扇形沟槽表面节流静压气体轴承的性能分析

关于气体轴承承载能力优化问题.为增大静压气体轴承的承载能力,提高轴承的刚度,设计了一种扇形沟槽表面节流式静压气体轴承,并运用计算流体力学软件Fluent计算轴承的性能,分析几何参数对轴承性能的影响.结果表明,在一定气膜厚度下,增大节流面积可显著提高承载能力,增大节流槽长度可以增加轴承刚度,而在气膜厚度较小时,均压槽可以同时提高承载能力和刚度.当轴承直径相同时,所设计的静压气体轴承较小孔节流式具有更高的承载能力和更大刚度.     

辐射状均压槽气浮支承静态性能仿真研究

为提高静压气体轴承静态特性,设计了一种新型径向槽结构静压气体轴承。建立了径向槽结构静压气体轴承CFD模型,分析了径向槽结构深度、半径、数目、角度和供气压力对静压气体轴承承载能力和刚度的影响。静压气体轴承承载能力随槽结构深度、数目、角度和供气压力增加逐渐增大,槽结构数目和供气压力对其承载能力影响尤为显著;静压气体轴承承载能力随槽结构半径增加先增大后减小;静压气体轴承径向槽结构深度、数目、角度、半径和供气压力影响静压气体轴承刚度及其刚度峰值所在的气膜厚度,槽结构半径、数目和供气压力对刚度值影响显著,槽结构角度和半径对静压气体轴承刚度峰值所在的气膜厚度影响显著。辐射状均压槽气浮支承静态性能仿真研究,为高承载和高刚度气浮支承研究发展奠定了良好的理论基础。     

基于AVR的静压气体轴承性能检测装置控制系统设计

为了实现对静压气体轴承气膜厚度,压力分布和承载能力的自动检测,设计了一种基于单片机的检测装置和控制系统;该系统采用ATmega16L单片机作为平台运动控制和数据处理的核心,结合软件控制步进电机的转向和转速,实现了极坐标定位,并采集承载力,气膜压力和气膜厚度等数据,通过LCD显示和键盘输入,较好地实现了人机交互;同时,装置可以通过RS232与上位机通讯,实现上位机的直接控制;把该系统对气体轴承性能参数的测量结果与仿真结果进行对比,结果表明该装置和系统是正确可行的.     

机载大气数据系统静压源误差修正方法研究

针对机载大气数据系统静压源误差问题,分析静压源误差的各影响因素,提出静压源误差的修正方案,以提高大气静压测量值的精度,进一步确保飞机飞行安全。以波音757机型为例,分析了静压源误差主要影响因素及其影响规律,用Solid Works软件进行飞机三维几何建模,GAMBIT软件划分计算域网格,FLUENT软件模拟飞机飞行环境仿真得到不同迎角和马赫数下的静压源误差值,并采用曲面响应法计算得到飞机静压源误差回归模型,根据模型对静压源误差进行了修正。经仿真结果与实际对比验证,该套修正方案具有很好的修正效果,能快速、准确的得到大气真实静压。采用计算流体力学(CFD)仿真方法分析飞机空气动力特性,简单方便、研究周期短、精度高、耗费成本低,有较高的研究和实际应用价值。     

气体静压导轨气膜厚度的电容式测试方法

气体静压导轨是超精密工程的核心基础技术之一,其气膜振动是影响加工精度的主要因素。提出了一种气体静压导轨气膜厚度的电容式测试方法,将气体静压导轨的节流器工作底面与实验台面当作电容式传感器的2个极板,当气膜厚度发生变化时,电容将产生较大变化。通过测量节流器与工作面间的电容,计算得到气膜厚度值。同时建立了不同凹面节流器电容与气膜厚度的数学模型。实验利用电容测量仪与电感测微测头同时对气膜厚度进行测量,结果显示两者误差为0.42μm,为气体静压导轨气膜厚度的测量提供了新的方法。     

飞机空速校准用静压测量装置轮廓结构绕流影响分析

介绍了针对一种面向飞机空速校准的外置式静压测量方法,为了减小测量装置轮廓结构绕流对静压测量的影响,从而提高静压测量精度,应用FLUENT对装置轮廓结构进行绕流影响分析,得到绕流影响最小的轮廓结构类型,并采用正交试验方法对收缩角度β、过渡长度L、最大直径ΦD、最小直径Φd共4个参数进行优化;仿真结果表明,测量装置轮廓采用圆弧型收缩过渡结构绕流影响最小,轮廓最大直径和过渡长度对静压测量绕流影响较为显著;最优参数组合为:β=33°,L=40mm,ΦD=50mm,Φd=22mm,优化后的结构对静压管的绕流影响减小了37.5%,提高了静压测量精度。     

超临界二氧化碳动压轴承紊流润滑模式研究

高速、大功率的机组工况条件使得超临界二氧化碳(S-CO₂)轴承工作在紊流润滑状态。以S-CO₂动压轴承为研究对象，基于Fluent软件建立轴承气膜仿真分析模型，采用广泛使用的两方程standard k-ε紊流模型，分析不同轴承偏心对气膜压力和承载力的影响，同时用经典的Ng-Pan紊流润滑模式进行计算对比。研究结果表明，两种紊流模式下S-CO₂轴承的压力分布在正压区更为吻合，并在此基础上分析了standard k-ε紊流模型下实际气体效应对轴承特性的影响。     

基于力平衡原理的非接触式眼压计研制

提出一种基于力平衡原理和空气静压技术相结合的非接触式眼压计设计方法.介绍了非接触式眼压计的总体结构、眼压测量模块和外框式气浮垫的设计.其中,眼压测量模块主要包括喷嘴、角膜对准系统及角膜压平光电检测系统,外框式气浮垫采用小孔节流式静压止推气体轴承结构,用于悬浮无摩擦的承载眼压测量模块.对外框式气浮垫的压力分布进行了计算和仿真,对角膜压平光电检测系统和非接触式眼压计的性能进行了测试.实验结果显示:在喷嘴到眼角膜距离为额定距离L的情况下,喷嘴喷出的气体可压平眼角膜,此时光电接收管接收到的光电信号最大,与进口仪器相比眼压测量平均值的绝对误差为1.3 mmHg,研制的非接触式眼压计可实现对眼压的非接触测量.     

双气腔油气式缓冲器充填容差仿真分析

在飞机起落架优化设计的研究中,双气腔油气式缓冲器具有功量吸收能力大,缓冲效率高的特点,但性能易受初始充填情况的影响,如何对双气腔油气式缓冲器进行仿真分析成为研究重点.首先建立起落架的数字模型,通过ADAMS软件中的Aircraft计算分析模块结合特性文件对起落架着陆撞击的动力学特性进行仿真.通过对比正常充填条件下的仿真结果与试验结果,发现误差在4.3％以内,仿真方法有效可信.依据缓冲器高低压气腔不同的充填情况,分别进行仿真,对比不同充填情形下的仿真结果,得出该型起落架缓冲器的充填容差特性.建立了一种研究双气腔油气式缓冲器双腔充填对缓冲性能影响的分析方法.仿真结果有一定的工程应用和参考价值.     

催泪剂焚烧炉气体燃烧室仿真

焚烧炉焚烧法是根据催泪弹的结构特点和药剂的理化特性确定的一种处废方法.焚烧炉分为固体焚烧室和气体焚烧室两大主体部分,其结构和参数是关系到药剂焚烧结果能否达到要求的关键.为验证设计的焚烧炉气体焚烧室的结构参数能否达到预定目标,为焚烧炉的实际生产运行提供参考.在根据要求设计出气体焚烧室结构参数的基础上,运用流体计算软件FLUENT对其中的气体燃烧室进行仿真.仿真结果与实际要求基本符合,说明气体燃烧室的设计能满足催泪剂销毁的要求.     

带有均压槽的气体静压推力轴承设计

针对空间机器人地面微重力模拟实验中存在侧向干扰力/力矩,工作台面不平整等特殊情况,设计了具有周向和径向均压槽的高承载力、高刚度圆盘气体静压推力轴承,并采用变形雷诺方程对轴承的承载特性进行了建模和数值分析.为了验证理论计算结果的正确性,使用Fluent对轴承的承载力特性进行仿真分析,并且分析了高压气体产生的冲击力对承载性能的影响.最后,在标准测试平台上对该轴承的承载力特性进行了实验,并与不带有均压槽的轴承进行对比分析,证明了结构设计和理论分析的正确性.     

Dynamic characteristics of micro air bearings for microsystems

This paper reports on the dynamic characteristics of micro air bearings that include thrust and journal air bearings for microsystems. The dynamic thrust air bearing employs a spiral groove configuration. Analysis shows that the motion stability and load capacity of a thrust air bearing imposes a contradictive requirement on the groove pattern of the air bearing. The dynamic journal air bearing is realized by using a plain circular trench with a narrow radial clearance of C, and a very small aspect ratio of bearing length versus diameter (L/D). Analysis on the shock tolerance of the journal air bearing shows that the shock tolerance increases with the bearing number, the bearing aspect ratio of L/D and its initial equilibrium eccentricity ratio ε ₀. The optimum values of the bearing parameters are explored and recommended. A prototype of turbine device has been designed based on the recommended bearing configurations and realized via microfabrication.     

A self-acting gas thrust bearing for high-speed microrotors

Micromachines rotating at high speeds require low drag bearings with adequate load capacity and stability. Such bearings must be compatible with the capabilities of microfabrication technology. A self-acting (hydrodynamic) gas thrust bearing was designed, fabricated and tested on a silicon microturbine. Conventional thrust bearing design techniques were adapted from macroscale literature. Microbearing design charts are presented that relate bearing performance to geometry. Such bearings exhibit a design tradeoff between load bearing capability and maximum operating speed (as limited by instabilities). The specific geometry described herein was intended to replace externally pressurized, hydrostatic thrust bearings in an existing device (a 4-mm-diameter silicon microturbine), thus the hydrodynamic bearing design was constrained to be compatible in geometry and fabrication process. The final design consisted of 2.2-/spl mu/m deep by 40-/spl mu/ wide spiral grooves around the 700-/spl mu/m diameter bearing. The bearings were fabricated in silicon with standard RIE and DRIE techniques. Test devices demonstrated lift-off and operation up to 450,000 rpm with a load capacity of 0.03 N. Measurements of load capacity and stiffness were consistent with the analysis.     

A pin fin microheat sink for cooling macroscale conformal surfacesunder the influence of thrust and frictional forces

Conventional microheat sink design primarily focuses on the use of continuous fin arrays to optimally dissipate thermal energy from electronic components. By contrast, this paper experimentally measures the thermal and structural performance of two micro pin fin heat sinks designed for use in load bearing applications such as mechanical seals and thrust bearings. One pin fin array is of low porosity, which is more optimal for load bearing capacity, and the other is of high porosity, which is more optimal for heat dissipation. By using these two extreme cases, the thermal-structural tradeoff found in load bearing microheat sinks is demonstrated. The heat sinks are constructed of nickel, electrodeposited onto a stainless steel thrust ring using a modified LIGA technique. Under forced air cooling, the thermal performance of each is compared to a simple model based on a combination of macroscale pin fin heat sink results and classical correlations for fins in cross flow. The low porosity design is also tested under the application of a 44.5 N thrust load at 2500 rpm and found to be structurally sound. Experimental temperature profiles demonstrate a substantial benefit of the microheat sink in cooling the load bearing surface     

6 自由度模拟卫星静压气浮轴承数值计算方法

针对失重模拟实验中常用的两种静压气浮轴承,推导了保角变换下的气孔直径公式和流量及承载能力 公式,研究了有限元建模及求解方法,并给出了具体实例以进行验证．基于平面和球面的静压气浮轴承设计了一种 6 自由度模拟卫星．试验结果表明,两种静压气浮轴承都满足了总体的技术指标要求．     

A method of reducing the windage power loss in a laser scanner motor using spiral-groove aerodynamic thrust bearings functioning as a viscous vacuum pump

We propose a spiral-groove aerodynamic thrust bearing functioning as a viscous vacuum pump in a laser scanner motor to reduce the windage power loss of a polygon mirror. The proposed bearing pumps out the air in the scanner housing using the pumping effect of the spiral-groove thrust bearing, reducing the inner pressure of the housing. The pumping performances and the static characteristics of the spiral-groove thrust bearings were investigated numerically and experimentally. Two numerical calculation methods were used to study the pumping characteristics of the spiral-groove thrust bearing. It was found that a bearing with 15 spiral grooves reduced the inner pressure of the housing to <0.01 MPa at 20,000 rpm and at bearing clearance of 2.5 μm, and this has sufficient load-carrying capacity to support the rotating shaft and the mirror.     

基于LabVIEW静压气体轴承性能检测装置的测控软件设计

采用LabVIEW设计了静压气体轴性能检测装置的测控软件.上位机软件通过串口与下位机进行指令传送和数据交换,控制检测装置运行,接收由AVR单片机采集的气体压力传感器、测力传感器和位移传感器的实验数据,同时对数据进行分析计算并实时显示和自动保存.实验结果表明,系统较好地实现了人机交互,自动化程度高、工作稳定性强、可操作性高.     

移动副速度对空气轴承影响的CFD仿真分析

研究空气轴承优化控制问题,针对高速移动副空气轴承对空气轴承气膜特性会影响定位精度特点,空气轴承采用非结构化网格实现了多节流器气膜的耦合,设计的密度可控的非均匀网格划分方案克服了最大最小尺寸比偏大给实际带来的困难。根据FLUENT用三维双精度耦合隐式标准k-ε粘性湍流两方程模型,仿真得到了不同移动副速度时,阵列多节流器耦合后的质量流量、气膜压强分布和速度分布,为辨识高速移动副时多节流器耦合的气膜数学模型提供了详实数据。当增大移动副速度时,耗气量减小但气膜承载力增加,为高速移动副空气轴承的优化设计提供了依据。     

TiO2薄膜制备及其气敏特性

NO2是一种强毒性气体,本文利用了溶胶一凝胶法在硅片及陶瓷管上制备TiO2纳米薄膜,并探讨了在制备过程中不同的因素对薄膜成膜质量的影响。并用马弗炉对硅片及陶瓷管上制备的TiO2纳米薄膜进行不同温度的退火处理。对其分别进行XRD的分析,和原子力显微镜分析。利用气敏测试系统对不同的退火温度下的气敏元件进行测试。研制出工作温度低,气敏特性强,响应恢复特性好的基于TiO2的NO2气敏传感器。     

Ultimate load carrying capacity of the Lu Pu steel arch bridge under static wind loads

This paper investigates the ultimate load carrying capacity of the Lu Pu Bridge under static wind loads through the spatial finite element model. Both geometric and material nonlinearities are involved in the analysis. The Lu Pu Bridge is a long-span half-through-type steel arch bridge with a 550 m-long central span under construction in Shanghai, China. This will be the longest central span of any arch bridge in the world. Three load combinations are used in the ultimate load capacity analysis of the bridge. Combination I: combined dead and live loads over the entire bridge. Combination II: combined dead and wind loads. Combination III: combined dead load, wind load and live load over the entire bridge. Ultimate load capacity of the bridge is first investigated under load combinations I and II. Attention is paid mainly to investigate the load capacity of the bridge under load combination III. In the case of load combination III, the influences of several parameters (i.e., loading sequence, three components of wind loads and wind loads of individual bridge element) on the ultimate load capacity of the bridge are discussed. It is concluded that wind loads result in significant reduction in the ultimate load capacity when applied wind loads become large.