Numerical simulation of passive control to self-excited thermoacoustic instabilities in a rijke tube

Thermoacoustic instabilities can be triggered at a certain condition in a Rijke tube type of combustor. To suppress it, the present work considers a passive control element for the system, placing a second heat element at the opposite side of the original one. In order to gain insight on the damping mechanism and evaluate the second heat element effecting on the combustion instabilities, a two dimensional numerical study has been conducted in time domain. The simulation is modelled by using finite volume method to solve the unsteady Navier-Stokes equations. It is found from the results that the passive control element can affect the ther- moaoustic instabilities significantly. With the control element, the pressure oscillation used to characterize the instabilities cannot keep steady in the original limit cycle and obviously decays to another a smaller one. The frequency of oscillation is also changed, which means the initial thermoacoustic instability system is decrease to a new one with smaller oscillations. Further study indicates that the input of second heating element's temperature determines the outcome of thermoacoustic instabilities decaying. The successful application of second heat element in a Rijke tube provides new possibilities for the passive control of thermoacoustic instabilities to reduce or remove the oscillations.