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A novel spiral micromixer with sinusoidal channel walls was designed to enhance the mixing index in the low to intermediate Reynolds number range (1 < Re < 100). To analyze the fluid flow, a set of numerical simulations were performed using the finite-difference method. The microchip was fabricated from polydimethylsiloxane, employing the soft-lithography technique. The degree of mixing was increased by 99.11 % when using the proposed micromixer, compared to 59.44 % for a simple spiral micromixer. The introduced microchannel drastically reduced the mixing length, increasing the mixing index of a 0.5-loop spiral-sinusoidal microchannel compared to that of the simple spiral microchannel with 1.5 loops. The mixing index of the 3-loop mixer was higher than that of the microchannel with 1.5 loops, and its pressure drop was increased. 相似文献
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The understanding of the flow characteristics and effect of gas-solid interactions in pneumatic risers is fundamental to investigate to ensure effective design cost-effective operation. Thus, to understand the effect of gas-solid interactions on the hydrodynamics of newly proposed conversing risers, this study mainly focused on predicting pressure drop in the dilute phase pneumatic conveying system. The experiments were conducted in a converging riser having a convergence angle of 0.2693°. Various solid particles such as sago, black mustard, and alumina have been considered to study the effect of particle sizes and density on the pressure drop. The experimental outcomes indicate that the total pressure drop increases with an increase in the solid density and gas mass flow rate. Moreover, smaller particle sizes are also increased the pressure drop. An empirical correlation is developed for the prediction of total pressure drop ΔPT in converging pneumatic riser via dimensional analysis. All dependent variables such as particle and air density, drag force, acceleration due to gravity, the mass flow rate of air and particle, the diameter of particle and converging riser, the height of converging riser were considered to develop the empirical correlation. The established relationship is tested, and experimental data have been fitted for its validation. The estimated relative error of less than 0.05 proved the significance of the developed correlation. Hence, it can be stated that the established relationship is useful in studying the effects of various parameters on the pressure drop across the length of the conversing riser. 相似文献
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The pressure drop prediction of wet gas across single-orifice plate in horizontal pipes had been solved satisfactorily under an annular-mist flow in the upstream of orifice plates. However, this pressure drop prediction is still not clearly determined when the upstream is in an intermittent flow or stratified flow, which is corresponding to a region of low FrG (gas phase Froude number) in the flow pattern map of wet gases. In this study, the wet gas pressure drop across a single-orifice plate was experimentally investigated in the low FrG region. By the experiment, the flow pattern transition in the downstream of single-orifice plates, as well as the effects of FrG and FrL (liquid phase Froude number) on ΦG (gas phase multiplier), were determined and compared when the upstream is in the flow pattern transition and the stratified flow region, respectively. Prediction performances were examined on the available pressure drop models. It was found that no model could be capable of jointly predicting the wet gas pressure drop in the low FrG region with an acceptable accuracy. With a new method of correlating FrG and FrL simultaneously, new correlations were proposed for the low FrG region. Among which the modified Chisholm model shows the best prediction accuracies, with the prediction deviations of ΦG being within 7% and 3% when the upstream is in flow pattern transition and stratified flow region, respectively. 相似文献
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建立了考虑水位骤降条件下的下伏隧道堤防模型,依托湘江某下伏隧道堤防工程,基于堤防边坡渗流原理,结合有限元应力计算,探讨了不同水位骤降速率下的浸润线情况,计算了堤防安全系数。研究结果表明:湘江水位骤降速率越快,浸润线变化范围越大,浸润线变化范围与水位降落速率成正比;湘江水位骤降速度在3 m/d^4 m/d,水位降到28.8 m时,堤岸失去稳定;水位骤降并非整个过程中堤岸均处于失稳状态,而是水位降至某高度后堤岸失稳,骤降速率增快对堤防安全系数有一定负面作用。研究结果对隧道下穿堤防建设具有一定指导意义。 相似文献
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为了降低煤层气井排采过程中的储层伤害,通过分析松河井田的资源开发条件及煤层气井排采数据,总结各排采阶段不合理排采控制引起的储层伤害特征,提出不同排采阶段合理的排采工艺对策。分析结果表明:松河井田煤层气资源丰度达到2.09×10^8m^3/km^2,煤层气资源开发条件较好;松河井田多煤层合层排采过程中,不合理排采控制工艺对煤层气井的产气量影响较大;排采初期以速敏伤害为主,排采中期以气锁和应力闭合伤害为主;修井作业及停抽期间,气锁效应及应力闭合对煤层造成伤害的可能性增大。合理的排采控制能够有效降低煤层气井的储层伤害,提高煤层气井产气量。 相似文献
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为探究颗粒负荷对小型旋风器内气固两相流动的影响,基于雷诺应力模型(RSM)和欧拉-欧拉方法的混合流模型(Mixture)进行气体-颗粒、颗粒-颗粒的相间耦合计算。采用粒径为0.5~5μm的颗粒组在40L/min、60L/min和80L/min的入口流量下模拟0~3kg/m3的5种不同颗粒浓度工况,通过对比旋风器内纯气相流场和颗粒负荷流场的不同,研究了颗粒的存在对流场的影响;探究了入口流量和浓度变化对旋风器内分离效率和压降特性的影响。基于模型有效性验证的数值模拟结果表明:较高颗粒浓度负荷使旋风器内的气相流场发生显著变化。随着入口流量的增大,旋风器的分离效率先增大后减小,压降呈非线性增大。随着颗粒浓度的增大,旋风器的分离效率逐渐增大,压降先减小后增大。 相似文献
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