Recent experience with different methods of drag prediction

During the recent past the process of engineering design has changed entirely because of rapid developments in computational simulations. In aerodynamic design, computational fluid dynamics (CFD) methods are slowly superseding empirical methods and design engineers are spending more and more time applying CFD tools to analyze and predict the aerodynamic characteristics of vehicles. The purpose of this paper is to review recent experiences in CFD-based drag prediction with an emphasis on flow solutions governed by the Euler and Reynolds-averaged Navier–Stokes equations. For these types of flow solutions, various drag analysis methodologies are outlined and applied to determine the drag of components of as well as whole-body airplanes, helicopters, and ground-based vehicles at subsonic and transonic flow conditions. The review demonstrates that although significant progress has been made, CFD-based drag prediction still faces a number of hurdles that must be dealt with before it will become more widely accepted.     

航空发动机H_∞混合灵敏度控制中权阵的选取

在进行Ｈ∞混合灵敏度控制器设计时,加权阵的选取一般较为困难。根据控制系统的动态性能指标及系统动态解耦要求来构造权阵,计算机仿真验证了这种方法的有效性。     

平面波压力扰动下压气机逐级动态响应分析

应用轴流压缩系统的逐级动态响应模型对平面波型压力扰动下的多级压气机瞬态响应及气动稳定性进行了较详细的数值分析。对－ ８级跨声压气机的数值模拟结果表明, 基于流动阻塞机理建立的压缩系统稳定性判别准则是合理和可靠的。结果还进一步建立进口扰动频率与压气机瞬态响应间的关联关系     

非正常情况下民机座舱压力控制系统性能分析

非正常情况下,民机座舱压力控制系统难以进行地面验证,为了解决该问题,从工程实际出发,建立系统数学模型,开展全飞行包线内系统性能仿真分析;同时,针对非正常情况(包括单空调组件故障、应急卸压、爆炸减压)下的系统性能进行仿真分析。结果表明:单组件故障时对座舱压力影响较小;飞机应急卸压时满足适航要求;爆炸减压时卸压很快,不同破孔面积对应的减压时间差别很小。     

基于仿真的飞机导管自动化生产线规划设计与优化

航空产品加工生产线正向着自动化、数字化和智能化的方向发展,自动化生产线对车间整体布局、物流和生产节拍都提出了更为严格的要求,对生产线进行规划仿真可以直观、准确地反映出生产线运行过程中可能出现的问题,并通过科学方法解决和优化这些问题.介绍了生产线规划仿真技术,在此基础上,对某型飞机导管自动化生产线的生产过程、工艺布局和物...     

飞机装配几何量质量检测体系构建及关键技术

针对新一代飞机装配过程几何量检测的高精度、高效率和高可靠性需求,分析了飞机装配过程几何量检测特征和具体的检测要求,提出了用于不同测量任务的测量方法,构建了装配几何量质量检测体系.研究了复杂装配现场多源异构整体测量工艺仿真及精度优化、三维点云数据的拟合与对齐和基于整体测量场的多系统协同测量3项关键技术,开发了装配检测质量...     

Reduction rules-based search algorithm for opportunistic replacement strategy of multiple life-limited parts

The opportunistic replacement of multiple Life-Limited Parts(LLPs) is a problem widely existing in industry.The replacement strategy of LLPs has a great impact on the total maintenance cost to a lot of equipment.This article focuses on finding a quick and effective algorithm for this problem.To improve the algorithm efficiency, six reduction rules are suggested from the perspectives of solution feasibility, determination of the replacement of LLPs, determination of the maintenance occasion and solution optimality.Based on these six reduction rules, a search algorithm is proposed.This search algorithm can identify one or several optimal solutions.A numerical experiment shows that these six reduction rules are effective, and the time consumed by the algorithm is less than 38 s if the total life of equipment is shorter than 55000 and the number of LLPs is less than11.A specific case shows that the algorithm can obtain optimal solutions which are much better than the result of the traditional method in 10 s, and it can provide support for determining tobe-replaced LLPs when determining the maintenance workscope of an aircraft engine.Therefore,the algorithm is applicable to engineering applications concerning opportunistic replacement of multiple LLPs in aircraft engines.     

Analysis of the cylinder block tilting inertia moment and its effect on the performance of high-speed electro-hydrostatic actuator pumps of aircraft

Electro-hydrostatic actuator (EHA) pumps are usually characterized as high speed and small displacement. The tilting inertia moment on the cylinder block produced by the inertia forces of piston/slipper assemblies cannot be ignored when analyzing the cylinder block balance. A large tilting inertia moment will make the cylinder block tilt away from the valve plate, resulting in severe wear and significantly increased leakage. This paper presents an analytical expression for the tilting inertia moment on the cylinder block by means of vector analysis. In addition, a high-speed test rig was built up, and experiments on an EHA pump prototype were carried out at high speeds of up to 10,000 r/min. The predicted nature of the cylinder block tilt at high speeds corresponds closely to the witness marks on the dismantled EHA pump prototype. It is suggested that more attention should be given to the tilting inertia moment acting on the cylinder block of an EHA pump since both wear and leakage flow between the cylinder block and the valve plate are very much dependent on this tilting moment.     

惩治危害航空安全犯罪国际公约与我国刑法相关规定比较研究

随着航空运输业的快速发展,航空安全问题日益引起人们的重视.劫持航空器、暴力危及飞行安全等犯罪严重危害航空安全,国际社会相继通过了一些国际公约予以规制,我国刑法也作出了相应的规定,力争严厉打击危害航空安全的犯罪,确保航空业的安全、高效.     

Analysis of conventional and asymmetric aircraft configurations using CEASIOM

One of the main drivers behind the SimSAC project and the CEASIOM software is to bring stability analysis and control system design earlier into the aircraft conceptual design process. Within this paper two very different aircraft are considered, a conventional T-tail based on the existing EA500 Very Light Jet and the second, a novel Z-wing configuration known as the GAV or general aviation vehicle. The first aircraft serves as a baseline comparison for the second, and the cruise case is considered as a benchmark for identifying potential drag reductions and aircraft stability characteristics. CEASIOM, the Computerised Environment for Aircraft Synthesis and Integrated Optimisation Methods, is used to generate aerodynamic data sets for both aircraft, create trim conditions and the associated linear models for classical stability analysis. The open-loop Z-wing configuration is shown to display both highly unstable and coupled modes before a multivariable Stability Augmentation System (SAS) is applied both to decouple and stabilise the aircraft. Within this paper, these two aircraft provide a test case with which to demonstrate the capabilities of the CEASIOM environment and the tools which have been developed during the SimSAC project. This new software suite is shown to allow conceptual development of unconventional novel configurations from mass properties through adaptive-fidelity aerodynamics to linear analysis and control system design.