Bi-swirl coaxial injectors were designed and manufactured for 420 N class moon exploration thruster. The injector design was based on the injector design requirements obtained from the reverse thrust design for the performance of the Astrium’s S400-12 model. The spray characteristics of the injector must be understood as it affects not only the combustion efficiency but also the overall efficiency of the system. In this study, the research on the spray characteristics of the closed-type, open-type and screw-type bi-swirl coaxial injectors by mass flow rate.
The pressure drop increased with increasing mass flow rate. and there was no difference between single-injection and bi-injection. In the case of the discharge coefficient, it was not influenced by the mass flow rate change and was greatly influenced by the geometry of the injector. In the case of spray angle, the inner spray angle increased and the outer spray angle decreased in the bi-injection. The breakup length decreased with increasing the mass flow rate, and the empirical equation was presented by confirming that it was influenced not only by the operating conditions but also by the geometry of the injector.
Thrust throttling experiments were performed on three bi-swirl coaxial injectors using gas injection method. Experiments were carried out by adjusting the GLR(Gas Liquid mass Ratio) and thrust ratio. The gas and liquid form a mixture through the aerator. In order to investigate the spray characteristics of the mixture, three different two phase flow model were compared and a suitable model was selected for this study.
The pressure drop increased with increasing GLR. The density of the mixture decreased as the gas was injected. It was also found that the discharge coefficient was influenced only by the geometry of the injector without being influenced by the GLR. In the case of spray angle, as the GLR increased, the spray angle was changed. The change of spray angle was studied using calculated spray pattern. The breakup length tended to decrease as the film thickness decreased and the axial velocity increased with increasing GLR.