Numerical Investigation on the Factors Influencing Local Supersonic Ring in the Micronozzle

Due to significant dimensional differences between micronozzles and normal nozzles, their flow field structures also exhibit notable distinctions. Under specific Nozzle Pressure Ratio (NPR), the micronozzle exhibit unique phenomena of supersonic ring, yet factors influencing their morphology remain insufficiently explored. Hence, this paper conducts a numerical investigation on the phenomenon of local supersonic ring in the micronozzle from three perspectives: species of working gas, total temperature, and expansion half-angle of micronozzles. Drawing upon theories of the shock wave and the boundary layer, the study elucidates the reasons behind the morphological variations through streamline plots, schlieren images, pressure, Mach number. The following conclusions are drawn: the species of working gas mainly affects the flow field Reynolds number, altering the dominant role of inertial and viscous forces and thus impacting the morphology of supersonic ring; total temperature primarily affects shock wave parameters by influencing the viscosity of the working gas, thereby exerting an influence; the expansion half-angle of micronozzles mainly affects the wave system inside the micronozzle by boundary layer separation, thereby influencing it. This exploration of factors affecting the unique phenomenon of supersonic ring in micronozzles can provide better engineering guidance for the design and operating environment of micronozzles.