DIFFUSER PERFORMANCE OF A MACH 6 OPEN-JET TUNNEL AND MODEL-BLOCKAGE EFFECTS AT STAGNATION TEMPERATURES TO 3,600° F

摘要

A diffuser evaluation program was conducted to develop an effective fixed area diffuser for a Mach 6 open-jet wind tunnel. In this program several diffuser parameters were varied and evaluated in terms of empty-jet starting efficiency and running efficiency with blunt models and support systems inserted in the air stream. Permissible model blockage for tunnel operation was defined for several variations of the diffuser parameters.nTest results show that good recoveries can be obtained with the fixed-area diffuser, and that blunt models (hemispheres) with up to l8-percent blockage can be operated in a tunnel with a properly designed diffuser. Investigation also shows that operation with blunt models requires the use of second-minimum area ratios appreciably larger than the optimum empty-jet values. Furthermore, better efficiencies were obtained with short free-jet lengths and second-minimum sections over 4 diameters in length.