Discontinuous Flux Splitter of Compressor Leading Edges at Supersonic Operation

Abstract

The leading-edge discontinuity problem is addressed for numerical solutions of the 2-D axisymmetric flow equations coupled to an analytical blading model formulation. While this discontinuity affects any 2-D solution because of the incidence angle, it needs a specific treatment under supersonic inflow conditions so that both the started and the unstarted rotor regimes (i.e., with either still supersonic or subsonic flow into the blade passage) can be properly described by the analytical blading model. The new flux splitter includes Levine’s theory for evaluation of the unique incidence at started regime, and generalizes it to the unstarted for evaluation of detached shock loss. A discontinuous Riemann solution through the leading edge determines whether the blade geometry and backpressure admit started operation; if they do not, the splitter automatically switches to the unstarted regime. The started mode, however, can be disabled when its computed mass flow exceeds the unstarted choke limit and does not make the rotor start. Capture of operation type as well as prediction of choke mass flow, shock loss, and impact on rotor performance are stressed through comparison to experimental and 3-D numerical results for the NASA Rotor 67 and Stage 37 test cases.