EFFECT OF VARIOUS ARRANGEMENTS OF TRIANGULAR LEDGES ON THE PERFORMANCE:OF A 23° CONICAL DIFFUSER AT SUBSONIC MACH NUMBERS

摘要

A brief investigation has been made to determine whether the use of annular ledges to promote turbulent momentum exchange will Improve the performance of a short, wide-angle diffuser. Results are presented of tests of a -23° conical diffuser with a 2:1 ratio of exit to inlet area with both rough and smooth triangular ledges, approximately one-tenth of the inlet boundary-layer thickness in height, installed in succession from the inlet to the exit. The results show that, although the flow in the diffuser without ledges was very unstable, the presence of a rough-ness strip near the inlet, with or without additional ledges, assured stable flow. For the configurations investigated, the static-pressure recovery and the total-pressure-loss coefficient were either unaffected or only slightly impaired by the installation of the ledges.