Numerical Investigation of Rotating-Stall in a Stage of an Axial Compressor with Two Different Approaches

Rotating-Stall (RS) through a cascade of an axial compressor has been numerically investigated by employing an unsteady two-dimensional finite-volume density based computer code. To validate the computer code, three test cases were prepared, and the good agreement resulting from comparison of the results has given adequate assurance of the code. The cascade problem was studied through different geometric approaches, which were classified in two main categories. The first was the semi-stage (single rotor-cascade), and the second was the complete stage. For each geometric approach, the number of blades was varied from a minimum number to a maximum value (variable cascade length). The RS modal characteristics and its development for all geometric cases were observed. The RS was incepted with a 40% reduction in flow coefficient and a 0.4% increase in the load coefficient from their normal operating values. In all cases, the captured modal characteristics of RS varies with the variation of the cascade length to a maximum value, and this triggers the same modes of RS. The variation of the modal characteristics of the RS, in the two main geometric approaches seems to be similar, but at different levels.