不同锥角V形球阀流动特性分析

V形球阀是一种性能优良的调节阀,但在一定条件下会发生空化,从而对管路造成损害.为了研究截流面积对V形球阀内部流动的影响,通过数值模拟的方法,对V形球阀在空化与非空化工况下的内部流场进行了研究,同时对比分析了不同锥角和不同开度下V形球阀流量特性、阻力特性、空化特性的变化规律.结果表明:V形球阀的流量系数随开度和锥角的增大...     

斜置双瓣止回阀内部流态的模拟与试验研究

为了改进普通止回阀存在的开启角度小、流阻系数大等不足,设计一种新型斜置双瓣止回阀,对其在30°、50°、70°、80°及全开工况下的内部流动特性进行分析,计算出流阻系数及流量系数。对其进行压力损失特性试验及流量特性试验,计算出每个工况下的流阻系数及流量系数,将其与模拟数据进行对比分析。研究结果表明,斜置双瓣止回阀的模拟结果与试验结果比较接近,开启角度大,压力损失小,流阻系数小,流量系数大,通流能力好。通过对斜置双瓣止回阀进行数值模拟及试验研究,斜置双瓣止回阀的设计对流体系统节能具有指导意义。     

中心型蝶阀流场的数值模拟与流动特性分析

利用FLUENT软件对DN250中心型蝶阀进行恒速定常流分析,模拟了不同开度的蝶阀流动情况并对其流动特征进行分析;针对模拟结果对流阻系数、相对流量系数及水动力矩系数三个重要参数进行计算分析,分析结果表明：开度在0°～30°内,流动扰动和阻力系数都较大,造成大量能量损失,不适宜阀板正常工作;阀板开度大于60°,流动阻力系数较小流态稳定,阀板受力较小,流体不会对阀板造成大的冲击;在蝶阀开度为70°时,水动力矩系数达到峰值0.193。研究结果为蝶阀设计提供重要参考依据。     

配流盘三角形节流槽抗空化结构改进研究

轴向柱塞泵配流盘三角形节流槽主要是减小柱塞腔及泵出口压力的波动.由于节流槽过流面积小,且槽两端压差大,流体高速流过节流槽的同时压力急剧减小,从而产生空化.为减小配流盘三角形节流槽的空化,提出对配流盘三角形节流槽抗空化的结构改进方案:预卸压阶段,在不改变节流槽通流面积的条件下,减小三角形节流槽倾角可提高其空化抑制性;预升...     

高压调节阀结构改进与汽蚀仿真

针对高压调节阀使用寿命偏低的问题,以串联型的多级降压结构为基础,提出一种优化的高压差调节阀结构。采用ANSYS Fluent对阀门内部的汽蚀现象进行仿真研究,得出静压、速度、气相体积分数等一系列数据,并讨论多级降压结构对阀门性能的影响。结果表明：阀门处于小开度下,容易产生汽蚀,汽蚀部位主要位于节流孔的阀芯与阀座处;相同工况下,优化后的调节阀能够有效抵抗气蚀,从而提高阀门的使用寿命。     

调压阀流体空化特性仿真及影响因素分析

针对船用二级调压阀空化问题,建立流域瞬态仿真模型,结合Singhal空化模型和标准k-ε湍流模型对调压阀流体空化现象进行数值模拟,通过流场气体体积分数分析,得出了流体空化强度及分布形态的演变规律,通过流体速度场和压力场分析,阐明了空化演变过程调压阀流场特性,进而研究了开度、流量和背压对调压阀流体空化现象的影响规律.结果...     

Study on the metrological performance of a swirlmeter affected by flow regulation with a sleeve valve

The metrological performance of flowmeters dominated by internal flow characteristics is often affected by flow regulation with valves in fluid transportation industries. This paper aims to study the metrological performance of a swirlmeter from the analysis of flow characteristics affected by flow regulation with a sleeve valve, and to have a comprehensive understanding from disturbed internal flow field in swirlmeter to fluctuation of flow signal, then to influence in metrological characteristic. With experimental setup developed and numerical simulation employed, throttling effect caused by flow regulation with the sleeve valve was considered in the context of positional relation between the swirlmeter and the sleeve valve (case I, sleeve valve at upstream and swirlmeter at downstream; case II, swirlmeter at upstream and sleeve valve at downstream) to compare the metrological performance under various operating conditions (including flow velocities and valve openings). Flow coefficients in two cases were comparatively examined to assess the throttling effect. Periodic pressure variation of the internal flow was monitored and its corresponding characteristic frequency (vortex precession frequency) in both cases was analyzed under different valve openings. It was found that the metrological characteristic of the swirlmeter in case II was extremely affected by the throttling effect spread upstream from the sleeve valve. In both cases, small valve openings were dominantly responsible for great relative errors in flow measurement. The flow mechanism of air compressed by throttling effect for depressing the vortex precession frequency in metrological characteristic was revealed through analyzing distributions of pressure and entropy production rate (EPR) of internal flow field. The average density of compressed air in the swirlmeter was adopted to evaluate the throttling effect, which was shown a greater dependence on operating conditions in case II. Furthermore, good correlation of average air density with operating conditions in sensitive case II was explored. Finally, this work can provide helpful insight for the metrological performance in fluid engineering.     

水压锥阀空化射流流场结构与流量特性的相关性研究

为了研究水压锥阀空化流场与流量特性的相关性,对两种阀座结构的水压锥阀内部的空化射流开展了三维动态流场仿真.结果表明,直角型锥阀和倒角型锥阀均在阀芯后沿存在分离流诱发的附着型空化,在阀口下游有漩涡空化;此外,倒角阀座流道内亦存在分离流现象并形成附着型空化.倒角型流道入口处的分离流造成流体的局部加速,对于0.6 mm开口度...     

液压滑阀径向间隙温度场的CFD研究

在中、高压系统中,节流作用使油温升高很快。油温升高使阀心受热膨胀,阀套与阀心间的配合间隙减小, 阀心有可能被卡死在阀套里。针对使用过程中因节流发热而发生的阀心卡死现象,建立了计算流体动力学 (Computational fluid dynamics,CFD)二维模型。对不同工作压力、不同径向间隙、以及不同开口的间隙内温度分布进行了解析。得到了各种情况下径向间隙内的温度场分布,并对计算结果进行了分析,得出工作压力、径向间隙和开口大小对径向间隙内温度分布的影响,为滑阀设计提供了理论参考。     

调节阀噪声分析与气穴研究

以套筒式调节阀为研究对象,通过流体动力学知识和噪声理论对其内部流场进行分析,得到套筒式调节阀产生振动的原因,并找出了调节阀内流道中产生气穴现象的位置。通过CFD数值模拟,计算出在某一开度下调节阀的速度矢量图,并与理论分析的气穴现象进行对比分析。该理论分析和CFD技术的采用,使得低噪声、高性能的套筒式调节阀的设计周期更短,成本更低,效果更好。     

基于Fluent的某滑阀内部流场仿真与分析

基于Fluent流场仿真软件,对某滑阀内部流场进行数值模拟和可视化研究。在相同计算条件下,分别对不同阀口开度下的三维模型进行稳态模拟仿真,得到滑阀内部流场的速度压力、流量特性以及流量系数的变化规律：在相同的压差条件下,随着阀口开度的增大,阀口处的最大速度、流场的最低压力、流量系数都随之降低。通过改变节流槽的形状进行仿真比较,得到流量系数与节流槽截面形状密切相关,在阀口开度相同的条件下,随着进出口压差的增大,半圆形节流槽滑阀的流量系数变化比较明显。研究为滑阀的优化提供了有效数据,并且对同类型产品的相关研究具有一定参考价值。     

Hydrodynamic characteristics and optimization design of a bio-inspired anti-erosion structure for a regulating valve core

Cavitation is the main failure mode of coal liquefaction regulating valve, which seriously limits the service life of the regulating valve. In order to restrain cavitation in the regulating valve, a bio-inspired anti-cavitation structure inspired by the red willow of valve core is proposed. Distributions of pressure, velocity and vapor volume fraction in the bionic valve under different openings (30%, 40%, 50%, and 60%) and inlet pressures (2.0MPa, 3.0MPa, 4.0MPa, and 5.0MPa) are discussed. In addition, the parameters of bionic valve structure are optimized using NSGA-II algorithm, the field synergy principle is applied to evaluate the flow field optimization in the bionic valve. The results show that the cavitation area and cavitation length in these bionic structures are reduced significantly compared with the traditional smooth structure. And the anti-cavitation performance of the trench structure is the best, when the inlet pressure is 3 MPa and the opening is 30%, the vapor volume is 0.10 mm³, the vapor volume is reduced by 98.07% compared with traditional smooth structure. Convex hull structure is the second. When the inlet pressure is 5.0 MPa, the vapor volume of the traditional smooth structure is as high as 148 mm³, and the vapor volume of the convex hull structure is 35 mm³, the vapor volume of the trench structure is 19 mm³. Through the field synergy theory to evaluate the internal flow field, it is found that the effective viscosity coefficient in the traditional smooth structure regulating valve varies from 0.7 to 1.2, that of the bionic trench valve changes from 0.1 to 0.5, both the flow resistance and energy consumption in the trench structure valve are reduced. It is proved that the bionic trench structure of the valve core can effectively improve anti cavitation performance and optimize the internal flow resistance of the flow field, which is of great significance to the optimal design of the control valve.     

动态压差控制阀流场及流量控制特性研究

针对变流量加热及冷却系统水力和热力失调的问题,设计一种动态压差控制阀.基于计算流体力学(CFD)方法,建立不同阀芯开度下动态压差控制阀三维流道模型.对比研究了不同阀芯开度下阀内流场分布以及流量变化,得出了动态压差控制阀在不同阀芯开度下阀内压降曲线的变化规律、阀芯节流口处速度曲线及湍动能曲线的分布规律,拟合了阀门出口流量...     

组合型节流槽对多路阀内流场特性影响的仿真研究

针对工程机械用多路阀阀口压损大、流速高,极易出现阀芯冲蚀磨损的问题,以某型号工程机械多路阀为例,设计不同组合形式的节流槽,研究多路阀阀口节流槽结构形式对阀口流阻损失及多路阀内部流场特征的影响。采用数值分析的方法研究了不同阀口节流槽形式在阀芯开启过程中阀口前后压差、流量、流速等流场特征。结果表明:阀芯采用不同组合型节流槽的流场特征明显不同,VU形节流槽较其他阀口出流线性特性更好,且具有良好的预升压效果,可进一步降低液流对阀芯的冲蚀,减小噪声、振动,保证多路阀工作的稳定性。对高压、大流量多路阀阀芯节流槽口的设计及提升多路阀综合性能具有一定的参考意义。     

液压支架用电液换向阀的动态特征及流场特性仿真分析

为了提高液压支架的机械控制能力,利用电液换向阀完成支架控制箱动作控制。该文采用流体动力学仿真了电液换向阀的动态特征及流场特性。研究结果表明:当时间到达0.14 s时二级阀芯发生运动,出口流量快速增大至一个峰值状态;随着阀芯到达一个稳定运动状态后,换向阀也达到1013 L/min的稳定出口流量。换向阀在高压大流量系统内工作时将会快速到达峰值压力,产生液压冲击作用并使支架立柱受到破坏。当流体由阀套流至阀芯时因为过流断面的面积会迅速降低,使压力下降4.1 MPa,形成压力集中损失的区域,同时在阀芯的主流道区域还会形成均匀的压力分布状态。从阀口的下游最初进入阀芯的主通道位置时将达到最大流速,等于109 m/s,表明该部位形成了最小的过流面积。     

Research on the measuring characteristics of a new design butterfly valve flowmeter

Flowmeters and control valves are important components of flow measurement and control in heating, ventilating, and air conditioning (HVAC) system, which directly or indirectly impact building room comfort and energy costs. Valves as resistance components produce differential pressure which in turn can be used for flow measurement. This paper studies the function among valve opening position, pressure difference and flowrate of a new designed butterfly valve. The flow model of the butterfly valve is established based on the Bernoulli equation, the discharge coefficient C under different valve opening conditions are studied by CFD simulations and verified by experiments. The simulation results show that the discharge coefficient C reached a stable value of 0.67–0.70 as Reynolds number exceeded 5000, and the permanent pressure loss ratio is range from 0.95 to 0.37 corresponding to opening range from 10° to 70°. The correctness of the simulation results of C is verified by experiments, in which C is about 0.60. With the corrected values obtained from experiments, the simulation results are instructive to practice. The new designed butterfly valve flowmeter can be used efficiently in HVAC system, especially in variable air volume (VAV) air conditioning system. And the work of this paper offers a reference for other types of valve flowmeters in fluid control processes.     

Experiment and simulation study on cavitation flow in pressure relief valve at different hydraulic oil temperatures

Hydraulic oil is the “blood” of hydraulic system, its high temperature in low-pressure hydraulic system would promote the development of cavitation and cause severe erosion of pressure relief valve. The influence of high oil temperature on the distribution of pressure field, velocity field and vapor volume fraction are discussed experimentally and numerically. The results show that with the increasing oil temperature, the viscosity of the oil decreases, and the flow rate increases, resulting the decreasing pressure at the orifice. Higher oil temperature promotes the occurrence of cavitation in the pressure relief valve, wider low-pressure zone could be found and cavitation bubble developed more fully and towards the valve core head. When the oil temperature increases from 303 K to 353 K, the cavitation intensity rises more sharply, but the growth rate of cavitation intensity increases firstly and then decreases with the increasing input pressure. Furthermore, based on the field synergy theory, the flow resistance and energy dissipation under different oil temperatures are evaluated. Both of large viscous dissipation and effective viscosity coefficient are mainly concentrated at the orifice, which are all effected by the oil temperature, so as to the characteristics of cavitation flow. The average field synergy cosine angle and the average viscosity coefficient decreases gradually with the increasing oil temperature, while the average vapor volume fraction increases. The energy dissipation is reduced by 3.3 × 10⁷ (W m⁻³) while the hydraulic oil temperature increases from 303 K to 353 K. Appropriate hydraulic oil temperature could provide favourable working conditions for the pressure relief valve which is beneficial for extending the hydraulic system's service life.     

Numerical and experimental studies on hydrodynamic characteristics of sleeve regulating valves

The sleeve regulating valve is a kind of control valve, which widely used in natural gas transportation. Jet flow generated in valve throats will impact on the surface of the valve body and the valve clack, and then cause the destruction of the valve. In this work, two regulators were designed to reduce the hydraulic impacts, and the effects of regulators on the hydraulic performance of the sleeve regulating valve are investigated in detail. Numerical and experimental studies were applied. Results indicate that the introduction of a regulator reduces the value of flow coefficient (K_V), and the reduction is greater with larger valve opening. Meanwhile, the flow coefficients for the valve with regulator I is a bit larger than that with regulator II. The results also demonstrate that the employment of regulator decreases the entropy production rate (EPR) of high EPR regions, reduces the pressure drop of valve throats, and slows down the velocity in the valve throats. Thus the impacts of the fluid on the throat walls are weakened by regulators. It is noted that the reduction of impact forces with regulator I (has small round holes) is larger than that with regulator II (with two rows of oval holes).     

Study on the influence of structural parameters on the flow and cavitation characteristics of tandem multi-stage pressure-reducing valves

Tandem multi-stage pressure-reducing valves (TMSPRV) are widely used for piping systems in the process industry. The flow coefficient is a central factor in valve design. The cavitation was caused by the local pressure of the fluid passing through the pressure-reducing valve being lower than the saturated steam pressure. Would cause serious damage to the pipeline system. Therefore, it is important to investigate systematically the effect of throttling structure parameters on the flow and cavitation characteristics of valves. In this paper, a combination of experimental and numerical simulations was used to study the effect of different structural parameters of valves on the flow coefficient. The results showed that increasing the flow channel inclination is beneficial to enlarging the flow coefficient. Meanwhile, the effects of different structural parameters on pressure and velocity of pressure reducing valves are discussed, the results indicated that increasing the inclination of the flow channel would reduce the vortex volume at the outlet. With the increase of the chamfer, the low-pressure area caused by the vortex in the near-wall surface decreases. Numerical simulations are conducted to investigate the effect of different structural parameters on the cavitation characteristics of valves. The numerical results showed that the flow channel inclination angle is 60° and the flow channel chamfer is less than 6 mm as the optimal value. In summary, considering the influence of structural parameters on flow coefficient, flow characteristics, and cavitation characteristics. The runner inclination angle is 60°, and the runner chamfer is 4 mm as the best value. The research work in this paper could provide technical support to achieve a better fluid pressure reducing and flow state of the TMSPRV under severe working conditions.     

挖掘机多路阀回转联阀口流场仿真分析

针对挖掘机多路阀回转联阀口部位采用CFD仿真的方法对阀口流道进行数值模拟。在Fluent软件中采用基于压力基求解模型、绝对速度公式方法和Realizable κ-ε湍流模型对多路阀回转联阀口流场进行稳态数值模拟,分析不同阀口开度、入口速度和出口负载下的速度和压力仿真云图,得到具体影响效果,并进行了相关的试验。结果表明:阀口开度的改变会显著影响阀口处流体的速度场和压力场的分布,阀口对流体具有节流作用,阀口开度越小节流作用越大;入口速度的变化对流体的速度场和压力场的分布影响不大,但是会明显影响流体的速度, 而对于压力大小的影响较弱;在 Fluent 仿真软件中,当设定边界条件为速度入口和压力出口时,对于出口压力,只改变压力的大小,对压力场分布基本不产生影响,最后通过试验验证了仿真的正确性。