碳氢燃料热声不稳定流动特性和边界实验分析

Experimental Analysis on Characteristic and Boundary ofThermo-Acoustic Flow Instability in Hydrocarbon Fuel

关键词:  超临界压力  航空燃料  热声不稳定  特性  边界

Key words:  Supercritical pressure  Aviation fuel  Thermo-acoustic instability  Characteristic  Boundary

摘要:

为保障空-油换热器安全稳定运行，对竖直上升圆管内超临界压力航空燃料的热声不稳定流动进行了实验研究。阐述了管壁温度的振荡特征和热声不稳定流动的诱发原因。考察了运行参数对流动稳定工况和流动不稳定工况界限的影响。取相邻流动稳定工况和流动不稳定工况的热流密度平均值作为边界，分析了该边界随进口拟过冷度的变化情况。通过临界拟相变数和拟过冷度数的比值表征，建立了热声不稳定流动边界与进口雷诺数和相对压力关联的预测准则。结果表明：拟沸腾效应导致了热声不稳定流动现象。进口温度和运行压力越低，热声不稳定流动越容易出现。提出的边界预测准则具有较高的精度，与实验结果的相对偏差在±15%以内。

Abstract:

In order to ensure the safe and stable operation of air-fuel heat exchanger, an experimental study on the thermo-acoustic flow instability of supercritical pressure aviation fuel in a vertical upward circular tube was conducted. The oscillation characteristic of wall temperature and the induced cause of thermo-acoustic flow instability were expounded. The effects of operating parameters on the border between flow stability conditions and flow instability conditions were described. Taking the averaged heat flux in the adjacent flow stability condition and flow instability condition as the boundary, variation of this boundary with the inlet pseudo-cooling degree was analyzed. The prediction criteria of thermo-acoustic flow instability boundary were established based on the ratio of critical pseudo-cooling number and pseudo-phase number which is related to the inlet Reynolds number and reduced pressure. Results show that the pseudo-boiling effect leads to the thermo-acoustic flow instability phenomenon. The lower the inlet fluid temperature and operating pressure, the more likely the thermo-acoustic flow instability will occur. The criteria for boundary prediction has a higher precision, the relative error with the experimental results is within ±15%.