last stable operating point is the your stall point, afterwards surge/rotating stall is begin to occur. Mostly this approach is enough for the numerical studies as indicated by many researchers.

As you know that surge is unsteady phenomena, in which compressor goes into cycle of low mass flow rate, low pressure ratio and then again high mass flow rate and high pressure ratio and this cycle repeats forever, unless some method applied to get rid of surge. This is also know as hysteric loop and is highly unsteady, therefore you need to use the unsteady RANS.

csmistry · September 28, 2011, 23:35

Dear sir,

This phenomena is known but the question is how to capture it in Computational analysis for different mass flow study.

Far · September 29, 2011, 08:10

do you want to say that " you want to simulate the post stall scenario?" or "you want to determine the stall point numerically"

csmistry · September 29, 2011, 23:41

Sir, both the things....

maryamprana · August 13, 2012, 16:51

Quote:

Originally Posted by Far

do you want to say that " you want to simulate the post stall scenario?" or "you want to determine the stall point numerically"

I found my question here, but unfortunately not the answer. Does anyone know the answer? "How to determine the stall point numerically?"

vicarious · October 31, 2012, 06:16

According to references (even recent ones), the prediction of rotating stall phenomena cannot be determined accurately by numerical simulations. But there is a point in compressor map that is the last stable performance of the compressor. At mass flow rates lower than this point, the compressor parameters, for example mass flow rates, starts to oscillate during unsteady simulation. The oscillation starts with a high amplitude part-span stall. if the oscillation's amplitude gets low, it means a full-span stall has occurred and the compressor is working under unstable region. Different values of the compressor's flow and head coefficients have to get extracted and simulated so you can determine the stall point.

September 28, 2011, 09:21	Stall in axial compressor	#1
csmistry Member mistry Join Date: Apr 2009 Location: India Posts: 69 Rep Power: 17	Dear sir, what will be the best way to predict stalling mass flow rate? While doing simulation at low mass flow rate convergence is a issue and even expert parameter say total pressure also fluctuates!!! Guide me for the same.

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September 28, 2011, 14:19		#2
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	your last stable operating point is the your stall point, afterwards surge/rotating stall is begin to occur. Mostly this approach is enough for the numerical studies as indicated by many researchers. As you know that surge is unsteady phenomena, in which compressor goes into cycle of low mass flow rate, low pressure ratio and then again high mass flow rate and high pressure ratio and this cycle repeats forever, unless some method applied to get rid of surge. This is also know as hysteric loop and is highly unsteady, therefore you need to use the unsteady RANS.

September 28, 2011, 23:35		#3
csmistry Member mistry Join Date: Apr 2009 Location: India Posts: 69 Rep Power: 17	Dear sir, This phenomena is known but the question is how to capture it in Computational analysis for different mass flow study.

September 29, 2011, 08:10		#4
Far Super Moderator Sijal Join Date: Mar 2009 Location: Islamabad Posts: 4,553 Blog Entries: 6 Rep Power: 54	do you want to say that " you want to simulate the post stall scenario?" or "you want to determine the stall point numerically"

September 29, 2011, 23:41		#5
csmistry Member mistry Join Date: Apr 2009 Location: India Posts: 69 Rep Power: 17	Sir, both the things....

October 31, 2012, 06:16		#7
vicarious Member Pedram Mojtabavi Join Date: Apr 2011 Location: Iran Posts: 66 Rep Power: 14	According to references (even recent ones), the prediction of rotating stall phenomena cannot be determined accurately by numerical simulations. But there is a point in compressor map that is the last stable performance of the compressor. At mass flow rates lower than this point, the compressor parameters, for example mass flow rates, starts to oscillate during unsteady simulation. The oscillation starts with a high amplitude part-span stall. if the oscillation's amplitude gets low, it means a full-span stall has occurred and the compressor is working under unstable region. Different values of the compressor's flow and head coefficients have to get extracted and simulated so you can determine the stall point.