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This paper describes a method of evaluation of the single and multistage compressors response to steady and unsteady inlet distortions. It allows also the evaluation of the appearance of unstable regimes and their characterization (rotating stall and surge). It is based on a linearized approach using mean line calculations. The compressor is considered as a series of vaned and vaneless spaces, and the corresponding equations are solved by use of Fourier series for time independent variables and by Laplace’s transform for time-dependent variables. An analogy between the compressor’s response and a servo-mechanism is developed, using Nyquist’s diagram. Results are compared with experimental data which prove the validity of the approach. A parametric study indicates which parameters can be modified to improve the flow stability.

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A base flow model has been proposed which, apart from predicting the base pressure, also predicts the wake angle and the trailing edge shock system to a good degree of accuracy. The method may also handle a round trailing edge which is important in transonic blades for reducing losses. The base pressure found in the above is then used in the prediction of some of the parameters in the heat-transfer model. The trailing edge heat-transfer model explains and correlates experimental data, for film cooling the trailing edge, obtained using short duration techniques. The results show that film cooling may be used in cooling the trailing edges of transonic blades effectively, provided that the coolant port is located just beyond a critical distance upstream of the trailing edge. The critical distance is the distance required for the coolant flow which separates at injection to reattach downstream and depends on the momentum ratio of coolant to mainstream flows, on the angle of injection, and the flow Reynolds number.