任意边界条件的弹性长方体封闭腔辐射声场分析

在弹性板边界施加假想的弹簧系统模拟板的不同边界条件,利用汉密尔顿函数和瑞利—李兹方法,建立了由1块四边弹性支承的弹性板及5块刚性板构成的封闭矩形腔外的辐射声场模型,推导了腔体外辐射声场的解析解。该模型考虑了任意边界条件下的弹性板与腔体内声场之间的耦合。将仿真计算结果与实验结果进行比较,验证了理论推导的正确性。算例表明:低频段时支承板的线弹簧的刚度变化对辐射声场的影响较旋转弹簧的大。     

Radiation characteristics of ring patch antennas with capacitive feed patch

Ring patch antennas have the characteristics of electrically small size as decreasing the width of the conducting portion compared to those of conventional patch antennas.In the ring patch antenna,using capacitive feed method is suitable for impedance matching.The effect of the size of the feed patch on the input impedance of the square ring patch antennas are analyzed and radiation patterns of the square ring patch antennas are compared to that of a square conventional patch antenna by the simulated results.     

不同厚度翼型对气动特性及叶片强度的影响

在小雷诺数条件下,采用N—S方程研究了-4°～10°迎角下不同厚度翼型对气动特性的影响规律,迭代计算结果表明：厚度较小的翼型在某一小攻角下获得最大的升阻比。并利用Solidworks软件,分析了三种不同厚度翼型叶片的应力分布,结果表明,三种翼型叶片均满足强度要求。     

Vibro-acoustic Radiation Characteristics Analysis of Railway Vehicle Wheel with Damping Ridges Based on Modal Strain Energy

The existing researches on the damping wheel mainly focus on investigating the influence of damping structure change on the vibro-acoustic control.The changes include the geometric size of the damping structure,the damping material parameters,and the placement,and so on.In order to further understand the mechanism in reducing the acoustic radiation of railway wheel with layer damping treatment,in this paper,the wheel is simply modified by a full-sized circular plate.The circle plate side has stuck circumference constrained damping ridges and radial constrained damping ridges on it.Based on a hybrid finite element method-boundary element method(FEM-BEM),the paper develops a vibro-acoustic radiation model for such a distributed constrained damping structure.The vibration and acoustic radiation of the circular plate is analyzed.In the analysis,the dynamic response of the system is obtained by using the 3D finite model superposition method.The obtained vibration response is used as the initial boundary condition in solving Helmholtz boundary integral equation for the sound radiation analysis.In the procedure,firstly,the modal analysis of the circular plate is performed to get the distribution of the system modal strain energy.Secondly,the vibro-acoustic radiation characteristics of the plate with different kinds of circumference damping ridges and radial damping ridges are compared in order to try to find the best effective damping ridge structure.Thirdly,using the distribution of the plate modal strain energy investigates the effect of the ridge distribution locations on the circular plate on its vibro-acoustic radiation.The calculation and analysis research results show that,the sticking circumference and radial damping ridges on the plate can control the vibro-acoustic radiation of the plate effectively in different frequency range.The distribution of the constrained damping ridge has an effect on reduction in vibro-acoustic radiation of the circular plate.The present research is very useful in the design of railway wheel with low noise level.     

变厚度板中水平剪切波的传播特性分析

为研究超声导波在储罐壁板等变壁厚结构中的传播特性,建立了SH波在空间自由边界中的传播模型,基于各向同性弹性介质Navier-Stokes方程,推导了变厚度板中SH波的频散方程,分析了变厚度板中水平剪切波走时t与倾斜角θ间的相互作用关系;通过简谐点源的远场响应并引入板厚与传播位移的非线性关系,得出了变厚度板中SH波的远场响应方程。在此基础上,仿真分析和实验验证了水平剪切波在不同倾斜角变厚度板中的传播特性,结果表明:在变厚度板的薄端激励水平剪切波并沿结构表面传播时,无频散现象,且无波包分离现象;但随着变厚度板倾斜角θ增大,水平剪切波的走时和接收信号幅值均逐渐递减,且呈非线性关系。     

具有不均等负重合量的非对称气动伺服阀压力特性研究

研究了一种具有不均等负重合量及均等负重合量的新型非对称气动伺服阀的压力特性。该非对称气动伺服阀的下游节流口面积为上游节流口面积的两倍。伺服阀的压力特性及零位压力取决于下游和上游开口面积比例和阀的负重合量。具有均等负重合量的伺服阀在零位时泄漏流量最大;具有不均等负重合量的伺服阀在零位附近某处时泄漏流量最大。理论结果和试验结果十分吻合。     

结构参数对三轴式内齿行星齿轮减速器动力学响应的影响

在建立弹性动力学模型的基础上,分析了轴承刚度,几何尺寸,啮合角,齿轮平均啮合刚度,内齿板质量等结构参数对具有三相内齿结构的三轴式内齿行星齿轮减速器的动力学特性的影响。研究发现:通过减小输出轴轴承的刚度、降低内齿板的质量可改善三轴式内齿行星齿轮减速器的动力学性能。     

基于自适应参数域遗传算法的机油泵性能曲面研究

通过对机油泵工作特性进行分析,建立机油泵工作特性曲面的数学模型。分别采用单种群基本遗传算法和自适应域多种群遗传算法求解了所建立的机油泵工作特性曲面模型的关键参数。通过计算和试验表明,自适应域多种群的遗传算法根据解的离散程度或集中程度动态调整参数域,使得求解空间收敛,搜索最优解的收敛速度较快,且所获得的解的质量更高,从而使机油泵工作特性曲面模型的预测精度更高。     

使用条缝翅片管换热器的空气源热泵机组除霜特性研究

对试验使用条缝翅片换热器及R410A工质的空气源热泵空调器的除霜特性进行了试验研究,测量了除霜过程中热泵样机的制热量、输入功率、室外换热器进出口温度及压力等参数的动态变化,分析了不同工况下热泵样机的除霜损失.试验结果表明:随着室外环境温度和相对湿度的降低,热泵机组在除霜过程中消耗的能量及从空调房间中吸收的热量增大,尤其在环境温度低于0℃时,除霜过程中的损失增大更快.由于随着环境相对湿度的增大霜层增长速度加快,除霜过程中的损失占结霜/除霜循环总耗能及总制热量的比例增加,因此热泵机组结霜/除霜循环的平均制热量及COP迅速减小.与使用平翅片换热器的热泵机组除霜性能的比较表明,随环境相对湿度的增加,条缝片换热器热泵机组的结霜/除霜循环平均性能衰减速度要快的多.