共查询到17条相似文献,搜索用时 156 毫秒
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根据单级节流孔板气蚀现象发生的机理,提出使用多级节流孔板可防止气蚀现象的发生,并系统地介绍了多级节流孔板级数、孔径、厚度等的计算方法. 相似文献
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多级节流孔板的设计计算 总被引:1,自引:0,他引:1
根据单级节流孔板气蚀现象发生的机理,提出使用多级节流孔板可防止气蚀现象的发生,并系统地介绍了多级节流孔板级数、孔径、厚度等的计算方法. 相似文献
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目前水及蒸汽的流量测量装置绝大部分是采用标准节流孔板(以下简称孔板)和标准节流喷嘴(以下简称喷嘴),而且一般均采用角接取压。孔板、喷嘴以前都采用人工计算,往往计算一只节流件要花费一天时间,在计算过程中需要反复查表,只要一个数据出错就全功尽弃, 相似文献
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使用计算流体动力学方法对核电机组二回路碳钢给水管道节流孔板下游的流场分布进行数值模拟,研究了入口流速和倒角角度对节流孔板下游流场和传质系数分布的影响。基于Sanchez-Caldera流动加速腐蚀(FAC)预测模型,计算分析了节流孔板下游FAC速率及分布与入口流速和倒角角度的关联性。结果表明:模拟结果和实验结果趋势基本一致;当倒角角度一定时,传质系数和FAC速率随入口流速的增加整体呈上升趋势,并且FAC速率峰值位置向下游略有偏移;当入口流速一定时,倒角角度的减小使得FAC速率峰值位置向孔板靠近,传质系数和FAC速率峰值在倒角角度为45°时最小。 相似文献
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节流孔板在火电厂中的合理使用 总被引:1,自引:0,他引:1
结合节流孔板在火电厂汽水管道中的应用,描述了汽水流过孔板时的热力学过程以及会发生的物理现象,分析了阻塞流产生的原因,以此为基础给出了确定节流孔板级数与孔径的方法,并结合具体实例说明了该方法的应用。 相似文献
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多级孔板泄洪洞是一种利用水流强剪切混掺而实现消能的内消能工形式,而抗空化空蚀性能是影响多级孔板泄洪洞安全运行的重要指标之一。本文以小浪底1号孔板泄洪洞为例,在水力学原型观测资料的基础上系统分析了多级孔板泄洪洞的空化特性,并结合几何比尺为1:40的减压模型试验资料分析了缩尺效应对初生空化数的影响。结果表明:水流空化数对库水位的变化不敏感,而初生空化数则随着库水位的升高而增大,受此影响,库水位越高时各级孔板发生空化水流对应的闸门开度越小;缩尺效应对多级孔板泄洪洞初生空化具有显著影响,经模型试验测得的初生空化数须进行缩尺效应修正;对于多级孔板泄洪洞,其结构尺寸和水流流速是影响初生空化数的主要参数,基于此提出了减压试验初生空化数的缩尺效应修正方法,经与原型观测资料对比,误差小于2%。相关成果利于深化对多级孔板泄洪洞水力特性的认识,有助于多级孔板泄洪洞的推广应用。 相似文献
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从水环式真空泵运行性能和估计的凝汽器空气泄漏量出发.分析了2台真空泵运行改单泵运行的可能性和母管制运行的优点,提出高、低压真空泵分列运行的机组可将4台真空泵改造成母管制并列运行,高压真空泵加装节流孔板形成二运二备(或一运三备)的运行方式;对于无高j低压真空泵区分的机组可采取一大一小或降低真空泵转速的节能运行方式。 相似文献
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Processing of experimental data on the pressure difference across a submerged perforated sheet (SPS) revealed that, at sufficiently high void fractions under SPS, the pressure difference across it became less than the pressure difference for the pure steam stream with the same flowrate. To find the cause of this, the effect of a liquid film, which can be formed on the SPS upstream surface as a result of water droplets’ impact and can smooth over sharp edges of holes in SDS, was examined. This can decrease the pressure drop across the sharp edges of holes. This assumption was checked through numerical solution to several model problems in the axisymmetric formulation for a steam flow in a round pipe with an orifice. The flow of steam and water was modeled using the viscous incompressible liquid approximation, while the turbulence was described by the k–ε model. The evolution of the interfacial area was modeled using the VOF model. The following model problems of steam flow through an orifice were studied: a single-phase flow, a flow through the orifice with a liquid film on its upstream surface, a flow through a chamfered hole, and a flow through the orifice with a liquid film on its upstream surface without liquid supply to the film. The predictions demonstrate that even the approximate account of the liquid film effect on the steam flow yields a considerable decrease in the pressure drop across the hole (from 8 to 24%) due to smoothing its sharp outlet edges over. This makes it possible to make a conclusion that the cause of a decrease in the pressure drop across SPS observed in the experiments at high void fractions is the formation of a liquid film, which smooths the sharp edges of the hole. 相似文献