液体火箭发动机推进剂泵诱导轮与离心轮的匹配

为获得诱导轮离心轮周向匹配的时序效应对离心泵外特性以及压力脉动的影响规律,阐释相关作用机制,采用基于分离涡仿真（DES）的离心泵三维全流道数值仿真方法,引入熵产理论以及压力脉动强度系数等先进分析方法对不同匹配角度下离心泵内能量损失机制及压力脉动特性进行了研究。结果表明：离心轮诱导轮的时序效应对泵外特性有一定的影响,随着匹配角度的增加,扬程和效率均呈现先减小后缓慢增大的趋势,扬程变化为0.8%,效率变化为1.2%,其影响机制由不同匹配角度下叶轮通道分离涡、叶轮叶片尾迹以及靠近隔舌处扩压器通道回流涡变化决定;时序效应对离心轮扩压器动静干涉效应影响显著,当诱导轮叶片尾缘位于离心轮相邻主叶片中间位置时,能够有效消除3倍频成分,显著降低泵内压力脉动水平,其中动静干涉区域以及隔舌处扩压器叶片表面压力脉动平均降幅分别达到14.5%和16.7%。     

微小整体叶轮五轴联动微细铣削加工试验研究

微小整体叶轮作为微型发动机的重要组成部分,其加工质量直接影响微型发动机的使用性能。针对微小整体式复杂叶轮流道狭窄、叶片扭曲大和长厚比大等特点,开展了微小复杂扭曲整体式叶轮五轴联动微细铣削加工方法研究。针对微小叶轮加工过程极易发生变形、过切和碰撞干涉等问题,对微小叶轮的加工过程进行工艺规划,建立了微小叶轮流道加工刀具选择的约束方程,计算出叶轮加工刀具的最大理论直径。通过CAM软件对叶轮进行切削仿真,验证了刀具选择和工艺规划的正确性。通过五轴联动微细铣削试验,得到了具有6个直径10mm的叶片、叶片最小厚度0.15mm、叶片最小相邻间距0.58mm的7075铝合金微小整体叶轮。     

无穷观问题的研究(Ⅳ)--自然数系统与无穷公理

本组系列论文（I）－（V）从数学和认识论的角度系统地研究了无穷观问题的历史发展和现状，确立了无穷观背世界的三分法原则，指出了两种无穷观相互排斥的局限性，形成了统一两种无穷于同一框架中的基本观点，并建立了一个统一实无限与潜无限同一框架中的公理集合论系统APAS。     

基于UG/Grip的低比转速离心泵叶轮数字化造型原理

运用UG/Grip技术对低比转速叶轮进行三维造型设计,获得了一种先进的低比转速叶轮参数化设计方法,从而能够及时、直观地考察叶片的水力特性和机械特性。同时可采用交互方式对叶轮设计参数进行修改,增强了叶轮计算机辅助设计系统的交互设计能力,有利于提高叶轮设计质量。     

A novel approach for predicting inlet pressure of aircraft hydraulic pumps under transient conditions

Cavitation caused by insufficient suction is a major factor that influences the life of aircraft pumps. Currently, pressurizing the tank can solve the cavitation problem under steady large-flow conditions. However, this method is not always effective under transient conditions (from zero flow to full flow in a very short time). Moreover, to apply and design other measures, such as a boost impeller, the suction dynamics during the transient period must be investigated. In this paper, a novel approach based on the pressure wave propagation theory is proposed for predicting the inlet pressure of an aircraft pump under transient conditions. First, a dynamic model of a typical aircraft pump is established in the form of differential equations. Then, the transient flow model of the inlet line is described using momentum and continuity equations, and the governing equations are discretized by the method of characteristics and the finite difference method. The simulated results are in good agreement with the results from verification tests. Further simulation analysis indicates that the wave velocity and transient time may influence the inlet and reservoir pressure as well as the size of the inlet line. Finally, solutions for upgrading the inlet pressure are discussed. These solutions provide guidelines for designing inlet installations.     

飞机自动着陆纵向块对角控制器设计

在阐述了块对角控制理论和分析飞机运动特性的基础上,把飞机纵向运动方程转化为块对角非线性系统,并设计了飞机自动着陆纵向块对角控制器。仿真结果表明,该控制器能够控制飞机自动着陆,跟踪性能良好。     

提高花键加工精度的工艺研究

发动机中力及扭矩的传递全部通过渐开线花键副来实现,由于发动机工作转速高,因而要求渐开线花键副传动非常平稳。通过本工艺方法的探索,采用新的工艺加工方法,提高了涡轮泵叶轮、轴的花键加工精度,保证了涡轮泵装配性能的要求。     

Numerical investigation of flow mechanisms of tandem impeller inside a centrifugal compressor

This study numerically investigated a single stage centrifugal compressor ‘‘Radiver’’ with a wedge diffuser and several tandem-designed impellers to explore the flow phenomena within the tandem impeller and the potential to enhance compressor performance. The results demonstrate that tandem design and clocking fraction (λ_s) significantly affects the compressor performance. The compressor stage with tandem impellers of Series A of boundary layer growth interruption alone are observed to have a widely operating range but efficiency and total pressure ratio penalty compared with that of conventional impeller. The tandem impeller with at least the same impeller efficiency as the conventional design is considered as a critical design criteria so that further modification process based on the flow characteristic of tandem impeller is necessary. In order to restrain the inducer wake and exducer shock losses, parameters modification of blade angle and thickness distributions are necessary and the modified tandem impeller of Series B is obtained. The modified tandem impeller with 25% clocking arrangement shows an 8.45% stall margin increase and maintains the total pressure ratio and efficiency as the conventional design, which proves the potential of tandem impeller to improve compressor stage performance. It is noteworthy that the tandem impellers of Radiver have not shown obviously balanced exit flow field and the fundamental mechanism of stall margin extending of tandem impeller lies on the improved impeller/diffuser matching performance resulting from the incidence angle variation at diffuser inlet.     

离心叶轮背腔复杂流态及调控方法研究进展

因叶轮/扩压器转静间断,离心压气机级中必然存在引气腔并对级性能产生影响,中小型航空发动机/燃气轮机用半开式离心叶轮中背腔引气影响尤为突出。从简化及真实离心叶轮背腔流态研究、复杂流态调控方法、对级气动性能影响、叶轮/扩压器/背腔多维度耦合模拟方法等方面进行了综述,展示了背腔引气对风阻损失、轴向力平衡、油/气密封及冷却气输送等多方面重要影响,并对其可能的先进设计方法进行了分析与展望。     

水泵叶轮的流动叠加设计方法与CFD仿真

叶轮叶片是复杂的空间曲面体,它直接影响到水泵的水力性能及运行稳定性.发动机水泵叶轮流动叠加设计是通过分析流体的流动规律,按其流动轨迹进行叶轮设计,将流体在离心水泵内的流动看作叶轮静止时的轴向和径向流动和叶轮旋转时的周向流动的叠加,从而用绕角流动和源环流的流体流动规律设计出叶轮的轴面轮廓和叶片骨线.通过CFD(Computational Fluid Dynamics)仿真,可以证明该方法从结构上避免了流体流动过程中由于空间的相对不均而造成的压力不均,减轻了回流、二次流,相应地减少能量的损失,提高水泵的效率.