涡轴发动机部件特性修正及更新方法

针对由航空发动机零部件制造、装配及性能退化引起的发动机模型与实际发动机之间的性能不匹配问题,提出1种基于粒子群优化算法(PSO)的发动机部件特性自动修正及更新方法。根据发动机部件级模型的输出数据和发动机性能分析软件GasTurb计算结果,以发动机关键测量参数所定义的目标函数最小为优化目标,利用PSO获取不同相对换算转速下的部件特性修正因子,并在线完成特性图的自动更新。并以某型涡轴发动机为对象进行仿真验证,结果表明:该方法可有效提高涡轴发动机部件级模型的精度,并直接输出更新后的部件特性。     

国际空间站舱内空气温湿度控制技术综述

与非载人航天器不同的是,载人航天器有环控生保系统,而舱内空气温湿度控制又是环控生保系统的一项重要内容。文章跟踪和介绍了国际空间站各舱内的温湿度控制方案,包括设计指标、硬件组成及所采用的技术;重点评述了国际空间站舱内温湿度控制系统的关键设备——冷凝干燥器组件及其降温除湿原理;最后结合NASA近年来研究的多孔渗水冷凝干燥器,指出未来冷凝干燥器的发展方向。     

太阳风粒子速度分布不对称性的产生机制

1引言太阳风中由于磁场的作用,在垂直磁场平面内质子做回旋运动．通常在此平面的质子速度分布函数是旋转对称的．实际观测中,虽然大部分由测量值内插得到的速度分布是旋转对称的,但少数是不对称的．产生这种不对称性的原因还不清楚．文献川提出o粒子与间断面相互作用可产生非回族对称分布．由于这种非旋转对称的速度分布应是不稳定的,因而会很快弛豫到了旋转对称的分布．很难解释非对称的分布可经常被观测到的事实．我们认为这种非对称分布的观测结果并不一定是真实的非回旋对称的分布函数产生的而可能是由于太阳风等离子体小尺度的不均…     

直升机整体式惯性粒子分离器研究现状

整体式惯性粒子分离器是一种直升机进气防护装置,其性能优异、应用广泛,对于保护直升机发动机、延长其使用寿命具有重要意义。本文从4 个方面对整体式惯性粒子分离器的研究现状进行归纳总结,包括：总结了现有直升机进气防护装置的类型及相关气动参数,梳理了整体式惯性粒子分离器现有的研究方法及取得的相关成果,分析了影响整体式惯性粒子分离器工作性能的因素,并展望了整体式惯性粒子分离器未来的发展方向。研究成果可为今后开展整体式惯性粒子分离器研究及优化设计提供一定参考。     

Particle Acceleration in Mercury’s Magnetosphere

This paper is devoted to the problem of particle acceleration in the closest to the Sun Hermean magnetosphere. We discuss few available observations of energetic particles in Mercury environment made by Mariner-10 in 1974–1975 during Mercury flyby’s and by Helios in 1979 upstream of the Hermean bow shock. Typically ions are non-adiabatic in a very dynamic and compact Mercury magnetosphere, so one may expect that particle acceleration will be very effective. However, it works perfectly for electrons, but for ions the scale of magnetosphere is so small that it allows their acceleration only up to 100 keV. We present comparative analysis of the efficiency of various acceleration mechanisms (inductive acceleration, acceleration by the centrifugal impulse force, stochastic acceleration in a turbulent magnetic fields, wave–particle interactions and bow shock energization) in the magnetospheres of the Earth and Mercury. Finally we discuss several points which need to be addressed in a future Hermean missions.     

An efficient analytical homogenization technique for mechanical-hygrothermal responses of unidirectional composites with applications to optimization and multiscale analyses

The elasticity-based Locally Exact Homogenization Theory (LEHT) is extended to study the mechanical-hygrothermal behaviors of unidirectionally-reinforced composites. Based on the framework developed previously, thermal and moisture effects are incorporated into the LEHT to study the homogenized and localized responses of heterogeneous materials, which are validated using available analytical and numerical techniques. The LEHT programs are then encapsulated as subroutines with Input/Output (I/O) interfaces, to be readily applied in different computational scenarios. In order to illustrate the efficiency of the LEHT, the theory is firstly coupled to the Particle Swarm Optimization (PSO) algorithm in order to minimize the axial thermal expansion mismatch in hexagonal and square fiber arrays by tailoring the fiber volume fraction. The LEHT is then implemented into the lamination theory to study fabrication-induced residual stresses arising during the cool-down process which introduces local laminate stresses owing to thermo-mechanical property mismatch between plies. Both of these applications illustrate the efficiency and accuracy of the LEHT in generating effective properties and local stress distributions, making the theory a golden standard in validating other analytical or numerical techniques as well as a reliable tool in composite design and practice for professionals and non-professionals alike.     

固体火箭喷管颗粒尺寸分级两相跨音速流场计算

本文中对固体火箭喷管颗粒尺寸分级的两相跨音速流场作了计算.气相控制方程采用隐式近似因子分解法求解,尺寸分级的颗粒控制方程采用特征线求解,然后,二者进行充分的耦合,可以获得固体火箭发动机含有任意颗粒质量分数和不同颗粒尺寸时轴对称喷管跨音速流场的参数分布.文中讨论了不同颗粒半径和质量分数对流场的影响,对单一颗粒尺寸和颗粒尺寸分级的参数进行了比较.两相耦合计算的迭代收敛速度取决于气相,本文中气相方程求解的格式除部分边界外是隐式的,CFL数可取至6左右,收敛速度快.特别是对颗粒尺寸分级的计算,得益更大,其得益的倍数为颗粒的分级数.     

On the ability of sliding mode and LQR controllers optimized with PSO in attitude control of a flexible 4-DOF satellite with time-varying payload

Precise pointing of the satellite and its payload is essential in the accurate accomplishment of a space mission. In this study, the system of a satellite and its payload are considered as 4-DOF equations of motion. The time-varying payload can observe one direction of the Earth independently, and the satellite can point to the Earth station by its 3-DOF motions simultaneously. Sliding mode and LQR controllers are designed for damping disturbances, and consequently high pointing accuracy. Environmental disturbances and the associated time delay of Low Earth Orbit (LEO) are applied to the system. An algorithm based on Particle Swarm Optimization (PSO) is proposed to find the optimum values of variables and Normalized Integral Square Error (NISE) of the two aforementioned controllers. Numerical simulations indicate the optimized magnitudes of target detection errors and control efforts in four directions. The results revealed that PSO-SMC can finely track the time-varying payload and has better efficiency in comparison with PSO-LQR.     

The dynamical environments analysis of surface particles for different shaped asteroids

Asteroids are coming to be a popular topic in the areas of astrophysical studies and deep space exploration recently. However, surface dynamics of asteroids is still a difficult problem. This paper aims at the motion analysis of surface particles for different asteroids. The dynamical analysis method of particles’ movement is given for three parts: global motion trend, local motion trend and static analysis. A dimensionless parameter ζ is defined to distinguish the predominant term to determine the distribution of effective potential. Three kinds of common asteroids: spheroidal asteroid, spindle-shaped asteroid and dumbbell-shaped asteroid are all discussed for those three parts with different parameter ζ. The motion trend of particles on the surface of each kind of asteroid is given. The static analysis of surface particles for different asteroids is also illustrated. Based on them, some common rules for different shaped asteroids are revealed. This paper could not only provide a reference for asteroid exploration missions but also be meaningful for the research of morphologic evolution of asteroids.     

Alfvén waves as a driving mechanism in stellar winds

Alfvén waves have been invoked as an important mechanism of particle acceleration in stellar winds of cool stars. After their identification in the solar wind they started to be studied in winds of stars located in different regions of the HR diagram. We discuss here some characteristics of these waves and we present a direct application in the acceleration of late-type stellar winds.