超临界压力下航空煤油传热恶化的分析与预测

Analysis and prediction of heat transfer deterioration of aviation kerosene under supercritical pressures

对竖直上升圆管内超临界压力航空煤油的传热恶化进行了实验研究。考察了浮升力和热加速对换热的影响机制,通过判别准则的适用性分析,选取能较好描述传热恶化的因子组,修正得到了合理的临界值,从而获得了适用于航空煤油的判别准则。基于可控参数建立了传热恶化临界热通量预测公式。阐述了传热恶化引发热声流动不稳定的过程。通过浮升力因子和热加速因子修正建立了换热关联式。结果表明:浮升力因子Bu和热加速因子Ac分别高于1.57×10^(-5)和4.92×10^(-6)时,两者将削弱边界层内剪切力,引发传热恶化现象。拟沸腾也是传热恶化和热声流动不稳定的诱因。

Experimental study on heat transfer deterioration of aviation kerosene in a vertical upward circular tube at supercritical pressures was conducted.The influence mechanisms of buoyancy and thermal acceleration on heat transfer were investigated.Based on the applicability analysis of determination criteria,the factors team which can better reflect the heat transfer deterioration were selected,and the reasonable critical values were obtained,thus the determination criteria for aviation kerosene was proposed.The prediction formula of critical heat flux of heat transfer deterioration was established based on the controllable parameters.The process of thermo-acoustic flow instability owing to heat transfer deterioration was analyzed.The heat transfer correlation was developed by the amendments of buoyancy and thermal acceleration factors.Results indicate that when the buoyancy factor Bu and the thermal acceleration factor Ac are higher than1.57×10^5and4.92×10^6,respectively,the heat transfer deterioration appears due to the weakened shearing stress in the boundary layer.The quasi-boiling is also the reason for heat transfer deterioration and thermo-acoustic flow instability.