Theoretical Study on Dynamic Characteristics of Liquid-Liquid Coaxial Swirl Injector

In order to study the dynamic characteristics of liquid-liquid coaxial swirl injector，the transfer functions of the inner and outer injectors of the coaxial injector were established by theoretical method. The transfer function of the inner injector refers to Bazarov’s injector dynamics theory. Based on the unsteady Bernoulli equation，the transfer function of the outer injector is derived by analyzing the relationship between the change in different velocity components of the liquid in the injector when the pressure drop oscillates. By combining the independent transfer functions of the inner and the outer injectors，the amplitude-frequency characteristics of the oscillations of the total flow rate and the oxygen-fuel ratio of the coaxial injector were obtained. The calculation results of a specific coaxial injector show that there appears sensitive frequency point within the calculated frequency range of the inner injector. The phase difference of flow oscillation between inner and outer injectors is large at high frequency when the pressure drop oscillations of them is synchronous. By only changing the number of tangential holes of the inner injector or the outer injector，the dynamic characteristics of the whole coaxial injector with oxygen to fuel ratio of 1.65，fuel-rich and oxygen-rich were analyzed. New sensitive frequency points were found in the calculation results of the three kinds of coaxial injectors. © 2022 Journal of Propulsion Technology. All rights reserved.