机车轴承返修中的清洗和防锈

本文叙述了机车轴承返修中的清洗和防锈问题，介绍用清洗剂清洗和脱水油脱水防锈的新工艺。     

航天飞机主发动机涡轮机械轴承的可靠性分析

本文讨论航天飞机主发动机(SSME)氧化剂与燃料涡轮轴承的可靠性分析。由于采用低粘度的低温流体来冷却轴承,轴承缺乏充分的润滑,这样导致轴承的预期寿命值少于设计要求的27000s。为改进没计,减少与轴承失效相关的风险,我们对轴承设计及轴承工作参数作了深入的评估研究。在决定性的轴承分析子程序中,我们应用了蒙特卡罗(Monte Carlo)估算方法来估算涡轮轴承系统可靠性曲线、概率密度曲线以及确定独立输入设计变量对系统寿命的相对影响。对于蒙特卡罗分析方法我们通过一些表明可靠性变化的例子,以及通过在热测试之前对改进的新设计方案的系统可靠性所进行的估算作了说明。     

载人航天器液体回路主动热控技术

液体回路主动热控技术是发展载人航天器必须解决的关键技术之一。和被动热控技术相比,其传热能力强,控温范围宽,控制精度高。本文系统地阐述了液体回路的组成、热控机理和调温方法,介绍了泵、阀门、热交换器等主要部件的作用、性能特点及国外的发展、应用状况等,并对一些关键技术进行了分析。     

构造拓扑修形齿面的面齿轮传动主动设计

为了改善加工参数较少的面齿轮传动的啮合性能,提出了用给定的啮合性能对面齿轮和小齿轮齿面进行拓扑修形设计的方法.面齿轮用插齿法加工,面齿轮与插齿刀的转角关系由预设的传动误差确定,由此确定面齿轮的拓扑修形齿面.然后用接触路径的位置及其方向和接触椭圆的大小构造小齿轮的拓扑修形齿面,该齿面用共轭点接触法磨齿加工,建立了小齿轮拓扑修形齿面与加工参数之间的线性方程.结果表明:齿面接触分析(TCA)获得的传动误差、接触路径与预设的传动误差、接触路径相同,TCA仿真的椭圆长度与预设椭圆长度相差范围为0.175 2~1.16mm.     

Characteristics of motorized spindle supported by active magnetic bearings

A motorized spindle supported by active magnetic bearings（AMBs） is generally used for ultra-high-speed machining. Iron loss of radial AMB is very great owing to high rotation speed, and it will cause severe thermal deformation. The problem is particularly serious on the occasion of large power application, such as all electric aero-engine. In this study, a prototype motorized spindle supported by five degree-of-freedom AMBs is developed. Homopolar and heteropolar AMBs are independently adopted as radial bearings. The influences of the two types of radial AMBs on the dynamic characteristics of the motorized spindle are comparatively investigated by theoretical analysis, test modal analysis and actual operation of the system. The iron loss of the two types of radial AMBs is analyzed by finite element software and verified through run-down experiments of the system. The results show that the structures of AMB have less influence on the dynamic characteristics of the motorized spindle. However, the homopolar structure can effectively reduce the iron loss of the radial AMB and it is useful for improving the overall performance of the motorized spindle.     

Active flutter suppression of a multiple-actuated-wing wind tunnel model

In this study, a multi-input/multi-output（MIMO） time-delay feedback controller is designed to actively suppress the flutter instability of a multiple-actuated-wing（MAW） wind tunnel model in the low subsonic flow regime. The unsteady aerodynamic forces of the MAW model are computed based on the doublet-lattice method（DLM）. As the first attempt, the conventional linear quadratic-Gaussian（LQG） controller is designed to actively suppress the flutter of the MAW model. However, because of the time delay in the control loop, the wind tunnel tests illustrate that the LQG-controlled MAW model has no guaranteed stability margins. To compensate the time delay, hence, a time-delay filter, approximated via the first-order Pade approximation, is added to the LQG controller. Based on the time-delay feedback controller, a new digital control system is constructed by using a fixed-point and embedded digital signal processor（DSP） of high performance. Then, a number of wind tunnel tests are implemented based on the digital control system.The experimental results show that the present time-delay feedback controller can expand the flutter boundary of the MAW model and suppress the flutter instability of the open-loop aeroelastic system effectively.     

基于A320飞机横航向控制律架构的LQ设计

前缘缝翼、襟翼活动面及其支承结构的疲劳试验是民用飞机取证前要开展的一项重要工作。在试验中采用主动驱动和随动加载方法加载,不仅能缩小试验规模,同时可提高试验精度。国内某型机采用此技术成功进行了前缘缝翼、襟翼及其悬挂结构的疲劳试验。从试验件及其支承设计、系统构成和载荷与运行三方面,介绍了一种适用于大中型固定翼飞机前缘缝翼和襟翼的疲劳试验技术。     

对火箭陀螺高速向心球轴承摩擦系数的研究

在运用滚动轴承理论、摩擦学滚动理论及弹性力学原理对火箭陀螺高速向心球轴承(简称高速球轴承)滚珠及内圈(或外圈)受力情况进行系统分析及研究的基础上,提出一组可直接计算高速球轴承摩擦系数的理论公式。从导出公式所示解析关系可清晰地看出,高速球轴承摩擦系数不仅与轴承内外径、滚珠对内圈(或外因)的滑动摩擦系数、滚珠半径及数量有关,而且还直接与轴承转速和当量动载荷等参数密切相关。