共查询到20条相似文献，搜索用时 609 毫秒
1.
Numerical investigation of cavitating flow behind the cone of a poppet valve in water hydraulic system 总被引：2，自引：0，他引：2
Computational Fluid Dynamics (CFD) simulations of cavitating flow through water hydraulic poppet valves were performed using
advanced RNGk-epsilon turbulence model. The flow was turbulent, incompressible and unsteady, for Reynolds numbers greater than 43000. The
working fluid was water, and the structure of the valve was simplified as a two dimensional axisymmetric geometrical model.
Flow field visualization was numerically achieved. The effects of inlet velocity, outlet pressure, opening size as well as
poppet angle on cavitation intensity in the poppet valve were numerically investigated. Experimental flow visualization was
conducted to capture cavitation images near the orifice in the poppet valve with 30° poppet angle using high speed video camera.
The binary cavitating flow field distribution obtained from digital processing of the original cavitation image showed a good
agreement with the numerical result.
Project supported by the National Natural Science Foundation of China (No. 59835160) and Scientific Research Foundation for
Returned Overseas Chinese Scholars, State Education Ministry of China (No. 50175097) 相似文献
2.
This paper has introduced the developments of water hydraulic axial piston equipments.According to the effects of physicochemical properties of water on water hydraulic components,a novel valve plate for water hydraulic axial motor has been put forward,whose moment exerted by the fluid field between valve plate and bearing plate is balanced entirely.The material screening experiment of valve plate is done on the test rig.Through numerical simulation the effects of some geometry parameters on the performance of water hydraulic motor have been studied.The silencing grooves on the valve plate in water hydraulic motor can reduce the pressure shock and the occurrence of cavitation effectively.It is evident that the appropriate structure should change the wear status between matching paris and reduces the wear and specific pressure of the matching pairs.The specimen with the new type valve plate is used in a tool system. 相似文献
3.
The power of hydraulic piston engines is much affected by the on-off valves which control the fuel injection of the piston assembly. Therefore, the opening time of the seat valve used as the on-off valve is optimized by minimizing the axial flow forces on the spool. A damping sleeve with orifices is proposed to change the valve internal geometry. Experimental and numerical investigations of the flow forces acting on the spool with and without the proposed damping sleeve are carried out to identify the differences in the flow field and to minimize the forces’ effect. The simulated results fit the experimental results well. Both results show that the proposed damping sleeve affects the pressure distribution along the spool cone surface and the jet stream direction significantly. The effects of the orifice’s width, height, and relative sleeve installation positions on the flow field and cavitation are assessed using simulation methods. As a result of the flow field changing, the damping sleeve can reduce the flow forces significantly and even reverse the forces’ direction at the cost of a little flow loss. The opening time of the seat valve can be reduced by 31% to 0.67 ms by using the proposed damping sleeve. 相似文献
4.
调节阀应用中技术问题的探讨 总被引：1，自引：0，他引：1
万卉丹 《河北能源职业技术学院学报》2005,5(4):62-64
选择和安装好调节阀,使调节阀在一个高水平状态下运行将是一个很关键的问题。收集完整的工艺流体的物理特性参数与调节阀的工作条件,掌握和确定调节阀体本身的结构、形式、材料等方面的特点,流量特性、压降、闪蒸、气蚀、噪音等问题,是选择调节阀考虑的重点。 相似文献
5.
分析了液压阀汽蚀产生的原因以及给液压阀带来的影响;给出了防止汽蚀破坏液压阀的方法,以延长液压阀的使用寿命,保证液压阀的可靠性. 相似文献
6.
电动截止阀是流体输送的重要元件.阀的传统设计方法很少从流体角度对其流道进行设计,其流阻系数比较大,容易造成局部压力损失.流体介质通过阀口时,流动方向发生变化,可能产生诸如局部涡流、空化、水锤和死水区等水流现象及湍流脉动噪声,对阀体有很强的破坏性,降低阀的使用寿命.基于RAN-S方程组和RNG k-ε湍流模型,利用CFD技术对全开启状态下的电动截止阀的内流道进行三维的湍流数值模拟,获得其总压图、速度矢量图、湍动能强度图.通过数值模拟,可以直观地显示阀的内流道中流体的流动过程.改变进出口段流道的长度、曲率以及阀杆在流道中的布局等,进出口的压力差相对于未改进前减少30%左右,速度突变区域明显缩小,局部涡流现象消失,湍动能强度也降低了15%左右. 相似文献
7.
Vortex-ring cavitation occurs when the pressure inside a torus-shaped core of a vortex ring falls below the vapor pressure of the ambient liquid. By generating a vapor bubble in a rigid tube, a toroidal cavity can be produced outside the tube. The pulsation and propagation behaviors of vortex-ring cavitation are studied using a high-speed video camera and a hydrophone. The experimental results show that the cavity continues to oscillate with a period that depends heavily on the maximal cross-section radius of the cavity and circulation of the vortex flow, under the influence of the surrounding vortex flow field. It is also shown that the cross-radial oscillation of the toroidal cavity can be measured both by a high-speed camera and hydrophone. Moreover, three different methods for estimating the circulation are compared to propose an accurate model of toroidal cavity oscillation. The phenomenon of a toroidal cavity impinging on a fixed wall is also investigated. 相似文献
8.
9.
In this paper,a new pressure reducing valve(PRV) with an orifice plate is proposed.The main objective is to explain the mechanisms of pressure reduction and energy conversion in the new PRV.A numerical simulation method was used to investigate the PRV internal flow field and to analyze the throttling effects of the orifice plate and the transform of thermal parameters as outlet pressure,outlet temperature,velocity,and superheat.A structure improvement method for the valve body and orifice plate is put forward to reduce energy loss.The governing equations for internal flow numerical simulation are composed of the continuity,momentum,energy and k-ε transport equations,based on isotropic eddy viscosity theory.Different valve plug displacement models were built to describe the double throttling process.Our analysis shows that the steam pressure drops twice and the degree of superheat increases.There are also lots of eddies which clog the flow channel and disturb the steam flow in the valve cavity after the valve plug and the outlet cavity.After modifying the structure,the numerical results show a better performance of steam flow. 相似文献
10.
为了探索油气在冷凝回收过程中的冷凝规律,采用气液两相流模型描述了油气在竖直管内湍流流动时的冷凝过程.采用有效传质系数描述了油气组分的质量传递.模拟了油气在管内冷凝时的温度、管内压力、液膜厚度和Nusselt数的变化,得到了入口油气和管壁的温差、雷诺数对冷凝率和Nusselt数的影响.结果显示：增大入口雷诺数能显著增强传热和冷凝,但是增大入口油气和管壁的温差对冷凝率的影响较小;另外,还发现传质阻力对油气冷凝率有较大影响.此模型的计算结果与先前的实验数据能够很好地符合. 相似文献
11.
：以液压控制系统中常用的滑阀为研究对象，通过对滑阀内流体流动的仿真计算，对本中采用的数值解析手法的差分方法、空间计算格子系等计算参数对计算结果的影响进行了分析和讨论。结果表明，上述计算参数对流场构造以及流量的计算结果影响相对较小。2种不同计算方法对滑阀轴向流体力的分析比较得出：作用在滑阀轴方向上的流体力对差分方法、空间计算格子系等计算参数非常敏感。如要得到较高精度的计算结果，采用压强和壁面切应力来直接计算流体力要比应用控制体内流体的动量守恒原理需要更密的计算格子系。这一结果有助于我们在进行流场数值计算时，根据不同的对象选取合适的解析手法和计算参数，节省计算时间，提高计算效率。 相似文献
12.
为保证测定结果的唯一性和稳定性,借鉴了储气筒活塞均匀移动稳压的原理,采用高精度玻璃筒代替传统的外接高压气瓶供气,气筒中密封可移动活塞,活塞在储气筒中匀速移动时受力平衡,储气筒中气体压力不变,通过对储气筒活塞加重块重量的设定,可以改变测量压差。在测定岩石渗透率的过程中,出口端压力为大气压,气体以稳定的状态通过岩心,得到相对稳定的渗透率值。虽然测定中采用的进口压力不同,结果有很大差异,然而当岩心在同一压差下测量时,测得的渗透率的误差可以保持在1％范围内,对不同的岩心在同一压差下测得的渗透率值大小也有了可对比性。 相似文献
13.
In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq. (19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline. 相似文献
14.
15.
Numerical study on performance of perforated plate applied to cryogenic fluid flowmeter 总被引：1，自引：0，他引：1
The perforated plate is one of the effective devices for measuring flow rate accurately. In this study, a perforated plate is investigated for its characteristics, mainly including discharge coefficient C and pressure loss coefficient ζ, when applied to cryogenic fluids with the help of ANSYS Fluent. Three cryogenic fluids are studied, including liquid nitrogen (LN2), liquid oxygen (LO2), and liquid hydrogen (LH2). For comparison, two states of water are also investigated. The realizable κ-ε model with standard wall function is used to describe the turbulence and simulate the near-wall flow. The Schnerr-Sauer cavitation model is used to investigate the effect of cavitation on the performance of the perforated plate. Simulation results indicate that the upper limit of Reynolds number of the perforated plate is significantly dependent on the properties of the measured fluid when the temperatures of the fluids are set as the normal boiling point temperatures and the outlet pressures are 0.2 MPa. 相似文献
16.
Detailed parametric study of three-dimensional gas-particle multiphase flow characteristics in U-beam tube bundle inertial
separators was conducted by numerical simulation. The carrier phase was treated in the Eulerian frame, the particles were
tracked in the Lagrangian frame, and particle-wall collision was considered. Simulation carried out at different inflow rate
and mass loading ratios revealed the pressure losses in the separators, velocity field of the gas phase, and the trajectories
of particles. The study results revealed the multiphase flow-dynamic features of the separators, and the relationship between
separator pressure losses and different inlet velocity. The numerical simulation can provide basis both for optimal design
of impacting-inertial separator used in circulating fluidized bed boiler; and for study of gas-particle multiphase circumfluence
flow.
Project supported by the Zhejiang Provincial Natural Science Foundation of China (No. 500065) 相似文献
17.
弹簧式安全阀阀球开启高度对排量的影响 总被引：3，自引：0，他引：3
分析了阀球开遍高度对排量的影响，并根据样机磨难结果及工业运行情况绘出了阀球开启高度与注量系数的关系曲线，为该结构的安全阀设计奠定了理论基础。 相似文献
18.
Numerical study of heat transfer characteristics of downward supercritical kerosene flow inside circular tubes 总被引：3，自引：0，他引：3
The heat transfer characteristics of China RP-3 aviation kerosene flowing in a vertical downward tube with an inner diameter of 4 mm under supercritical pressures are numerically studied. A ten-species surrogate model is used to calculate the thermophysical properties of kerosene and the re-normalization group (RNG) k-ε turbulent model with the enhanced wall treatment is adopted to consider the turbulent effect. The effects of mass flow rate, wall heat flux, inlet temperature, and pressure on heat transfer are investigated. The numerical results show that three types of heat transfer deterioration exist for the aviation kerosene flow. The first type of deterioration occurred at the tube inlet region and is caused by the development of the thermal boundary layer, while the other two types are observed when the inner wall temperature or the bulk fuel temperature approaches the pseudo-critical temperature. The heat transfer coefficient increases with the increasing mass flow rate and the decreasing wall heat flux, while the inlet bulk fluid temperature only influences the starting point of the heat transfer coefficient curve plotted against the bulk fluid temperature. The increase of inlet pressure can effectively eliminate the deterioration due to the small variations of properties near the pseudo-critical point at relatively high pressure. The numerical heat transfer coefficients fit well with the empirical correlations, especially at higher pressures (about 5 MPa). 相似文献
19.
介绍了一种自行研制的空调表冷器热工性能测试系统,该系统是通过对实验室现有空气调节处理过程实验台进行改造制得。在压缩机和节流阀之间装设套管式蒸发器,制得冷冻水,经水泵送入表冷器中,与空气进行换热后重新返回套管式蒸发器中。通过温控器实现表冷器入口冷冻水温度的控制,表冷器进出口冷冻水温通过布置热电偶进行测量,冷冻水流量通过转子流量计进行测量,利用原有干湿球温度计测量空气进出口干湿球温度,进而在不同工况下实现表冷器析湿系数、热交换效率、接触系数和换热量的测试。依据测试结果分析风量、风速、冷冻水流量对表冷器热工性能的影响。 相似文献
20.
平衡阀的应用 总被引：1，自引：0，他引：1
周俊丰 《河北职业技术学院学报》2007,7(2):13-14
平衡阀是一种具有特殊功能的阀门,它具有良好的特性,能够合理分配流量,实现流量定量,有效地解决供热系统中存在的室温冷热不均问题。 相似文献