Application of Analytic Redundancy-based Fault Diagnosis of Sensors to Onboard Maintenance System

Analytic redundancy-based fault diagnosis technique (ARFDT) is applied to onboard maintenance system (OMS). The principle of the proposed ARFDT scheme is to design a redundancy configuration using ARFDT to enhance the functions of redundancy management and built in test equipment (BITE) monitor. Redundancy configuration for dual-redundancy and analytic redundancy is proposed, in which, the fault diagnosis includes detection and isolation. In order to keep the balance between rapid diagnosis and binary hypothesis, a filter together with an elapsed time limit is designed for sequential probability ratio test (SPRT) in the process of isolation. Diagnosis results would be submitted to central maintenance computer (CMC) together with BITE information. Moreover, by adopting reconstruction, the designed method not only provides analytic redundancy to help redundancy management, but also compensates the output when both of the sensors of the same type are faulty. Our scheme is applied to an aircraft’s sensors in a simulation experiment, and the results show that the proposed filter SPRT (FSPRT) saves at least 50% of isolation time than Wald SPRT (WSPRT). Also, effectiveness, practicability and rapidity of the proposed scheme can be successfully achieved in OMS.     

CFD Study of NO_x Emissions in a Model Commercial Aircraft Engine Combustor

Air worthiness requirements of the aircraft engine emission bring new challenges to the combustor research and design. With the motivation to design high performance and clean combustor, computational fluid dynamics (CFD) is utilized as the powerful design approach. In this paper, Reynolds averaged Navier-Stokes (RANS) equations of reactive two-phase flow in an experimental low emission combustor is performed. The numerical approach uses an implicit compressible gas solver together with a Lagrangian liquid-phase tracking method and the extended coherent flamelet model for turbulence-combustion interaction. The NOx formation is modeled by the concept of post-processing, which resolves the NOx transport equation with the assumption of frozen temperature distribution. Both turbulence-combustion interaction model and NOx formation model are firstly evaluated by the comparison of experimental data published in open literature of a lean direct injection (LDI) combustor. The test rig studied in this paper is called low emission stirred swirl (LESS) combustor, which is a two-stage model combustor, fueled with liquid kerosene (RP-3) and designed by Beihang University (BUAA). The main stage of LESS combustor employs the principle of lean prevaporized and premixed (LPP) concept to reduce pollutant, and the pilot stage depends on a diffusion flame for flame stabili-zation. Detailed numerical results including species distribution, turbulence performance and burning performance are qualita-tively and quantitatively evaluated. Numerical prediction of NOx emission shows a good agreement with test data at both idle condition and full power condition of LESS combustor. Preliminary results of the flame structure are shown in this paper. The flame stabilization mechanism and NOx reduction effort are also discussed with in-depth analysis.     

基于混杂系统模型的航空器4D航迹推测

为实现对未来大流量、高密度、小间隔条件下空域实施管理,4D航迹推测是国内新一代空管自动化系统最为核心的一项技术。首先基于飞行剖面不同飞行阶段的航空器动力学模型,构造了在不同飞行阶段之间转移,而在同一阶段航空器重量、校正空速、高度和距离等状态连续变化的混杂系统模型。通过温度和风速风向修正航空器真空速及地速,利用混杂系统递推法求解航空器4D航迹。实际算例表明,本文提出的混杂系统模型推测得到的水平航迹和垂直剖面能够准确地反映航空器的飞行状态变化,单架航空器4D航迹推测计算时间可以控制在2 s以内。     

论空中交通管制中的非常态运行对飞行安全的影响

空中的飞行局势瞬息万变,由于特殊天气、空军活动、流量限制、航空器不正常以及人员、设备等因素导致的非常态运行对飞行安全影响很大。本文联系空管实际,对这些常见的非常态运行情况逐一进行分析,并提出相应的解决措施,以确保航空安全。     

中南地区协同流量管理系统设计研究

本文从我国民航空管的实际情况出发,指出了我国建设协同流量管理系统的必要性,并以中南地区为例在其现有流量管理系统的基础上,初步规划了中南地区协同流量管理系统的总体构架及建设步骤,详细设计了系统的主要功能程序及其数据处理流程,为完善建设中南地区流量管理系统拓展了思路,为我国空管全面引入协同决策理念提供了借鉴和参考.     

复杂产品系统的风险管理实现研究

提出了一套跨研制单位持续项目风险管理机制.在其风险因素识别阶段.提出了以核对表和鱼刺图为基础的基于特征一因子法的风险因素识别法;在风险量化阶段,提出了先基于模糊综合评判进行单个风险量化、后基于改进PERT方法进行风险整体量化的实现方法:在风险应对阶段,提出了基于人工神经网络和框架知识表示及推理相结合的风险应对方法,建立了混合型专家系统.以实现风险应对智能化.最后,以具体实例说明了该项技术的可行性.     

综合化飞行器管理计算机技术研究

目前国外新一代飞机的设计中,为进一步提高飞机的性能,同时降低系统费用,采用飞行器管理系统综合管理包括飞行控制、发动机控制、机电公共设备管理等飞机平台的功能.飞行器管理系统核心是飞行器管理计算机,细粒度可配置飞行器管理计算机不同于以往基于通道容错的计算机系统,它是基于模块级容错的计算机系统,细粒度可配置飞行器管理计算机设计利用综合化技术,通过采用通用的、标准的模块,提高系统的可靠性和可用性.它既要具有飞行控制系统的多余度安全,同时又需要满足发动机控制、机电管理等不同系统、不同余度配置的安全要求.另一方面飞行器管理计算机从系统结构、容错技术等方面要适应不断变化的微电子技术和计算机技术的发展,保持飞机平台具有相对的稳定性,更要具有灵活的系统配置能力.主要介绍了细粒度可配置飞行器管理计算机体系结构、软件要求、容错结构的实现.     

复杂信息系统中单点登录的设计与实现

使用令牌机制,设计了一种适用于复杂信息系统门户平台的单点登录模型,实现了用户的统一身份认证和授权管理。用户一次登录门户就能自动访问所有授权的应用子系统或子模块,方便系统管理的同时有效提高了系统的安全性。最后以某保障信息系统为背景,描述了模型的技术实现。     

某燃气轮机空气雾化喷嘴的试验研究

进行了某型燃机空气雾化喷嘴燃油喷雾特性的试验研究。得到以下结论：在油压不变的情况下,雾化锥角总是随着空气压力的增加有所减小,索特尔平均直径SMD随之迅速减小,整体减小幅度大约在10-30μm;气压不变时,雾化锥角和索特尔平均直径随着油压的增加而稍有增大;当气压为0.3MPa时,索特尔平均直径基本都保持在30μm以内。     

高性能战斗机燃油热管理系统

针对高性能战斗机的特点,介绍了利用燃油作为主要热沉的燃油热管理系统FTMS(Fuel Thermal Management System).以F-22的热管理系统为原型,在对其技术方案及研究方法进行了相关分析后,通过MATLAB工具建立了系统各部件的动静态仿真模块.并在此基础上,搭建了燃油热管理系统的仿真平台,利用该仿真平台对燃油热管理系统的性能及燃油代偿损失等进行预测和评估.计算结果表明,燃油热管理系统性能要好于传统的空气循环制冷系统,在热管理方面可作为我国新一代高性能飞机设计研究的一个备选方案.