Experimental study of rotor blades vibration and noise in multistage high pressure compressor and their relevance

Rotor blades fault of aeroengine compressor is mostly caused by mechanical and aerodynamic excitation. And the excitation factor of high intensity sound wave to rotor blades should not be ignored. Experimental researches are conducted on a multistage high pressure compressor. When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents typical characteristic for discrete multi-tone in the compressor. The amplitude of blade vibration displacement and the sound pressure level of characteristic frequency noise increases and decreases simultaneously and reaches the maximum value at the same time. This frequency merely occur on a certain speed range and is locked in a specific range which presents no variation with the rotating speed. When high level vibration occurs on the first stage of rotor blades, the noise spectrum presents a sharp peak and the propagation state of the characteristic frequency is a helix structure in the compressor. It can be confirmed that acoustic resonance occurs in the multistage compressor. The acoustic resonance frequency and its side band frequencies are generated by modulation of a rotating noise source at the rotor speed which is the excitation source of the rotor blades vibration.     

A reduced order model for coupled mode cascade flutter analysis

A Reduced Order Model(ROM) based analysis method for turbomachinery cascade coupled mode flutter is presented in this paper. The unsteady aerodynamic model is established by a system identification technique combined with a set of Aerodynamic Influence Coefficients(AIC). Subsequently, the aerodynamic model is encoded into the state space and then coupled with the structural dynamic equations, resulting in a ROM of the cascade aeroelasticity. The cascade flutter can be determined by solving the e...     

航天国际合作项目的特点和管理模式

随着经济全球化趋势的不断加强,航天方面的国际承包项目、国际合作必然会越来越多,提高我国航天国际合作项目的管理水平迫在眉睫。文章整合了国际上常见的一些工程项目管理模式,从融资和建设角度出发,对这些模式的特点、实施方式作出了详细分析,尤其对各种模式在应用中存在的优势及特点以及适用范围进行了研究,对于发展适合中国航天领域的国际合作项目管理模式提供了参考。     

基于远场模式的散射体形状成像

对线性抽样法的电磁场逆散射求解进行了研究。为避免迭代和优化法的正问题求解,用积分算子将散射物边界数据映射到散射场的远场模式,针对第一类积分方程的不适定性,用Tikhonov正则化法求解,并用高阶收敛算法确定正则化参数以快速数值实现。数值计算结果表明：线性抽样法＋确定正则化参数的高阶收敛算法可较好地滤除噪声,减少了确定正则化参数的计算量。     

固推约束下的火星表面起飞上升制导律设计

针对受固推约束的火星上升器(MAV)起飞上升问题,设计了上升段、无动力滑行段、入轨段三段式火星表面起飞上升全过程制导策略。首先,根据实际任务需求进行了上升器标称轨迹优化。其次,在上升段引入了阿波罗制导方法,通过类攻角和类侧滑角的控制实现对标称轨迹的跟踪。为减少上升段末端偏差对无动力滑行段与标称轨迹间误差的影响,提出了一种通过调整倾侧角改变上升器所受气动力进而控制飞行轨迹的技术路线,并设计了相应的滑模制导律。另外,兼顾固推发动机的能量管理需求,针对入轨段设计了Lambert制导策略,并参考标称控制量对其进行修正,使得上升器能够在控制能力有限的情况下完成较高精度的入轨。最后,通过典型场景火星表面起飞上升全过程数值仿真验证了所设计策略的有效性和鲁棒性。     

叶片裂纹故障的多普勒在线监测技术仿真研究

本文研究了文献[1]介绍的叶片裂纹故障声学多普勒在线监测技术的监测原理;提出了一种新的基于裂纹叶片振动响应波形不对称性的监测方法;编制了这两种方法的计算及信号处理程序。仿真计算证明这些程序是可行的,同时表明,本文建立的新的监测方法在监测有效性、可靠性方面具有优势。      

HTPB推进剂细观损伤机理的声发射实验研究

采用测定单轴定速拉伸条件下标准哑铃形ＨＴＰＢ推进剂件声发射（ＡＥ）信号的方法,对ＨＴＰＢ复合固体推进剂在载荷作用下细观损伤及其扩展的机理进行了研究。实验结果表明：声发射累计能量对应于细观损伤产生和扩展两个不同阶段,提出了一个描述ＨＴＰＢ复合固体推进剂细观损伤扩展的物理模型,该模型解释了不同拉伸速率下ＨＴＰＢ复合固体推进剂破坏了后出现的不同物理现象。     

Observer-based adaptive sliding mode backstepping output-feedback DSC for spin-stabilized canard-controlled projectiles

This article presents a complete nonlinear controller design for a class of spin-stabilized canard-controlled projectiles.Uniformly ultimate boundedness and tracking are achieved,exploiting a heavily coupled,bounded uncertain and highly nonlinear model of longitudinal and lateral dynamics.In order to estimate unmeasurable states,an observer is proposed for an augmented multiple-input-multiple-output(MIMO) nonlinear system with an adaptive sliding mode term against the disturbances.Under the frame of a backstepping design,an adaptive sliding mode output-feedback dynamic surface control(DSC) approach is derived recursively by virtue of the estimated states.The DSC technique is adopted to overcome the problem of ‘‘explosion of complexity" and relieve the stress of the guidance loop.It is proven that all signals of the MIMO closed-loop system,including the observer and controller,are uniformly ultimately bounded,and the tracking errors converge to an arbitrarily small neighborhood of the origin.Simulation results for the observer and controller are provided to illustrate the feasibility and effectiveness of the proposed approach.     

湿热老化后碳纤维复合材料层间剪切强度实验方法对比研究

通过短梁法和双切口法研究湿热老化对T700/TDE-85复合材料层间剪切强度的影响,讨论两者吸湿规律随老化时间的变化关系,并对试件断口形貌进行分析。结果表明:两种试件吸湿规律均符合Fick第二定律,但两者平衡吸湿率和吸湿时间有所差别,双切口法试件的吸湿速率和平衡吸湿率均比短梁法试件高;双切口试件所测层间剪切强度受湿热老化影响比短梁明显,短梁试件每隔500 h层间剪切强度保持率为74.5%,61.0%,53.2%,50.6%,双切口每隔500 h层间剪切强度保持率为60.9%,38.3%,42.6%,33.0%;短梁试件失效模式随着湿热老化时间的增长变化比双切口更为复杂。     

新型喷管控制系统故障模式分析及模拟

为提高新型喷管控制系统的可靠性及故障安全性,对该系统进行故障模式研究,并采取相应的对策以保证该系统在故障状态下能够安全工作。为保证控制系统对故障的处理策略正确,需要对故障进行模拟并验证该系统对故障的处理逻辑。对新型喷管控制系统进行了介绍,对该系统(控制器、传感器、通讯、伺服阀、电磁阀及作动筒等部件)的故障模式、解决方法、故障影响进行了初步分析。对该系统故障模拟系统进行了介绍并对如何进行故障模拟进行了初步研究。验证结果表明:喷管控制系统能够检测到预设故障并正确处理。