随着运载器和航天器向着重型化、重复使用和长期在轨方向发展。液体推进剂的使用规模必将成倍增长，这要求液体推进剂增压系统携带更多增压气体的同时自身结构质量要小，且安全可靠。超临界氦增压技术可以满足上述要求，有效提高航天器有效载荷。目前，只有欧美掌握该技术。该技术的实现，最关键的是氦要在球腔内中通过换热吸收适当热量维持超临界态。因此，掌握腔内自然对流换热特性，控制系统换热热量，维持稳定超临界压力，是临界增压技术实现的重要前提。申请者拟从理论和实验两方面入手，在国内率先开展4.2K-77K温区下球腔内超临界氦自然对流换热特性研究。通过数值模拟和实验研究，探索超临界氦在低温下流固耦合换热、温度压力耦合变化规律，提出低温球腔内换热实验关联式。在此基础上，制定合理热量输入策略，对超临界氦压力变化进行有效的预测和控制。本研究可以为我国尽早突破超临界氦增压技术打下坚实基础，具有重要的学术意义和工程应用价值。

As launch vehicle and spacecraft develop toward direction of heavy-duty, re-use and long-term on-orbit, the use of liquid propellants will increase exponentially. This requires a more reliable and safe liquid propellant pressurization system, which can carry a larger amount of pressurized gas while its own structural quality is small.Supercritical helium pressurization technology can meet the above requirements and effectively improve spacecraft payload. Currently, only Europe and the United States master the technology. The most important thing in the realization of this technology is to keep helium in the state of cryogenic supercritical by absorbing appropriate heat in a spherical cavity. In-depth study of the characteristics of natural convective heat transfer in the spherical cavity and effective control of heat input is an important prerequisite for the realization of cryogenic supercritical helium pressurization technology. The applicant intends to take the lead to study the thermodynamic characteristics of the natural convection heat transfer process of cryogenic supercritical helium in the spherical cavity at 4.2K-77K temperature zone from both theoretical and experimental aspects. Through numerical simulation and experimental research, the law of fluid-solid coupling heat transfer, temperature-pressure coupling change and cryogenic heat transfer experimental correlation in spherical cavity is proposed. On this basis, a reasonable heat input strategy is established to effectively predict and control the supercritical helium pressure change. The research of this project can lay a solid foundation for China to break through the cryogenic supercritical helium pressurization technology as soon as possible, and it has important academic research significance and engineering application value.