6.5%Si钢双辊薄带连铸布流水口结构优化的三维数值模拟

采用ANSYS Fluent软件建立三维数学模型对6.5%Si钢双辊2.0 mm薄带连铸设计的布流水口及熔池区域进行了数值模拟,并根据1/4流体区域模型的流动及传热计算结果,优化了原设计结构;取消布流孔与熔池区域接触倾角,保证水孔总横截面积不变,将直布流水孔流向从Y向改为X向,水平布流水孔设计成3个,2个10mm×12 mm及1个21 mm×12 mm孔,布流水孔的间距为33 mm,同时侧布流水孔的截面积变为7 mm×10 mm。经模拟结果验证,优化结构更利于凝固区的形成。

上湾选煤厂浅槽重介质分选机上升流系统改造实践

为了解决上湾选煤厂浅槽重介质分选机上升流系统堵塞的问题,在对产生原因分析的基础上,提出了上升流系统改造方案,并以305浅槽重介质分选机为对象予以实施。生产实践表明:浅槽重介质分选机上升流系统的结构改造,对其分选效果基本没有影响,而上升流系统堵塞频率下降80多个百分点,因此节约了大量生产成本,并带来了可观的经济效益。

EXPERIMENTAL STUDY OF HTC FOR FILM COOLING OF PARALLEL-INLET HOLES

The parallel-inlet holes with one-row, two-row and three-row film hole arrangements and different di- ameters are proposed to experimentally study their cooling characteristics. Detailed experimental processes and results are described and carried out. Results indicate that heat transfer coefficient （HTC） is increased with the increase of blowing ratio. When the blowing ratio is lower, the distribution of HTC along the heated wall can be divided into three regions. For larger blowing ratio or diameter, the cooling characteristics oi parallel-inlet film holes are similar to those of convective heat transfer around flat. Furthermore, when hole diameter is deter- mined, the arrangement patterns of film hole and the blowing ratio take a great influence on HTC.

Variation in Grain Size Distribution in Debris Flow

Grain composition of debris flow varies considerably from fluid to deposit, making it uncertain to estimate flow properties （e.g., density, velocity and discharge） using deposit as done in practice. Tracing the variation of grain composition is thus more important than estimating some certain properties of flow because every debris flow event consists of a series of surges that are distinct in properties and flow regimes. We find that the materials of debris flows, both the fluid and the source soils, satisfy a universal grain size distribution （GSD） in a form of P （D） = CD-zexp（-D/Dc）, where the parameters C, p and De are determined by fitting the function to the grain size frequency. A small At implies a small porosity and possible high excess pore pressure in flow; and a large D~ means a wide range of grain composition and hence a high sediment concentration. Flow density increases as 11 decreases or Dc increases, in a power law form. A debris flow always achieves a state of certain mobility and density that can be well described by the coupling of p and Dc, which imposes a constraint on the fluctuations of flow surges. The GSD also describes the changes in grain composition in that it is always satisfied during the course of debris flow developing. Numerical simulation using the GSD can well illustrate the variation ofμ and Dc from source soils to deposits.

CFD Simulation of Orifice Flow in Orifice-type Liquid Distributor

In this study,a suitable CFD(computational fluid dynamics)model has been developed to investigate the influence of liquid height on the discharge coefficient of the orifice-type liquid distributors.The orifice flow in different diameters and liquid heights has been realized using the shear stress transport(SST)turbulence model and the Gamma Theta transition(GTT)model.In the ANSYS CFX software,two models are used in conjunction with an automatic wall treatment which allows for a smooth shift from a wall function(WF)to a low turbulent-Re near wall formulation(LTRW).The results of the models coupled with LTRW are closer to the experimental results compared with the models with WF,indicating that LTRW is more appropriate for the prediction of boundary layer characteristics of orifice flow.Simulation results show that the flow conditions of orifices change with the variation of liquid height.With respect to the turbulence in orifice,the SST model coupled with LTRW is recommended.However,with respect to the transition to turbulence in orifice with an increase in liquid height,the predictions of GTT model coupled with LTRW are superior to those obtained using other models.

Variation in pore distribution along sample length in sintered 7xxx aluminum alloy

An experimental and computational fluid dynamics (CFD) numerical study of the sintering of an Al?7Zn?2.5Mg?1Cu alloy in flowing nitrogen was presented. Three rectangular bars with dimensions of 56 mm × 10 mm × 4.5 mm each, equally spaced 2 or 10 mm apart, were sintered in one batch at 620 °C for 40 min in a tube furnace. The pore distribution in the selected cross section of sintered samples was found to be dependent on the sample separation distance and the distance from the cross section examined to the sample end. A three-dimensional (3D) CFD model was developed to investigate the nitrogen gas behavior near each sintering surface of the three samples during isothermal sintering. The variation in porosity in the cross section of each sintered sample along sample length was found to be closely related to the nitrogen gas flow field near the sintering surfaces.

Relationship between heterogeneity of source rocks and genetic mechanism of abnormally high pressure

Based on the micro-fluorescence observation of polished sections of source rocks,two types of micro-layers with different wetting properties formed in thermal evolution,i.e.,oil-wetting and water-wetting micro-layers,are distinguished.The wetting property is found closely related to the abundance of organic matter and its occurrences with inorganic minerals.The alternating distribution and intercrossing of two types of micro-layers formed many separated spaces with different wettabilities.The strong capillary forces in these separated spaces with different wettibilities obstruct the cross flows of pore fluids and result in nearly independent and closed fluid systems.As a consequence,these spatially superposed spaces in source rocks bear the overburden pressure and then abnormally high pressures have developed in the whole source rock unit.Therefore,the abundance and occurrences of organic matter are the main inner factors influencing the formation of abnormally high pressures,whereas the formation,distribution and development of micro-layers with different wettabilities during the evolution of source rock determine the intensity and spatial distribution of abnormally high pressures.