Advance on calculation methods of fluid-solid coupled heat transfer with regenerative cooling system

Regenerative cooling technology for engines is a critical thermal protection method for high-speed propulsion systems, such as liquid rocket and scramjet engines. By circulating liquid fuel through regenerative cooling channels to absorb heat from combustion chamber walls, it safeguards structural integrity against overheating and failure while enhancing thermal efficiency by utilizing the heated coolant in the combustion process. This technology serves as a foundational enabler for achieving high-Mach-number flight and deep-space exploration missions.

A systematic review was conducted on the computational methods and research progress in fluid-structure coupled heat transfer for regenerative cooling systems. The review focused on the calculation models and critical influencing factors for heat transfer between hot gas and solid walls, as well as heat transfer within coolant channels. Three fluid-structure coupled heat transfer calculation methods were proposed. For gas-wall heat transfer, engineering practices commonly used empirical correlations such as the Bartz method and Eckert reference-enthalpy method combined with 1D (one-dimensional) or CFD (computational fluid dynamics) simulations. While these engineering methods (e.g., Bartz and Eckert approaches) offered high computational efficiency, they struggled to capture the influence of local flow field characteristics on heat flux. CFD methods, though capable of improving accuracy, heavily relied on high-fidelity physical models and involved significant computational costs. For coolant channel and solid wall heat transfer, three types of models—1D, quasi-two-dimensional (quasi-2D), and 3D—were predominantly used. One-dimensional models simplified complexity but neglected temperature stratification and local flow effects, resulting in lower computational precision. Three-dimensional models provided higher accuracy but incurred substantial computational expenses. Researchers used 3D CFD methods to analyze the effects of factors such as corrugated tubes and ribbed channels on enhanced heat transfer in channels. Additionally, special factors such as coolant secondary flow, supercritical property variations, and fuel pyrolysis had to be considered. These phenomena required empirical correlation corrections or CFD modeling to capture their unique physical characteristics. Regarding fluid-structure coupling, three primary methods were identified: (1) Monolithic solution approach: This reduced interface coupling errors by unifying governing equations but required significant computational resources for complex problems, which were challenging to achieve in engineering practice at the time. (2) Partitioned approach based on empirical correlations: This leveraged empirical formulas to simplify calculations but required careful selection of correlations, as each had specific applicability ranges. (3) Partitioned approach based on continuity boundaries: This achieved precise coupling via temperature and heat flux continuity conditions but relied on high-fidelity flow simulations. For transient heat transfer analysis, current studies at the time often adopted decoupling strategies for phased simulations due to time-scale effects. Future research was suggested to prioritize the development of spatiotemporal coupling methods that balanced computational efficiency and precision, enabling more robust and adaptive thermal analysis in dynamic operating conditions. This work provided a comprehensive overview of current advancements and challenges in regenerative cooling system design, emphasizing the need for integrated approaches that combined empirical models with high-fidelity simulations to address complex multi-physics phenomena.

High-Mach scramjet engines have become a critical direction for the development of next-generation aerospace propulsion systems. To meet the demands for refined design of engine thermal protection systems, it is essential to further enhance the predictive accuracy of thermal protection systems. For this purpose, research efforts on simulating heat transfer processes in regenerative cooling systems should focus on three key areas: (1) high-fidelity modeling of complex physicochemical processes, (2) high-confidence simulation of fluid-structure coupled heat transfer, and (3) high-efficiency simulation of transient fluid-structure coupled heat transfer. These advancements are crucial to fulfilling the precision requirements for advanced thermal protection system design.