飞机起落架收放作动器的设计方案与仿真分析

为了适应飞机多电化发展需求,针对某小型飞机的起落架收放机构特点,设计了一种能源双余度、集成一体化、高比功率起落架液压作动器,提出了一种具有到位缓冲功能的单出杆对称液压缸的设计方案。基于AMESim建立了起落架液压收放器和收放机构的模型,并对起落架收放运动进行了仿真。仿真分析结果表明,所设计的能源双冗余液压系统、作动器到位缓冲结构,原理合理可行,为实际工程应用奠定了基础。     

基于EHA的多轮系飞机刹车系统的建模与仿真

介绍了一种采用电动静液作动器(EHA)代替原有液压作动机构的飞机多轮系防滑刹车系统,在重点分析EHA的系统组成原理和工作特性的基础上.建立了EHA及多轮系飞机刹车系统的数学模型,采用Matlab/simulink对其进行仿真.仿真结果表明:所建立的模型基本正确,结果与真实刹车基本吻合;采用EHA代替液压系统能极大改善飞机刹车性能.     

飞机研制过程中仿真生命周期管理的研究

通过分析在飞机研制过程中的系统工程模型,以面向多专业耦合协同仿真及设计、仿真、验证一体化,实现飞机研制的多学科优化设计为目标,研究系统工程方法对研制过程中仿真生命周期的有效管理。并在该理论基础上,实施构建基于系统工程的仿真生命周期管理系统,从而确保研制过程中仿真的可靠性、可控性及协同性,以达到缩短研制周期、控制研制成本及保证研制质量的目的。     

航空发动机反推作动器楔形缓冲结构研究

为了削弱航空发动机反推作动器在展开过程末端的强烈机械冲击，将楔形液压缸缓冲结构应用于该反推作动器。本文建立了该反推作动器节流缓冲的数学模型和Simulink仿真模型，对该作动器在缓冲过程中的速度特性和时间特性进行仿真，分析了速度和压力对其缓冲特性的影响。研究结果表明，本文提出的楔形缓冲结构有助于减小航空发动机反推作动器活塞与筒体的碰撞速度，能有效削弱工作末端的冲击；在保证运行速度不变的前提下，可以通过适当降低系统的通油压力来提高反推作动器的节流缓冲效果。     

基于PNN网络的余度作动器智能故障诊断

提出了一种基于概率神经网络(PNN)的余度作动器故障诊断方法,分析了传统阀芯位置监控器的设计思想及设计缺陷,构建了基于PNN网络的阀芯位置监控器,最后完成了基于PNN网络的作动器仿真实验。实验结果表明,基于PNN的阀芯位置监控器具有较强的故障诊断能力,有效地提高了作动器两通道工作时识别阀芯位置监控器的故障准确率,可以成为作动器智能故障诊断与健康管理的重要方法之一。     

考虑起落架动力学特性的防滑刹车系统仿真研究

以某型飞机参数作为依据,建立了带有起落架数字模型的飞机防滑刹车系统模型,通过系统仿真及与实际刹车过程对比分析,证明了此系统模型是实用的,较真实的反映出了飞机防滑刹车的作动过程。     

基于联合仿真的飞机空调系统故障影响

飞机空调系统是飞机的重要组成部分,由于其在飞行过程中环境和工作参数变化较大,易于受到多种因素的影响而成为故障率较高的飞机系统之一。飞机空调系统故障主要发生在飞行过程中,在地面状态难以复现,因此基于联合仿真的飞机空调系统故障影响分析对飞机设计验证和地面维修具有重要意义。首先根据飞机空调系统原理建立了冲压空气进气口模型、发动机压气机模型、压力调节与预冷组件模型、制冷组件模型;然后基于AMESim-Simulink联合仿真平台,模拟飞行过程中空调系统组件性能动态变化过程;最后对典型故障如预冷器泄漏、预冷器空气活门卡死、压力传感器冲击、冲压空气进气作动筒卡死等故障进行模拟,再现了飞行过程中空调系统故障情况,分析了空调组件性能的变化过程。     

基于均值的副翼作动筒载荷事件划分方法

副翼是民用飞机重要操纵面之一,主要功用是产生飞机滚转力矩,用于改变飞机的航向。现代中大型飞机的操纵系统大都采用伺服作动器-操纵面装置,当操纵面受到铰链力矩时作动器也相应受载。以民用飞机副翼作动筒为研究对象,基于试飞实测数据与主操纵面作动筒载荷计算模型,提出了一种基于均值的作动筒载荷事件划分方法。结果表明,该事件划分方法效果理想,较好地反映出了不同飞行事件之间载荷均值的差异。通过对14 000次飞行作动筒载荷历程进行雨流处理,给出了相应的载荷谱及载荷幅值、均值分布直方图,总结出相关分布规律。该疲劳载荷谱及相应的分布规律对工程实践中的寿命计算具有重要意义。     

作动器故障下的无人机容错控制方法

在执行任务过程中,无人机的传感器、作动器等均可能出现故障。文章针对常规布局无人机的作动器故障,提出了 1种反步法和控制分配相结合的容错控制方法。首先,建立无人机数学模型,并对作动器故障进行分类和建模;然后,根据模型设计反步最优控制器和基于控制分配的容错控制器;最后,通过仿真验证表明,所设计的容错控制方法能够实现作动器故障下的姿态快速稳定控制,且稳定性好,基本无侧滑角,各操纵面均在约束范围内,达到容错控制要求。     

基于热管技术的飞机电作动机构散热特性

针对飞机电作动机构在工作过程中发热严重的情况,开展了相关散热技术研究。利用试验数据拟合出电作动机构产热量的经验关系式,提出基于热管-燃油系统的飞机电作动机构冷却方法,建立描述电作动机构散热系统流动与传热过程的数值模型,并验证了其可靠性。通过数值模拟研究不同因素对散热系统散热性能的影响规律,结果表明:数值模拟与试验误差在14.6%以内;与自然对流散热相比,热管-燃油散热方式可使电作动器温升降低12.61%,对于驱动器,风扇冷却效果优于热管-燃油散热方式;当热管等效导热系数达到7 000 W/(m·K),电作动机构已达到较好的散热状态,继续增大热管等效导热系数对提高散热系统散热性能效果不明显。研究可为电作动机构高效散热系统的设计提供参考。     

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.