Identification of Noise Sources in a Heated Jet Flow

Abstract

A heated jet facility has been recently designed and installed at the Gas Dynamics and Turbulence Laboratory (GDTL) at the Ohio State University. The purpose of this facility is to simulate the exhaust flow conditions from both a commercial aircraft (jet exhaust Mach number of 0.9) and an advanced military aircraft (jet exhaust Mach number of 2.0). Previously, the GDTL used, with great success, an ideally expanded Mach 1.3 cold jet since this jet’s exhaust velocity was close to an actual commercial jet engine exhaust. The exhaust of a commercial jet engine, though, is heated due to the combustion process that takes place in the combustor of the engine. Since a Mach 0.9 heated jet flow is typical of commercial engines, this new heated jet facility will provide a more accurate model of an actual jet engine’s exhaust, which will be the focus of this proposed research. The GDTL put a major effort in recent years in designing flow, acoustic, and mathematical tools to identify noise sources in a Mach 1.3 cold jet. The main goal of this research is to use some of these tools to obtain detailed jet noise source data in a Mach 0.9 heated jet. This data will be used to gain preliminary understanding of the differences between the noise generated in a heated flow and the noise generated in a cold flow to help develop ways to mitigate this noise. This thesis will focus on the steps taken thus far to ensure that this new heated jet facility is operating as expected and providing “clean” noise data. Some preliminary analysis of heated jet noise spectra, up to 600 oF at angles of 30o and 90o to the jet axis, and the subsequent results and conclusions will also be discussed including issues encountered with the lowering of the jet’s Reynolds number with heating.