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Predict And Analysis For Compressor Stall Based On Chaos Theory

Posted on:2008-03-11Degree:DoctorType:Dissertation
Country:ChinaCandidate:K H GaoFull Text:PDF
GTID:1102360218957126Subject:Aerospace Propulsion Theory and Engineering
Abstract/Summary:PDF Full Text Request
With the development of the technology of aeronautical engine the rate ofpressurization in single stage is increased, and meanwhile the requirements on themaneuverability of aircraft are increased, which will make the engines operated underunstable conditions. The stalling and surging will be formed. It is necessary to studythe stability of air compressor in order to make engines work stably off design point.Traditional study method of theoretical modeling on the stall of air compressor mayignore some nonlinear character of engines, and trial run on trestle can not simulatethe in-flight state completely. Both of them have limitation.According to the system theory, the dynamic structure characters of the entiresystem are studied concerned with certain output parameter. Namely, the. pressuresignal of air compressor is studied directly with the method of nonlinear dynamicsystems analysis based on chaos theory. Main tasks are as follows:1.Dynamic structure characters are studied from the viewpoint of geometry.Thephase space of air compressor before and. after stall is studied from the viewpoint ofgeometry based on the theory of phase space.reconstruction, which can reflect thechanges in the dynamic system. Thereafter VRA map of the data before and post stall is also plotted, then the predictability of the data is studied.2.Stall phenomena is detected by structure function and correlation integral. Thepressure data in the course of stall is analyzed with the arithmetic of structure-function and correlation-integral respectively. Arithmetic of the structure function issimple with a clear physical sense which can be used to study the unstable flow fieldbefore and during stall phenomena.3.Chaos exponents of the engine system are calculated. Based on denoisedpressure signal within the compressor the Lyapunov exponent and correlationdimension of the aerodynamic system are calculated. According to the exponents, thecharacters of the system is investigated. And the two exponents will be evidence ofthe chaotic attractor. Then complexity of the system can be judged by the correlationdimensions.4.Chaotic attractor arithmetic is improved. After judging that dynamic systemexist chaos, stall prediction based on chaotic attractor arithmetic is studied. Chaoticattractor arithmetic is improved by adopting the distance factor, advantages lie in new algorithm is simpler and can reduce the calculate quantity. Then reliability andaccuracy of the new chaotic attractor arithmetic is confirmed by the data predicted.5. New strategy for engine instability controlling is put forward. Based on formertask, a new strategy for engine instability control is put forward. The strategy basedon Lyapunov exponents of the dynamic system. Feasibility and superiority is showedbya typical example, and then some beneficial ideas are proposed.
Keywords/Search Tags:Compressor, Nonlinear Dynamic System, Phase-space Reconstruction, Structure Function, Chaotic Attractor, Stall Prediction, Chaotic System Control
PDF Full Text Request
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