Indirect Combustion Noise: Large Eddy Simulation of a full scale Lab nozzle

Abstract

In 1998, the X-Noise collaborative network project was created uniting 32 European partners (companies, universities, institutes). The objective of this project is to reduce the exposure of community to aircraft noise precisely by a factor 2 (-10 dB) in 2020. At the beginning of 2010, a drastic decrease of the aero-acoustic noise by 5dB was reached and led to an increase in the relative contribution of combustion noise. In this report, the nozzle of the test bench located at EM2C Laboratory was studied using the LES 3D solver CEDRE. The description of the combustion noise, which can be divided into direct and indirect noise, and the methods used for its prediction and its analyse will be explained. Then the DISCERN project will be detailed. After that the numerical simulation of the nozzle will be performed. The acoustic transfer functions of the system will then be calculated using the CEDRE code. But due to time constraints, the calculation has been fully performed on a coarse mesh and the analysis of the results from the fine mesh is still under way. For the coarse mesh, the acoustic transfer functions seems to be much higher than the results from the analytical MARCAN solver. The first hypothesis might be the creation of a jet in the divergent part of the nozzle. This jet leads to an uncontrolled and undesired acoustic disturbances. As a conclusion, the geometry has to be changed, the angle of the divergent part should be decreased to avoid the detached ow. Under this condition, the study of the acoustic noise generated by the injection of entropy uctuation will be more accurate.