一种高空飞艇螺旋桨结构多目标优化设计方法

为了远离旋转激振力的影响避免桨叶共振,需要提高桨叶的弯曲频率,这不可避免的会增加质量。为了解决低质量与高频率之间的矛盾,提出了一种螺旋桨两目标优化方法。以桨叶最小质量和最大弯曲频率作为两个优化目标,以复合材料的铺层角度、铺层厚度和铺层区域作为设计变量,以最大应变、桨尖最大位移和桨叶50%、75%和85%剖面处的扭转角作为约束,使用非支配排序遗传算法(NSGA-Ⅱ)对螺旋桨进行优化设计,得到了关于质量和频率的Pareto解集。转速为520 r/min的两叶桨的转频为8.76 Hz,穿越频率为17.33 Hz,根据频率在Pareto解集上选取远离这两个点的方案。通过制造与测试,得到的实物桨叶频率为12.29 Hz,距离两个共振点都较远,有效的避免了桨叶共振。      

螺旋桨周期变距系统在螺旋桨飞机姿态控制上的应用研究(下)

二、周期变距桨的设计 1.周期变距螺旋桨的结构形式 周期变距螺旋桨结构主要由桨毂、变距摇臂、桨叶、倾斜盘、桨轴、作动器、操纵拉杆组成.     

带气弹稳定性约束的复合材料浆叶减振优化设计

研究以降低直升机旋翼激振力为目标的复合材料桨叶结构动力学减振优化设计 ,分析了桨叶结构特性及桨尖后掠角等参数对N次 /转旋翼桨毂振动载荷的影响。在建立的桨叶二维结构特性有限元分析方程中 ,计入了桨叶剖面翘曲变形的影响 ,并利用哈密尔顿原理推导了旋翼桨叶的一维非线性运动微分方程。以桨毂交变载荷为目标函数 ,直接以复合材料桨叶典型剖面构造节点数据、铺层设计参数和桨尖后掠角等为设计变量 ,引入桨叶挥舞惯量、固有频率和气弹稳定性约束 ,进行旋翼的动力学优化设计 ,并结合 3片桨叶旋翼的设计进行了算例分析 ,优化结果使 3次/转的桨毂载荷降低了 2 4 .9%～ 33%。     

桨毂三维有限元应力分析

某型螺旋桨毂坐标系的确定,此桨毂为整体形结构,沿径向均匀装置四个桨叶,如图1所示,以飞机飞行方向定位,桨毂旋转平面定为XOY平面,沿桨叶轴线方向为X轴坐标,在旋转平面内与X轴垂直方向为Y坐标,Z轴坐标则为通过旋转轴心而与飞行方向相反的轴线。在旋转平面的后端面,用端齿与发动机主轴连接,以传递扭矩及轴向位伸;其前端面安装螺旋桨整流罩,罩内装置液压调节活塞,整体结构内为空心,桨叶变距机构由此空间操纵四个桨叶。桨叶的离心力和气动力通过桨轴传递至桨毂。      

基于独立桨距控制的旋翼减振规律研究

独立桨距控制(IBC)能够改善旋翼气动环境,降低桨毂振动载荷。本文以SA349/2直升机为例,桨叶气动力计算采用Leishman-Beddoes动态失速模型和Pit-Peters动态入流模型,利用Fortran程序编译成为Adams子程序;桨毂载荷计算采用工程上应用较为广泛的Adams和Nastran软件,建立旋翼弹性桨叶气弹耦合模型。在周期变距基础上施加二阶、三阶谐波变距,研究独立桨距控制减振作用的规律。     

TB飞机螺旋桨桨毂螺栓的试制

国外引进的ＴＢ飞机是一种单发、轻型飞机。该机型装用的是哈泽尔系列两叶螺旋桨。螺旋桨桨毂由前、后两半桨毂组成,用１０根桨毂螺栓将前、后两半桨毂连接在一起夹紧固定桨叶。螺旋桨转动时,桨毂螺栓承受全部的拉伸载荷和剪切载荷,在变速运动中还要承受额外的附加载荷。因此,对螺栓的材料和机械性能有严格要求。我厂在维修、翻修该型螺旋桨时,由于螺旋桨的数量多,所以桨毂螺栓的需用量大。为了减少维修费用,使该桨毂螺栓的生产国产化,保证足够的备件,我们选用国产航空金属材料进行试制,生产出所需的桨毂螺栓,满足了使用要求,而…     

直升机旋翼桨叶气弹优化减振设计方法

从振源着手通过设计参数的最优选择设计直升机旋翼桨叶,使传递到机身的交变载荷最小达到降低振动水平的目的是旋翼桨叶设计思想的进步。本文在简单概述该方法的基础上,以某4桨摆振柔软的无铰复合材料桨叶为研究对象,将其大梁模拟为一单闭室复合材料盒形梁,研究了通过铺层角的优化选择,降低4次/转的桨毂交变力与力矩的情况。数值算例表明方法效果良好。      

一种高效率螺旋桨设计方法

提出了一种高效率螺旋桨设计方法,该方法根据给定的飞行速度、螺旋桨转速、拉力、螺旋桨直径、桨叶数、翼型,能够计算出最大效率螺旋桨的几何特性,包括:桨叶的弦长分布、桨距角分布、效率、拉力系数、扭矩系数、功率系数.分别按爬升状态和巡航状态的工作参数设计了某型飞机的螺旋桨,得到了桨距角和弦长沿径向的分布.对螺旋桨的缩比模型(直径为0.84m)进行了风洞试验,风洞试验结果表明:螺旋桨在巡航状态的效率是83.02%,爬升状态的效率是79.13%.      

复合材料螺旋桨结构多目标优化设计

在螺旋桨桨叶结构设计的工程实践中,减轻重量和增加扭转刚度是两个主要目标,而复合材料的应用增加了螺旋桨结构的可设计性。以某复合材料螺旋桨为例,基于有限元方法,以桨叶的复合材料铺层数量与铺层角度为优化设计变量,以螺旋桨桨叶强度、弯曲刚度为约束条件,采用快速非支配遗传算法(NSGA-Ⅱ)对该复合材料螺旋桨进行多目标优化设计。得到了关于两个目标函数的帕累托解集,即综合考虑桨叶质量与扭转刚度两个指标的最优设计参数集。本文为复合材料螺旋桨的结构设计提供了一种有效的思路。     

SR20飞机螺旋桨系统工作原理及典型故障分析

基于SR20飞机恒速螺旋桨的系统构造,通过对该型飞机螺旋桨、调速器的构造和桨毂润滑机制的工作原理进行分析,深入阐述了诸如发动机转速损失、发动机超转/全功率转速不足、螺旋桨桨毂油脂过多等典型故障的故障原因及表征现象,提供了螺旋桨系统类似故障的诊断方法及故障排除措施,为该型飞机螺旋桨、调速器的日常维护、故障排除和预防提供了有力依据。     

The effect of inlet conditions on the flow and heat transfer in multiple rotating cavity with axial throughflow

This paper discusses experimental results from two different build configurations of a heated multiple rotating cavity test rig.Measurements of heat transfer from the discs and tangential velocities are presented.The test rig is a 70% full scale version of a high pressure compressor stack of an axial gas turbine engine.Of particular interest are the internal cylindrical cavities formed by adjacent discs and the interaction of these with a central axial throughflow of cooling air.Tests were carried out for a range of non-dimensional parameters representative of high pressure compressor internal air system flows(Re up to 5×106 and Rez up to 2×105).Two different builds have been tested.The most significant difference between these two build configurations is the size of the annular gap between the(non-rotating) drive shaft and the bores of the discs.The heat transfer data were obtained from thermocouple measurements of surface temperature and a conduction solution method.The velocity measurements were made using a two component,LDA system.The heat transfer results from the discs show differences between the two builds.This is attributed to the wider annular gap allowing more of the throughflow to penetrate into the cavity.There are also significant differences between the radial distributions of tangential velocity in the two builds of the test rig.For the narrow annular gap,there is an increase of non-dimensional tangential velocity V/Ωr with radial location to solid body rotation V/Ωr=1.For the wider annular gap,the non-dimensional velocities show a decrease with radial location to solid body rotation.      

Research on Auto-detection for Remainder Particles of Aerospace Relay Based on Wavelet Analysis

Aerospace relay is one kind of electronic components which is used widely in national defense system and aerospace system. The existence of remainder particles induces the reliability declining, which has become a severe problem in the development of aerospace relay. Traditional particle impact noise detection (PIND) method for remainder detection is ineffective for small particles, due to its low precision and involvement of subjective factors. An auto-detection method for PIND output signals is proposed in this paper, which is based on direct wavelet de-noising (DWD), cross-correlation analysis (CCA) and homo-filtering (HF), the method enhances the affectiv-ity of PIND test about the small particles. In the end, some practical PIND output signals are analysed, and the validity of this new method is proved.     

Preparation of Highly Dispersed Antimony-doped Tin Oxide Nano-powder via Ion-exchange Hydrolysis of SnCl4 and SbCl3 and Azeotropic Drying

Antimony-doped tin hydroxide colloid precipitates have been synthesized by hydrolysis of SnCl4 and SbCl3 using: (1) an ion-exchange hydrolysis to remove chlorine ions, and (2) isoamyl acetate as an azeotropic solvent to obviate water. The obtained dried powder is of high dispersivity without any need for further grinding. The size and dispersivity of the final particles are investigated with the aid of TG-DTA, BET, XRD and TEM. After having calcined, the antimony-doped tin oxide nanopowder possesses a tetragonal rutile structure with high dispersivity, uniform particles and low hard agglomeration.     

Effects of Mo on the Microstructure and Hydrogen Sorption Properties of Ti-Mo Getters

The effects of Mo on the microstructure evolution, porosity and hydrogen sorption properties of Ti-Mo getters are investigated in this work. The results show that the addition of Mo prolongs the densification process of Ti-Mo getters and results in a significant amount of sintered pores. With the Mo content increasing, the porosity of getters firstly increases reaching the maximum value as it at- tains about 7.5wt.%, and then drops. At the room temperature, the hydrogen sorption property of getters increases progressively with the Mo content increasing, but the tendency is not very clear before its content lies below 2.5wt.%. When the Mo content achieves about 7.5wt.%, the hydrogen sorption property proves to be the best. The discussion is made about the above mentioned phenomena inclusive of hydrogen sorption properties of getters under different activation conditions (from 500-750 ℃).     

超声速燃烧数值模拟中的湍流与化学反应相互作用模型

高精度数值模拟有助于理解超声速湍流燃烧中湍流与化学反应的相互作用,可为发动机燃烧室等工程应用设计提供可靠的预测模型。除直接数值模拟外,目前在湍流燃烧应用中使用的大涡模拟和雷诺平均Navier-Stokes模拟均需要借助模型模化发生在湍流小尺度上的流动与化学反应过程对湍流大尺度运动的影响。现有的湍流与化学反应相互作用模型大致可分为:火焰面类模型和概率密度函数类模型,2类模型在不同的应用中各自具有优势和局限性。此外,现有模型大都基于低马赫数燃烧,而超声速燃烧中通常会伴随快速混合、局部熄火和再着火以及激波等复杂过程,这为发展其中的湍流与化学反应相互作用模型提出了更多的挑战。     

适于低轨卫星IP网络的单核共享树组播算法(英文)

为了解决低轨卫星IP网络中现有典型源组播算法的信道资源浪费问题,本文提出了一套单核共享树组播算法,即核心群合并共享树(CCST)和加权核心群合并共享树(w-CCST)算法。CCST 算法包括动态近似中心(DAC)选核方法和核心群合并组播路径构建方法。DAC方法专为周期、规律运动的低轨卫星网络提出,不需要复杂的星上计算。在核心群合并方法中,以核节点作为初始核心群,通过核心群和剩余组成员的最短路径方法逐步扩展直至整棵组播树构建完成,从而使得组播树的树代价最小,大大提高了网络的带宽利用率和组播传输效率。w-CCST 算法中所提出的加权因子可以调整树代价和端到端传播时延之间的折衷程度,因此,可以通过调整加权因子来适度增大树代价、降低端到端传播时延以支持某些端到端时延要求苛刻的实时组播业务。最后,与低轨卫星 IP 网络中典型算法进行了性能比较,仿真结果说明,CCST 算法的平均树代价比其它算法显著降低,w-CCST 算法的平均端到端传播时延小于 CCST 算法。     

Jet Vectoring Control Using a Novel Synthetic Jet Actuator

A primary air jet vectoring control system with a novel synthetic jet actuator (SJA) is presented and simulated numerically. The results show that, in comparison with an existing traditional synthetic jet actuator, which is able to perform the duty of either “push” or “pull”, one novel synthetic jet actuator can fulfill both “push” and “pull” functions to vector the primary jet by shifting a slide block inside it. Therefore, because the new actuator possesses greater efficiency, it has potentiality to replace the existing one in various appli- cations, such as thrust vectoring and the reduction of thermal signature. Moreover, as the novel actuator can fulfill those functions that the existing one can not, it may well be expected to popularize it into more flow control systems.     

Nonlinear Adaptive Slewing Motion Control of Spacecraft Truss Driven by Synchronous V-gimbaled CMG Precession

The slewing motion control of a truss arm driven by a V-gimbaled control-moment-gyro (CMG) is a nonlinear control problem. The V-gimbaled CMG consists of a pair of gyros that must precess synchronously. The moment of inertia of the system, the angular momentum of the gyros and the external disturbances are not exactly known. With the help of feedback linearization and recursive Lyapunov design method, an adaptive nonlinear controller is designed to deal with the unknown items. Performance of the proposed controller is verified by simulation.     

An SOR Implicit Time-accurate Scheme in Calculating Unsteady Flows

A new time-accurate marching scheme for unsteady flow calculations is proposed in the present work. This method is the combination of classical Successive Over-Relaxation (SOR) iteration method and Jacobian matrix diagonally dominant splitting method of LUSGS. One advantage of this algorithm is the second-order accuracy because of no factorization error. Another advantage is the low computational cost because the Jacobian matrices and fluxes are only calculated once in each physical time step. And, the SOR algorithm has better convergence property than Gauss-Seidel. To investigate its accuracy and convergency, several unsteady flow computa- tional tests are carried out by using the proposed SOR algorithm. Roe’s FDS scheme is used to discritize the inviscid flux terms. Un- steady computational results of SOR are compared with the experiment results and those of Gauss-Seidel. Results reveal that the numerical results agree well with the experimental data and the second-order accuracy can be obtained as the Gauss-Seidel for unsteady flow computations. The impact of SOR factor is investigated for unsteady computations by using different SOR factors in this algorithm to simulate each computational test. Different numbers of inner iterations are needed to converge to the same criterion for different SOR factors and optimal choice of SOR factor can improve the computational efficiency greatly.