Cfd Analysis in Coaxial Injector of a Cryogenic Rocket Engine And Evaluation of Atomisation Characteristics Using Simulant Fluids

A Study of atomisation and mixing of 2-phase propellants using simulant fluids injected from a coaxial injector of an operating cryogenic rocket engine is carried out and presented along with the CFD analysis of flow within it. The original injector jet (Jet 3) designed, modeled and analysed has swirl for LOX (water) alone with GH2 (air) having no swirl. Injector jet having inner casing and outer sleeve is modeled using I-DEAS software and analysed for inner core fluid domain (liquid) and annular fluid (air) domain. Results of flow analysis inside jet revealed asymmetric nature of air flow at exit due to the air fluid domain itself is not axisymmetry in the original jet. This non-axisymmetry of 2-phase fluids at the exit of injector jet will obviously affect the characteristics of atomisation and mixing of fluids. Data obtained from atomization experiments done on this jet using stimulant fluids (water in LOX side and air in GH2 side) such as particle distribution and Sauter Mean Diameter (SMD), fairly matches with the predictions made using CFX software and associated codes which enabled to evaluate the analysis software. Further, the air flow at exit has been made axisymmetric by modifying the air passage in the injector jet (Jet 3 Mod) and the effect of this modification on atomisation and mixing of 2-phase fluids is predicted using the CFX software. In combustion better efficiency with less instability is to be attained. For meeting both simultaneously articles size distribution after injection has to be neither very finer nor coarse. Comparison of predicted data on atomisation revealed that the modified Jet (Jet 3 Mod) is relatively better to give stable combustion with higher performance.