制冷压缩机的现状与发展趋势

本文介绍能够促进制冷机CFCs工质替代,并明显提高家用制冷机(冰箱、空调器等)能源效益的新一代制冷压缩机及其研究现状.它采用直线振荡电机驱动活塞式压缩机,通过简单的控制方案可以实现无级能量调节,电效率可高达85%.     

带尾缘劈缝冷气喷射的涡轮叶栅性能实验及计算

通过平面叶栅实验和CFD数值计算方法,研究了叶片尾缘全劈缝冷气喷射下涡轮叶栅流场和气动性能。试验和计算发现,在冷气喷射条件下用不同损失系数描述涡轮叶栅性能,结论明显不同,用考虑冷气能量的能量损失系数评价气冷涡轮叶栅性能较为准确和客观。在较小的冷气流量下,劈缝冷气喷射使叶栅能量损失降低,尾缘劈缝冷气喷射可改善近尾迹区域的流动,减小尾迹亏损,降低尾迹掺混损失。尾缘劈缝冷气射流方向偏向叶片某型面,则尾迹损失峰值朝此型面偏移。     

跳跃式弹道参数估算及其效率

简要地介绍了跳跃式弹道的发展过程和应用前景,并针对标准跳跃式弹道,详细研究了其过渡段、转弯段、滑翔段和再入段的弹道参数估算问题,通过参数估算,可以方便快捷地计算跳跃式导弹的性能,此外对跳跃式导弹的关键技术和飞行效率问题进行简单的描述,为进一步研究跳跃式导弹奠定了基础。     

基于局部主动轮廓模型的飞机壁板铆接孔定位方法研究

对飞机壁板铆接孔的定位方法进行了研究,提出了一种基于局部主动轮廓模型的铆接孔定位方法。首先通过基于灰度直方图的全局阈值分割和形心法进行铆接孔的粗定位;然后以粗定位坐标为圆心建立遍历圆,并以遍历圆作为限制条件构造能量圆,建立能量方程求解遍历圆内能量最小的像素点为铆接孔的精定位位置;最后进行视觉引导铆接孔定位试验,试验测得定位误差小于0.05mm,满足飞机壁板自动铆接的工艺要求,且比传统的区域主动轮廓模型定位精度高,具有一定的可行性。     

磁悬浮姿控/储能飞轮能量转换控制系统设计与实验研究

针对磁悬浮姿控/储能飞轮(ACESFW)的能量释放问题,采用直流降压斩波原理,设计了一种能量转换控制器,提出对降压斩波器输出进行软件功率因数校正的转换控制方法,将高速ACESFW存储的动能,转变为稳定直流电能输出。仿真和地面试验结果表明,所设计的能量转换器转换效率高,电压输出稳定,高频纹波小,可以满足星上设备的供电要求。     

A new error-controllable method for smoothing the G01 commands

In real machining, the tool paths are composed of a series of short line segments, which constitute groups of sharp corners correspondingly leading to geometry discontinuity in tangent. As a result, high acceleration with high fluctuation usually occurs. If these kinds of tool paths are directly used for machining, the feedrate and quality will be greatly reduced. Thus, generating continuous tool paths is strongly desired. This paper presents a new error-controllable method for generating continuous tool path. Different from the traditional method focusing on fitting the cutter locations, the proposed method realizes globally smoothing the tool path in an error-controllable way. Concretely, it does the smoothing by approaching the newly produced curve to the linear tool path by taking the tolerance requirement as a constraint. That is, the error between the desired tool path and the G01 commands are taken as a boundary condition to ensure the finally smoothed curve being within the given tolerance. Besides, to improve the smoothing ability in case of small corner angle, an improved local smoothing method is also proposed by symmetrically assigning the control points to the two adjacent linear segments with the constrains of tolerance and G3 continuity. Experiments on an open five-axis machine are developed to verify the advantages of the proposed methods.     

State of art on energy management strategy for hybrid-powered unmanned aerial vehicle

New energy sources such as solar energy and hydrogen energy have been applied to the Unmanned Aerial Vehicle(UAV), which could be formed as the hybrid power sources due to the requirement of miniaturization, lightweight, and environmental protection issue for UAV. Hybrid electrical propulsion technology has been used in UAV and it further enforces this trend for the evolution to the Hybrid-Powered System(HPS). In order to realize long endurance flight mission and improve the energy efficiency of UAV, many researching works are focused on the Energy Management Strategy(EMS) of the HPS with digital simulation, ground demonstration platforms and a few flight tests for the UAV in recent years. energy management strategy, in which off-line or on-line control algorithms acted as the core part, could optimize dynamic electrical power distribution further and directly affect the efficiency and fuel economy of hybrid-powered system onboard.In order to give the guideline for this emerging technology for UAV, this paper presents a review of the topic highlighting energy optimal management strategies of UAV. The characteristics of typical new energy sources applied in UAV are summarized firstly, and then the classification and analysis of the architecture for hybrid power systems in UAV are presented. In the context of new energy sources and configuration of energy system, a comprehensive comparison and analysis for the state of art of EMS are presented, and the various levels of complexity and accuracy of EMS are considered in terms of real time, computational burden and optimization performance based on the optimal control and operational modes of UAV. Finally, the tendency and challenges of energy management strategy applied to the UAV have been forecasted.     

Experimental investigation on dynamic response of flat blades with underplatform dampers

One test rig with three blades and two Under-Platform Dampers (UPDs) is established to better understand the dynamical behavior of blades with UPDs. A pre-loaded spring is used to simulate the centrifugal load acting on the damper, thereby achieving continuous adjustment of the pressing load. UPDs with different forms, sizes and materials are carefully designed as experimental control groups. Noncontact measurement via a laser Doppler velocimeter is employed and contact excitation which is performed by an electromagnetic exciter is adopted to directly obtain the magnitude of the excitation load by a force sensor mounted on the excitation rod. Particular attention is paid to the influence of the contact status of the contact surfaces, e.g. the pressure-sensitive paper is used to measure the effective contact area of the UPDs. The experimental variables are selected as the centrifugal force, the amplitude of the excitation force, the damper mass, the effective contact area, and the damper material. The Frequency Response Function (FRF) of the blade under different experimental parameters is obtained by slow frequency sweep under sinusoidal excitation to study the influence of each parameter on the dynamic characteristics of the blade and the mechanism analysis is carried out combined with the experimental results.     

一枚Chaff火箭观测到的湍流谱

在一个异常强水平风速和极端大风切变层内, 垂直速度扰动谱表明几个相当重要特征:(1)垂直速度扰动谱有二个区域, 一个在低频区, 有谱斜率一1.65, 这个谱斜率接近于惯性子区内-5/3谱斜率, 另一个在高频区, 有谱斜率-7.11, 它接近于粘性子区内-7谱斜率.(2)垂直速度扰动谱有一个崩溃点, 约位于70m, 这与计算的内尺度有好的一致.(3)由垂直速度扰动谱计算的湍流能量耗散率是0.087m2·s-3, 这比MAP/WINE试验中得到的值约大一个数量级.      

非热电子束流在耀斑环中能量的沉积

本文计算了非热电子束流通过库仑碰撞和反向电流过程在均匀截面的耀斑环中的能量沉积,讨论了非热电子束流对耀斑软X射线等离子体的加热和耀斑非热模型的能量收支平衡问题。