【作者】 蒋爱华；

【导师】 华宏星；

【作者基本信息】 上海交通大学 ， 机械设计及理论， 2012， 博士

【摘要】 研究流体激励诱发离心泵基座的振动,对进一步减小基座振动传递至其他设备引起的设备故障与传递至板壳结构引起的辐射噪声有重要意义。本文的目的在于从泵内表面-蜗壳-支架-基座与叶轮-转轴-支撑-基座两条流体激励力传递途径分别研究流体激励所诱发垂直于离心泵基座方向的振动,并分析离心泵基座振动的混沌非线性特性。运用Pro-E与ICEM建立离心泵流域的几何模型与网格,基于计算流体力学运用CFX分析了离心泵的稳态流场与瞬态流场,并积分得出空间三个方向泵内表面所受流体合力与叶轮所受流体合力与合力矩,运用分段拟合的方法建立了泵内表面流体合力数学模型,运用统计方法分析了叶轮各表面对叶轮所受流体合力与合力矩的贡献,通过流域内压力脉动值与转轴振动位移的测试证明了分析结果的准确性。根据试验台架,建立包括蜗壳、电机模型、电机、支架与离心泵基座系统的FEM模型,通过对比模态分析结果与LMS模态测试验证FEM模型的正确性,基于流场计算所得瞬态流场各时间步泵内表面流体压力,分析了流体激励泵内表面-蜗壳-支架-基座所诱发的瞬态响应。基于达朗伯原理建立了包含有离心泵基座的四圆盘三轴段、垂直于基座方向的转子动力学模型;基于配重法运用光电传感器、电涡流位移传感器与所构建的LabVIEW刚度辨识虚拟仪器测试了转子支撑的刚度,并分析了叶轮内流体质量对转子系统固有频率与振型的影响;基于Newmark算法运用Matlab分析了流场计算所得叶轮径向流体激励作用下转子系统的瞬态响应,并分析了转子动力学中将流体力简化为圆盘附加质量建模方法的准确性;通过仅电机转动与电机离心泵共同转动的实验对比分析了所设计台架中电机与离心泵对基座振动的贡献量;对比分析了流体力两个途径激励离心泵基座诱发的振动,并与实验结果做了对比。从统计理论出发,提出三种方法修正两个一维数组所构成平面上,数据对所对应点在该平面上的概率分布矩阵,从而改进Cellucci的互信息算法,并由该改进算法计算了Lorenz序列的最佳延迟时间,而后得出最大Lyapunov指数验证了改进算法的有效性。运用改进的互信息算法与Tisean3.0伪最近邻点算法工具包对四个测试点所得离心基座振动位移进行了延迟时间与嵌入维数的分析,并依据该延迟时间与嵌入维数重构了相空间,运用Tisean3.0小数据量算法工具包分析了各振动位移时间序列的最大Lyapunov指数以判断系统混沌非线性特性。通过以上研究得出了以下主要结论:1)运用CFD计算可以有效地得出离心泵所受流体力与力矩;叶轮径向流体合力主要以叶轮转动频率,而非叶片通过频率进行波动,蜗壳所受流体空间三个方向合力、叶轮所受其它方向流体力与绕三个方向的合力矩均主要以叶片通过频率进行波动;运用分段拟合的方法所得到蜗壳流体力数学模型比单段拟合与正余弦函数逼近有更好的精度;叶片所受流体径向合力是叶轮所受径向流体力的主要来源,叶轮前盖板外表面与后盖板外表面之间的压力差决定叶轮所受轴向力的大小,前盖板流体压力分布的不均匀程度决定叶轮绕径向转矩的大小,运用离心泵转轴振动位移与叶轮径向流体力的对比可以验证流场计算的正确性。2)建立的蜗壳、电机模型、电机与基座系统FEM模型是可靠的;流体激励泵内表面-蜗壳-支架诱发垂直于基座方向振动的位移幅值与加速度幅值均较小;离心泵起动阶段所产生初始压力脉动在非稳态振动阶段对基座振动有较大影响;泵内表面局部压力脉动是宽频激振源,会诱发出离心泵系统的各阶模态振动。3)所建立的转子动力学模型是正确有效的;所提出支撑刚度不拆卸测试方法是有效可行的;建立的支撑刚度辨识虚拟仪器系统能够可靠地得出转子支撑刚度;叶轮内流体质量对转子系统的中频固有频率有一定影响,而对系统低频与高频固有频率与各阶振型影响较小;流体力激励叶轮-转轴-基座所诱发的基座振动主要频率为转子的基频;正弦外激励作用下,将流体力简化为叶轮内20%与40%水质量所得基座振动均远小于将流体激励力直接作用于系统所引起的基座振动;流体激励力是诱发离心泵基座振动的主要原因;流体力激励泵内表面-蜗壳-支架-基座所引起的基座振动远小于激励叶轮-转轴-支撑-基座所引起的基座振动;流体激励诱发离心泵基座振动的主要来源是流体激励转子系统所诱发的基座振动;流体激励作用下离心泵基座振动位移的最大峰值频率为转轴转动频率,而振动加速度的最大峰值频率为五倍转动频率;从流体激励力的两条传递途径分别研究其所诱发基座振动的方法是有效可行的。4)等间距划分时间序列所构成平面会得到错误的互信息值;当时间序列长度不为边缘划分区间个数整数倍时,Cellucci算法将会得到错误的最佳延迟时间;所提出的三种互信息改进算法不仅能够消除Cellucci算法的缺陷,并且计算速度快;并且使用较长序列计算互信息时所得结果更加稳定;三种互信息改进计算方法是有效可靠的;流体激励诱发的离心泵基座振动位移信号具有明显的吸引子存在;各振动位移的最大Lyapunov指数均略大于零,因此本文所研究离心泵系统的基座振动具有混沌特性存在。更多还原

【Abstract】 Researches on vibration of centrifugal pump base by fluid inciting are significant for reducing equipment faults, which are caused by the vibration transferring from the base, and noise emission of shells which connect with the base. The aims of this dissertation is to investigate the fluid inciting centrifugal-pump-base vibration which is vertical to the base from two different routes, including the route that fluid force transferring to pump base via interior surfaces of pump, volute and brackets as well as that via impeller, rotor and supports, and detect chaos of the base vibration.To analyses fluid field in centrifugal pump by CFX based on CFD theory, geometry models and mesh of fluid field are built by Pro-E and ICEM respectively. Then three-dimension gross fluid forces on pump interior surfaces and impeller as well as three-dimension gross fluid torques on impeller are integrated by stable and transient CFD results. Also, multi-section curve fitting of gross pump interior fluid forces as well as analysis on the contributions of fluid forces and torques on each surface of impellers to the gross are done. And measurements on pressures of different locations in pump and vibration displacements of shaft on two vertical directions are mad use of affirming the correctness of simulation results.Base on test bench designed, a FEM model including volute, motor model, motor, bracket and pump base is built. And model test of the bench by LMS is also done for validating the veracity of FEM model by comparing the results of simulation and measurement. With fluid pressure on pump interior surfaces by transiently simulating in CFX, the pump base transient response, which is excited by fluid force via interior surfaces, volute and brackets, is calculated.Besides, a four-pan and three-shaft-section rotor dynamic model which is on pump base is also built based on Alembdert principle. And stiffness of springs which connect rotor and pump base are measured by photoelectric sensor, electric eddy-current displacement sensors and virtual instrument built by LabVIEW based on additional weight method. With the stiffness and rotor model, influence on inherent frequencies and model shapes by weight of fluid in impeller is studied, too. And then rotor-model transient response incited by radial fluid force on impeller pan is computed by Matlab program based on Newmark algorithm. Accuracy of rotor modeling method, which regards fluid inciting forces as additional weight on impeller, is also discussed. Further, contributions to pump base vibration by motor and centrifugal pump respectively are compared based on measurement two conditions, including motor running only and pump also rotating. At last, compare of vibrations, incited by fluid forces transferring from two routes mentioned above, is finished, and validation by measurement is carried out as well.With revised probability matrix, which represents distribution that points corresponding to data pairs of two one-dimension arrays land on the plane formed by the two arrays, three improved algorithms of Cellucci mutual information algorithm are upraised base on statistic method for optimal time delay in phase space reconstruction from time series. And validation of the algorithms by maximal Lyapunov exponent with reconstructed phase space by time series of Lorenz is checked out.By the improved mutual information algorithms and the False Nearest Neighbor (FNN) Algorithm toolbox in Tisean3.0.0, optimal time delays and embed dimensions are calculated for phase space reconstruction from vibration displacement time series measured on four points of pump base. To judge whether chaos is in pump base vibration, the maximal Lyapunov exponent is also computed by the Small Data Quantity (SDQ) Algorithms toolbox in Tiean3.0.0 with the reconstructed phase space.The conclusions are gained as following from the researches above:1)The fluid forces and torques can be gained effectively by CFD simulation. And except the radial impeller fluid force which repeats after impeller rotating one circle, frequencies of the other gross fluid forces and torques on impeller and volute are the same as vane pass frequency. Multi-section curve fitting of fluid force on volte can acquire mathematic model which is better than those of sole section curve fitting and Sin function fitting. And the radial fluid force on vanes of impeller is the biggest contribution to radial fluid force on impeller. Difference of pressure on impeller-front-cover out surface and back-cover out surface decides the axial fluid force on impeller. And unsymmetrical distribution of fluid pressure on impeller-front-cover out surface decides the impeller radial torques. Compare between radial vibration displacement of pump shaft and impeller radial fluid forces can validate the correction of CFD results.2)The FEM model including volute, motor model, rotor and pump base is feasible for simulating transient response analysis. Vibration acceleration and displacement vertical to pump base by fluid force inciting the base via interior surfaces, volute and bracket are gender. But the initial pressure pulsations when pump startups strongly effects the base vibration in the period that base vibrates unsteadily. The fluid pressure pulsations on pump interior surfaces are inciting forces with wide frequencies, and each inherent model of pump system is working when pump is running.3)The rotor dynamic model is reliable, and the support stiffness measurement method is also feasible. The virtual instrument system for support stiffness discrimination is reliable for the pump rotor system and the . The fluid weight in impeller effects on middle-rang-order inherent frequencies of rotor system obviously, while it has less effect on low-order and high-order inherent frequencies. The frequency of pump base vibration incited by fluid forces via impeller-rotor system is focus on the frequency that rotor rotates. The base vibration with additional Sine incitation when the radial fluid force on impeller is regarded as impeller pan additional weight which equals to 20% and 40% of fluid weight in impeller respectively is much less than that when the radial fluid force is loaded on impeller directly. The vibration of centrifugal pump base is mainly caused by fluid inciting force. And the base vibration caused by fluid force via pump interior surfaces, volute and brackets is much less than that caused by fluid force via impeller, rotor shaft and springs. The pump base vibration is mainly resource from vibration caused by fluid force on rotor system, other than vibration caused by motor running. The frequency with the biggest amplify of centrifugal-pum-base vibration displacement is shaft rotating frequency, while that of vibration acceleration is five times of rotating frequency.The method calculating pump base vibration via two fluid force transfer route is feasible and available.4)Equal distance partition the plane formed by two column time series may lead to inaccurate mutual information. When length of time series is not multiple of number that the plane is partitioned, Cellucci’s mutual information receive the wrong optimal time delay for phase space reconstruction from time series. The improved three new mutual information algorithms can not only overcome the fault of Cellucci’s algorithm but also much faster than Fraser’s mutual information algorithm. And the improved algorithms can gain more steady results with longer time series length. So the improved algorithms are feasible and available. It also can be known that the attractors of the base vibration displacements exist evidently. And the maximal Lyapunov exponents of the four vibration-displacement signals are a little bigger than zero, so there is chaos existing in the pump vibration system.更多还原