Cavitating flows of organic fluid with thermodynamic effect in a diaphragm pump for organic Rankine cycle systems
Cavitating flows of organic fluid with thermodynamic effect in a diaphragm pump for organic Rankine cycle systems
复制标题
DOI：
10.1016/j.energy.2021.121495
复制
发表时间：
2021-12
期刊：
影响因子：
9
通讯作者：
Wenguang Li;Zhibin Yu
中科院分区：
文献类型：
--
作者：
Wenguang Li;Zhibin Yu
在小/微尺度有机朗肯循环（ORC）中输送有机流体时，隔膜泵经常经历空化和随后的流体流动振荡。迄今为止，很少对隔膜泵在有机流体中的汽蚀行为进行研究。首次采用k-ω湍流模型、ZGB空化模型、阀体一维运动刚体运动模型和动网格技术，利用ANSYS 2019 R2 CFX对R245 fa有机工质在隔膜泵吸入冲程内的三维非定常空化流动进行了数值模拟。考虑了R245 fa汽蚀过程中的热力学效应。确定了汽蚀起始的汽相体积分数阈值，识别了汽蚀起始和发展状态，阐明了汽蚀过程中的涡产生和熵产率。汽蚀开始出现在阀座的边缘，然后在阀门表面上。随着空化的发展，阀上的压力和力、阀开度和速度由于汽泡溃灭循环而剧烈振荡。在不同的曲轴转角下，发生了膨胀空化和流动诱导空化。在所研究的情况下，最大温度下降为0.549 K。阀腔内的体积积分熵产生率与空化状态相关。
Diaphragm pumps often experience cavitation and subsequent fluid flow oscillation when delivering an organic fluid in small/micro scale organic Rankine cycle (ORC). The cavitation behaviour of diaphragm pumps has rarely been investigated for organic fluids so far. Three-dimensional, unsteady cavitating flows of organic fluid R245fa in a diaphragm pump were simulated with ANSYS 2019R2 CFX in suction stroke in terms of the k-ω turbulence model, the ZGB cavitation model, rigid body motion model for one-dimensional motion of valve and moving mesh technique for the first time. The thermodynamic effect in cavitation of R245fa was considered. The vapour volume fraction threshold for cavitation inception was determined, and the cavitation inception and cavitation developed states were identified, and vortex production and entropy generation rate during cavitation were clarified. Cavitation inception emerges at the edge of the valve seat, then on the valve surface. With cavitating development, the pressure and force on the valve, valve opening, and velocity oscillate violently due to vapour bubble collapse cycles. Expansion cavitation and flow induced cavitation happen in sequence at different crank rotational angles. The maximum temperature depression is 0.549 K in the cases studied. The volume-integrated entropy generation rate in the valve chamber correlates to cavitation states.