| Double-blade centrifugal pump has good transport performance and non-clogging performance,and is widely used in sewage treatment,municipal drainage,metallurgy,mining and chemical industry.Compared with the traditional multi-blade centrifugal pump,the dynamic loads on the double-blade centrifugal impeller are more complex,and the unsteady characteristics of the internal flow are more obvious.This complex working condition seriously affects the internal flow structure and the stability of the rotor of the double-blade centrifugal pump.Therefore,this paper focuses on the study of the fluid pulsation characteristics in the double-blade centrifugal pump,and the structural dynamic characteristics of the rotor system in the pump under the fluid excitation force and rotor dynamic coupling.In this paper,computational fluid dynamics?CFD?and fluid-solid coupling method are used to study the flow characteristics and pressure fluctuation characteristics of centrifugal pumps under five different flow rates?0.4Q?0.6Q?0.8Q?1.0Q?1.2Q?and three different rotating speeds(2040 r·min-1?2460 r·min-1?2900 r·min-1).The deformation and stress characteristics of structures under complex loads are also analyzed.The vibration characteristics and excitation mechanism of each position of the pump body are revealed.The conclusions are as follows:?1?Taking 100ZW100-15 double-blade centrifugal pump as the research object,a three-dimensional fluid domain and solid domain calculation model were established.On the basis of grid independence verification,the unsteady flow field in the fluid domain under the standard working condition was numerically calculated.The results show that the numerical results are in good agreement with the experimental results under the design and large flow conditions.However,under the small flow conditions,due to the strong separation flow and unstable vortices in the pump,there are still some deficiencies in the prediction accuracy of the existing turbulence model,and the error between the two is large.?2?The transient flow field of the double vane centrifugal pump under different working conditions was calculated,and the flow characteristics in the pump were obtained.The pressure fluctuation in the volute and impeller passage of the centrifugal pump and the radial force distribution of the impeller were predicted.The results show that the pressure fluctuation in the volute region is more significant under the condition of small flow rate,and the decrease of rotational speed will significantly reduce the fluctuation amplitude.The smaller the rotational speed,the greater the peak value of the radial force.?3?By studying the influence mechanism of different operating parameters on the dynamic response characteristics of the rotor system of double-blade centrifugal pump,the influence mechanism of flow rate and rotational speed on the equivalent force and deformation law of the pump rotor system under the coupling action of fluid load and rotor dynamic load are analyzed.And the modal characteristics and vibration characteristics of the rotor system under different operating parameters are obtained,and the transmission medium of the centrifugal pump is revealed.The results show that the deformation of the rotor system is mainly impeller,and the deformation increases gradually from the axis of impeller to the outer edge of impeller,while the stress mainly concentrates on the key position.The variation of flow rate has little effect on the magnitude of deformation and stress,but the reduction of rotational speed can significantly reduce the deformation and stress.?4?Vibration characteristics of centrifugal pumps at different working conditions and rotating speeds were measured by vibration acceleration sensors.The results show that blade frequency is the main excitation frequency of vertical Y direction monitoring points?1#and 4#?vibration of centrifugal pump body and bearing body at high speed,but at low speed,double-blade frequency is the dominant frequency of pressure fluctuation at vertical Y direction monitoring points.The vibration characteristics of centrifugal pump in horizontal X direction are broadband vibration,and the excitation frequency is mainly high frequency.The excitation source may be the harmonic effect of the motor and the resonance of the structure.By studying the unsteady flow mechanism and the dynamic characteristics of the rotor system of a double-blade centrifugal pump,the flow characteristics and pressure fluctuation characteristics of the flow passage components in the pump under different working conditions are clarified,and the relationship between the radial force acting on the impeller and the operating parameters is revealed.The effects of different operating parameters on the deformation and stress of the rotor system are analyzed,and the relationship between the deformation period of the rotor system and the structural mode are revealed.The vibration characteristics of centrifugal pumps at different positions are further revealed through experiments,which provides theoretical support for the improvement of double-blade centrifugal pumps. |
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