Scale Model Investigations of the Effects of Flow Conditioning Devices

A scale model was constructed of a portion of a supersonic wind tunnel to perform experiments on various flow conditioning devices. The various devices researched were: swirl vanes, screens, honeycombs, and various combinations thereof. Each flow conditioning device was analyzed to show its effect on total pressure profiles, static pressure profiles, test section flow angularity, test section turbulence, and acoustic noise. Of most concern are the effects flow conditioning devices have on temporal fluctuation of previously mentioned parameters. The data from these experiments were used as the basis for selecting a screen-honeycomb combination to be installed in the full-scale tunnel. The selected configuration consisted of two diffuser exit screens in combination with a long cell honeycomb in the stilling chamber. The selected configuration also included the existing screen across corner 4 and swirl vanes. It was concluded that these devices provide a net benefit and should not be removed. This configuration reduced test section flow angularity fluctuations to a very low level in the test section of the model; however, it did not eliminate transitory stall in the crossleg diffuser. Intermediate screens installed in the diffuser and, most likely, screens of some other treatment at the inlet of the diffuser would be required to completely eliminate unsteadiness in the diffuser. These treatments would involve both installation cost and an increase in operation cost because of the associated increase in power requirements due to their location in high-speed flow. The experimental data, however, do show that intermediate screens in the diffuser are very effective at reducing flow unsteadiness downstream of the screen location. This thesis presents a discussion on the methodology to conduct the experimental program and the results each combination of flow conditioning devices had on the various research parameters