Date of Publication :18th July 2017

Abstract: The shock formation in rocket engine nozzles have been a significant area of study for researchers. The oblique shock formation has an adverse effect on the efficiency of nozzles. Here a CFD analysis of three contour nozzles with change in divergence angle was conducted using ANSYS Fluent. Supersonic jets emanating from a chocked, axisymmetric nozzle at different pressure ratios are analyzed here. The variation of shock structure with change in divergence angle is studied. While varying the geometry the length and area ratio of nozzles was kept constant. Care was taken to keep the nozzle exit angle zero degree. No shock free condition was observed even at design Mach number of M=1.5. Simulation has been done on a clear conical nozzle of divergence angle of 2.950, contour nozzles of divergence angles 40 and 50 respectively. The increase in divergence has shown considerable effect in flow properties. The pressure variation along center line was low for high divergence angle. The better design among the three was analyzed by comparing the static pressure, Mach number and density variation along the center line. These flow parameters were compared for two different pressure ratios. The contour nozzle with divergence angle 50 was found to be the best among the three in design. The axial velocity at the exit was compared among them the nozzle with highest divergence angle had higher axial velocity at exit, so it was inferred that the thrust exerted on the walls was higher. By analyzing the flow characteristics the nozzle with high divergence angle showed improved results.

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