微通道直角突缩弯道气体流阻特性

采用有限体积方法,研究了矩形截面微通道直角突缩弯道局部流场及压力损失机理,重点考虑了雷诺数和弯道进出口截面面积比对局部流场及压力损失的影响,雷诺数范围为1~200,特征尺寸为500 μm.研究表明,低雷诺数时压力损失主要由壁面摩擦产生,弯道压力损失系数与具有相同中心线长度的直通道的压力损失系数变化趋势相同,但在数值上较小,突缩弯道会引起弯道内速度型发生变化,影响弯道压力损失;而高雷诺数时,压力损失主要由弯道内角位置的速度分离及漩涡产生,突缩弯道会抑制速度分离及漩涡产生,进而降低弯道压力损失.根据计算结果,拟合了弯道压力损失系数与雷诺数及进出口截面面积比的关系式.

Pressure losses in gas flow through sudden contractive sharp bends in micro channels

Flows through sudden-contractive sharp bends in rectangular cross-section micro channels were studied by using finite volume method. Specifically, the effects of Reynolds number and cross-section area ratio on local flow patterns and bend pressure losses were investigated. Reynolds number ranges from 1 to 200 and the characteristic length is 500 μm. Skin frictions mainly contribute to the pressure losses at low Reynolds numbers while flow separation and vortices dominate the losses at high Reynolds numbers. For low Reynolds numbers, the variation of bend pressure loss coefficient with Reynolds number is similar to the loss of a straight channel with the same center-line length, but the bend loss has a smaller value. The sudden-contractive cross section inhibits the flow separation at high Reynolds number and reduces the pressure loss. The velocity profiles at the cross section of the bend were affected by the contraction. Correlations of pressure loss coefficient as a function of Reynolds number and cross-section area ratio were fitted.