A visualized study of interfacial behavior of air–water two-phase flow in a rectangular Venturi channel

A visualized investigation was carried out on the effect of the diverging angle on the bubble motion and interfacial behavior in a Venturi-type bubble generator.It was found two or three large vortexes formed in the diverging section,resulting in strong reentrant jet flow in the front of the bubbles or slugs rushing out of the throat.The jet flow in return bumps into the ongoing bubbles or slugs,leading to strong interaction between the gas and liquid phases.The diverging angle has significant influence on the reentrant flow process and the performance of the bubble generator as well.Increasing the diverging angle results in the reentrant flow moving further forward to the upstream and intensifies the interaction between the two phases.As a consequence,the breakup or collapse of bubbles becomes more violent,whereby finer bubbles are generated.As such,the reentrant flow strongly links to the performance of the Venturi channel taken as a bubble generator,and that a moderate increase in the diverging angle can improve its performance without additional increase in flow resistance like that by increasing liquid flow rate.

平行通道管间脉动试验过程中系统不稳定现象分析

在平行通道管间脉动试验过程中,系统出现了同频率等幅同相脉动和水锤现象。本文对此进行分析讨论的结果表明,回路系统中混凝器的存在容易引起系统的流动不稳定。用文丘里管流量计测量脉动流量除了应考虑测量系统的动态测量要求外,还必须对测量的平均流量和振幅加以修正。

PEMFC流道结构对电池水管理影响的研究

质子交换膜燃料电池(PEMFC)水管理是影响其电性能及耐久性的关键因素之一。基于VOF两相流模型,对直流道、局部窄直流道、文丘里流道以及波浪形流道在不同气体流速下液态水的运动状态进行模拟,研究不同流道结构的排水性能。结果表明:当气体流速较低时,表面张力和壁面的粘附力的作用大于气体惯性力的影响,液态水在流道壁面上大量积聚,堵塞GDL中的水/气通道;局部窄直流道和文丘里流道“窄处”的文丘里效应,对气体具有加速作用,增强了流道排水性能,但同时也会增加气体压力;兼顾电池水管理与系统效率,需要优化局部窄直流道和文丘里流道的结构尺寸及宽窄变化频率。

类文丘里十字型流道中的液滴流态分析

目的:研究类文丘里十字型流道中液滴流态形成原因。方法:采用流体体积法以及二维模型,对类文丘里十字型流道中液滴生成进行数值模拟。结果:通过改变毛细数和流量比,在类文丘里十字型流道中观察到三种典型流态,即挤压态、滴落态和射流态。各流态之间的形貌变化和压力呈现出不同规律。结论:毛细数和流量比的变化会改变液滴生成过程中的主导力,进而改变液滴生成流态。