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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.
基于有限体积方法,对嵌入式行星螺杆挤出机内流场进行了三维等温数值模拟。通过简化的物理模型来模拟螺杆的几何结构,使用用户自定义程序设定了行星螺杆运动的边界条件。分析了挤出机螺槽内压力和速度的分布;使用粒子追踪技术观察了螺杆内流体运动轨迹和粒子分布规律;对粒子在螺杆内的停留时间分布进行了统计。结果表明行星螺杆对流体运动产生了周期性扰动。初始位置在一起的两个粒子,终点位置却相距很远。示踪粒子的具有对初始敏感的混沌特性,粒子的运动轨迹具有无序性,说明流体存在着混沌效应。 相似文献
3.
KOTA K LANGRISH T.A.G 《浙江大学学报(A卷英文版)》2007,8(2):301-312
INTRODUCTION Abbott (1990) reported that wall deposition inspray dryers may pose a potential fire risk and com-promise hygiene requirements, and reduce productquality and yield. Spray dryer hazards include igni-tion of explosible dust clouds, dust deposits, bulkpowder deposits and flammable vapour. Kieviet(1997) noted that wall deposition affected the resi-dence time distribution of particles, and particularlythat an important factor in determining residencetimes with high wall deposition… 相似文献
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5.
北京市传统大学生宿舍室内空气环境的模拟 总被引：2，自引：0，他引：2
本文旨在通过流场分布来研究北京市传统学生宿舍里的室内空气环境(包括室内压力场与速度场的分布情况)。文中采用k-ε双方程湍流模型来模拟空气介质，应用计算流体力学(CFD)的方法来求解室内空气流动，运用有限体积法来处理控制方程，并用Fluent模拟流场分布结果。分析结果表明，学生床上的通风情况跟床的位置有很大的关系。 相似文献
6.
提出将CFD引入“汽轮机原理”的教学中,通过CFD强大的图形后处理功能,形象、直观地展示汽轮机通流部分流体参数变化,改善多媒体教学方法。以汽轮机原理的核心内容“级的工作原理”为例,展示了CFD应用于级内流场的讲授过程,以图形结果形象地解释了级内流体的压力、速度、速比及反动度等参数变化规律。CFD的引入能够丰富多媒体教学资源,提高教学效果,激发学生科研兴趣。 相似文献
7.
利用ANSYS软件对空调压缩机排气管弯管处流体流场进行了数值模拟。得到了流体流经弯管处的压力分布和速度矢量分布图。由此研究了流体在流经弯管处时速度和压力的变化,找出了造成压力损失的主要原因,流场的变化情况,以及管道中易损坏的部位,为多相流系统的设计提供了合理的依据。 相似文献
8.
磁场作用下的磁性流体行波泵研究是行波泵设计的基础。通过分析了行波磁场作用下的磁性流体的运动方程,从而进一步推导了行波磁场作用下的磁性流体的速度方程、旋转速度方程和单位时间内的流量方程,并通过实验进行了验证。研究表明：行波磁场作用下的磁性流体会产生流动现象;行波磁场作用下的磁性流体流量与磁极旋转的角度有直接关系,磁极旋转的角度越大,其流量也越多;行波磁场的强弱对磁性流体流量也会产生影响,磁场越强,其流量越大;行波磁场的频率只能影响磁性流体的流速,对流量不产生任何直接影响。 相似文献
9.
Micro-pin-fin cooler mounted on the power chip enables the heat removal to meet modern microsystem requirement. Carbon nanotubes
(CNTs) have been proven as a potential material for micro-coolers due to the superior thermal conductivity, good mechanical
property and so forth, and there appear various applications of CNTs in the micro-cooler technology. In the present paper,
an analysis of the thermal and hydraulic characteristics of the micro-pin-fin heat sink was conducted, where air was used
as the cooling medium and an impinging jet was introduced to enhance the heat transfer. Three-dimension computational fluid
dynamics (CFD) simulations were carried out for micro-pin-fin coolers with various parameters, including the pin-fin size
and pattern as well as the jet velocity and nozzle diameter. The flow field and thermal properties of the micro-pin-fin heat
sink were obtained, and the heat removal efficiency was evaluated. 相似文献
10.
针对某厂连铸中间包,本文按照几何相似和Fr准数相等的原则建立水模型并采用刺激-响应的测量方法对中间包内钢液流动状态进行评价。研究发现,现有挡墙结构能够使中间包内部流体流动状况得到较大改善;随着拉速的增加,钢液在中包内的平均停留时间和滞止时间减小,不同流之间的均匀性降低;随着中包液位的增高,平均停留时间和不同流之间的均匀性都有所增加。因此建议应当保证钢液良好的纯净度、均匀性以及生产过程的稳定性,并将中间包液面稳定在某一相对较高的高度。 相似文献
11.
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
12.
Fluent是流体力学中通用性较强的商业CFD软件。将Fluent软件引入流体力学多媒体教学中,可对定常不可压缩流体在圆管内流动进行数值模拟,分析流体层流、紊流的两种流动状态,验证管内流体速度及切应力分布。实践表明,在流体力学课堂上配以Fluent数值模拟,有助于学生消化较难理解的理论知识,增强学习兴趣,提高教学效果。 相似文献
13.
Residence time is an important indicator for river environmental management. In this paper, a 3D hydrody-namic model has been successfully applied to Little Manatee River to characterize the mixing and transport process and residence time. The model employs horizontal curvilinear orthogonal grids to represent the complex river system that consists of branches and bayous. The model has been satisfactorily calibrated and verified by using two continuous data sets. The data sets consist of hourly observations of all forcing boundaries, including freshwater inputs, tides, winds, salin-ity and temperatures at bay boundary, and air temperatures for model simulations. The data sets also consist of hourly observations of water levels, salinity, and temperature at several river stations. The calibrated and verified hydrodynamic model was used to predict residence time in the Little Manatee River. Under the minimum flow of 0.312 m3/s, the pulse residence time (PRT) is 108 days. Model simulations were also conducted for 17 flow scenarios. Empirical regression equations have been satisfactorily derived to correlate PRT to freshwater inflow. Correlation coefficient R2 is 0.982 for PRT. 相似文献
14.
CFD Analysis of Gas Distributor in Packed Column--Prediction of Gas Flow and Effect of Tower Internals Geometry Structure 总被引：1，自引：0，他引：1
Computational fluid dynamics (CFD) simulations were carried out on the gas flow patterns of twin-tangential annular deflector gas distributor in the absence of liquid flow in a packed column (6.4 m in diameter), and the gas flow field in the column was presented close to reality on the whole. Furthermore, after ame-lioration of this gas distributor frame, turbulence energy and turbulence energy dissipation rate were both decreased greatly.Simulation results showed that the flow pattern and the distribution of gas flow were strongly affected by the column bottom frame; the proper column bottom frame could decrease the flow pressure drop greatly. Multifold factors, such as the column bottom geometry structure and distributor structure which affects the distribution capacity, must be considered. 相似文献
15.
Jin-yuan Qian Bu-zhan Liu Zhi-jiang Jin Jian-kai Wang Han Zhang An-le Lu 《浙江大学学报(A卷英文版)》2016,17(1):54-64
The pilot-control globe valve (PCGV) is a novel globe valve with a piston-type valve core and a small pilot valve. It can utilize a pressure difference to control the state of the main valve by the pilot valve. In this paper, a mathematical model of PCGV is established and a computational fluid dynamics (CFD) method is used to numerically simulate its flow and cavitation characteristics. Analysis of the pressure difference between the upside and downside of the valve core and comparison with similar previous work increase the reliability of the simulation. Then an analysis of flow and cavitation characteristics is carried out with three comparisons: a comparison between opened and closed states, a comparison between different inlet velocities, and a comparison between different valve core displacements. The results demonstrate that the vapor volume fraction reaches its peak point at the valve seat near the outlet tube, and that a higher inlet velocity or smaller valve core displacement can cause greater cavitation damage. This study can help further design work for optimization and engineering applications of PCGV. 相似文献
16.
Spin flash dryer has the advantages of both fluidized bed dryer and pneumatic dryer. It has predominance in dealing with thermal sensitive materials. In this paper, the distribution of the air velocity in the spin flash dryer is discussed,which indicates that the rotating air in the dryer chamber can be divided into two areas,potential flow area and plane swirl area. Experiments show that air tangent velocity effects the process of granulation most remarkably. The radial distribution and moisture content of the particles have their intrinsic rules along either the diameter or height of the drying chamber. Besides, the operating parameters of predrying on bleaching powder are optimized. To meet the strict standard of the wet-pressing granulator on the moisture content of the feeder,a narrow lap is made at proper height in the wall of the drying chamber,where a chute and a rotating valve are installed in order to predry the filter cake and remove a part of water. Then the material is fed into the wet-pressing granulator. 相似文献
17.
CFD Analysis of Gas Distributor in Packed Column ——Prediction of Gas Flow and Effect of Tower Internals Geometry Structure 总被引：2，自引：0，他引：2
Asoneofinternalparts,thefeedgasdistributorplaysanimportantroleinapackedcolumn.Thesmoothoperationandbetterqualityofproductsaregreatlyinfluencedbyitsperformance,especiallyinthecolumnwithlargediameter,shortpackedbedandlowpressuredrop.Duetotheimpor tanceoftheuniformityofinletgasdistribution ,itisessentialtodesignagoodfeedgasdistributor.However,fewtheoreti calandexperimentalapproacheshavebeencarriedoutinthisareasofarduetothecomplexityofthefluidflow[1 ,2 ] . Theliquidflowstructureisimprovedbyanew… 相似文献
18.
谢文彬 《荆门职业技术学院学报》2009,24(11):31-35
文章通过一个典型的太阳双带耀斑事件（2001年4月10日,NOAAAPt9415）研究耀斑带分离速度和纵向磁场强度的关系。这个耀斑事件具有很清晰的双带结构而且沿耀斑带的磁场变化很大,有利于研究耀斑带的分离速度和磁场分布的关系。结果表明：耀斑带的分离速度负相关于纵向磁场,而且这种负相关在耀斑峰值的时候最弱。 相似文献
19.
Viscosity reduction is an important process in mining heavy oil.To predict the temperature variation and viscosity variation of heavy oil in flow direction,computational fluid dynamics(CFD) was adopted to simulate the process of heat transfer and flow in this paper.Moreover,an objective function,namely viscosity reduction efficiency,was established to analyze the effect of viscosity reduction.The results indicate that circulating hot water can reduce viscosity significantly,and that the effect of viscosity reduction depends on the inlet temperature and inlet volumetric flow rate of hot water.There is a maximum temperature of heavy oil in flow direction.With the inlet volumetric flow rate of 2.0m3/h and the inlet temperatures of 60,℃,70,℃ and 80,℃,viscosity reduction efficiencies are 94.6%,96.7% and 97.3%,respectively.With the inlet temperature of 70,℃ and the volumetric flow rates of 1.5m3 /h,2.0 m3/h and 2.5m3/h,viscosity reduction efficiencies are 94.4%,96.7% and 97.2%,respectively. 相似文献
20.
综述了CFD数值模拟在调节阀中的应用,对某一广泛应用的套筒型调节阀应用三维建模软件内部流场建立模型,通过前处理器生成计算网格,应用CFD软件中的k-ε模型进行求解,得到调节阀内部流场的压力和速度的可视化图形。 相似文献