Dynamic Characteristics of A Simplex Swirl Injector by the Pressure Fluctuation of Low Frequency Range

Generally, combustion instability is generated by the mutual coupling between the heat release and the acoustic pressure in the combustor. On the occasion, the acoustic pressure generates the oscillation of the mass flow rate of propellant injected fromatomizers, and this oscillation again affects the combustion in the combustor. So, the dynamic characteristics of the injector have been studied to control the combustion instability using an injector itself in Russia from 1970's. In order to study the injector dynamics, a mechanical pulsator for the forced pressure oscillation was produced and the method to quantify the mass flow rate of the propellant that is oscillating at the exit of the injector was developed. With the pulsator and the method, pulsating values of the mass flow rate, pressure, liquid film thickness, and axial velocity generated at the exit of the simplex swirl injector were measured in low frequency range of the fluctuated pressure in real time. And dynamic characteristics of each parameter were analyzed using these pulsating values acquired at the exit of the simplex swirl injector. From these results, it can be understood that the dynamic characteristics which mean the relative differences of the phase and the amplitude between the input and the output of the simplex swirl injector are changed.