Theoretical Investigation of the Dynamics of a Gas-Liquid Coaxial Swirl Injector

In this paper, a linear dynamic characteristics model of a gas liquid coaxial swirl injector is developed by dividing the injector into two parts: the recessed chamber and the section before the recessed chamber. The gaseous injector flow before the recessed chamber is considered to be steady; only the response of the mass flow rate at the exit of coaxial injector to the pressure fluctuation at the liquid injector inlet has been investigated. The dynamic characteristics of the coaxial swirl injector can now be considered as two processes: the dynamics of the liquid swirl injector and the dynamics of the recessed chamber. The transfer function of the whole injector is obtained by combining the transfer functions of these two processes. The influence of the injector configuration and working condition on the injector dynamic characteristics was also studied. A smaller mixing ratio, larger mass flow rate, higher ambient pressure, smaller ratio of recess length to diameter, and larger geometry parameter would decrease the amplitude response of the mass flow rate pulsation, but these parameters have little effect on the phase frequency of the coaxial swirl injector.