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clifford bradford July 3, 1999 15:34

counterrotating turbomachinery
does anyone know of any published research concerning counterrotating turbomachinery (propfans, compressors, turbines,even turbopumps). I've been searching diligently but i can't seem to find any. I know there have been some designs for counterrotating turbomachinery (F-22 engines and a few propfan designs) but ican't find any published. I'd like to do research involving counterrotating machinery, specifically the unsteady flow through counterrotating turbines and/or compressors so anything you might know of published or unpublished will be of help. thanks

Ji Lucheng July 4, 1999 21:12

Re: counterrotating turbomachinery
Hi, Clifford,

I also will do counterrotating turbomachinery design, but I couldnot find more useful references, the only one I known is a paper of ASME in 1985, the author is Ruixian Cai. I think the counterrotating turbomachinery had no more problems than conventional turbomachinery, solely more large relative motion speed.

Good Luck, Ji

clifford bradford July 6, 1999 12:39

Re: counterrotating turbomachinery
Ji, I've been told of some reference on this subject which I will put below. There are other issues than just the high relative speeds which will probably be only obvious if you think three dimensionally and look at engine schematics (there's agood one in Lakshminarayana's recent book on turbomachinery): -first the lack of stators means that rotors are subject to rotor-rotor interaction which is not likely similar to rotor stator interaction, because the stator isn't present to "mix out" the wakes, shocks etc. -a conterrotating machine has two tip vortex flows since the hub of hub of one stage is the tip of the other (the schematic mentioned above will make this clear. -counterrotating machines also allow the designer to take advantage of the lack of stators eg. in an hp turbine the rotor sees lower stagnation temperatures than a stator due to the relative motion so the turbine inlet temperature can be higher. -i do agree with you that the aerodynamics may not be much different from that of a conventional machine but the structural dynamics of the machine is likely to be much different due to higher blade passing frequencies, complex bearing arrangements etc. but there are also opportunities for example have you thought that it is possible to have alternate stages running at different rpms :). you might sy why? but you never know. doing this may allow structural designers to avoid the naturally higher resonant frequencies of these machines.

here are the references(you already have one of these): Ozgur,C. Nathan,G.K.: A Study of Counterrotating Turbines Based on Design Efficiency." ASME Journal of Basic Engineering, Sept. 1971, pp. 395-404

Lois,J.F.: "Axial Flow Contra-Rotating Turbines". ASME Paper 85-GT-218, 1985

Cai,R.: "Basic Analysis of Counter-Rotating Turbines." Int. Journal of Turbo and jert Engines, Vol. 9, 1992, No. 1, pp. 1-10

also: There is a good amount of literature available on contra-rotating fans/compressors. You may search in the ASME Journal of turbomachinery from 1987 onwards. A few good ones are in 90/91/92 and 97 issues (I don't exactly remember the years). Hope this helps.

clifford bradford July 13, 1999 17:25

Re: counterrotating turbomachinery
btw the paper number for the reference by Cai is ASME 90-GT-108

ken elms July 14, 1999 17:47

Re: counterrotating turbomachinery
Try Rene` Van den Braembussche at and for the turbomachinery issues you raise. good luck

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