Conceptual Aerodynamic Design of Pintle Nozzle for Variable-Thrust Propulsion

Comprehensive theoretical studies have been carried out for the geometry optimization of a pintle nozzle for variable-thrust propulsion. We designed the pintle such that, at the final pintle position, the integrated shape facilitates the scaled-down version of the shockless main nozzle. Numerical studies have been carried out using a validated two-dimensional transient, an implicit Reynolds-averaged Navier-Stokes equations (RANS) solver with a k-omega Menter's shear stress transport (SST) turbulence model. At the quasi-steady and dynamic conditions, the numerical results have shown excellent agreement with the theoretical results. In the dynamic condition, the effects of shock train, shock impinging, and the shock location on the overall thrust are studied, and we observed a monotonic increase in thrust during the pintle movement toward the exit and achieved the maximum thrust at the highest area ratio (nozzle exit area to throat area) position. The diminishing of the shock-strength pattern and the movement of the shock-impinging point towards the nozzle exit are captured in the numerical simulation and reported herein. We concluded that the prudent aerodynamic shape optimization of the external surface contour of the pintle and the inner surface contour of its associated nozzle ensures improved performance for the variable-thrust propulsion of aerospace vehicles.