Combined effects of inlet airflow temperature and upper expansion angle on the performance of scramjet nozzle

Abstract

Purpose The purpose of this paper is to study the combined effects of inlet airflow temperature and the expansion angle of the upper expansion surface (upper expansion angle) on the performance of the scramjet nozzle. Design/methodology/approach The Spalart-Allmaras turbulence two-dimensional model of the nozzle is established for the study. The influence of inlet airflow temperature on the performance of the nozzle is analyzed by detecting the change of the wall pressure of the nozzle. The three angles are chosen for the upper expansion angle (βb) in the model: 8°, 12° and 16°. The temperature of inlet airflow is 600–1,800 K. Findings The study results show that when the βb is 8° and 16°, the wall pressure of the nozzle has a complicated and large fluctuation with the inlet airflow temperature, while the wall pressure has little change as βb is 12°; the thrust coefficient, pitching moment coefficient and lift coefficient of the nozzle fluctuate greatly with the increase of the inlet airflow temperature when βb is 8° and 16°, while the thrust coefficient, pitching moment coefficient and lift coefficient have little fluctuation as βb is 12°. Originality/value The study of the combined effects of the inlet airflow temperature and upper expansion angle on the performance of the scramjet nozzle can provide guidance for the design of scramjet nozzles.