电动缸式钢包长水口机械手的技术改造

介绍了宝钢5号连铸机钢包长水口机械手的设备构成及技术性能,阐述设备长时间运行所存在的问题,针对问题提出了设备改进的措施。     

Solution of transport equations on unstructured meshes with cell-centered colocated variables. Part II: Applications

This paper describes applications of the discretization procedure presented in the companion paper [A.W. Date, Solution of transport equations on unstructured meshes with cell-centered colocated variables. Part I. Discretization, Companion Paper, this volume]. Six problems having different domain complexities, presence of body and surface forces and, boundary conditions are solved. Where possible, the solutions are compared with published experimental or numerical data.     

Experimental investigation of vortex tube refrigerator with a divergent hot tube

Energy separation performance of vortex tube can be improved by using a divergent hot tube. Experiments are carried out to investigate the influence of the geometrical parameters on vortex tube refrigeration capacity by using nitrogen as the working fluid. In this work, the parameters are focused on the divergence angle of hot tube, length of divergent hot tube and number of nozzle intakes. Experimental results present that there is an optimum angle for obtaining the highest refrigeration performance, and 4° is the optimal candidate under our experimental conditions. Divergent tube length which exceeds a critical length has slight effect on the refrigeration capacity. The critical length to diameter ratio is L/D = 12 in our experiment. Increasing number of nozzle intakes increases the sensitivity of temperature reduction and can obtain the highest possible temperature reduction. Moreover, similarity relations for the prediction of the cold exit stream are presented and confirmed by the experimental data.     

可熔金属芯铸造纯Cu氧枪喷头的工艺设计及试验

介绍了运用可熔金属芯,采用砂型铸造方法铸造纯Cu氧枪喷头的工艺方案。针对180mm的3孔氧枪喷头的铸造成形工艺进行了设计,包括工艺流程、可熔金属芯制备、工艺参数的设计,并验证了这一方法的可行性。     

几何结构参数对磨料水射流喷嘴磨损规律影响的模拟分析

建立了前混合磨料水射流喷嘴物理模型。基于FLUENT软件,采用颗粒轨道模型、Grant弹性恢复系数和E/CRC磨损模型对磨料水射流喷嘴内的磨损特性进行了数值模拟。结果表明:当喷嘴收缩角为20°以上时,喷嘴磨损呈现两个严重磨损区,分别在喷嘴圆柱段入口处前较短距离范围内和喷嘴圆柱段出口处前较短距离范围内;随着喷嘴收缩角的增大,磨料颗粒与喷嘴圆柱段壁面碰撞次数和速度增加,同时随着喷嘴长径比的增大,喷嘴圆柱段壁面磨损速率整体增加,严重磨损区范围扩大,结果均使喷嘴圆柱段的磨损加剧。以喷嘴壁面磨损速率的面积加权平均积分表征喷嘴整体的磨损程度。随着收缩角和长径比的增大,喷嘴壁面磨损速率的面积加权平均积分增大,喷嘴的磨损整体而言越严重。因此,从减小喷嘴磨损的角度而言,喷嘴的收缩角和长径比宜取小值。     

Effect of nozzle orifice geometry on spray, combustion, and emission characteristics under diesel engine conditions

Diesel engine performance and emissions are strongly coupled with fuel atomization and spray processes, which in turn are strongly influenced by injector flow dynamics. Modern engines employ micro-orifices with different orifice designs. It is critical to characterize the effects of various designs on engine performance and emissions. In this study, a recently developed primary breakup model (KH-ACT), which accounts for the effects of cavitation and turbulence generated inside the injector nozzle is incorporated into a CFD software CONVERGE for comprehensive engine simulations. The effects of orifice geometry on inner nozzle flow, spray, and combustion processes are examined by coupling the injector flow and spray simulations. Results indicate that conicity and hydrogrinding reduce cavitation and turbulence inside the nozzle orifice, which slows down primary breakup, increasing spray penetration, and reducing dispersion. Consequently, with conical and hydroground nozzles, the vaporization rate and fuel air mixing are reduced, and ignition occurs further downstream. The flame lift-off lengths are the highest and lowest for the hydroground and conical nozzles, respectively. This can be related to the rate of fuel injection, which is higher for the hydroground nozzle, leading to richer mixtures and lower flame base speeds. A modified flame index is employed to resolve the flame structure, which indicates a dual combustion mode. For the conical nozzle, the relative role of rich premixed combustion is enhanced and that of diffusion combustion reduced compared to the other two nozzles. In contrast, for the hydroground nozzle, the role of rich premixed combustion is reduced and that of non-premixed combustion is enhanced. Consequently, the amount of soot produced is the highest for the conical nozzle, while the amount of NO_x produced is the highest for the hydroground nozzle, indicating the classical tradeoff between them.     

锅炉汽包接管断裂失效分析

对汽包上连接安全阀管路接管的断裂失效原因进行了综合分析 ,在排除了可能引发事故的诸多因素之后 ,找出了断裂发生的根本原因是由于安全阀排气管路的出口方向在设计上是不合理的 ,并提出了改进措施     

Modelling of compressible gas-liquid flow in a convergent-divergent nozzle

A two-fluid model for compressible flow of gas bubbles dispersed in liquid moving through a convergent-divergent nozzle, which is used for a gas-assisted atomization, is presented. The model is developed for flows with high values of the gas volume fraction—up to the phase inversion values. Drag and virtual mass forces are considered. A new method is proposed to correct the virtual mass coefficient for the high bubble loadings. The mixture k-ε turbulence model is adapted for the nozzle flow. The particle number density equation is solved to calculate the distribution of the locally averaged bubble diameter. Curvilinear body fitted grids are utilized to represent the nozzle shape accurately. It is shown that for numerical stability it is necessary to discretize implicitly the virtual mass term and solve the momentum equations for two phases simultaneously in a coupled way. The comparison between the experimentally measured and the predicted pressure profiles along the nozzle wall demonstrated good overall agreement. Gravitational effects are analysed by modelling a three-dimensional case. The examination of the flow through the nozzle reveals the non-uniformities of the bubble size and volume fraction distributions. It is confirmed that the virtual mass force plays a major role in accelerating/decelerating flows with a relatively low interfacial drag.