The behavior of the fluid flowing through vertical sharp-edged orifices with the same cross-section area but different geometry was investigated experimentally on typical "large orifice" and "small orif...The behavior of the fluid flowing through vertical sharp-edged orifices with the same cross-section area but different geometry was investigated experimentally on typical "large orifice" and "small orifice".The profiles of orifice discharge coefficient curves of circular,elliptical,square,rectangular and triangular orifices were similar,and the profile of the circular one is the highest and that of the triangular one is the lowest.It can be concluded that the orifice’s geometry has some effect on orifice discharge,but it is not the key parameter,because it doesn’t change the orifice’s flow mechanism essentially.The effects of the orifice’s geometry on energy losses were evaluated based on the analysis of the hydraulic radius of orifice,interfacial tension in acute angle,and penetrating phenomenon of jet flow through non-circular orifices,which might complement the flow mechanism of the circular orifice the authors studied before.Afterwards,the orifice flow was simulated with CFD software Fluent 6.2 in order to investigate the effect of orifice’s geometry on velocity distribution and energy losses of orifice discharge.It can be seen from the simulated flow field that the geometry of orifice had little effect on the overall range and velocity distribution of the contributing flow region in front of the orifice,and the energy dissipation in front of the orifice still could be calculated by the hemisphere model.It may help to understand that the difference of mechanical energy losses in orifice flow appears after flowing into the orifice.展开更多
According to the experimental data of the orifice discharge coefficient for the flow through a vertical sharp-edged orifice obtained in the previous study of this work,a theoretical criterion for flow mechanisms of sm...According to the experimental data of the orifice discharge coefficient for the flow through a vertical sharp-edged orifice obtained in the previous study of this work,a theoretical criterion for flow mechanisms of small orifice（viz.thick-walled orifice and nozzle） and large orifice（viz.thin-walled orifice） was proposed based on the ratio of orifice diameter to plate thickness.It can help explain the dissipation of the mechanical energy loss in the flow process for the two flow mechanisms under different operating regimes.The main parameters such as orifice diameter,plate thickness and liquid head were correlated,and a semi-empirical model for orifice coefficient and an empirical model with high precision at the stable region were developed.展开更多
研制一种适合对各种液压孔口或缝隙进行高低温流体力学试验的新型试验装置,运用该装置对具有不同几何参数的液压阻尼孔进行在-50~80℃宽温度范围内的流动特性试验,研究以普通抗磨液压油HM46和低温抗凝减振器油TITANSAF5045为工质及其温...研制一种适合对各种液压孔口或缝隙进行高低温流体力学试验的新型试验装置,运用该装置对具有不同几何参数的液压阻尼孔进行在-50~80℃宽温度范围内的流动特性试验,研究以普通抗磨液压油HM46和低温抗凝减振器油TITANSAF5045为工质及其温度变化时对液压阻尼孔流量-压力特性曲线、幂指数和流量系数的影响,研究表明,在低温条件下,液压阻尼孔的流量系数均因油液黏度增大、流动性变差而呈线性下降的趋势,从宏观上看,HM46通过液压阻尼孔时的流动稳定性较差,其对应流量系数的下降幅度明显大于TITAN SAF 5045对应的下降幅度,厚壁小孔流量系数的下降幅度明显大于薄壁小孔对应的下降幅度。研究所获得的新型试验装置、试验数据分析方法和具体理论公式为深入研究和优化现代液压元件在宽温度范围内的动态性能提供新型试验平台与理论基础。展开更多
文摘The behavior of the fluid flowing through vertical sharp-edged orifices with the same cross-section area but different geometry was investigated experimentally on typical "large orifice" and "small orifice".The profiles of orifice discharge coefficient curves of circular,elliptical,square,rectangular and triangular orifices were similar,and the profile of the circular one is the highest and that of the triangular one is the lowest.It can be concluded that the orifice’s geometry has some effect on orifice discharge,but it is not the key parameter,because it doesn’t change the orifice’s flow mechanism essentially.The effects of the orifice’s geometry on energy losses were evaluated based on the analysis of the hydraulic radius of orifice,interfacial tension in acute angle,and penetrating phenomenon of jet flow through non-circular orifices,which might complement the flow mechanism of the circular orifice the authors studied before.Afterwards,the orifice flow was simulated with CFD software Fluent 6.2 in order to investigate the effect of orifice’s geometry on velocity distribution and energy losses of orifice discharge.It can be seen from the simulated flow field that the geometry of orifice had little effect on the overall range and velocity distribution of the contributing flow region in front of the orifice,and the energy dissipation in front of the orifice still could be calculated by the hemisphere model.It may help to understand that the difference of mechanical energy losses in orifice flow appears after flowing into the orifice.
基金supported by the National Natural Science Foundation of China(20806090)
文摘According to the experimental data of the orifice discharge coefficient for the flow through a vertical sharp-edged orifice obtained in the previous study of this work,a theoretical criterion for flow mechanisms of small orifice（viz.thick-walled orifice and nozzle） and large orifice（viz.thin-walled orifice） was proposed based on the ratio of orifice diameter to plate thickness.It can help explain the dissipation of the mechanical energy loss in the flow process for the two flow mechanisms under different operating regimes.The main parameters such as orifice diameter,plate thickness and liquid head were correlated,and a semi-empirical model for orifice coefficient and an empirical model with high precision at the stable region were developed.
文摘研制一种适合对各种液压孔口或缝隙进行高低温流体力学试验的新型试验装置,运用该装置对具有不同几何参数的液压阻尼孔进行在-50~80℃宽温度范围内的流动特性试验,研究以普通抗磨液压油HM46和低温抗凝减振器油TITANSAF5045为工质及其温度变化时对液压阻尼孔流量-压力特性曲线、幂指数和流量系数的影响,研究表明,在低温条件下,液压阻尼孔的流量系数均因油液黏度增大、流动性变差而呈线性下降的趋势,从宏观上看,HM46通过液压阻尼孔时的流动稳定性较差,其对应流量系数的下降幅度明显大于TITAN SAF 5045对应的下降幅度,厚壁小孔流量系数的下降幅度明显大于薄壁小孔对应的下降幅度。研究所获得的新型试验装置、试验数据分析方法和具体理论公式为深入研究和优化现代液压元件在宽温度范围内的动态性能提供新型试验平台与理论基础。
