Estimation of Flow Field Properties and Thrust Performances of Axisymmetric Plug - Nozzles using CFD Simulations

Abstract

The objective of the presented work is to investigate the slipstream effects on the flow properties and thrust performances of a full-length and truncated annular plug nozzle of a small rocket launcher during a suborbital flight. The nozzle flow properties are investigated for three characteristics flow conditions (M∞ = 1.3, 2.59 and 9.7), using CFD simulations. When the rocket launcher flies through the atmosphere, the body geometry produces a slipstream with conditions in the nozzle area that are different from the undisturbed environment. The in-flight behavior of the truncated plug nozzles is complicated and affected also by recirculation regions that take place behind the shroud and plug base. In this paper special emphasis is given to investigate the slipstream effects between the hot exhaust plume from the rocket engine and the external coaxial supersonic/hypersonic air flow and their influence on the slope and position of different shocks generated in the separated flow region (realignment shocks, recompression shocks, plug base lip shock and trailing shocks). Also analyzed is the pressure distribution on the shroud base, spike supersonic ramp and spike base for closed-wake operations to determine the overall engine performance. The results of the numerical simulations confirm the altitude-compensating features of the annular truncated plug nozzles.