Flow Regimes in Curved Subsonic Diffusers

An extension and refinement of the work of Moore and Kline (NACA TN 4080) is presented for the flow regimes found in straight-walled diffusers. A systematic map of flow regimes in curved diffusing passages is presented, in steps of ten degrees, for a range of flow turning angles from 0 to 90 degrees. Each curved diffuser geometry tested had a circular arc center line and a linear area distribution normal to the center line. The line of first appreciable stall showed a peak in divergence angle as a function of the ratio of center line length to throat width for all values of turning angle equal to, or greater than, fifty degrees. The divergence angle at the transition to the fully developed stall regime was found to decrease monotonically with increase in turning angle at fixed values of the ratio of center line length to throat width in all cases.