固液混合油辣椒多相流灌装的数值模拟

以固液混合油辣椒多相流的灌装过程为主要研究对象,采用流体力学计算软件Fluent对其灌装过程进行数值模拟,分别对直径为36、48、60 mm的计量缸在灌装过程中的密度场、各相体积分数的分布状况进行研究。数值模拟结果表明:随着灌装机构计量缸直径的增大,灌装流场的密度均匀性变好,高密度和低密度区域明显减少,直径为60 mm的计量缸其固液混合油辣椒多相流流体的各相体积分数和密度分布比其他两种较好,体积分数与初始设定基本吻合,研究结果为灌装装置的结构设计和灌装工艺提供了理论依据。     

钛渣流态化氯化流动特性的数值模拟

基于双流体模型,结合钛渣的物性参数,采用Fluent软件对钛渣流态化氯化过程的数学模型进行了模拟,通过不同的临界流化速度,对钛渣流态化氯化的流动特征进行了研究。结果表明：Grace修正公式适合钛渣流态化氯化最小流化速度的计算;在最小流化速度下,床层首先形成乳相,随着流化时间的延长,在中部形成小气泡;在完全流化速度下,床层首先经历节涌过程,然后进入完全流化。     

农产品空气能热泵烘房温度场的数值模拟与验证

农产品热泵烘房温度场均匀性是影响农产品干燥品质的重要因素。本文选用5HGR-35型农产品热泵烘房,通过交互式CAD/CAM系统(UG)软件建立热泵烘房3D模型,运用理论分析与计算流体动力学(Computational fluid dynamics,CFD)模拟相结合的方法,研究其内部温度场分布情况,对现有结构烘房的温度场建模模拟,分析模拟结果并对现有结构进行优化。通过模拟得出结论:送风速度越大,烘房内热空气更新越快,换热效果越好。综合温度场分布以及农产品烘干要求,烘房内合理的送风速度为11 m/s左右;在11 m/s风速下,烘房空载时在15 min左右达到设定温度(65℃);小推车设计高度加大300~310 mm烘房内部温度场更均匀;烘房顶部均匀加入3块长×宽×高=2900 mm×20 mm×300 mm的挡板,可以使烘房内部温度场更均匀;小推车与烘房之间及相互之间保持30 mm左右间隙摆放更有利于烘房内部温度场的分布;验证试验中,模拟温度与实测温度吻合性良好。上述结论对烘房的进一步优化设计具有一定的指导意义。     

太阳能辅助热泵干燥粮食的数值模拟研究

粮食的干燥过程实质上是多孔介质热湿耦合传递的过程.基于多孔介质热质传递理论,通过数值模拟的方法,针对利用太阳能辅助热泵干燥粮食时热风随时间变化的情况,采用综合温度和空气绝对湿度作为瞬态边界条件来对干燥过程中粮食内部温度和水分的变化进行模拟研究.模拟结果显示小麦水分在干燥150 h后达到安全水分13.6％(干基),而实验结果显示小麦水分在干燥135 h后达到安全水分13.6％(干基),二者对比相差不大,并且模拟温度与试验温度吻合较好.     

壁面马赫数分布规律可控的新型内收缩基准流场设计方法

根据有旋特征线理论,设计出了沿程马赫数下降规律可控的轴对称基准流场,分析了基准流场的几何参数(前缘压缩角及中心体半径)的影响规律,发现选取较小的前缘压缩角和中心体半径有利于得到性能优良的基准流场;然后在设计状态Ma=6时研究了三种典型的马赫数下降规律对这种轴对称流场性能的影响。最后考虑了粘性的影响,并进行了粘性修正探索,结果表明,采用附面层位移厚度修正方法后,基准流场的壁面压力分布和无粘情况吻合良好。      

热带太平洋中部地区热力异常对我国南方冬季降水影响的数值模拟

为了分析冬季热带太平洋中部海温升高对中国南方冬季降水的影响,本研究利用国际太平洋研究中心的区域气候模式（IPRC-RegCM）对2008年初南方典型的大范围雨雪天气过程进行数值模拟。结果表明：该模式能够较好的模拟出此次持续性降雨（雪）过程的雨带分布。且当在热带太平洋中部海域加入扰动热源后,中国南方大部分地区均以上升气流为主,南海地区水汽输送增强,有利于我国南方雨雪天气的发生。     

粘贴加固混凝土氯离子扩散的理论模型和数值模拟

基于物质非稳态扩散理论,采用现有研究对Fick第二定律的修正方法,并将粘贴加固考虑为对氯离子扩散方程边界条件的调整,提出可用于粘贴加固混凝土的氯离子扩散理论模型。利用ABAQUS、MATLAB PDE tool、MATLAB自编程3种方法均可对粘贴加固混凝土梁的氯离子扩散过程进行数值模拟。对比未加固与加固构件的氯离子扩散规律,发现粘贴加固可降低钢筋表面的氯离子浓度值,延缓氯离子浓度到达临界锈蚀浓度的时间,增加材料使用寿命,并且加固时间越早,增加寿命越长。     

尾矿坝变形细观力学机理的颗粒流数值模拟

以新建四川省盐源县平川铁矿黄草坪尾矿库为工程背景,通过堆坝模型试验与室内土工试验,获得尾矿坝干滩面几何特征、颗粒分布规律及尾矿力学性质。基于离散元理论,采用PFC 2D数值模拟软件进行双轴试验,与土工试验结果对比,得到尾矿细观力学参数,并分析尾矿坝颗粒接触力分布、颗粒位移与坝体结构变形特征。结果显示：1)初期坝中颗粒间接触力较大,形成的力链大致呈45°倾斜向上;坝体尾矿颗粒接触力随着埋深的增加而增大,在基岩凸起处接触力较大且集中。2)初期坝颗粒位移不明显,堆积坝少数尾矿颗粒沿坡面向下滚动,具有较大位移;尾矿堆积坝存在较为典型的滑移面,滑移面上部区域颗粒位移较大。3)初期坝结构变化不明显,尾矿堆积坝中靠近初期坝内坡面附近结构变形显著。     

冷却干燥通风过程中粮仓内热湿耦合传递的数值模拟

基于多孔介质传热传质的理论,建立了一种冷却干燥通风过程中粮仓内热湿耦合传递的数学模型。借助数值模拟的方法,对冷却干燥通风过程中粮仓内温度和水分的变化进行了模拟研究,得到了冷却干燥通风过程中粮堆内部热量传递和水分迁移的基本规律。     

机械式冷藏集装箱内温湿度场的数值模拟及其试验研究

以配置了上送风管的机械式冷藏集装箱为研究对象,采用番茄为试验物料,建立三维k-ε紊流计算模型,结合多孔介质模型及组分输运模型,采用非稳态求解方法,计算装载货物情况下集装箱内部的动态温湿度场;同时对该模型相应点的温湿度变化过程进行试验验证研究。结果表明,果蔬在冷藏集装箱运输过程中,自身的呼吸作用及通过箱壁从外界传入的热量对温度场的影响较大,造成货物内部与靠壁面处的温度较高;由于货物区温度较高,且热湿空气被水分含量较低的冷空气取代,致使在同等水蒸气含量下货物区的相对湿度较周围空气区低。模拟计算结果与试验验证结果能较好地吻合,建立的模拟模型可为果蔬冷藏集装箱内温湿度的监测与控制提供技术依据。     

Numerical simulation and optimization of flow and temperature fields for wide slab cast mold

Fluid flow and temperature distribution in a wide slab continuous caster mold are simulated using the commercial software FLUENT. The research results show that the longitudinal cracks in the wide slab surface with an original submerged entry nozzle (SEN) mainly are caused by weak upper flow circulation in the mold, slow heat exchange near the meniscus, and non uniform melting of the mold powder. Therefore, a modified SEN with smaller outlet thickness, a 15° downward port angle, and convex bottom is designed to overcome the disadvantages of the original nozzle. The characteristics of the molten steel flow are analyzed by numerical simulation. The results indicate that the parameters of the optimum SEN are more highly optimized than the original SEN. The trial results also show that the optimum SEN possesses a better application effect.     

Grain growth of continuous casting slab solidification based on cellular automata model

The cellular automaton (CA) method is coupled with finite difference method to establish a stochastic nucleation and growth model. According to the actual production conditions, the solidification structure of continuous casting slab is simulated and the evolution law of the inner structure is reconstructed. It is showed that grain transformation is from equiaxed crystal to columnar crystal and then to equiaxed crystal. Thickness of three crystal layers are different in various production technological systems, thickness of surface equiaxed crystal and inner equiaxed crystal are reduced, and the results of the columnar crystal thickness are contrary, while casting speed and superheat are increasing. The results show well agreement with the stochastic nucleation, preferred growth, competitive growth and random orientation of grain.     

Numerical simulation of remodeling in mandible under orthopedic loads

The research on the remodeling in mandible under the action of orthopedic loads is important for the determination of orthopedic scheme. a three-dimensional finite element model of mandible and temporomandibular joint is established. Using Cowin Remodeling Law, the finite element simulation of the remodeling in mandible during the orthopedics under the action of orthopedic loads is carried out. Comparing the numerical results after remodeling with those before remodeling, it is demonstrated that the normal remodeling greatly affects the distribution of strain and strain gradient on the surface, therefore the effect cannot be ignored in the determination of the orthopedic scheme.     

Numerical simulation of lahar in Changbai Mountain region

Lahar is one of most serious volcanic disaster, threats people’s lives and property security of volcanic region. The numerical simulation result can predict the characteristics of lahar, provide reference materials for making disaster prevention plan, and make the measure of lahar disaster relief transition from passive to active. Selected the area near the Tianchi as the research region, and divided the research region into forming region, circulation region and accumulation region. In order to establish the calculation model, divided the circulation region and accumulation region into many meshes, which are small enough to meet the calculation accuracy. The calculation time step length is also identified very small as 0.001 min. Calculated the average and peak velocity of lahar, triggered by the assuming medium and small eruption of Tianchi volcano, through the Delft 3D software. The longitudinal variation of lahar frontal average and peak velocity is acquired by the numerical simulation result. The time to area inundation by lahar, triggered by medium eruption, is obtained by calculation. The lateral variation of lahar depth at each cross-section is simulated. Although there is some different between the assumption of this research and the actual condition, flow velocity and accumulation situation of lahar are calculated in quantity and extension by numerical simulation, these result has reference value for preventing and reducing lahar disaster.     

Numerical Simulation in Flow Field of CNG Vehicle Catalytic Converters

The steady flow in the catalytic converters of CNG was simulated. The gas can breakaway in the entering pipe and the flow of the gas can convergence well in the exhaust pipe. The flow distributing mainly depends on the flow capability of the expanding pipe. The pressure falls apparently in the carrier of catalytic converters. The noble metals in the center of the catalytic converters are consumed more quickly than the edge zone.     

Numerical simulation of desulfurization characteristics in CFB flue gas with bypass

This paper uses the standard k-ε model, DPM, Species Transport and Finite-Rate Chemistry model to simulate momentum, energy and composition equations of a new CFB desulfurization tower with gas bypass. The numerical simulation results agree well with the experimental results. The characteristics of desulfurization and flow resistance of two desulfurization towers are analyzed by numerical simulation, and the influence of SO2 concentration to desulfurization efficiency of bypassing desulfurization tower is also analyzed. The results show that both desulfurization and flow resistance characteristics of bypassing desulfurization tower are better than those of non-bypassing desulfurization tower. The desulfurization efficiency of bypassing desulfurization tower decreases with the increase of SO2 concentration, the desulfurization efficiency increases with the increase of the relative humidity of bypassing desulfurization tower.     

Numerical simulation of gas solid characteristics in double inlet square cyclone separator

This paper uses RSM turbulence model to conduct the numerical simulation on the gas flow field in double inlet square separator and calculate the velocity field and pressure distribution in the seperator. At the same time, it simulates the solid particle trajectories in the separators using Lagrangian model. The results show that the velocity field and pressure distribution in double inlet square separator have good symmetry, but the flow swirl intensity is insufficient and easy to decay; different sizes and different injection locations bring significant differences for the particle trajectories; injecting small particles can be easy to form flow short-circuit phenomenon inside the separator, injecting particles near the top of separator can be easy to form top ash ring phenomenon inside the separator; these phenomena have adverse factors to the separation efficiency. When the separation cylinder corners of square separator are changed into cutting-shaped chamfers, the flow field in the separator can be improved, and the separation efficiency of separator can be effectively improved.     

Numerical simulation of the mechanism of atypical dynamic phenomena in mines

An atypical dynamic phenomenon of mines, including its action forms and definition, were put forward, based on the mining accident at the Furong Mining Group Company in Sichuan, P. R. China. The mechanism of the atypical dynamic phenomenon was revealed by analyzing rock stress distribution, calculating the first and cycle broken distance of each thick and hard roof, and analyzing the balance structure of broken rock based on the three dimensional finite element software. The first stratum of the bent, sunken, aged strip was influenced by the geological conformation and the coal mining activity. This created the first break of the key stratum and led to the atypical dynamic phenomenon. We show that the key factors affecting the phenomena are the roof and floor structures, surrounding rock, and initial stress and rock burst tendency of the key stratum.     

Numerical simulation of carbon dioxide storage in unmineable coalbed

The injection of carbon dioxide (CO2) in deep unmineable coalbeds（CO2-ECBM） is a very attractive option for geologic CO2storage. The CO2 is stored and at the same time the recovery of coalbed methane is enhanced. The revenue of methane (CH4) production can offset the expenditures of the storage operation. The processes involving in the CO2-ECBM include multi-components gas adsorption,diffusion,and gas-water two phase flow in coalbed. On the basis of above processes,a model considering adsorption induced coal matrix swelling is developed, which can be used to describe multi-components gas adsorption/desorption-diffusion-flow in coalbed. The finite difference method is used to solve this model,and the comparison of the results with the existed model suggests the model is valid. Then the model is applied to evaluated the influence of permeability of coal seam,different gas adsorption induced swelling,CO2/CH4 adsorption capacity ratio,pore model considering matrix swelling,and gas composition of injection gas on CO2 sequestration and methane production, and these results are very important for site selection and technological parameters optimum of CO2-ECBM project.     

Numerical simulation of contact problems in high pressure reciprocating pump systems

The cylinder bodies of reciprocating pumps easily fail from cracks due to complex external loads. Based on the working principle of reciprocating pumps, hydrodynamics, and a numerical method for surface to surface contact problems, a contact model involving a cylinder body, a valve base, and a valve pocket is established. Considering pressure fluctuation, flow pulsation, alternate loads, and the impact of the inlet and outlet valves, a finite element model for the complete system is established. Using this model, the contact state of the complete system is analyzed, and the stress distribution, contact state, contact stress distribution of the interface, and position of the weak part are obtained.