Recent Improvements in Combustion Noise Investigation: from the Combustion Chamber to Nozzle Flow

For a long time, engine noise has been dominated by fan and jet noise. With their reduction for modern turbojets, for instance, combustion noise is no longer negligible and efforts are concentrated on its understanding. The objective of the European project RECORD is to help to understand the fundamental mechanisms of core noise, in order to reduce it. In this paper, the recent advances achieved within the project for the noise generated through a nozzle are presented. This work includes the definition of a combustion test bench at the EM2C laboratory, equipped with various  diagnostic techniques and an outlet nozzle to pressurize the chamber and generate entropy noise. Reactive simulations of this facility are performed by ONERA and CERFACS using LES. Finally, simulated flow fields are post-processed to determine direct (acoustic) and indirect (entropy) contributions to the global noise generated by the nozzle. This work is a first step before the modeling of a full engine, including the turbine stages.