基于MATLAB/Simulink的变频电机系统能耗实用模型

变频电机系统能耗分析需要对系统各环节建立准确的损耗计算模型。针对目前有限元模型建模繁琐、计算量大的现状,在考虑了变频电源谐波对铁耗电阻影响的基础上,建立了计及铁耗等效电阻的异步电机数学模型及PWM变频器主电路损耗模型,提出一种基于MATLAB/Simulink的变频电机系统实用模型,实现了变频电机系统各环节损耗准确分析。通过对不同工况下变频器、电机和系统总效率的仿真分析,揭示了传统忽略变频器能耗的损耗分析方法对系统最佳运行点估算存在一定误差。为了验证模型正确性,对一组5.5 kW变频电机系统进行了试验对比,验证了文中模型能够正确有效地模拟变频电机系统运行。研究成果为进一步研究系统能耗最优控制策略提供了重要理论支撑。     

铝合金壳体阳极化膜颜色异常分析

铝合金壳体在阳极化处理后表面阳极化膜存在颜色异常(发黑)现象。本文通过对壳体阳极化膜表面及基体形貌观察、金相分析和成分分析对发黑的原因进行了分析。结果表明壳体阳极化膜发黑的原因是由于该区域存在成分偏析(合金含量高),导致该区域的晶粒尺度比正常区域小、耐蚀性比正常区域差,膜层微观结构与正常区域存在差异,膜层内部化合物较多,致使该区域膜层呈现黑色。     

基于MATLAB/Simulink的滑油系统建模仿真与优化

为分析滑油系统特性，研究其与航空发动机协同工作及设计问题，基于滑油系统元部件的流量、压力和换热特性在MATLAB/Simulink下开发了通用仿真模块库，构建了包含供油、回油、通风和热力系统的全系统仿真模型.以某型涡扇发动机及其滑油系统为例，计算了高温起飞工况下滑油系统主要工作参数值，并与商业软件Flowmaster对比计算结果，相对误差保持在3.8%以下.利用全系统仿真模型的拓展性，成功与GasTurb发动机模型进行联合仿真，使用遗传算法优化滑油系统设计参数，通过改变供油分配比例使最高回油温度降低4.12%，可为滑油系统的设计及改进提供参考.      

基于神经网络算法在机场油库安全的应用

机场油库是储存航空油料的重要基地,其安全因素包含多个方面。通过对机场油库的安全分析,采用神经网络方法,建立机场油库安全评价模型,基于MATLAB软件神经网络工具箱对其进行求解,并将结果应用到油库的安全评价中。结果表明该方法与模糊综合评价方法基本一致,研究成果对油库安全监测和预测有着重要的意义和实用价值。     

Hardware qualification for scientific ballooning missions

The European Stratospheric Balloon Observatory (ESBO) initiative aims at simplifying the access to stratospheric balloon missions. We plan to provide platforms and support with instrument design in order to support scientists. During the design process, the inevitable question of qualification for the harsh flight conditions arises. Unfortunately, there is no existing standard for qualification of stratospheric ballooning hardware. Thus, we developed a qualification procedure for use within ESBO and similar projects.In this paper, we present our analysis of the environmental conditions in the stratosphere. While conditions at typical balloon float altitudes are similar to the space environment, there are also some relevant differences. For example, the thermal environment is dominated by radiation and thermal conduction, but the remaining atmosphere still supports a certain amount of convection. The remaining atmospheric pressure in the stratosphere also leads to reduced arcing distances. Vibrational loads are far less than for space missions, but quasi-static or shock loads may occur. The criticality of radiation increases with mission duration.Based on the environmental conditions, we present the qualification procedures for ESBO, which are based on the European Cooperation for Space Standardization (ECSS) standards for space systems. Overtesting against too high requirements leads to overengineering, driving mission cost and mitigating the advantages of balloons over space missions. Therefore, we modified the ECSS standards to fit typical scientific ballooning missions over several days at altitudes up to 40 km. Furthermore, we analyzed design rules for space systems with regard to their relevance for scientific ballooning, including material and component selection. We present the experience from the hardware qualification process for the ESBO prototype STUDIO (Stratospheric UV Demonstrator of an Imaging Observatory). Even though boundary conditions are different for each individual mission, we aimed for a broader approach: We investigated more general requirements for scientific ballooning missions to support future flights.     

Through-thickness heterogeneity in creep properties of friction stir welding 7B50-T7451 aluminum alloy thick plate joint: Experiments and modeling

Through-thickness heterogeneity in creep properties of 7B50-T7451 aluminum alloy Friction Stir Welding(FSW) joints was investigated. Creep tests for three slices of the FSW joint were conducted at the temperature of 150–200 °C and applied stress of 60–225 MPa. The theta projection method was used to predict creep curves and minimum creep rate. The results show that the minimum creep rate increases and creep rupture life decreases with the increase of creep temperature and applied stress. Creep p...     

大规格TA7ELI冷氦气瓶半球等温冲压工艺北大核心CSCD

对未来运载火箭用大直径TA7ELI钛合金冷氦气瓶半球的等温冲压工艺进行了研究。采用有限元分析软件对半球等温冲压过程进行了数值模拟并开展了成形试验验证,同时结合成形前后材料显微组织、力学性能的变化,进一步分析了工艺过程对材料性能的影响规律。研究结果表明,等温冲压过程中材料的应力应变由芯部逐渐扩展到边缘,成形进程达到中后期时载荷最大,成形后半球壁厚最薄位置在球底中心边缘处。等温冲压后TA7ELI材料的组织形态和尺寸变化较小,且半球各处室温和20 K下的强度与成形前相比基本一致,成形后材料的室温延伸率均有所提高,20 K下球底处材料的延伸率有所降低但仍满足要求。