A coherent jet oxygen supply plays a key role in the process of electric arc furnace steelmaking: it provides the necessary oxygen for the smelting of molten steel and promotes the flow of the molten pool. Compared with coherent jets in current use, the supersonic combustion coherent jet shrouded in supersonic methane gas could improve the impact capacity and stirring intensity of the molten pool. In order to reduce the smelting cost, the characteristics of the supersonic combustion coherent jet shrouding the supersonic methane and nitrogen mixtures must be studied. Computational fluid dynamics software is used to simulate the supersonic combustion coherent jet under various methane–nitrogen mixing conditions. The six-component combustion mechanism of methane and the Eddy Dissipation Concept combustion reaction model are selected. In agreement with thermal experiments, the simulation results show that the inclusion of a small amount of nitrogen has little effect on the combustion of supersonic shrouding methane gas. However, as the nitrogen content increases, the combustion region of supersonic shrouding gas becomes shorter in length, resulting in decreases in the lengths of the high-temperature, low-density region, and the high-turbulence-intensity region. These effects weaken the ability of the shrouding gas to envelop the main oxygen jet. The potential core length of the main oxygen jet decreases significantly; this decrease first accelerates and then decelerates. These results demonstrate the feasibility of including a small amount of nitrogen (about 10 wt%) in the supersonic shrouding methane gas without substantial negative impacts on the characteristics of the supersonic combustion coherent jet.

The satellite–rocket separation shock environment involves transient structural responses during spacecraft release. Although its direct influence on the main structure of the satellite is limited, it can easily cause shock-sensitive precision instruments or components to fail. Nowadays, the shock response spectrum (SRS) experiment is conducted to simulate the dynamic load environment of spacecraft. There are lots of studies on the spectral pattern of SRS. Most of the existing studies focus on the qualitative effects of the shock parameters on SRS; however, quantitative relationships between key shock parameters and SRS characteristics remain relatively limited. In this study, the air cannon-based shock experiment and numerical simulation based on ANSYS/LS-DYNA 2022R1 software are conducted to investigate the influence of shock parameters on SRS. The SRS curves are fitted to quantitatively characterize their spectral features. Massive experimental and simulation datasets are systematically processed to establish the relationship between SRSs and three key shock parameters: felt thickness, bullet length, and air source pressure. A quantitative relationship based on random forest is established to map the shock parameters to the characteristics of the SRS curves. SRS curves can be calculated based on this relationship, enhancing the efficiency of SRS calculation and reducing the need for repeated SRS experiments and simulations.