微波暗室反射率电平对微波场强校准的影响

论述了微波暗室静区反射率电平的测量方法和微波场强校准原理,分析了反射率电平对标准场法微波场强校准的影响。     

Antenna for precise orbit determination

The ESA SWARM mission will consist of three satellites that will measure the Earth magnetic field. The system calls for metre accuracy knowledge of the measurement locations. To achieve this a GPS receiver is used. At least four GPS signals are tracked to determine the code and carrier ranges, from which the position can be derived. The accuracy improves when using more GPS satellites and by averaging over many measurements. The latter is achieved in ground processing with a model-based orbit prediction, resulting in cm accuracy. The main error contributions in the processing are often measurement errors due to satellite multi-path effects. The multipath effects are characterized by measuring the antenna on a 1.5 m mock-up, representing the 9 m long satellite. In order to verify that the mock-up is representative, extensive electromagnetic simulations were made. The simulations included the antenna and the complete satellite and were then reduced to the antenna and a section of the satellite. The actual design of the antenna was performed with several levels of software. First, a fast bodies-of-revolution simulation found a geometry with the right coverage. Then, a finite element method simulation allowed us to match the antenna at two frequencies simultaneously.     

基于半分析式方法的全球导航星座设计

导航星座设计涉及诸多参数的优化组合,设计目标就是寻找一组参数组合,使其构成的星座在指定覆盖区域既能获得最优的星座性能,又节省系统建设成本和星座长期维持费用。首先,提出评价导航星座性能的技术指标、可用性算法以及半分析式星座设计方法;然后,详细论证设计参数对导航星座性能的影响,进而综合分析得到3种全球导航星座设计方案;最后,通过对比研究3种星座方案的性能指标和导航定位仿真结果,说明导航星座设计方法和设计方案的可行性。     

再生冷却推力室的多学科设计优化

以某型火箭发动机的再生冷却推力室为研究对象,建立了关于推力室的几何型面、质量、流动、传热和结构应力的仿真模型,在iSIGHT软件平台上利用基于响应面模型的协同优化算法对其进行了分布并行的多学科设计优化(MDO),优化目标为权衡推力室质量、出口比冲和冷却通道压降的综合改善。改进的计算结果表明了MDO在推力室设计中的可行性和实用性。     

微涡喷发动机离心甩油盘环形折流燃烧室的设计与实验研究

微涡喷发动机是低成本的结构简单的燃气涡轮动力装置,特别适合于推动巡航导弹、(雷达)假目标、轻型直升机、无人侦察机和航空靶机。离心甩油盘环形折流燃烧室由于具有燃油雾化质量好,轴向长度短,高空性能好等优点,很适合作为微涡喷发动机动力装置的燃烧室。本文主要研究了离心甩油盘环形折流燃烧室的气动热力学参数和几何参数的设计,并通过实验研究验证参数设计的合理性。      

一种双基站低轨道区域覆盖δ星座设计

在双基站理论研究基础上 ,进行了定倾角区域性覆盖双基站δ星座设计 ,采用倾角为 41°的回归轨道 ,用点覆盖数值仿真的方法设计了对地面站与空间站的一重覆盖与二重覆盖下的星座构型。且星座中各星之间 ,各星与空间站之间均可建立星际链路 ,保证数据在空间站、地面站及星座之间连续传递     

有声腔推力室的声学振型及其阻尼特性研究

为确定多声学模态压力振荡条件下带有1/4波长管声腔推力室的声学振型及其阻尼特性,揭示1/4波长管声腔对推力室压力振荡的抑制作用机理,对有声腔推力室和无声腔推力室进行近圆周壁面的定容弹激励仿真,激发了多模态的声学振型,给出了推力室压力分布的时空演化,并采用半带宽法定量评价每个激发声学振型的阻尼特性.结果表明:1/4波长管...     

Towards intelligent design optimization: Progress and challenge of design optimization theories and technologies for plastic forming

Plastic forming is one of enabling and fundamental technologies in advanced manufacturing chains. Design optimization is a critical way to improve the performance of the forming system, exploit the advantages of high productivity, high product quality, low production cost and short time to market and develop precise, accurate, green, and intelligent (smart) plastic forming technology. However, plastic forming is quite complicated, relating to multi-physics field coupling, multi-factor influence, multi-defect constraint, and triple nonlinear, etc., and the design optimization for plastic forming involves multi-objective, multi-parameter, multi-constraint, nonlinear, high-dimensionality, non-continuity, time-varying, and uncertainty, etc. Therefore, how to achieve accurate and efficient design optimization of products, equipment, tools/dies, and processing as well as materials characterization has always been the research frontier and focus in the field of engineering and manufacturing. In recent years, with the rapid development of computing science, data science and internet of things (IoT), the theories and technologies of design optimization have attracted more and more attention, and developed rapidly in forming process. Accordingly, this paper first introduced the framework of design optimization for plastic forming. Then, focusing on the key problems of design optimization, such as numerical model and optimization algorithm, this paper summarized the research progress on the development and application of the theories and technologies about design optimization in forming process, including deterministic and uncertain optimization. Moreover, the applicability of various modeling methods and optimization algorithms was elaborated in solving the design optimization problems of plastic forming. Finally, considering the development trends of forming technology, this paper discusses some challenges of design optimization that may need to be solved and faced in forming process.     

变推力发动机仿真计算分析

分析了变推力发动机采用的双调模式,用流量调节器控制推进剂流量。流量定位针栓式喷注器控制喷注压降,保证喷注速度基本不变。根据发动机系统特点建立了主要组件的数学模型,并根据模型进行了仿真计算,最后对发动机前管路流阻影响进行了分析。     

冷却环带喷注结构对煤油超临界液膜的影响研究

针对液氧/煤油补燃发动机液膜冷却过程,建立了超临界条件下的液膜冷却模型,分析了冷却环带喷注结构对局部流动和冷却效果的影响.在超临界条件下,煤油和周围燃气为同种流体,用同一组方程来描述其流动与传热过程,对3种典型冷却环喷注结构的流动进行了数值模拟.结果表明:冷却环带的出口角度、台阶结构和喷射角对局部流动和传热有显著影响,出口角度小于90°的台阶式结构可减小局部回流从而有利于推力室的热防护.