Design and Testing of Scaled Ejector-Diffusers for Jet Engine Test Facility Applications.

Design, fabrication and cold flow testing of a modeled jet engine test facility were conducted in an effort to provide an inexpensive vehicle to study geometric variations in diffuser geometry which could improve system efficiency. The design, which is based on Mach number similitude, consists of two configurations currently in use at the Naval Air Propulsion Center, Trenton, NJ. A constant area diffuser and a variable area diffuser with translating centerbody were modeled. Baseline mapping of the operating characteristics for each diffuser with representative scaled engines was conducted to provide a reference against which alternative geometries would be evaluated. The constant area plus two variants were tested. A five-sixths and two-thirds reduction were studied to investigate the potential for increasing efficiency for a specific engine diffuser combination at NAPC. Secondary flow provisions were incorporated into the design to allow variation of this parameter. The modeling results were consistent with theory and the test apparatus produced repeatable results. A two dimensional double ramp wedge capable of being translated in a rectangular duct was suggested as an alternative diffuser geometry.