CAA Simulation and Intensity Based Evaluation of a Model Experiment for Indirect Combustion Noise

Abstract

The efficient prediction of combustion noise by azonal approach is discussed. Forthe so called propagation zone an optimized finite difference method adopted from fantone noise propagation is applied together with alinear perturbation approach based on the Euler equations. Special attention is payed to the indirect noise generation in the propagation zone, where initially quiet perturbations of the fluid state radiate noise when accelerated or decelerated in av arying base flowregime. Anon-isentropic mathematical model is chosen. The approach is compared with apreviously published experiment for the assessment of indirect combustion noise. The numerical results showthe strong influence of reflections from the inflowboundary of the plenum on the resulting pressure response in the outlet duct. By assuming reasonable reflections from the plenum, the observed time signal of the pressure reaches ar easonable agreement between numerical simulation and experiment. Furthermore, the acoustic intensity is used to showthe good quality of the numerical solution. Finally,the intensity based source location identifies the nozzle as adominant source of sound, with large magnitudes of generation and annihilation of acoustic energy.The source power found in the heated volume is more than twoorders of magnitude smaller than in the nozzle. This result again underlines the importance of indirect combustion noise. PACS no. 43.20.Mv,43.28.Kt, 43.60.Jn ACTA ACUSTICA UNITED WITH ACUSTICA Richter et al.:M odel experiment forindirect combustion noise Vol. 95 (2009)

Combustion noise

“…The DLR experiment generated interest in the community and initiated multiple theoretical and numerical methods to explain the experimental results [78,[98][99][100][101]. Leyko et al [99] studied numerically and analytically the DLR experiments in an axisymmetric and a fully threedimensional configuration.…”