Investigation on nonlinear thermoacoustic effects of Rijke tube

Based on the energy conservation,nonlinear thermoacoustic effects of Rijke tube including excited regime, saturation and higher harmonics were analyzed.The simulation method of the modeling with external flow field,which could couple the inner of a Rijke tube with its outer space was carried out to obtain the acoustic characteristics about the process of self-excited oscillation.The experiment research was also performed to validate the simulation and model result.The nonlinear parameters which influence the acoustic waveform distortion were analyzed.Based on the results, the shrinkage of nozzle for changing the acoustic impedance was applied to reduce nonlinear effects experimentally.The results show that the self-excited mode could be influenced by the position of appearance of higher harmonics.The distortion of pressure wave of Rijke Tube was induced by the acoustic losses of vortices on nozzle for large amplitude oscillation.The method that the shrinkage of nozzle could reduce the waveform distortion was confirmed.