Research On Vibration Of Centrifugal Pump Base Incited By Fluid Force

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.