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|Title:||Mathematical modelling of axial flow compressors.|
|Presented at:||University of Leicester|
|Abstract:||With the advancing technology of jet engines and more stringent specifications about fast transients, complex questions are having to be answered at an early stage of development. To make some headway in answering these questions various one dimensional models of a multistage axial flow compressor have been developed. These are based on the principles of conservation of mass, linear momentum and energy, and use the steady state stage characteristics to introduce the effects of the blading. The compressor speed has been assumed to be constant since the transients considered were faster than the response of the control systems normally controlling them. It has been shown both by applying a stability test to the linearised system equations and by digitally simulating the full non-linear differential equations, that models entered a region of dynamic instability in the region of compressor surge but that increasing the complexity of models does not necessarily improve surge prediction. An investigation of the dynamic response of some of the models has indicated that their stability depended on the operation of stages over some finite time interval, and that when the models were subjected to sinusoidal fluctuations in either inlet total pressure or temperature there was a change in time meaned stage matching which resulted in stages being matched nearer stage stall; the overall time meaned effects being a reduction in both surge pressure ratio and equivalent inlet flow. This same investigation indicated that as frequency increased the complexity of the models required did also, and that exponential decreases in inlet total pressure could produce quasi-steady operation above the steady state surge line. It has been concluded that the investigation has shown encouraging results and that there were many possible uses of similar models where the transient operation of compressors was important.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Leicester Theses|
Theses, Dept. of Engineering
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