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应用CFD模拟软件Fluent 6.2对开孔率30%的新型导流型防风网与传统方孔、圆孔平板网的受力与结构稳定性进行了研究。分析了不同风速下方孔、圆孔、导流型3种不同开孔型式网板受风荷载作用情况。模拟结果表明:导流型防风网受风荷载作用与传统方孔、圆孔网板相比差别不大,且风荷载都是随着风速不断加大,呈现二次方性增长,当风速由3 m·s-1增加到15 m·s-1时,风荷载增长约20倍;不同开孔网板的力臂与固定网高之比相差不大,且随来流风速增加变化不大;产生网板阻力的主要原因是网板近壁面的前后压差和网后气流湍动形成的拖曳涡。 相似文献
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《过程工程学报》2017,(4)
采用RNG k-ε湍流模型和欧拉双流体多相流模型模拟了气液逆流接触洗涤器内的两相流场,将计算结果用实验验证.通过考察两相流速、湍流强度、压降、气含率等参数验证了模型的可靠性,对不同喷嘴结构和操作条件下的泡沫区流场特性进行了模拟分析.结果表明,气液撞击形成的泡沫区湍流强度高,气液两相径向与切向速度较大,轴向速度较小,可用湍流强度大小表征泡沫区的大小.泡沫区占整个洗涤器的体积分数β随气液质量流量比增大先增大后减小,气液质量流量比为0.0096时达峰值;随进液轴/切流量比增大β先增大后减小,流量比为0.66时达峰值.喷口直径为8 mm、切向进液倾斜角为60°时气液传质效果最好. 相似文献
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环形分布器是实现导热介质在列管式固定床反应器壳程均匀流动的关键部件,文中采用计算流体力学方法(CFD)对环形分布器内的变质量流动进行了模拟研究。首先计算了环形通道内的速度和静压力分布,在此基础上研究了穿孔阻力系数随开孔几何结构以及入口流体流速的变化规律。模拟结果表明:环形通道内存在较明显的速度梯度和压力梯度;随着流体不断分流,在流道内的流动速度不断减小,静压力逐渐增大。因此,需要沿流动方向将开孔直径逐渐减小,以增大穿孔阻力,从而实现流体的均布。对穿孔阻力系数变化规律的研究结果表明:穿孔阻力系数ξ与出口和主流道的流速比ui/u、厚径比δ/di和入口雷诺数Re0有关。在模拟范围内,ξ先随ui/u的增大而减小,到达一个临界值后,ξ不再随ui/u的增大而变化;δ/di对ξ影响不太明显;当Re0属于湍流范围时,ξ随Re0的变化不太明显,但是总体随Re0的增大而减小。 相似文献
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鼓泡流化床风室及分布板区域流动特性的数值模拟 总被引:1,自引:0,他引:1
采用计算流体力学(CFD)软件对采用切向进风和垂直进风情况下不同开孔率气体分布 板的鼓泡流化床流态化特性进行研究,模拟风室及分布板区域的气体流动轨迹及其速度分布变化.结果表明:气体在切向进风形式下接近层流运动的上升状态,与垂直进风形式所产生的无序湍流上升状态相比,垂直进风形式下气体速度在空间分布更加均匀,受边界条件影响所导致的风室内局部风速过高情况较少;分布板开孔率在0.15%~1.0%变化时,随开孔率增大,气体压降逐渐减小,气体均匀性逐渐稳定;气体分布板开孔率为0.5%时,气体分布均匀性和分布板压降较合理. 相似文献
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The transport properties of ionic liquids (ILs) are crucial properties in view of their applications in electrochem-ical devices. One of the most important advantages of ILs is that their chemical–physical properties and conse-quently their bulk performances can be well tuned by optimizing the chemical structures of their ions. This will require elucidating the structural features of the ions that fundamentally determine the characteristics of the nanostructures and the viscosities of ILs. Here we showed for the first time that the“rigidity”, the order, and the compactness of the three-dimensional ionic networks generated by the anions and the cation head groups determine the formation and the sizes of the nanostructures in the apolar domains of ILs. We also found that the properties of ionic networks are governed by the conformational flexibility and the symmetry of the anion and/or the cation head group. The thermal stability of the nanostructures of ILs was shown to be con-trolled by the sensitivity of the conformational equilibrium of the anion to the change of temperature. We showed that the viscosity of ILs is strongly related to the symmetry and the flexibility of the constitute ions rather than to the size of the nanostructures of ILs. Therefore, the characteristics of the nanostructures and the viscosities of ILs, especially the thermal stability of the nanostructures, can be fine-tuned by tailoring the symmetry and the conformational flexibility of the anion. 相似文献
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Investigation of the effects of fatty acids on the compressive strength of the concrete and the grindability of the cement 总被引:1,自引:0,他引:1
In cement industry, a great energy consumption has been observed during grinding of clinker. To reduce this consumption, some waste products have been used as grinding aids.In this investigation, the effects of sunflower oil (SO), oleic acid (OA), stearic acid (SA), myristic acid (MA) and lauric acid (LA) on the fineness and strength of the cement have been examined. These aids were added into clinker in certain ratios based on the cement clinker weight and the grinding has been done for a definite time at the same condition.All of the fatty acids used increased the fineness as compared with the cement without the grinding additives. SO and OA decreased the strength significantly, LA decreased it to a lesser extent and SA increased it definitely according to the common cement. But MA did not alter the strength of the cement as much as SA. In addition, the covering of the balls influences the grinding of cement clinker unfavourably. 相似文献
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组合凹模的应力分析是一个非常复杂的问题,对其进行精确分析是解决模具寿命的关键。本文采用有限元分析软件Ansys对转子的组合凹模进行了分析,为转子组合凹模的优化设计提供了依据。 相似文献