基于吸热型碳氢燃料的再生冷却技术是一种应用在超燃冲压发动机中的有效热防护手段。碳氢燃料作为冷却剂吸收了来自高温燃气的热量之后再被喷注进燃烧室中，在这期间其温度会升高至热力学临界温度以上并发生裂解。在冷却通道中，碳氢燃料呈现出了复杂的流动与传热特性，表现为显著的流动失稳和传热恶化等现象。同时，碳氢燃料的多组分构成、其物理性质在临界温度附近的急剧变化，以及冷却通道中的对流换热与冷却结构中的固体导热的相互耦合，都给碳氢燃料的主动冷却研究带来了重重困难。在现有的实验研究手段中，使用整台超燃冲压发动机的地面试验成本高、周期长、影响因素多，不利于独立开展碳氢燃料的主动冷却研究；使用电加热管的实验研究则不能全面反映出碳氢燃料在燃烧室壁面这样的平板冷却结构中的流动与传热特性，包括结构中的温度分布以及冷却通道之间的流量分配等问题。

本文设计并建造了一套用于碳氢燃料主动冷却研究的辐射加热实验系统。实验系统以通电石墨作为平面辐射热源，对内嵌冷却通道的平板结构施加均匀可控的单侧辐射热流，实现了在面积为1000 mm×40 mm的区域上可调节的、最大热流密度为1 MW/m²的、均匀程度在10%以内的加热条件；以柱塞泵作为碳氢燃料的供给设备，为平板冷却结构提供可调节的、最大质量流量为100 g/s的入口条件；以氮气作为背压调节手段，为平板冷却结构提供可调节的、最高压力为5 MPa的出口条件。在这套辐射加热实验系统中，由不同材料制成的、具备不同几何参数的平板冷却结构都能够在可控的边界条件下开展长时间的主动冷却研究，这对于了解碳氢燃料在实际的超燃冲压发动机中的流动和传热特性具有重要意义，同时也给相关的数值模拟研究提供了对照条件。

本文通过辐射加热实验系统观察到了超临界压力下碳氢燃料在临界温度附近的流动失稳现象，发现这样的失稳现象与两相流动中的Ledinegg失稳具有相似的发生机制，可以通过调节管路的流阻特性加以抑制，从而使得碳氢燃料的出口温度能够稳定保持在临界温度附近物性急剧变化的区域；发现碳氢燃料在高温时的结焦积碳作用会极大地改变冷却通道的流阻特性，继而显著改变碳氢燃料的流动状态；还观察到了碳氢燃料在平板冷却结构中的流量分配失稳现象。

Regenerative cooling with hydrocarbon fuels is used as an effective thermal-management solution in various high-speed vehicle engines, ranging from rocket, ramjet/scramjet to many other combined cycle applications. However, the flow and heat transfer characteristics of industrial hydrocarbon fuels, which always consist of many species, is quite complicated due to the rapid changes in fuel states and their thermo-physical properties. In near-thermodynamic-critical-pressure region, the heat transfer deterioration may be encountered together with the instability. Hence the effects of various factors such as heat flux, mass flux, pressure levels and channel geometry in such regions merits systematic investigation.

In this study, an experimental system was designed to simulate the heat exchange between the hot gas and the fuel-cooled wall in a scramjet combustor. Thermal radiation from an electrically-heated graphite plate is employed to unilaterally heat up a multi-channeled cooling plate. A maximum heat flux of 1 MW/m² was achieved for an effective heating area up to 1000 mm×40 mm. Precise control of the back pressure of coolant (up to 5 MPa) in a unique way was also demonstrated.

With the developed experimental system, studies of flow and heat transfer in hydrocarbon-cooled structures were performed. The Ledinegg instability of hydrocarbon fuels at supercritical pressures was observed near the critical-temperature region. By regulating the external characteristics of the flow system, the instability was restrained successfully. Besides, flow-rate distribution instability of hydrocarbon fuels was observed in the multi-channeled cooling plate.