几何对称横向射流入射对尾喷流红外辐射特征抑制的数值研究

降低高温核心区长度是减小尾喷流红外辐射的有效途径。针对某轴对称收敛喷管,研究1种横向射流主动强化尾喷流掺混与红外抑制技术,采用横向射流技术强化外流与热喷流的掺混,通过数值模拟方法研究了2股横向射流喷射频率与流量变化对强化尾喷流掺混与红外抑制特性的影响规律。结果表明:在与横向射流流动方向垂直的探测面上尾喷流辐射强度衰降明显,探测角度为90°时红外辐射强度衰降可达48%。随着2股射流流量差的减小,强化掺混与红外抑制效果逐渐增强。     

应变片横向效应对应变测量的影响与修正

首先介绍了应变片横向效应,并对其引起的应变测量误差进行分析;然后分别对T型应变片、450应变花和600应变花测量的应变结果进行修正;最后用两个工程实例说明此方法在实际工作中的应用。     

水下喷雾发动机非设计点性能分析

针对水下喷雾发动机非设计工况下运行特性,建立数学模型并开展数值模拟研究,分析了航行体速度及环境压力对发动机性能的影响等,以期全面了解发动机特性,为其设计工作奠定理论基础。计算结果表明:当发动机应用于航行速度大于发动机设计速度的航行体时,需增大通入气体质量流率,但发动机推力略有减小,推进效率增大;环境压力大于发动机设计工况时,需减小气体质量流率,同时发动机推力及推进效率均减小。通过反馈控制调节气体质量流率及压力,可使发动机动力输出满足航行体一定速度范围内航行的推力需求。      

人体上呼吸道内稳态气流运动特性的PIV初步试验研究

人体上呼吸道内气流组织形式的研究对于进行气溶胶在呼吸道内的沉积分析具有重要的意义.应用粒子图像速度仪(Particle Image Velocimetry,PIV)对人体上呼吸道内的稳态气流运动特性进行了试验研究,研究结果表明:口腔中、下部气流速度略大,其它位置速度相对较小,咽部外壁气流速度较大,高速气流贴近喉部和气管内壁向下流动,在内壁形成高速区域.咽部外壁、喉部和气管内壁分布的气动剪切力较大,承受的气动负荷较大,容易造成壁面劳损和组织损伤.     

基于脑电和眼动信号的人机交互意图识别

意图识别在人机交互（HCI）领域受到广泛关注,传统人机交互意图识别方法单纯依靠脑电（EEG）或眼动数据,不能很好地利用2种方法优点。为此,提出了一种融合脑电和眼动数据的人机交互意图识别方法,通过采集脑电和眼动信号,进行特征提取,输入机器学习模式识别网络进行意图识别,并基于Dempster-Shafer （D-S）证据理论进行决策层融合得出最终识别结果。招募了20名有效受试者进行交互意图识别实验,结果表明,基于脑电和眼动信号的人机交互意图识别方法识别准确率高于单纯依靠脑电和眼动数据的方法,可为下一步飞行器和武器系统人机交互系统自适应设计提供理论依据和技术支持。     

Performance comparison of aero-ramp and transverse injector based on gas-pilot flame

A direct performance comparison between the four-hole aero-ramp injector and single transverse injector in a dual-mode scramjet combustor was conducted. The mixing characteristics of two injectors were calculated by solving the three-dimensional (3-D) compressible Reynolds-averaged Navier-Stokes equations (RANS), with the help of the shear-stress-transport (SST) k-ω turbulence model. The numerical results show that the far field mixing efficiency of the aero-ramp injector is higher than that of the single transverse injector. High enthalpy vitiated air was heated to a total temperature of 1200K by hydrogen-oxygen combustion, entering the isolator entrance at a Mach number of 2.0. Non-reacting experimental conditions involved sonic injection of nitrogen to safely simulate ethylene injected into the combustor at a jet-to-free stream momentum flux ratio of 2.6. Schlieren photographs were obtained to analyze the shock structure around the injectors. Reacting test conditions involved sonic injection of ethylene at the jet-to-free stream momentum flux ratios ranging from 0.5 to 2.7. High speed camera was used to capture the flame structures in the near-field combustion. The experimental results show that the aero-ramp injector produce sustained combustion over a wider range of fuel-air ratios than the single transverse injector. At the identical jet-to-free stream momentum flux ratio, the aero-ramp has a larger isolator margin than the single transverse injector, demonstrating a better ability for avoiding overflows. However, the air specific impulse and total temperature recovery of two injectors, which are calculated by the one-dimensional (1-D) performance analysis code, are almost identical.      

Real-time evaluation method of flight mission load based on sensitivity analysis of physiological factors

As the complexity of flight missions continues to increase, sending a timely warning or providing assistance to pilots helps to reduce the probability of operational errors and flight accidents. Monitoring pilots’ physiological data, real-time evaluation of mission load is a feasible technical way to achieve this. In this paper, a set of flight tasks including aircraft control, humancomputer interaction and mental arithmetic tests are designed to simulate five mission loads at different flight d...     

Water movement on the convex surfaces of porous media under microgravity

A plant growth system for crop production under microgravity is part of a life supporting system designed for long-duration space missions. A plant growth in soil in space requires the understanding of water movement in soil void spaces under microgravity. Under 1G-force condition, on earth, water movement in porous media is driven by gradients of matric and gravitational potentials. Under microgravity condition, water movement in porous media is supposed to be driven only by a matric potential gradient, but it is still not well understood. We hypothesized that under microgravity water in void spaces of porous media hardly moved comparing in void spaces without obstacles because the concave surfaces of the porous media hindered water movement. The objective of this study was to investigate water movement on the convex surfaces of porous media under microgravity. We conducted parabolic flight experiments that provided 20–25?s of microgravity at the top of a parabolic flight. We observed water movement in void spaces in soil-like porous media made by glass beads and glass spheres (round-bottomed glass flasks) in the different conditions of water injection under microgravity. Without water injection, water did not move much in neither glass beads nor glass spheres. When water was injected during microgravity, water accumulated in contacts between the particles, and the water made thick fluid films on the particles surface. When the water injection was stopped under microgravity, water was held in the contacts between the particles. This study showed that water did not move upward in the void spaces with or without the water injection. In addition, our results suggested that the difficulty of water movement on the convex (i.e. particle surfaces) might result in slower water move in porous media under microgravity than at 1G-force.     

横向变过载对固体火箭发动机绝热结构设计的影响

针对新一代防空导弹高机动作战特点,研究了复杂横向变过载对固体火箭发动机绝热结构工程设计的影响。同时考虑过载值和过载角度的瞬时变化,对发动机绝热层进行网格划分,并对烧蚀厚度进行编程计算,进而按照安全裕度设计准则得到不同位置的绝热层设计厚度。与传统设计结果相比,考虑横向过载的变化可以显著减少了发动机的结构质量,提高了发动机总体性能,绝热质量减小了53.7%,总冲提高了6.84%。      

人体手端点到点运动的优化轨迹生成与控制

考虑肢体肌肉的生理特征和肌肉收缩的动力学行为,利用肌肉等长收缩的最小功准则研究了人体手端点到点运动的优化轨迹生成与控制问题.讨论了肌肉收缩的动力学特性,建立水平面内上肢运动的动力学模型,提出将肌肉等长收缩的最小功准则作为优化的目标函数,运用最优化理论将手端点到点的运动问题转化为最优控制问题,设计了求解手端运动优化轨迹的迭代算法,得到了手端运动的控制规律和优化轨迹.算例仿真表明该方法对手端运动优化轨迹的预测是有效的.