Effects of Inlet Conditions on Performance of Two-Dimensional Subsonic Diffusers

Abstract

Performance data and flow characteristics for subsonic two-dimensional plane-wall diffusers are presented for the following conditions. (a) Wall-length to throat-width ratios of 8.0, 12.0, and 48.0, (b) total divergence angles from 2.5 to 40 deg, (c) extremely thin inlet boundary layers to fully established channel flow, (d) a vaned diffuser with L/W1 = 8.0 and quite thick inlet boundary layers. Flow conditions and variations of flow regimes for L/W1 = 48.0 are compared. No real gain in recovery or pressure effectiveness is achieved by use of very large L/W1 . L/W1 = 20 – 25 appears to be maximum useful range in the absence of boundary-layer control. A few data are given where the inlet flow of the diffuser is distributed by obstructions. Recovery and effectiveness are found to be strongly dependent on type and amount of inlet turbulence.