低温流体流动沸腾失稳预测模型

Prediction Model for the Flow Boiling Instability of Cryogenic Fluids

针对液氮等低温流体在通道内的沸腾两相流动失稳问题,建立了典型液氮沸腾流动失稳的动力学模型,基于非线性稳定性理论,对液氮沸腾流动稳定性进行分析,获得了流动失稳判据。基于失稳判据并结合液氮沸腾的流动特性分析,提出了以无量纲参数表示的流动失稳预测模型。将模型预测结果与文献实验数据对比,在17个工况中,模型成功预测了15个工况的流动稳定性,准确率达88.2%。流动失稳的理论分析结果与实验吻合良好,能够用于液氮沸腾失稳的预测。模型分析结果显示:在液氮的沸腾失稳过程中,加速压降作用非常显著;相同长径比的通道,失稳边界基本重合;提高流体饱和压强有助于抑制流动失稳。

A dynamic model for the flow boiling instability of liquid nitrogen is established to investigate the flow boiling instability of cryogenic fluids in channels.Based on the nonlinear stability theory,the flow boiling stability of liquid nitrogen is analyzed,and the flow instability criterion is obtained.According to the instability criterion and the flow boiling characteristics of liquid nitrogen,a new model consisting of dimensionless parameters is established to predict the occurrence of unstable flow.Compared with the experimental data reported in the literature,the proposed model successfully predicts the flow stability of 15 out of 17 experimental cases.Obviously,the presided results by the established model agree well with the experimental data with an accuracy of 88.2%,indicating that the model can be used to predict the boiling instability of liquid nitrogen.The analysis results reveal that,the acceleration pressure drop plays an importance role during the boiling instability of liquid nitrogen.For channels with the same length-diameter ratio,the stable/unstable flow boundaries almost coincide.Besides,increasing the saturation pressure can help suppress the flow instability.