Experimental design to determine the effect of temperature and Mach number on entropy noise

Abstract

The Osney Laboratory sought to create an entropy noise test rig that could determine the relationship between entropy noise and the flow parameters of temperature change and nozzle Mach number. The apparatus simulates entropy noise in an aero engine. In the test rig, compressed air enters an anechoic labyrinth, flows through a settling chamber that straightens airflow, and then goes to the entropy wave generator. The entropy wave generator forms entropy waves through electric heating. Entropy waves are then accelerated in a convergent-divergent nozzle to produce entropy noise. Microphones at the end of the rig detect entropy noise readings as acoustic sound. Air exits through an anechoic termination. The test rig allows for easy changes in temperature and Mach number so variation in entropy noise with different input values can be tested. Project stages include literature compilation, 3D computer-aided design, part revision, material specification, and finally supervision of manufacture.