Computational Characterization of a CD Nozzle with Variable Geometry Translating Throat

Nozzles constitute the exhaust system of jet engines. They are designed to regulate the flow properties to provide the required thrust force for all flight conditions. In the present work, the simulation of a de Laval nozzle outfitted with a throat shifting mechanism is compassed. The mechanism adds a variation in the throat geometry during the translation of the throat. A convergent–divergent (CD) nozzle is designed for Mach 2 initially. The geometry of the throat is varied by keeping the settling chamber pressure constant. The scope of the effort was to investigate the characteristics over the range of geometries (throat diameters, 10, 9.5, 9, and 8.5 mm) and operating conditions. The simulation of the nozzle flow is carried out using ANSYS CFX. Shear stress transport (SST) turbulence is used for the flow simulation. Grid-independent study is also performed for better mesh results. The simulation is carried out for chamber pressures of 8, 9.5, 11.5, and 14 bar. The Mach number, pressure, velocity, and temperature readings are taken along the nozzle axis and also the important cross sections of the nozzle for all cases. Thrust is calculated for all the cases and compared. Plot comparison of variations in the parameters was done, and optimum results were inferred.