Dynamic Characteristics of Simplex Swirl Injector in Low Frequency Range

Abstract

Combustion instability is generally generated by mutual coupling between heat release and acoustic pressure in the combustor. Acoustic pressure causes the mass flow rate of propellant injected from atomizers to oscillate, which affects the combustion process. Since the early 1970s, great efforts have been made in Russia to elucidate the underlying mechanisms of the injector’s dynamic characteristics to better manage combustion instability. In the current work, to characterize the injector dynamics, a mechanical pulsator was developed to produce forced pressure oscillation. An analytical method was also developed to quantify the mass flow rate of the propellant oscillating at the injector exit. The pulsating values of the mass flow rate, pressure, liquid film thickness, and axial velocity generated at the simplex swirl injector exit were all measured and quantified in real time in a low frequency range of the fluctuating pressure. Furthermore, the dynamic characteristics of each parameter were analyzed using these pulsating values. Because of themeasured time and position differences between themanifold and the orifice of the swirl injector, phase and amplitude differences were identified and further characterized between the input and output values.