丙二醇改性水溶液的发汗冷却实验研究

针对液态水相变发汗冷却实验中的振荡、表面温度分布不均及结冰现象,对液体冷却剂进行调研,选取丙二醇添加剂对液态水改性,在主流温度573K,雷诺数1.2×10⁴的亚声速高温风洞中实验研究了不同丙二醇改性水溶液浓度和注入率下多孔平板的相变发汗冷却特性。结果表明：随丙二醇浓度增大,多孔平板对改性水溶液的渗透率增大,多孔平板表面温度的振荡幅度减小,同时振荡周期内温度波峰降低。因此,使用丙二醇改性水溶液作为冷却剂,发汗冷却结构表面温度分布更加均匀,热疲劳损伤减小,承温极限升高,进而烧蚀风险降低,这对有效且高效的热防护系统设计具有重要意义。另外,注入率越大平板表面冷却效果越好,表面温度的振荡幅度越小,因此增大注入率也是改善多孔板表面温度波动的有效方式。

Experimental Investigation of Transpiration Cooling Using Modified Propylene Glycol Aqueous Solution

In this work, liquid water was modified by adding propylene glycol(PG) to solve the oscillation, uneven surface temperature distribution and freezing phenomena observed in experiments of transpiration cooling with liquid water. In a subsonic high temperature wind tunnel with mainstream temperature of 573K and Reynolds number of 1.2 x 10_⁴, the transpiration cooling performance of porous plate was studied experimentally under the influence of different concentration and injection rate of aqueous solution modified by PG. The results indicate that with the increase of PG concentration, the permeability of the porous plate with the modified water solution penetrating through increases, the oscillation amplitude of the surface temperature of the porous plate reduces, and the temperature peak during the oscillation period decreases at the same time. Therefore, using water solution modified by PG as coolant, the surface temperature distribution of transpiration cooling structure is more uniform, and the thermal fatigue damage is reduced. It can also increase the temperature limit and reduces the ablation risk, which is of great significance for effective and efficient thermal protection system design. In addition, the larger the injection rate, the better the cooling effect of the plate surface and the smaller the oscillation amplitude of the surface temperature. Hence, increasing the injection rate is also an effective way to improve the surface temperature fluctuation of the porous plate.