航空发动机压气机转子叶片声激振试验研究

对引起航空发动机压气机高压转子叶片振动故障的原因进行了分析.指出压气机在某种非正常工作状态下产生的高声强噪声中所包含的高强度声波,是激起转子叶片共振或颤振的原因之一,通过理论分析和实验研究,得出了如下结论:当转子叶片在机械激振和气动激振作用下已处于高应力工作状态时,如果再叠加由声波激起的共振应力,就会导致裂纹甚至折断.     

船用透平末级长叶片振动性能研究

针对某船用新型末级长叶片,为了获得共振转速和对应动频率,对叶片转子试验组件在高速动平衡试验台上进行动频试验,叶片振动信号经感应元件拾取后由遥测发射机和接收机传输至信号分析系统,获得多个通道下的叶片振动信息.试验数据表明,末级叶片靠近额度工作转速附近的"三重点"共振转速为一阶模态家族节径数k=7和k=8的共振转速均能避开运行工况,对应的动频率与数值分析结果对比可知:节径数k=7、k=8时的动频值相差不超过5%;数值计算和试验分析均证明叶片在工作转速内是安全可靠的.     

CAE技术在汽轮机高温强度计算中的应用

为分析某百万千瓦超超临界汽轮机高压缸旋转部件在高温以及高离心力载荷下的强度状况,建立高压缸第一级动叶片的模型.根据蠕变试验数据,采用最小二乘法拟合幂蠕变方程中的各个参数,并详细介绍各参数的拟合、优化和验算过程;用CFD分析软件计算流体域内的对流传热系数并插值到有限元计算程序中,分析叶根倒角处危险区域的蠕变应力状况.数据验算结果表明,利用拟合数据计算得到的蠕变应力值与试验值比较接近,证明该方法可靠;CAE计算结果表明,叶根倒角处危险区域蠕变应力考核合格,并且有充足的安全裕量.     

热致轴向窜动引发的双盘转子扭转振动分析

以航空发动机整机系统的结构特点及复杂的运行环境为研究背景,运用Lagrange方法建立双盘转子在不平衡激励和轴向窜动影响下的弯扭耦合动力学模型;针对温度非均匀分布以及热膨胀性质引起的转轴轴向窜动,导出转/静盘面接触时环带面摩擦力与摩擦力矩表达式;最后采用4阶Runge-Kutta方法对系统进行数值求解.对系统进行动力学分析的结果表明,对于非对称双盘转子结构,热膨胀所积蓄的温度内力引发的转子轴向窜动将改变转子系统的固有特性,所产生转静件盘面环带面摩擦力与力矩,是造成转轴扭转振动的关键因素之一.     

基于热-流-固耦合方法的涡轮叶片数值计算

将流体动力学方法与有限元方法相结合,在定常流场分析的基础上,采用单向和双向热、流、固耦合的计算方法获得了转子叶片在设计工况下的应力和变形情况,并比较了两种方法的计算结果.单向耦合计算中分析了离心、气动、热载荷对叶片应力、变形的影响,并按照斯贝发动机EGD-3应力标准对叶片强度进行了校核.计算结果表明：两种计算方法在涡轮叶片强度分析中是可行的,双向耦合能更准确地反映转子叶片的真实工况.     

涡轮叶片辐照晶体测温安装方式建模及仿真

针对辐照晶体传感器测量复杂工况条件下涡轮叶片表面温度时的安装问题，仿真分析了晶体温度传感器在涡轮叶片上的2种安装方式。选取航空发动机涡轮叶片吸力面的缘板处、叶片尾缘处和气膜孔背面3个位置，模化辐照晶体传感器在涡轮叶片工况下的安装条件，采用表面粘贴和开槽封胶2种安装方式建模，导入ANSYS Workbench进行流-固耦合有限元仿真，分析高温胶和辐照晶体在复杂工况下的应力、变形和温度等特性。结果表明，表面粘贴式安装的晶体传感器温度更高，但高温胶和晶体传感器所受应力远大于开槽封胶式安装所受应力，由此可知表面粘贴式安装的测温精度更高，但其牢固性不如开槽封胶式安装。研究结果可为采用辐照晶体测量航空发动机涡轮叶片温度的试验测试提供基础支撑。     

双转子涡喷发动机气动性能优化控制研究

航空发动机的控制规律作用巨大,它决定了发动机能否获得设定的稳态工作下性能指标,同时保证工作过程中的压气机和涡轮的气动稳定性;双转子涡喷发动机气动性能优化控制的目的就是有效地挖掘发动机的使用潜力;研究方法采用部件特性法对发动机进行稳态建模,并针对某双转子涡喷发动机的稳态模型进行三种不同稳态控制规律下的仿真,得到发动机性能参数的不同变化趋势,并对其进行了详细的分析;结果表明:保持低压转子转速不变的情况下,随着压气机进口总温的增加,高压转子转速上升,涡轮前温度升高,发动机推力增加;保持涡轮前温度不变的情况下,随着压气机进口总温的升高,低压压气机气动负荷变重,低压转子转速降低;高压转子转速也下降,但是下降幅度很小;燃油流量增加;保持高压转子转速不变的情况下,随着压气机进口总温的升高,燃油流量有一定的增加,低压转子转速有所降低;推力受多重因素的影响,推力值变化趋势较为复杂。     

民航大涵道比涡扇发动机总体性能参数敏感性分析

基于Gasturb总体性能分析软件对民航大涵道比涡扇发动机高空巡航阶段的3个监控性能参数受5个气路部件效率影响的敏感性进行分析;研究发现高空巡航阶段高压压气机、高压涡轮的效率降低对排气温度影响较大,风扇、增压级和低压涡轮的效率降低影响稍小;五大气路部件的效率降低会带来排气温度、燃油流量的上升,而对高压转子转速则有正和负的效应,其中低压轴上的3个部件的效率降低会增加高压转子转速;而高压轴上的两个部件的效率降低会导致高压转子转速的下降,这与发动机以风扇转速作为被控参数的控制规律有关。     

跨音速轴流压气机叶片造型及数值仿真

针对跨音速轴流压气机的多圆弧叶片.提出了一种基于锥面展开面的叶片造型方法.设计了某型压气机第一级转子,通过三维粘性流计算软件NUMECA对此孤立转子进行了性能仿真,仿真结果与实验结果符合较好;分析了叶型厚度分布对转子性能的影响:采用标准厚度分布对叶片重新生成,并与多圆弧叶片进行了对比,结果表明用标准厚度生成的叶片更薄一些,性能也更佳;同时当叶型最大厚度的位置后移时,转子的稳定工作范围变宽,效率略有降低.     

全流域立磨选粉机动叶片形状的分级特性研究

为研究立磨选粉机动叶片形状对于立磨全流域流场及分级筛选性能的影响,以HRM1700X立磨为研究对象,应用MRF模型模拟选粉机转子的旋转,运用DPM模型的双向耦合计算方法求解颗粒运动轨迹,实现了立磨全流域三维流场的建模与计算,并通过试验进行验证.通过模拟研究四种不同动叶片形状下速度场、压力场以及颗粒分级筛选性能的变化规律,对比发现LV型动叶片相比直型动叶片,分级粒径更小,颗粒分级效率更高,其计算模型和研究成果对指导高效立磨选粉系统具有重要的工程应用价值.     

Analysis of thermal stresses due to moving frictional load in an infinite elastic layered medium

The temperature and stress distribution of an infinitely long elastic layered medium subjected to a moving frictional load traversing with constant speed over the surface are analyzed. A quasi-static theory is applied by use of a coordinate transformation. In this paper, the temperature and thermal stress distributions are obtained by means of a Fourier transformation. Numerical results are obtained for the cases of both uniform and parabolic pressure. Examining the results, it is found that the thermal principal stress is much higher than the mechanical principal stress. The Young's modulus ratio and the thermal conductivity ratio of the layered medium also play important roles in the thermal stress distribution.     

Boundary geometric control of a counter-current heat exchanger

The present article deals with the boundary geometric control of a counter-current heat exchanger whose control is designed considering a model based on two partial derivative equations describing the variations of internal and external temperatures. The objective consists in controlling the internal fluid temperature, at the heat exchanger outlet, by manipulating the jacket temperature at its inlet boundary in spite of the variation of the temperature of the internal fluid at the heat exchanger inlet. The control law is designed considering the partial differential equation describing the temperature of the internal fluid, and the manipulated control is the boundary condition for the partial differential equation describing the temperature of the jacket fluid. The performances of the controller have been evaluated by simulation and the results show that it provides good regulation and tracking performances. The robustness of the controller has also been studied when velocities of both internal and external fluid, and physical properties of the heat exchanger are subjected to sudden fluctuations. For noisy measurements and for practical implementation, the moving average filtering and Kalman estimation approaches that provide the required state temperatures to be used in the controller are discussed. The control by manipulating the jacket flow rate has also been considered to compare the respective benefits of both strategies.     

Investigation of the internal stress effects on static and dynamic characteristics of an electrostatically actuated beam for MEMS and NEMS application

Internal stress is often encountered in fixed–fixed beam based devices with micron or sub-micron length scales during device fabrication or operation. In this paper, we have investigated the effects of internal stress on static and dynamic characteristics of an electrostatically actuated cylindrical beam. The beam has been modelled using Euler–Bernoulli theory including the nonlinearities due to beam stretching and electrostatic forcing. The analysis has been carried out by solving the governing differential equations using a Galerkin based multi-modal reduced order modelling technique. A standard collocation based numerical scheme has also been used to confirm the results of the reduced order method. Our study shows that internal stress significantly influences the static and dynamic characteristics of the beam. We also find that, when compressive internal stress is high, it is important to include higher modes in the reduced order model. A design technique to achieve high resonant frequency stability under temperature variation, for electrostatically actuated beam oscillators, has also been proposed as a result of this investigation.     

移动荷载作用下非线性基础梁内共振分析

研究了有限长弹性基础上梁在移动载荷作用下的内共振响应.建立了移动集中力激励的非线性粘弹性基础支承的有限长Euler-Bernoulli梁模型,并对非线性偏微分方程进行离散,在第三阶固有频率与第一阶固有频率成三倍关系时,采用多尺度方法导出了3:1内共振的可解性条件,研究了有无移动载荷时基础阻尼和非线性刚度对梁内共振条件下自由振动响应和受迫振动响应的影响规律.在此基础上,应用Lyapunov第一方法确定了系统的稳定性条件.     

Modeling of fluid flow in a tube with a moving indentation

The time-dependent flow in a tube with a moving indentation is numerically simulated using a dynamic mesh model. The model was used to simulate the flow in a tube with an indentation moving at different frequencies. The model was validated for a two-dimensional channel with a moving indentation. The results exhibited good agreement with the available experimental results. The results show that a single vortex was formed at a wall frequency of 0.1 Hz and was swept out of the tube at the end of the period. At a higher frequency of 1 Hz, vortex doubling occurred with reverse flow dominating downstream of the indentation. The results also show that the wall shear stress was larger for the higher frequency case of the moving indentation.     

湍流环境中多弱感知机器人气味源搜索算法

针对湍流环境中机器人空间感知能力的不足, 提出一种多弱感知机器人气味源搜索算法. 该算法建立了气味源位置概率分布的近似表达式, 机器人通过自由能最小化获得移动方向. 各机器人之间通过共享位置信息实现协同, 通过设定内部温度达到搜索过程中探索和利用的平衡. 仿真结果验证了所提出算法的有效性.

     

Energy-based control of a distributed parameter bi-zone model with moving interface

In this work, a model-based control of the melt temperature of a distributed parameter bi-zone model with moving interface of an extrusion process is studied. An energy-based controller is derived using internal energy as a storage function and controlled variable with the screw speed as control input. The stability of the controller is proved through the use of a Lyapunov-like candidate function. Finally, the practical usefulness of the method is illustrated by some closed-loop simulations of the experimentally verified model of the extrusion process. The interconnection of the moving interface is performed under the assumption of variable viscosity along the extruder and a finite-volume scheme is used for the discretisation of the dynamic model.     

煤矿冲击地压和煤与瓦斯突出感知报警方法研究

提出了基于温度的冲击地压和煤与瓦斯突出感知报警方法:使用红外热像仪等监测物体温度,使用甲烷传感器监测环境甲烷浓度;当物体温度高于煤矿井下环境温度和已暴露煤岩温度,并且高于环境温度和已暴露煤岩温度的物体数量较多、体积和面积较大,则判定发生冲击地压、煤与瓦斯突出、矿井火灾或瓦斯和煤尘爆炸事故;进一步判别高温物体温度,若大于设定阈值,则判定发生矿井火灾或瓦斯和煤尘爆炸事故,反之,则判定发生冲击地压或煤与瓦斯突出事故;进一步分析甲烷浓度变化,若甲烷浓度迅速升高,则判定发生煤与瓦斯突出事故,反之,则判定发生冲击地压事故。提出了基于速度的冲击地压和煤与瓦斯突出感知报警方法:使用激光雷达、毫米波雷达、超声波雷达、双目视觉摄像机等监测物体移动速度,使用甲烷传感器监测环境甲烷浓度;当物体移动速度不小于设定阈值时,则判定发生冲击地压、煤与瓦斯突出或瓦斯和煤尘爆炸事故;进一步判别速度异常物体的数量、体积和面积,若速度异常物体的数量较少、体积和面积较小,则判定发生瓦斯和煤尘爆炸事故,若速度异常物体的数量较多、体积和面积较大,则判定发生冲击地压或煤与瓦斯突出事故;进一步分析甲烷浓度变化,若甲烷浓度迅速升高,则判定发生煤与瓦斯突出事故,反之,则判定发生冲击地压事故。提出了多信息融合的冲击地压和煤与瓦斯突出感知报警及灾源判定方法:监测并融合温度、速度、加速度、掩埋深度、声音、气压、风速、风向、粉尘、甲烷浓度、设备状态、微震、地音、应力、红外辐射、电磁辐射、图像等多种信息,感知冲击地压和煤与瓦斯突出;通过不同位置参数变化的幅度、先后时序关系及传感器损坏情况,判定灾源。     

低温冻结石门揭煤煤体温度及力学性能变化规律研究

为研究低温冻结石门揭煤煤体温度及力学性能变化规律,制作煤样时将U形铜管预埋在内并进行注液氮冻结,通过温度测量、红外热成像、单轴压缩等试验分析了不同冻结时间下煤样内部及表面温度和应力-应变变化特征。试验结果表明:随着冻结时间的增加,煤样内部及表面温度呈下降趋势;煤样表面最低温度位于U形铜管附近,煤样表面最高温度位于煤样边界;在压密阶段,随着冻结时间的增加,煤样应变逐渐减小,压密阶段缩短;在弹性变形阶段和屈服阶段,随着冻结时间的增加,煤样最大应力和弹性模量均呈增大趋势。     

ASSET-2: real-time motion segmentation and shape tracking

This paper describes a system for detecting and tracking moving objects in a moving world. The feature-based optic flow field is segmented into clusters with affine internal motion which are tracked over time. The system runs in real-time, and is accurate and reliable