台阶型旋转热管传热性能的试验研究

利用具有自蒸发循环的旋转热管冷却技术对旋转零部件 ,如电机主轴、切削刀具、混炼机转子、机床主轴等进行冷却 ,可大大减少转轴的热应力 ,提高转轴的使用寿命。设计了一种便于旋转热管内部工质既能顺利进行自蒸发循环 ,又利于制造加工的台阶型内部结构 ,介绍了实验装置 ,对台阶型旋转热管的启动性能、表面均温性能、最佳充液量和导热性能进行了试验研究。结果表明 ,台阶型旋转热管在 1min之内能迅速启动起来 ,表面均温性良好、没有过热点 ;其导热性能与旋转热管内部工质的流型、充液比V+ 、工作温度θ、转速n等因素有关。自蒸发循环旋转热管冷却技术与其他循环水冷却系统相比 ,具有良好的表面均温性、高效的导热性、无泄露 ,节约用水等优点。     

冬小麦-夏玉米轮作周期内碱解氮、硝态氮时空变化及施氮安全值的研究

利用 3年 6季氮肥试验研究了冬小麦—夏玉米轮作制度下 ,冀东褐土剖面碱解氮、NO-3 -N含量时空迁移变化和土壤氮素安全值指标。结果表明 ,土壤碱解氮自上而下依次递减 ,NO-3 -N呈“V”字型变化 ,二者均与施肥水平及植株生长状况密切相关 ,在 2 0～ 40cm区域出现碱解氮亏缺区 ,N2处理较为明显。N2处理的地下水NO-3 -N含量已超标 ,建议高产条件下土壤环境投氮安全值为 42 0～ 450kghm- 2 较为适宜     

Lubricant Spin-Off from Magnetic Recording Disks

As the rotation rate of magnetic recording disks increases over the next few years, lubricant spin-off from the disk surface may be significant. Lubricant thickness was measured as a function of spin time at 10000 rpm on typical carbon overcoated magnetic recording disks initially lubricated with 10–135 Å of perfluoropolyether Zdol. The viscosity of the lubricant film increased as the film thickness decreased with spin time. Lubricant spin-off in response to air shear stress on the free surface was approximately described by viscous flow. The rate of lubricant removal by evaporation was compared to the spin-off removal rate in films between 10 and 50 Å thick. Dispersion interaction and chemisorption are expected to retain a molecularly thin film of lubricant on the disk surface.     

On the temperature and specific energy during electrodischarge diamond grinding (EDDG)

Electrodischarge diamond grinding (EDDG) is a hybrid machining process comprising conventional grinding and electrodischarge machining (EDM) as its constituent processes. It has the potential of shaping advanced engineering materials. Temperature of the workpiece and material removal rate are chosen as responses in full factorial (3³) design with current, pulse-on time, and wheel speed as process parameters. Specific energy is a vital consideration for any machining process. EDM is known for its inefficiency. Experiments were conducted with a specially fabricated bronze disk as tool electrode to evaluate specific energy in EDM, and the results were compared with that of EDDG. It has been found that specific energy required in EDDG is less than that in EDM with a rotating disk electrode.     

水合抛光加工的运动学特性

建立了旋摆驱动方式下水合平面抛光过程中工件的运动学模型,揭示了抛光盘开孔方式对蓝宝石衬底的水合抛光均匀性影响规律。旋摆驱动条件下,杉木抛光盘的开孔方式对蓝宝石衬底水合抛光加工全局均匀性和局部均匀性具有重要的作用,局部均匀性的阶梯状分布为直线、圆环和螺旋线开孔方式的共性特征。与直线、圆环开孔方式相比,在一定的参数取值条件下,螺旋线开孔方式可更好地实现水合抛光加工的全局均匀性和局部均匀性要求。     

浅析转动小刀架车削圆锥零件的技巧

转动小刀架车削圆锥零件是普通车床加工圆锥体最常见的方法。为了提高普通车床采用转动小刀架车削圆锥零件的加工质量和效率,本文从几个方面浅谈一下转动小刀架车削圆锥零件的技巧。     

Mixed convective heat transfer enhancement in a ventilated cavity by flow modulation via rotating plate

The present study numerically explores the mixed convection phenomena in a differentially heated ventilated square cavity with active flow modulation via a rotating plate. Forced convection flow in the cavity is attained by maintaining external fluid flow through an opening at the bottom of the left cavity wall while leaving it through another opening at the right cavity wall. A counter-clockwise rotating plate at the center of the cavity acts as an active flow modulator. Moving mesh approach is used for the rotation of the plate and the numerical solution is achieved using arbitrary Lagrangian-Eulerian finite element formulation with a quadrilateral discretization scheme. Transient parametric simulations have been performed for various frequency of the rotating plate for a fixed Reynolds number (Re) of 100 based on maximum inlet flow velocity while the Richardson number (Ri) is maintained at unity. Heat transfer performance has been evaluated in terms of spatially averaged Nusselt number and time-averaged Nusselt number along the heated wall. Power spectrum analysis in the frequency domain obtained from the fast Fourier transform analysis indicates that thermal frequency and plate frequency start to deviate from each other at higher values of velocity ratio (>4).     

旋转机械无线监测中的多普勒效应

由于应用无线通信技术对旋转机械进行状态监测时,无线设备安装在转轴上随轴高速旋转,无线设备之间的相对位置发生变化,因此会产生多普勒效应,影响无线通信。针对这一问题,首先,提出了两种无线设备安装方式;然后,建立了旋转运动中无线设备的多普勒频移理论模型,并分析了影响无线通信的因素;最后,对水润滑轴承水膜压力进行无线监测试验,引入误码率和丢包率研究了其与轴转速之间的关系,并对多普勒频移理论模型进行验证。理论与试验分析结果表明:多普勒频移与无线设备摆动圆直径、轴转速以及电磁波入射角密切相关,尤以转速影响为甚;在433 MHz通信频率下,无线监测方法不能很好地用于转速接近或超过10kr/min的旋转机械;转速对丢包率的影响大于误码率,丢包率为误码率的2~3倍。     

长距离伪斜机头旋转开采技术研究

针对负伪斜状态下综采工作面机头旋转开采过程中存在的问题，通过对工作面1号支架进行精确定位安装、采取合理的调斜和进刀方式等技术工艺，解决了负伪斜旋转开采过程中工作面支架和输送机容易下窜的技术难题。该技术的成功应用，提高了工作面的采出率，为综采工作面旋转机头开采提供了技术参考。     

液黏离合器旋转动密封泄漏特性试验研究

为探究并改善液黏离合器旋转动密封的泄漏特性，采用Tr1-6Kr-22A变速试验台开展其密封性能试验，对比分析操作参数和结构参数对各个泄漏通道泄漏量的影响规律。结果表明：操纵油泄漏量整体偏大，润滑油泄漏通道受压力影响最小；随着操纵油压力的增加，各泄漏通道泄漏量亦随之上升，但高压工况下泄漏量增势平缓；各泄漏通道泄漏量与转速存在正相关关系，但油压对密封泄漏量影响较转速更为明显；密封环带宽度对泄漏量影响较大，较宽的密封环带可有效降低密封总体泄漏量；采用较宽密封环带的试验工装各个通道泄漏量最小，且受操作参数影响较小，适用于压力波动较大的场合，而在转速波动较大时密封泄漏量出现阶跃特性。