超临界压力航空煤油热声振荡与传热恶化实验研究

Experimental Studies on Thermoacoustic Oscillation and Heat Transfer Deterioration of Aviation Kerosene

关键词:  超临界压力  航空煤油  热声振荡  传热恶化  实验研究

Key words:  Supercritical pressure  Aviation kerosene  Thermoacoustic oscillation  Heat transfer deterioration  Experimental study

摘要:

为了深入理解超燃冲压发动机再生冷却系统中碳氢燃料的流动传热规律，对竖直上升圆管内RP-3航空煤油的超临界对流换热做了实验研究。详细探讨了质量流速、热流密度、压力等对管壁温度和换热系数分布的影响，并拟合得到了过渡区和湍流区的对流换热经验关系式。结果表明:近临界和较高压力下的换热呈现出迥异的特征。在近临界压力过渡区的高进口过冷度工况，近壁流体密度和黏度的综合作用引起了热声振荡现象，使换热显著增强；而主流温度处于拟临界温度附近时却出现了由近壁流体体积急剧膨胀导致的传热恶化现象。在高压力下，过渡区热声振荡和湍流区传热恶化都不会出现，但低质量流速时强浮升力使过渡区进口段出现了严重的壁温飞升现象。新关系式具有良好的适用性，预测值与实验值的相对误差在20%以内。

Abstract:

In order to get a deeper understanding of the flow and heat transfer characteristics of hydrocarbon fuels in the regenerative cooling system of scramjet engines，an experimental study on supercritical convective heat transfer of RP-3 aviation kerosene in vertical upward circular tubes was investigated. Effects of mass flux，heat flux and pressure on the distribution of wall temperature and heat transfer coefficient were discussed in detail，and two convective heat transfer empirical corrections applicable to the transition and turbulent-flow regions were also respectively developed. Results indicate that quite different features are exhibited under near-critical and relatively high pressure. Under the high inlet subcooling conditions with near-critical pressure，the combined effects of density and viscosity near the wall cause the thermoacoustic oscillation phenomenon in the transition region，so that the heat transfer is significantly enhanced. By contrast，a heat transfer deterioration phenomenon appears due to the rapid volume expansion of near-wall fluid when the bulk fluid temperature is near the pseudo-critical temperature. Both of the thermoacoustic oscillation in the transition region and heat transfer deterioration in the turbulent-flow region would not occur under relatively high pressure. However，at low mass fluxes，a serious wall temperature soaring phenomenon occurs in the inlet section of the transition region because of the strong buoyancy force. The two new corrections have good applicability，and the relative errors between the predicted values and experimental results are generally within 20%.