PCB喷淋系统应用浅谈

文章针对PCB厂水平线如何计算、选择合适的喷嘴进行了初步的探讨,并结合实际应用展示了选择合适的喷淋系统,以有利于生产品质的提升。     

基于Fluent的新型布水器的设计与分析

针对传统多孔布水器布水不均匀、布水口易堵塞的现象,提出了双臂单孔的新型布水器的设计.该结构包括中央旋转水管和可调控的布水横管,中央旋转水管带动端部的布水横管实现圆周运动,使圆形水池内污水均匀覆盖.建立了布水器的数学与运动学模型,利用Fluent对不同扩散角的喷嘴内外流场进行数值模拟,优化喷嘴参数,使新型布水器达到预期的布水均匀效果.     

Numerical Study on the Effect of Cavitation on Flow and Diesel Fuel Atomization Characteristics

Computational fluid dynamics (CFD) models based on the turbulent mixture multiphase model were applied to consider the effect of cavitation on the spray of diesel fuel. The effects of injection pressure and length‐to‐width (L/W) ratio on the velocity distribution, cavitation number, discharged coefficient, and nozzle exit velocity were investigated and the performance of the model was compared with the experimental data. The results indicate that the cavitation generated in the nozzle has a strong impact on the fuel injection and spray quality, whereas the L/W ratio is a highly effective parameter for cavitation behavior. In addition, by increasing the L/W ratio, the range of cavitation number, wall friction, and flow resistance increase but in the cavitation region the velocity profile in radial and axial directions, spray cone angle, nozzle exit velocity, and the discharged coefficient decrease.     

钢管表面高压水除鳞效果分析与对策

介绍了钢管表面高压水除鳞系统的工作原理;分析了影响钢管表面高压水除鳞效果的设备问题;探讨了钢管表面生红锈的化学机理。通过改进高压单向截止阀设计和曲轴进油口的密封形式,并通过实验对比选择小直径喷嘴解决了钢管表面生红锈的问题,并在保证钢管表面不生红锈的同时取得了良好的除鳞效果。     

Durchsatzverhalten von Hohlkegeldüsen

A semi empirical relationship is proposed for swirl nozzle discharge coefficients. It considers the theoretical background and is matched to an extended own experimental database and to data from manufacturers of industrial nozzles. The equation considers the liquid viscosity and can be used for very different nozzle designs.     

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 the influence of momentum thickness on the development of a slightly heated plane jet

The influence of nozzle selection and consequent impact of momentum thickness is rarely investigated in heated horizontal plane jets. In the present work an experimental study is performed using a two dimensional converging nozzle and then by attaching a channel to the nozzle with air issued at a moderate Reynolds number of 4000 and at an inlet temperature of 60 °C. A hotwire anemometer is used to measure velocity and temperature fields. The ratio of heat to momentum transport is 1.33 for nozzle jets and 1.4 for channel jets. Half widths based on mean excess temperature and velocity is higher for channel jets. The influence of buoyancy is negligible for the present case. But the spread of temperature as a scalar is important in the transport process.     

Accuracy prediction model of an orifice-compensated aerostatic bearing

In order to reduce the synchronous radial error motion of the orifice-compensated aerostatic bearing, an accuracy prediction model was built to discuss the direct relationship among the synchronous radial error motion, the roundness error, and the nozzle number. It was found that increasing the nozzle number delayed the appearance of the obvious peak of the averaging coefficient and roughly reduced the synchronous error motion. The optimized nozzle number was n_p = 2 × 3 × 5 × 7 × …, which was equal to the product of the prime numbers within the prime sequence. The existence of axial grooves and the increase in the nozzle row number didn't reduce the synchronous error motion, but it might cause an increase in the synchronous error motion. The accuracy prediction model gave a simple method for predicting the synchronous radial error motion of the orifice-compensated aerostatic bearing.     

燃烧器摆动机构的设计和改进

四角布置燃烧器喷嘴上下摆动，改变火焰中心位置，是锅炉汽温调节和炉膛吸热控制的重要手段。燃烧器喷嘴不能摆动，再热器只能以喷水降温，降低了电厂循环效率。本文详细分析了不能摆动的各种原因并提出了改进措施。     

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.