Interaction of LOX/GH2-Spray Combustion with Acoustics

Abstract

The response of a cryogenic LOX/H2-spray flame to acoustic pressure and velocity fluctuations has be investigated experimentally for pressure levels up to p=1MPa. The dimensions of the combustion chamber are chosen to have transversal acoustic modes at eigenfrequencies representative to full scale rocket combustors. A siren wheel periodically opening a secondary nozzle was used to excite pressure oscillations in the cylindrical combustor at levels up to p'/p~10%. It has been found that the secondary nozzle detunes the eigenfrequencies of the cylindrical resonator in a characteristic way. A 2D-modal analysis of the acoustic behavior of the resonance volume has been done and results agree very well with the experimental findings. By analyzing the temporal and spatial distribution of the flame response to the acoustic excitation the question is addressed whether there is a coupling of combustion and acoustics and whether this coupling is due to velocity or pressure sensitive processes. From the experimental data it is concluded that there is a positive coupling, and the coupling is due to pressure sensitive processes.