A quasi three-dimensional method has been developed to calculate the transonic flow in a compressor rotor. The method allows changes in the stream tube thickness and mean radius evolution through the rotor. This blade-to-blade method uses original concepts in order to be rapid (≈ 3–4 sec CPU on a HP 715 workstation), to find the precise location of the shocks (and thus the flow values on them) and the flow distribution around the profile, and finally to cover a large field of “Off-Design” operating points. Thus, it can be used in the process of optimization of a transonic compressor. The supersonic flow at the inlet as well as the oblique shock configuration inside the cascade are calculated by methods based on the characteristics theory. Conditions with attached shock wave (and thus unique incidence angle) or with detached shock wave can be calculated. Quasi-3D equations were developed (Bölcs and Tsamourtzis, 1991). The subsonic flow is calculated by a streamline curvature method, with some new concepts, and finally the shock in the inter-blade canal is found by a combination of the supersonic and subsonic flow values. This method was combined, in a S1 - S2 calculation, with a throughflow method (Sayari and Bölcs, 1995) in order to be validated by comparing the results with the measurements provided by NASA - Lewis Research Center, on a transonic compressor rotor (Strazisar T.; 1994).

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