Optimization of ejector design using CFD analysis

The satellite launch vehicle, GSLV has a cryogenic upper stage, which uses the cryogenic engine. In order to test and qualify the upper stage engine, used in a high-altitude Test Facility is used. The HAT facility is configured with a vacuum chamber, a second throat diffuser, a gas cooler, and an ejector and the diffuser system. Each subsystem has to be analyzed numerically and optimized for its better performance. This report deals with the Ejector system. In the first step, the basic dimensions of the ejector are derived from the one-dimensional gas dynamic equation. This report describes the performance of Ejector (designed by ID), the need for optimization, optimization of the Ejector system using CFD. A 2 – dimensional axis-symmetric geometry with nozzle and mixer system is considered for the analysis. A two – dimensional structured mesh, standard k-e modeling for turbulence and species transport (not reacting) equations for species transport is considered for the analysis. The effect of varying the Nozzle exit diameter was studied to optimize the ejector for both no-load and full load conditions using CFD fluent software. It is found that the suction pressure at no load and full load for area ratio 4.6 is the lowest and it is matching with the one-dimensional value as per the design document of Cryo- rocket engine HAT facility Based on the result the optional area of 4.6 is arrived for the desired no load and full load pressure. The tangential shear mixing of passive and active fluid is achieved as the area ratio 4.6. It is found that the suction pressure at No load and full load for the distance of 925 mm and it is matching with the one-dimensional value as per the design document of the Cryo-rocket engine HAT facility. In general, no-load pressure parallel the small spacing from mixture throat at the minimum and full load pressure parallel be higher. Based on the above result the spacing of 925 mm is suitable for the no-load and full load pressure requirement. It is found that the suction pressure at No load and Full Load for pressure 25 bar is the lowest and it is matching with the one-dimensional value as per the design document of Cryo-rocket engine HAT facility. The ejector mixer throat is designed for the chocking condition of the desired flow rate. Based on the above, the optimum of the GN2 supply rate of 60 kg/s is best suitable for the desired no load and full load condition.