All-supersonic diffusing blade rows, suitable for a “rotating diffuser” or diffuser-compressor, were studied. Typical blade shapes for low wave drag were investigated in relation to simple theoretical design limitations for flow starting and running. A tentative design criterion for the permissible strength and running. A tentative design criterion was derived from empirical shock-boundary layer interaction data. A blade shape (No. 6) satisfying the assumed design requirements at zero and small negative incidence angles for design Mach number 2.5 was obtained.nTesting of a cascade model (blade shape No. 6) at Mach 2.5 has been started. Initial difficulties with model vibrations and tunnel starting have been largely overcome, but design flow conditions have not yet been achieved in the cascade. This is ascribed to blocking of the flow passage adjacent to the cascade, caused either by air leaks or passage geometry, or both. It is believed that this can be remedied with reasonable additional effort and that tests can be carried out successfully with the existing equipment.
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