Stability Analysis of a Coupled Helmholtz Resonator with Large Eddy Simulation

Lean Premixed combustion, which allows for reducing the production of thermal NOx, is prone to combustion instabilities. There is an extensive research to develop a reduced physical model, which allows - without time-consuming measurements - to calculate the resonance characteristics of a combustion system consisting of Helmholtz-resonator-type components (burner plenum, combustion chamber). For the formulation of this model numerical investigations by means of compressible Large Eddy Simulation (LES) are carried out. In these investigations the flow in the combustion chamber is isotherm, non-reacting and excited with a sinusoidal mass flow rate. The foregoing investigations concentrated on the single combustion chamber as a single resonator.

In this paper the results of the numerical investigations of a coupled system will be presented. The reduced physical model was extended for the coupled system of burner and combustion chamber. By means of numerical simulation and the physical model the resonance characteristics of a combustion system can be predicted already during the design phase. In order to predict the resonant characteristics of the coupled system and to provide an insight into the flow mechanics 10 compressible LES were carried out. The results are in very good agreement with the experimental investigations.