基于量子遗传支持向量机的流体惯容预测模型

为进一步研究惯容器的实现形式与力学性能特征,研制了新型流体惯容器装置。首先,在单通道伺服激振台架上进行力学性能测试,分析其非线性因素及对力学输出的影响机理;然后,考虑采用基于统计理论的支持向量机方法建立流体惯容器的力学输出预测模型,分别研究了不同激振频率、不同位移输入条件下的流体惯容器力学性能输出;最后,利用全局搜索能力较优的量子遗传算法优化径向基函数的方差与惩罚因子,并将构建的预测模型与试验输出结果相对比。结果表明:利用支持向量机构建的流体惯容器力学输出预测结果与试验吻合良好,采用量子遗传算法优化的预测模型具有更高的预测精度,其方差降幅最大可达到61.36%,说明构建的预测模型正确合理,可为准确掌握流体惯容器动力学特性提供新思路。     

关于密封间隙气流激振的一个非线性理论模型

本文从流体弹性耦合的角度,研究了密封间隙气流激振的机理,建立了一个描述转子密封系统气流激振的非线性理论模型,分析了密封间隙气流激振的非线性特性及防治措施。     

流体激振及其对离心叶轮转子的影响

求出了离心泵叶轮所受的流体激振力,并研究了离心泵在考虑流体激振力时的动态特性。建立了在该状态下的运动微分方程。分析了流体激振力对离心泵叶轮系统的振动及其轴心轨迹的影响,为离心泵的监控和设计提供了理论依据。     

带有支座松动故障的离心泵叶轮转子分岔特性分析

将离心泵叶轮转子系统简化为中间带有刚性圆盘的柔性转子,在引入非线性横向流体激振力的条件下,建立带有支座松动故障的不平衡离心叶轮转子在非线性轴承油膜力作用下的振动模型,并推导系统的无量纲运动方程.运用数值积分法研究系统的分岔特性,分析横向流体激振力以及松动端轴承支座质量对该类离心泵叶轮转子系统非线性动力学特性的影响.     

裂纹角的大小对裂纹转子振动特性的影响

将离心叶轮转子系统简化为Jeffcott转子系统,在考虑非线性油膜力的基础上,综合考虑了系统的流体激振力,建立了含有裂纹故障转子的动力学模型。运用数值积分法分析了不同裂纹角下系统响应随转速变化的分岔图、相图和Poincare映射图等,结果表明,裂纹深度一定的情况下,随着裂纹角的增大,流体激振力和非线性油膜力对转子系统分岔特性的影响也逐渐增大。     

流体动力润滑螺旋槽非接触机械密封的发展及应用

详细地分析了非接触机械密封商业产品中的一些二维及三维流体动力槽形、特别是螺旋槽形的动态性能,包括对径向对称与径向弯曲类槽形的流体动力品质;明确地提出了避免非接触机械密封系统发生“半频自激涡动”及流体膜“共振振荡”的理论概念及螺旋槽非接触干气密封应采取顺流方式以获得高刚度而增加其运行稳定性和液体湿式密封应采取逆流方式以实现密封的无泄漏的设计准则;系统地阐述了非接触机械密封在离心气体压缩机和液体泵类上应用的2类体系及其干运行非接触气体密封的检验规范。     

闪底泵振动故障的监测诊断分析及处理

针对常减压装置中闪底泵存在的由于振动过大而导致机械密封损坏的问题,应用设备状态监测与故障技术对该泵进行了监测诊断.结果表明,振动过大是由叶轮流体激振造成的.通过对该泵叶轮直径重新进行核算,提出采用减小叶轮直径的措施来避免叶轮流体激振现象,使泵振动值大幅下降,保证了闪底泵的安全运行.     

汽动给水泵轴振跳变分析及处理

针对国华定洲电厂600MW机组FK4E39K型汽动给水泵发生的突发性轴振跳变进行了分析诊断,引起汽泵突发性轴振跳变的主要原因为转子失稳、流体动力激振和轴承油膜失稳、动静碰磨等,据此提出了有针对性的处理措施,实施后取得了良好的效果。     

反旋流抑制密封间隙内流体激振研究

大型水泵机组、水轮发电机组中由于转子偏心导致的流体激振会增大转子的振动,影响转子的安全运行。该文根据密封模型搭建了实验台,研究了喷水、喷气等反旋流方法对密封间隙内的流体激振的影响,对比了在不同情况下转轴振动幅值变化,结果表明具有合适喷射位置和喷射流量的反旋流对密封间隙内的流体激振起抑制作用,并初步得到抑制密封间隙内流体激振最佳喷射位置和喷射流量。通过数值模拟计算了在不同的喷射位置、不同喷射速度的反旋流对密封间隙内流场的影响,在一定程度上解释了实验结论,二者所得的规律统一,为反旋流技术抑制流体激振在工程上应用提供有效的依据。     

先导式套筒调节阀的流体激振原因及处理

论述了先导式套筒调节阀产生流体激振的各种原因,提出了相应的处理方法。     

风诱导塔振动对塔气动特性影响研究

塔设备风诱导振动对卡门涡脱落及气动特性的影响规律研究对于塔设备共振预测和设计计算十分重要,对塔设备振动下的气动特性问题进行数值模拟研究。采用数值求解N-S方程结合Transition SST湍流模型的方法模拟塔设备周围气流的非定常流动,获得塔外表面的风压系数分布,并结合试验数据验证了文中模拟方法的准确性;继而将塔设备振动简化为正弦运动,采用弹簧动网格技术实现网格动态生成。研究了塔设备振动频率以及振幅的变化对横向力系数、阻力系数和涡脱落频率等气动参数的影响规律,结合塔设备共振条件,指出了气动特性的改变对塔设备共振预测的影响规律。     

一种Hilbert变换法在非线性系统分析中的应用

Hilbert变换是信号处理领域常用工具之一,将Hilbert变换法改进并应用到信号分解和非线性系统振动分析中。振动信号的多谐波性,使得Hilbert变换法提取信号的瞬时频率和瞬时相角可以通过滤波的方法分离成快变和慢变两部分,从而提取系统的振动分量;通过迭代计算,依次获得振动信号中所有谐波分量;将非线性振动方程用瞬态幅值相关的瞬态参数表示,从而求解系统的频响关系曲线方程。通过相应的数值模拟计算,验证了改进的Hilbert变换法在非线性振动分析的有 效性。     

蜗壳壁厚对离心风机振动噪声影响的数值研究

采用数值方法分析了蜗壳壁厚对离心风机在气动力激励下蜗壳受迫振动辐射噪声的影响.首先采用CFD方法模拟了风机内部的非定常流动,得到蜗壳壁面的非定常气动载荷分布;然后采用有限元方法计算蜗壳在非定常载荷作用下的受迫振动特性;最后采用边界元方法预测了蜗壳受迫振动激发的噪声声场及声功率.基于上述方法,比较分析了蜗壳壁厚对振动噪声辐射功率的影响.结果表明,并不是蜗壳的壁厚越大,其振动噪声越低,而是对应确定的激励频率,存在最佳的壁厚尺寸或各部分不同壁厚的尺寸组合.     

Vibration reliability sensitivity analysis of general system with correlation failure modes

The vibration problem of the general system is the main object of research. The material properties and geometry of general system are random parameters because of the manufacturing environment, technical conditions, manufacturing and installation errors, multiphase materials, features and other factors. According to the relation criterion that the difference between the natural frequency and the driving frequency of general systems is not beyond a specific value, the vibration reliability mode and vibration reliability of general systems are defined considering the correlation of the multi-order natural frequency and the random characteristics of structure size and material, and the vibration reliability analysis method for avoiding the resonant is carried out. The second-order joint failure probability is obtained by using the numerical integration method. Based on the reliability design theory and sensitivity analysis method, the vibration reliability sensitivity of the general system with correlation failure modes is extensively discussed and a numerical method for vibration reliability sensitivity design is presented. The variation regularities of vibration reliability sensitivity are obtained and the effects of random parameters on vibration reliability of the general system are studied. The presented method provided the theoretic basis for the reliability design of the general system. A numerical example demonstrated that the proposed method is effective.     

Non-linear torsional vibration characteristics of an internal combustion engine crankshaft assembly

Crankshaft assembly failure is one of the main factors that affects the reliability and service life of engines.The linear lumped mass method,which has been universally applied to the dynamic modeling of engine crankshaft assembly,reveals obvious simulation errors.The nonlinear dynamic characteristics of a crankshaft assembly are instructionally significant to the improvement of modeling correctness.In this paper,a general expression for the non-constant inertia of a crankshaft assembly is derived based on the instantaneous kinetic energy equivalence method.The nonlinear dynamic equations of a multi-cylinder crankshaft assembly are established using the Lagrange rule considering nonlinear factors such as the non-constant inertia of reciprocating components and the structural damping of shaft segments.The natural frequency and mode shapes of a crankshaft assembly are investigated employing the eigenvector method.The forced vibration response of a diesel engine crankshaft assembly taking into account the non-constant inertia is studied using the numerical integral method.The simulation results are compared with a lumped mass model and a detailed model using the system matrix method.Results of non-linear torsional vibration analysis indicate that the additional excitation torque created by non-constant inertia activates the 2nd order rolling vibration,and the additional damping torque resulting from the non-constant inertia is the main nonlinear factor.The increased torsional angular displacement evoked by the high order excitation torque relates to the non-constant inertia.This research project is aimed at improving nonlinear dynamics theory,and the confirmed nonlinear parameters can be used for the structure design of a crankshaft assembly.     

Numerical Study of Flow Characteristics due to Interaction Between a Pair of Vortices in a Turbulent Boundary Layer

This paper represents a numerical study of the flow field due to the interactions between a pair of vortices produced by vortex generators in a rectangular channel flow. In order to analyze longitudinal vortices induced by the vortex generators, the pseudo-compressibility method is introduced into the Reynolds-averaged Navier-Strokes equations of a 3-dimensional unsteady, incompressible viscous flow. A two-layer κ-ε turbulence model is applied to a flat plate 3-dimensional turbulence boundary to predict the flow structure and turbulence characteristics of the vortices. The computational results predict accurately the vortex characteristics related to the flow field, the Reynolds shear stresses and turbulent kinetic energy. Also, in the prediction of skin friction characteristics the computational results are reasonably close to those of the experiment obtained from other researchers.     

旋转锯片空气动力学噪声特性计算与分析

为分析旋转刀具在气流作用下的声学特性,基于多场耦合计算方程建立了流场-结构-声场联合仿真模型,通过弹性体与流场的动力学计算得到了结构强迫振动响应,利用边界元法将振动响应信息作为声学边界,获取了锯片的声场辐射信息,噪声预估值与实测结果吻合良好。研究了锯片旋转过程中周围流场媒介的层流、湍流特性对锯片振动的影响规律;揭示了流-固耦合作用对声场时域、频域影响作用机制;确定了锯片空载噪声辐射的方向特性;分析了锯片尺寸结构对噪声的影响规律,为低噪声锯片的设计提供了参考依据。     

Nonlinear transient response analysis for double walls with a porous material supported by nonlinear springs using FEM and MSKE method

In this paper, we newly propose a fast computation method for the nonlinear transient responses including coupling between nonlinear springs and sound proof structures having porous materials using FEM. In this method, we extend our numerical method named as Modal Strain and Kinetic Method (i.e. MSKE method proposed previously by Yamaguchi who is one of the authors) from linear damping analysis to nonlinear dynamic analysis. We assume that the restoring force of the spring has cubic nonlinearity and linear hysteresis damping. To calculate damping properties for soundproof structures including elastic body, viscoelastic body and porous body, displacement vectors as common unknown variable are solved under coupled condition. The damped sound fields in the porous materials are defined by complex effective density and complex bulk modulus. The discrete equations in physical coordinate for this system are transformed into nonlinear ordinary coupled differential equations using normal coordinates corresponding to linear natural modes. Further, using MSKE method, modal damping can be derived approximately under coupled conditions between hysteresis damping of viscoelastic materials, damping of the springs and damping due to flow resistance in porous materials. The modal damping is used for the nonlinear differential equation to compute nonlinear transient responses.Moreover, using the proposed method, we demonstrate new vibration phenomena including nonlinear coupling between nonlinear springs and soundproof structures by use of a simplified model. As a typical numerical example of the soundproof structure, we adopt double walls with a porous material. The double walls are supported by nonlinear concentrated springs. We clarify influences of amplitude of the impact force on nonlinear transient responses. We focused on the vibration modes, which magnify the amplitudes of the double walls. In these modes, the internal air of the porous material played a role of a pneumatic spring. Under a very large impact force as a severe condition, there exist the complicated nonlinear couplings between these modes and the super harmonic components of the rigid modes of the whole structure with large deformations in the nonlinear springs.     

Coupled bending and torsional vibration of a rotor system with nonlinear friction

Unacceptable vibrations induced by the nonlinear friction in a rotor system seriously affect the health and reliability of the rotating machinery. To find out the basic excitation mechanism and characteristics of the vibrations, a coupled bending and torsional nonlinear dynamic model of rotor system with nonlinear friction is presented. The dynamic friction characteristic is described with a Stribeck curve, which generates nonlinear friction related to relative velocity. The motion equations of unbalance rotor system are established by the Lagrangian approach. Through numerical calculation, the coupled vibration characteristics of a rotor system under nonlinear friction are well investigated. The influence of main system parameters on the behaviors of the system is discussed. The bifurcation diagrams, waterfall plots, the times series, orbit trails, phase plane portraits and Poincaré maps are obtained to analyze dynamic characteristics of the rotor system and the results reveal multiform complex nonlinear dynamic responses of rotor system under rubbing. These analysis results of the present paper can effectively provide a theoretical reference for structural design of rotor systems and be used to diagnose selfexcited vibration faults in this kind of rotor systems. The present research could contribute to further understanding on the self-excited vibration and the bending and torsional coupling vibration of the rotor systems with Stribeck friction model.