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This article is badly assembled and its title is misguided, since it refers exclusively to Axial Flow compressors used on aviation gas turbines in the compressor map illustrations, but then it gives references to CENTRIFUGAL compressors no longer used on aviation engines on airplanes. The phenomena description for Compressor Surge is described in relation to Axial Flow compressors only, but not for centrifugal ones. Overall, it needs to be re-written to improve it to Wikipedia standards. Question: Is it proper to show Isentropic efficiency(?) or should it be Polytropic Efficiency instead? Amclaussen.
Hi Amclaussen,
Centrifugal stages are widely used on todays smaller aircraft engines both on their own and as a final stage after some axial stages.
Perhaps mention could be made in the article (unless the title is changed to Axial Compressor Map)that the maps shown also apply in general form to other turbomachinery configurations like centrifugal stages, mixed axial/centrifugal (ie anything in between the two extremes), overall maps for combined axial and centrifugal (as mentioned above, I have one in front of me as I write), turbocharger impellers.
Also, as you point out, mention could be made that the surge mechanism (as best understood today) is basically similar for both axial and radial turbomachines, except that for c/f stages the situation is more involved because one or both of the two main components (impeller and diffuser) may stall individually or simultaneously. A reference should be given here both to confirm the source of the info and to allow follow-up study, so ref 'Rotating Stall and Surge Control: A Survey by Bram de Jager'.
If I can take the liberty of answering your question... Isentropic (or adiabatic) efficiency appears to be the norm for compressor maps if you look at any compressor test results available on-line or in books, eg 'Axial Compressor Development at Rolls-Royce Derby, 1946-1962' by A. McKenzie. The author of the article does say ' some maps use polytropic efficiency' so that allows the learner to follow up the distinction easily on line. Pieter1963 (talk) 01:29, 24 December 2012 (UTC)