CFD analysis of natural convection heat transfer augmentation from square conductive horizontal and inclined pin fin arrays

Numerical investigations on natural convection heat transfer from a vertical isothermal plate with pin fins have been made by solving the Navier–Stokes equation along with the energy equation. Average Nusselt number for the plate with different configurations of pin fins have been obtained. It was observed that the maximum increase of the average Nusselt number occurs at S_v/L?=?0.2 for θ?=?45° with fin height of 24?mm (H/t?=?8). The average Nusselt number increases with fin aspect ratio and decreases with angle of inclination. There is not much difference between the average Nusselt number for in-line and staggered arrangement of fins for the range of parameters studied in the present work. A correlation is developed to predict the average Nusselt number of the plate as a function of fin spacing in stream- and span-wise direction, aspect ratio of fins and its angle of inclination.     

电液控制的销齿翻车机液压传动系统设计

目前销齿翻车机控制系统主要采用机械联动或者是机电结合使用,文中研究机电液一体化技术,采用集中液压站控制实现动作的无级调速,为后续的使用寿命提供理论依据。     

Friction and wear behavior of styrene butadiene rubber‐based composites reinforced with microwave‐devulcanized ground tire rubber

In this work, the tribological properties of a new material obtained by revulcanization with styrene butadiene rubber (SBR) and devulcanized ground tire rubber (GTR) were investigated. GTR was devulcanized using the microwave method at a constant power while varying the microwave exposure time. Devulcanized rubber (DV‐R) and untreated GTR were revulcanized by mixing with SBR at different rates (10, 30, 50 phr). To determine friction and wear characteristics of the samples, pin (ball) on disc and abrasion tests were conducted. Scanning electron microscopy (SEM) was employed to observe the worn surfaces of the composites to correlate the experimental test results to the wear mechanisms. All of these tests and experiments were performed on original vulcanized rubber samples for comparison. The composites exhibited different friction and wear behavior due to morphology, dispersion behavior and devulcanization functionalization of ground tire rubber. In general, DV‐R/SBR composites exhibited improvement in both mechanical and tribological properties. However, the enhanced compatibility of DV‐R resulting from the specific chemical coupling of DV‐R with SBR was crucial for the mechanical, friction and wear properties. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42419.     

一种3线制半双工SPI接口设计

SPI(serial peripheral interface)总线是由Motorola公司提出的一种4线制同步串行外设总线接口,包括时钟、使能、输入和输出4根引脚,主要用于CPU与各种外围器件以串行方式进行通信。为了进一步减少接口,介绍了在一款用于射频芯片数据/控制接口的3线制SPI接口的电路设计,通过采用半双工工作模式,接口电路在减少一个引脚的情况下实现双向通信。介绍了3线制SPI接口的电路结构及其工作原理。该SPI接口在0.18μm工艺下实现的版图总尺寸约为240μm×460μm,在10 MHz工作频率下的功耗约为2 mW,通过仿真验证,3线制SPI接口功能正确。     

抽芯盖注塑模具设计

分析了抽芯盖塑件的使用要求和结构特点,介绍了抽芯盖注塑模具的结构组成及工作原理。该模具一模两腔,采用斜导柱和斜推杆两种侧抽芯机构,结构合理,运行可靠。生产实践表明塑件可满足使用要求。     

汽轮机前轴承座滑销系统销孔加工方案解析

汽轮机滑销系统是保证汽轮机安全高效运行的重要部件之一,其中,Ф50_0＋015mm的骑缝销孔在滑销系统中起着关键的定位作用。由于此销孔特征为深孔加工,所定位的2个零件材质不同,成为汽轮机行业的加工难题。通过对改进加工工艺路线、设计外冷镗刀杆、选择合理的加工刀具和工装以及合理选择润滑油及润滑方式等方面进行综合分析,制定了一套合理的加工方案,有效保证了销孔的加工质量和精度,在同类产品制造中具有广泛的借鉴作用。     

卧式双面镗前轴主销孔车端面机床

介绍了一种一次装夹可完成前轴主销孔粗、精镗削加工及主销孔拳头两端面车削加工的专用机床.加工时先用插销机构插主销孔定位,保证了主销孔的壁厚均匀.加工不同系列的前轴只需更换相应的定位块、插销,粗调整后支座定位销位置即可,夹紧压板能旋转90°便于装卸工件.     

集中润滑系统在易开盖组合成型中的应用

易开盖组合成型中应用集中润滑系统来替代传统的人工润滑方式,可以在保证设备正常运行的同时,使润滑油用量更加经济合理,设备润滑部分的维护时间和成本大大减少,生产效率有效提高。文中主要对集中润滑系统在易开盖组合成型中的应用进行分析阐述,包括集中润滑系统的特点、组成、设计选型以及控制系统等。     

爆破销安全阀

介绍了一种应用欧拉临界载荷公式设计的新型安全阀结构特点和工作原理,论述了阀门安装和维护方法。     

不同活塞销孔衬套-活塞销摩擦副匹配性能研究

活塞销孔衬套-活塞销是柴油机重要的摩擦副之一,其匹配性能的优劣直接影响使用寿命和动力特性。为探讨不同制备工艺的活塞销孔衬套与柴油机在用活塞销的匹配性能,将分别采用挤压和旋压工艺制备的活塞销孔衬套,以及进口衬套分别与柴油机在用活塞销匹配,在摆动摩擦副摩擦磨损试验台进行承载、抗咬合和耐磨损性能试验。试验结果表明：制备工艺对摩擦副匹配性能具有一定的影响;从摩擦扭矩、摩擦温度、宏观形貌和磨损量4个方面分析,相同工况下挤压衬套承载极限、抗咬合性能和耐磨损性能均优于旋压衬套,具备对标进口衬套的能力,可为国内活塞销孔衬套的选配提供参考。