Austenitic stainless steel(ASS)is a common material used in high-pressure hydrogen systems.Prolonged exposure to high-pressure hydrogen can cause hydrogen embrittlement(HE),raising significant safety concerns.Selective Laser Melting(SLM),known for its high precision,is a promising additive manufactur-ing technology that has been widely adopted across various industries.Studies have reported that under certain SLM manufacturing conditions and process parameters,the HE resistance of SLM ASS is signifi-cantly better than that of conventionally manufactured(CM)ASS,showing great potential for application in high-pressure hydrogen systems.Thus,studying the HE of SLM ASS is crucial for further improving the safety of high-pressure hydrogen systems.This paper provides an overview of the SLM process,reviews the mechanisms of HE and their synergistic effects,and analyzes the HE characteristics of SLM ASS.Addi-tionally,it examines the influence of unique microstructures and SLM process variables on HE of SLM ASS and offers recommendations for future research to enhance the safety of high-pressure hydrogen systems.
Rotating detonation engine is known as a new concept engine which has the property of self-pressurization and continuous thrust supply. It has already shown ambitious potential for applications in the aviation and aerospace field. As the injection structure is the foundation for researchers to design the engine, the evolution process of the flow distribution under different injection schemes has been studied in this article. A model with dual-side injection in an annular combustion chamber has been adopted, and by solving the three-dimensional Reynolds-averaged Navier-Stokes equations, a series of works have been conducted aiming on transformation in nozzle diameter and swirling injection angle. The results indicate that the addition of nozzle diameter is beneficial for enhancing the momentum of the fuel jet flow, increasing the radial penetration depth and promoting the diffusion as well as the mixing of propellant components. It is also suggested that the increments of swirl injection angle leads to the decrease in fuel jet momentum, causing significant deflection of flow in the radial direction and reducing mixing efficiency. It proves difficult for the fuel jet with low injection momentum to mix adequately with the oxidizer mainstream, severely affected by main flow impacts and finally distributed along the inner and outer wall, forming a low banding concentration zone in the center area of combustion and non-uniform distribution.
The liquid propulsion system of Mars Ascent Vehicle (MAV) provides orbital control thrust, as well as attitude control forces and torque, which is crucial for ensuring the MAV’s payload capacity, precise orbital insertion, and reduced energy requirements. The system needs to undergoe complex mission profiles, including Earth-to-Mars transfer, Mars orbital insertions, Mars EDL (Entry, Descent, and Landing) flight, and storage on the Martian surface before being operational. In this paper, the strict constraints on structural mass, envelope size, and available energy faced by the MAV’s liquid propulsion system were addressed. Key technologies required for lightweight, miniaturization, and high-precision orbit insertion, such as thrust, specific impulse, environmental adaptability and reliability, were systematically reviewed. A design solution incorporating low-freezing-point propellants, medium-chamber-pressure engines, surface tension common-bottom tanks, and a highly reliable, highly integrated system was proposed. The results provide an important reference for the formulation of Mars ascent vehicle’s design scheme.
After over 60 years of development, the space propulsion field in China has made tremendous progress in terms of technology system and product pedigree, and has supported major engineering applications including manned spaceflight, applied satellites, and deep space exploration. However, considering the requirements of future major aerospace missions in China, the technical level of current space propulsion systems is still insufficient, and it is urgent to plan directions for the innovative development and breakthroughs of the field. This study reviews the development status of the space propulsion systems from the aspects of electric, chemical, nuclear, and new-concept space propulsion, and analyzes the requirements of future applications. Specifically, high-performance, low-cost space propulsion systems are required to support the networking of low-Earth-orbit (LEO) small satellites; high-thrust, reusable low-temperature chemical propulsion technologies are required for new space-transportation systems; and multi-type, long-life space propulsion technologies are required for deep-space applications. The results demonstrate that the space propulsion field in China still faces multiple challenges. First, the system reliability and lifespan require further improvement. Second, the space propulsion systems of China still lag behind the advanced international level in terms of product maturity of some technologies. Third, this field typically has a high product cost. Fourth, there are few types of optional technologies, and the research progress of key technologies is lagging. Therefore, we propose the following suggestions: (1) optimizing technology options through top-level planning, (2) improving the development mechanism of the field by emphasizing basic research, and (3) clarifying and promoting scientific research and development in key technological directions, thereby achieving in-orbit applications of the propulsion systems for LEO small satellites, Earth–Moon space transfer, and deep space exploration (including manned spaceflight).
