Forward Flight Effects on the Internal Noise of an Ejector Nozzle

The effect of forward flight upon the noise internal to an ejector was investigated in a series of experiments. A nozzle system that simulated a mixer/ejector nozzle was designed and tested under both heated and unheated conditions in GTRI’s Anechoic Free-jet Flight-simulation Facility. The nozzle system consisted of a round nozzle surrounded by an ejector that was fed through a series of pipes. The round nozzle system was tested in both a baseline configuration and with a spoiler in the exit plane of the round nozzle that served to vastly increase the internal noise. By using the spoiler, it was insured that the noise in the far field was dominated by internal mixing noise over a majority of the frequency range. Source location measurements were made to provide further confidence that the noise under consideration was generated inside the ejector. It was found that the measured internal noise radiation pattern has a very distinctive lobe that is centered near an emission angle of 60°. It was also found that the effect of forward flight upon the internal noise was minimal at polar angles near the exit plane of the ejector. In the forward arc the internal noise increased with forward flight. The measurements made in this study can be used to increase the accuracy of flight noise predictions of a future aero-engine system that are based upon static ground tests for mixer/ejector nozzles.