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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.

In this paper, the study focuses on influential factors of the vibration modal of the equipment bay of a carrier rocket and the structural improvement of the equipment bay by using finite element modal analysis. The finite element analysis focuses on the influences of the mass of the inertial bracket, the thickness of parts of the inertial bracket, and the stringer thickness on the first modal frequency of the equipment bay. As the analytical results show, the vibration displacement of mounting panels can be greatly reduced when the equipment bay is added with mass, and the vibration of the equipment bay with mass mainly occurs on the inertial bracket (without mass, the maximum vibration displacement occurs on the mounting panel); the top surface thickness of the inertial bracket has the maximum influence on the first modal frequency of the equipment bay, the stringer thickness and the side thickness of the inertial bracket have relatively high influence on the first modal frequency, the rib thickness of the inertial bracket has relatively low influence on the first modal frequency, and the beam thickness of the inertial bracket has the minimum influence on the first modal frequency.