航空发动机FADEC系统的喘振自动标定技术

发动机喘振故障作为一种多发故障,是航空发动机的一种不稳定工作状态,并在很短的时间内造成机件的严重损坏,严重危及飞行安全。近年来已日渐成熟的全权限数字电子控制系统(FADEC)通过数字化电路在发动机即将出现喘振或喘振初期,及时准确的识别出喘振,进而采取相应的消喘措施,避免发动机由于喘振处理不及时导致出现严重故障。但由于喘振传感器长时间的使用出现漂移,导致FADEC无法准确的判断发动机喘振状态。本文根据喘振电路原理以及喘振传感器标定原理,设计了喘振标定电路模型,并根据模型设计了喘振自动标定方法,通过模型仿真和硬件在回路仿真验证了该自动标定算法的有效性,验证结果表明,通过喘振传感器的自动标定技术,可以解决喘振传感器的自动漂移问题,降低了由于喘振传感器漂移导致无法及时准确判断发动机喘振的风险。     

航空发动机飞行试验喘振故障分析研究

针对发动机在飞行试验中出现的喘振停车故障,通过分析风扇和压气机可调导向叶片调节、尾喷管喉道面积调节、主燃油控制、进气扰动、消喘控制等影响因素,逐一查找喘振原因并制定排故措施。分析结果表明:发动机供油量设计与喘振裕度不匹配导致发动机在加速过程中出现了喘振,发动机稳定裕度不足是喘振的主要原因;发动机消喘切油过深使发动机出现停车,启动供油和消喘切油的综合作用引起发动机出现转速悬挂,直接导致发动机排气超温和消喘失效;减小发动机加速供油量以及关小压气机可调导向叶片可以有效提高发动机稳定裕度,但会影响发动机加速性能。     

WZ-8发动机放气活门故障分析

航空发动机设计有防喘振装置防止发动机喘振,WZ-8发动机采用放气活门中间级放气的方式解决喘振问题,放气活门故障会导致发动机喘振裕度下降,可靠性降低,影响飞行品质,甚至是影响飞行安全。通过对放气活门故障原理的研究,分析产生的原因,结合历史故障数据总结排故方法,能有效的避免重复故障的产生,优化预防性工作内容,缩短排故时间,提高机务维护质量。     

某型发动机飞行试验喘振故障分析 ——兼论其对商用大涵道比涡扇发动机研制过程的启示

飞行试验是新型号航空发动机适航取证的重要环节,是全面检验航空发动机性能的重要手段。发动机喘振是指发动机在运行过程中,其气流沿压气机轴线方向出现的低频高幅震荡现象。喘振具有多发性、突发性的特点,极易导致发动机工况恶化并出现机械损伤。在航空发动机飞行试验过程中发生喘振,有可能影响飞行安全并造成严重后果。本文根据某型发动机飞行试验中发生的喘振故障,分析产生喘振故障的原因及典型解决措施,探讨其对商用大涵道比涡扇发动机研制的启示。     

基于临界B参数的航空发动机压气机喘振监测研究

喘振是航空发动机压气机的一种常见故障,对喘振开展有效监测是航空飞机安全运行的重要保障。本文提出了一种基于临界B参数的航空发动机压气机喘振监测新方法。在Moore-Greitzer不可压缩压气机模型基础上,分析了航空发动机压缩系统方程的稳定性,采用分岔理论推导了压气机临界B参数的表达式,得到了压气机全工况临界Bcr参数曲面图,可实现对运行状态中的压气机喘振进行实时监测及预防。     

基于扩压器优化提升发动机加速性的方法

本文对某型航空涡轴发动机的喘振现象进行研究.通过开展厂内专题试验确定了该发动机喘振发生的"首发"为离心压气机部件,采用气动仿真方法找到气流分离位置为径向扩压器叶片叶背的叶根处.对径向扩压器结构进行优化设计,并进行串装试车验证,改善了发动机的加速性,改进设计有效.     

采用排除法分析航空发动机喘振故障

分析了航空发动机在飞行中出现的一次喘振故障现象及其所执行的消喘程序。采用排除法,依次比较了喘振发生时发动机本体各部分的工作过程以及进排气条件,筛选出了可能的致喘因素。结果表明,超音速飞行过程中,进气道喉道剧烈的放大动作引起的发动机进气扰动以及被试发动机个体较小的稳定工作裕度共同造成了此次喘振故障。另外,提出了相应的改善措施。     

航空发动机喷口闭环控制系统与调整方法研究

航空发动机喷口闭环控制检查调整耗时长,调整不当会影响航空发动机加力性能,使航空发动机出现喘振、加力爆燃、喷口烧蚀、低压转速超转等安全隐患。对此,分析了航空发动机喷口闭环控制系统的组成和工作原理,并对调整方法进行研究。针对检查中经常遇到的四种情况,分别给出了调整方法。     

轴流压气机从失速到喘振瞬间过程:激波管模拟和试验比较（英文）

高速高压(HSHP)比的压气机喘振是气体瞬间丧失压缩能力并伴随有气流反流现象。它通常存在于动态型涡轮压气机中,特别是现代航空发动机中的轴流式压气机。按照牛顿运动定律,改变任何物体运动的状态都需要力的作用。那么可以引起像喘振这样剧烈流体运动的力是什么?究竟是什么触发了它的发生以及如何量化瞬态喘振现象?本文试图回答这些问题,并讨论在瞬态阶段从旋转失速到喘振的动力学。人们普遍接受的观点是,不管是低速或高速压气机,旋转尖峰或旋失速可以引发喘振。Greitzer模型是当今最好的动态喘振模型。然而,它没有包含喘振初期的瞬态特性中的关键要素:及极短的持续时间(毫秒量级)和在喘振周期中反流阶段实验观察到的从后面级向进口移动的激波存在。本文采用间接方法,即通过使用经典激波管的类比来解决从失速到喘振的瞬态动力学问题。该关联是基于观察到的叶栅单元内部的突然气流降低触发失速和喘振这个事实。类比推理表明,喘振起始会同时产生一对非线性压缩波和膨胀波(CWEW)以及诱生反向气体流动(IRFF)。瞬时流动反转的动力是向上游传播的压缩波推力和向下游传播的膨胀波拉力的协同作用。然后将分析结果与先前研究人员的实验结果进行比较,并得出结论:使用激波管理论,喘振激波和逆流(IRFF)的强度可以从已知的喘振前工况和喘振路径来估算。所提供的方法可以作为一种教学工具,用于理解从失速到喘振的瞬态过程中的物理现象,并为设计人员提供一种简单计算方法,或为未来更精确的CFD全面喘振建模提供洞察力(物理直观)。     

某涡扇发动机空中启动喘振悬挂分析

对某涡扇发动机在空中启动过程中出现喘振悬挂现象进行了分析,并通过分析,给出了喘振悬挂的原因是由启动供油量与发动机转子加速率不匹配引起的。根据上述分析,对发动机空中启动进行了调整。通过试验,验证了调整的正确性,为同类型发动机出现该现象时对其分析提供了参考。     

Minimal Realization of Linear Graph Models for Multi-physics Systems

An engineering system may consist of several different types of components,belonging to such physical"domains"as mechanical,electrical,fluid,and thermal.It is t...     

Quantum Cooperative Robotics and Autonomy

The intersection of Quantum Technologies and Robotics Autonomy is explored in the present paper.The two areas are brought together in establishing an interdisci...     

考虑进油孔有限长滑动轴承油膜力的近似解析解

针对具有进油孔的有限长滑动轴承油膜力求解问题,采用变分原理和分离变量法,求得了有限长滑动轴承油膜压力分布的近似解析表达式。将油膜压力分布的近似解析表达式在油膜存在区域上进行积分,即得到了油膜力。将提出的计算有限长滑动轴承油膜力方法与无限长轴承模型、有限元方法的计算结果进行了比较,发现了提出的方法与有限元方法的计算结果很接近。最后,研究了进油孔位置和进油压力对油膜存在区域、油膜力等的影响,研究结果表明进油孔位置和进油压力对油膜存在区域和油膜力有较大的影响。     

三绕组变压器的双绕组等效建模及在Matpower中的应用

针对实际电网存在着大量的三绕组变压器,但国际上一些著名商业软件,如BPA仿真软件、Matpower这一权威潮流计算开源软件,均只提供双绕组变压器模型,限制了其在具有三绕组变压器的电力系统中的应用的问题,潮流计算是自主开发的电力系统各种应用软件的核心模块,因此依托国际权威开源程序进行二次开发,是一种较好的选择。对Matpower要求的数据格式进行了归纳,对变压器的一般的等值电路及带理想变压器的等值电路和带标幺值的等值电路进行了分析研究,提出了三绕组变压器转换为双绕组等效模型的建模方法,使得原先只适应双绕组变压器的潮流计算软件可以适用于三绕组变压器电网的潮流计算;最后以Matpower软件为例进行了案例计算,并用PSASP仿真软件进行对比验证。研究结果证明,所提出的建模方法是有效的。     

On the Relation of Load to Average Gap in the Contact Between Surfaces with Longitudinal Roughness

A computer simulation model for the contact between longitudinally-oriented rough surfaces has been formulated. This model closely duplicates the actual surf ace contact deformation behavior by taking into account the elastic interactions between the asperities. There were no assumptions made about the shapes, or any deformation behavior of the asperities, except for their obeying the laws of elasticity. The plastic deformations on the high asperity peaks were taken into account by setting a ceiling on their contact pressures at the material hardness value. The simulations used real surface profiles which were digitized from unworn circumferentially ground steel surfaces. Each pair of these profiles was mathematically combined to form an equivalent rough profile pressing against an infinitely rigid flat and having the appropriately adjusted elastic modulus. A total of 28 different pairs of profiles were used in the simulations. Each contacting pair was subjected to 30 different load levels and the local contact pressures and deformations were calculated. The contact simulations yielded some important mathematical relationships between parameters, such as the real area of contact, average gap, and average asperity load through statistical curve fitting. Two analytical functions were generated to relate the average load to average gap and the real area of contact to load.     

Fifth International Summer School on Screw-Theory Based Methods in Robotics

正3-11 September,2014University of Bologna,Bologna,Italy www.summerscrews.org summerscrews2014.ing.unibo.it SUMMER 20SCREWS 14In 2014,our screw-theory school comes to the world's oldest university.In early September,Summer Screws'14 will gather six experts in the application of screw theory in robotics and up to 40 participants at the University of Bologna,Bologna,Italy.The school will teach attendees how to apply existing methods and empower them to develop new ones in their own research.The basic theoretical notions will be introduced in a rigorous manner,emphasizing examples,applications,and exercises.Scholarships are available.     

INTEGRAL EQUATION METHOD＇S APPLICATION IN HOLE-EDGE STRESS OF COMPOSITE MATERIAL PLATE WITH DIFFERENT SHAPED HOLES

The strength of composite plate with different hole-shapes is always one of the most important but complicated issues in the application of the composite material. The holes will lead to mutations and discontinuity to the structure. So the hole-edge stress concentration is always a serious phenomenon. And the phenomenon makes the structure strength decrease very quickly to form dangerous weak points. Most partial damage begins from these weak points. According to the complex variable functions theory, the accurate boundary condition of composite plate with different hole-shapes is founded by conformal mapping method to settle the boundary condition problem of complex hole-shapes. Composite plate with commonly hole-shapes in engineering is studied by several complex variable stress fimction. The boundary integral equations are founded based on exact boundary conditions. Then the exact hole-edge stress analytic solution of composite plate with rectangle holes and wing manholes is resolved. Both of offset axis loadings and its influences on the stress concentration coefficient of the hole-edge are discussed. And comparisons of different loads along various offset axis on the hole-edge stress distribution of orthotropic plate with rectangle hole or wing manhole are made. It can be concluded that hole-edge with continuous variable curvatures might help to decrease the stress concentration coefficient; and smaller angle of outer load and fiber can decrease the stress peak value.     

INDUSTRIAL ENGINEERING AND VISUALISATION-A PRODUCT DEVELOPMENT PERSPECTIVE

Taking the actual project of teaching and researching process for example, the relationship between the industrial engineering and product development is discussed. And use the novel visualization technology to support the industrial engineering and product development. How to use the new computer modeling and simulating technologies to support the product development and industrial engineering, is introduced especially. The support includes both domestic products and industrial systems. The visualization and computer technologies take a very important role in some system or multi-direction modeling, those technologies mentioned above can help the industrial engineers study the effect of design on the whole life circle, including the producing steps. So the engineers can avoid making the wrong decision which may cause bad effects on the whole industrial engineering.     

电站锅炉模糊风险评价方法研究与应用

针对电站锅炉风险等级评价问题,将模糊综合评价技术应用到电站锅炉风险等级评价中。开展了电站锅炉失效影响因素及模糊评价因素的重要程度分析,建立了一套科学合理适于在线评价的电站锅炉风险评价体系,提出了模糊综合评价技术与改进的模糊层次分析法相结合的模糊风险评价方法,利用改进的模糊层次分析法计算了指标体系中各层指标权重。对某一台电站锅炉的实际运行工况影响子因素进行了模糊风险评价,采用模糊合成算子进行模糊综合运算得到电了站锅炉运行工况影响子因素的评价向量。研究结果表明:电站锅炉的运行工况影响子因素的风险评价等级为第6级,失效可能性等级为小,该电站锅炉运行工况良好。     

Short-Term Relay Quality Prediction Algorithm Based on Long and Short-Term Memory

The fraction defective of semi-finished products is predicted to optimize the process of relay production lines, by which production quality and productivity ar...