DOI: 10.21276/sjet.2016.4.9.5

Pages: 412-417

A numerical analysis is carried out to determine the flowfield and starting characteristics of a straight cylindrical supersonic exhaust diffuser of a high-altitude simulation of a high expansion ratio rocket nozzle. The flow field inside the high-altitude facility is analyzed for a conical nozzle of expansion ratio of 25, diffuser inlet-to-nozzle throat area ratio of 28.9, and diffuser length-to-diameter ratio of 11.7. The variations of enthalpy with entropy are shown for the conical nozzle and the straight cylindrical supersonic exhaust diffuser in order to understand the thermodynamic behavior of the flow field. The evacuation performance of supersonic exhaust diffuser under steady operation and associated flow behaviors during the starting of the diffuser are analyzed with help of the Mach contour plots. The starting and break down conditions are achieved when at exit pressure of the nozzle is approximately equal to vacuum chamber pressure. The present numerically simulation delineates complex flowfield inside the diffuser very close to the starting condition.