超临界压力下航空煤油传热恶化判别准则

Criterion for Heat Transfer Deterioration of Aviation Kerosene under Supercritical Pressures

关键词:  超临界压力  航空煤油  传热恶化  浮升力  热加速  判别准则

Key words:  Supercritical pressure  Aviation kerosene  Heat transfer deterioration  Buoyancy  Thermal acceleration  Criterion

摘要:

为防止航空发动机热防护中的传热恶化现象，对竖直上升圆管内超临界压力RP-3航空煤油的换热开展了实验研究。着重考察了热流密度、进口压力、进口温度等运行参数对传热恶化的影响。探究了传热恶化特性，获得了传热恶化起始条件判别准则。进一步分析了浮升力和热加速对传热恶化的影响，建立了适用于航空煤油新的浮升力和热加速判别准则，以及考虑两者影响的换热关联式。结果表明：航空煤油传热恶化出现在Nu/Nu₀<0.5的条件下。以此作为依据，当浮升力因子Bu>1.6×10^-6或热加速因子Ac>3.3×10^-6时，引发传热恶化现象。换热关联式兼顾了浮升力和热加速影响，具有较高的预测精度。

Abstract:

In order to prevent the heat transfer deterioration phenomenon in thermal protection of aero engine, an experimental investigation on heat transfer of RP-3 aviation kerosene in a vertical upward circular tube under supercritical pressures was conducted.Effects of the operating parameters, including the heat flux, inlet pressure and inlet temperature, on heat transfer deterioration were studied. The characteristics of heat transfer deterioration were explored, and the criterion for initial condition of heat transfer deterioration was obtained. Furthermore, the effects of buoyancy and thermal acceleration on heat transfer deterioration were analyzed. The new determination criterions for buoyancy and thermal acceleration applied to aviation kerosene were established, the heat transfer correlation considering the effects of both was developed. Results indicate that the heat transfer deterioration of aviation kerosene occurs in the condition of Nu/Nu₀<0.5, based on which, it is found that the heat transfer deterioration phenomenon appears when the buoyancy factor Bu>1.6×10^-6 or the thermal acceleration factor Ac>3.3×10^-6. The heat transfer correlation takes into account the effects of buoyancy and thermal acceleration, and has high prediction accuracy.