Radial Force Fluctuation Research Articles

Analytical representation and characteristics optimization for radial electromagnetic force of the switched reluctance motor under airgap eccentricity

Aiming at the influence of radial electromagnetic force on vibration and noise of the switched reluctance motor (SRM), the radial electromagnetic force under airgap eccentricity is represented based on the virtual displacement principle and Maxwell stress tensor. Multi-objective optimization of motor electromagnetic characteristics including magnetostatic torque, radial electromagnetic force fluctuation, and unbalanced radial force amplitude is completed. First, the analytical representation for the radial electromagnetic force is obtained by the virtual displacement principle, and the expression of the unbalanced radial force caused by airgap eccentricity is deduced. Then, the spatial distribution of the radial electromagnetic force is modeled by the Maxwell stress tensor, which makes the radial electromagnetic force characterization more comprehensive. In order to improve the electromagnetic characteristics of the SRM under airgap eccentricity, sensitivity analysis and multi-objective optimization are carried out to obtain the optimal solution set of the motor structure parameters. The simulation results show that the radial electromagnetic force fluctuation and the unbalanced radial force amplitude decreases by 64.09% and 23.05%, respectively, when the magnetostatic torque is sacrificed by 6.36%, which provides a framework for multi-objective optimization of motor structure parameters.

Modeling and suppression of unbalanced radial force for in-wheel motor driving system

Considering the negative vertical dynamics effect of switched reluctance motor on an in-wheel motor driving system, this article presents a modeling and suppression method for unbalanced radial force of the in-wheel motor driving system. To tease out the coupling relationship within the in-wheel motor driving system, this investigation, respectively, explores the principle of unbalanced radial force and the coupling relationship between rotor eccentricity and road excitation based on the suspension response model with unbalanced radial force under road excitation. The switched reluctance motor nonlinear analytical model was fitted by the Fourier series, and its radial electromagnetic force was modeled and analyzed by the Maxwell stress tensor method. To mitigate the influence of radial electromagnetic force fluctuation and unbalanced radial force amplitude value under eccentricity condition on the in-wheel motor driving system, the elitist non-dominated sorting genetic algorithm was adopted to improve radial electromagnetic force fluctuation and unbalanced radial force amplitude value of the switched reluctance motor. The simulation results show that the proposed optimization method can suppress the radial electromagnetic force fluctuation and unbalanced radial force amplitude value, and the negative effect of vertical dynamics of the in-wheel motor driving system is conspicuously mitigated.

A Study on the Influence of Tire Speed and Pressure on Measurement Parameters Obtained from High-Speed Tire Uniformity Testing

In order to improve the test conditions of the tire uniformity test and the effect of the speed and tire pressure on the uniformity parameters, the uniformity test of the tire under different speeds and tire pressure was carried out by a high-speed uniformity test machine, and the experimental data were analyzed and fitted by the regression analysis method. This paper introduces the definition of uniformity and the uniformity parameters of automotive tires; the working principle of a high-speed uniformity testing machine is briefly described, a mathematical model of the uniformity testing machine is established, and the signal acquisition process of the tire uniformity parameters and the calculation method of the uniformity parameters are described. The test result indicates: As the speed increases, the radial force fluctuation, lateral force fluctuation, tangential force fluctuation, and turning torque fluctuation of the tire increase, and the positive torque fluctuation first increases and then decreases; with the increase of tire pressure, the radial force fluctuation and the tangential force fluctuation of the tire increase, and the lateral force fluctuation, the turning torque fluctuation, and the returning moment fluctuation are all reduced. Compared to the low speed uniformity test, the high speed uniformity test can better reflect the uniformity of the tire, reducing the speed of the vehicle can reduce the radial runout and lateral sway of the tire; increasing the tire pressure can reduce the left and right swing of the vehicle.

Research on Radial Force of Permanent Magnet Synchronous Motor Based on Maxwell

In the existing permanent magnet motor drive system, the vibration and noise problems caused by motor and driver are more and more obvious and complex. Among them, the radial electromagnetic force fluctuation problem of permanent magnet synchronous motor (PMSM) stator is the most important cause of vibration and noise. The radial electromagnetic force fluctuation of PMSM stator is the main source of vibration and noise. In order to lay a solid foundation for studying the distribution of vibration and noise, the radial electromagnetic force of 12 slot 14 pole PMSM is calculated by combining Maxwell stress method and Lorentz force method. Based on the Maxwell platform, a solution model is established to analyze the radial electromagnetic force of motor in time and space. The time–space analysis diagram of radial electromagnetic force in no-load section and load section is given; it is helpful to avoid resonance point and realize low-noise design of motor.

Numerical study on instantaneous radial force of a centrifugal pump for different working conditions

Purpose Instantaneous radial force induced from unsteady flow will intensify vibration noise of the centrifugal pump, especially under off-design working conditions, which will affect safety reliability of pump operation in severe cases. This paper aims to conduct unsteady numerical computation on one centrifugal pump; thus, unsteady fluid radial force upon the impeller and volute is obtained, so as to study the evolution law of instantaneous radial force, the internal relationship between radial force and pressure pulsation, the relationship among each composition of radial force that the impeller received and the influence of leakage rate of front and back chamber on radial force. Design/methodology/approach The unsteady numerical simulation with SST k-ω turbulence model was carried out for a low specific-speed centrifugal pump using computational fluid dynamics codes FLUENT. The performance tests and pressure tests were conducted by a closed loop system. The performance curves and the pressure distribution from numerical simulation agree with that of the experiment conducted. The unsteady pressure distributions and the instantaneous radial forces induced from unsteady flow were analyzed under different flow rates. Contribution degrees of three components of the radial force on the impeller and the relation between the radial force and leakage rate were analyzed. Findings Radial force on the volute and pressure pulsation on the volute wall have the same distribution tendency, but in contrast to the distribution trend of the radial force on the impeller. In the component of radial force that the impeller received, radial force on the blade accounts for the main position. With the decrease of flow rate, ratio of the radial force on front and back casings will be increased; under large flow rate, vortex and flow blockage at volute section will enhance the pressure and radial force fluctuation greatly, and the pulsation degree may be much more intense than that of a smaller flow rate. Originality/value This paper revealed the relation of the radial force and the pressure pulsation. Meanwhile, contribution degrees of three components of the radial force on the impeller under different working conditions as well as the relation between the radial force and leakage rate of front and rear chambers were analyzed.

Dynamic effects on cutting forces with highly positive versus highly negative cutting edge geometries

Understanding the influence of the cutting edge geometry on the development of cutting forces during the milling process is of high importance in order to predict the mechanical loads on the cutting edge as well as the dynamic behavior on the milling tool. The work conducted in this study involves the force development over the entire engagement of a flute in milling, from peak force during the entry phase until the exit phase. The results show a significant difference in the behavior of the cutting process for a highly positive versus a highly negative cutting edge geometry. The negative edge geometry gives rise to larger force magnitudes and very similar developments of the tangential and radial cutting force. The positive cutting edge geometry produces considerably different developments of the tangential and radial cutting force. In case of positive cutting edge geometry, the radial cutting force increases while the uncut chip thickness decreases directly after the entry phase; reaching the peak value after a certain delay. The radial force fluctuation is significantly higher for the positive cutting edge geometry. The understanding of such behavior is important for modelling of the milling process, the design of the cutting edge and the interactive design of digital applications for the selection of the cutting parameters.

Influence of impeller staggered arrangement on radial force and pressure fluctuation for a double-suction centrifugal pump

Influence of impeller arrangement on performance, radial force, and pressure fluctuation for a double-suction centrifugal pump is investigated. In comparison of the original impeller with staggered angle α of 0°, the maximum improvement of pump efficiency is 2.19% for impeller with α of 30°, and the maximum improvement of pump head is 1.76% for impeller with α of 20°. The radial force vector on impeller is related to the staggered angle, and the phase angle of radial force vector is equal to the staggered angle. The staggered arrangement can effectively reduce the amplitude of radial force fluctuation. In comparison of case 0, the maximum amplitude of radial force fluctuation for case 30 reduces by 15.8%. The dominant frequencies of the radial force fluctuation for α = 0°, 10°, and 20° are fBP, while the dominant frequency for α = 30° is 2 fBP. An empirical formula is proposed to predict the radial fluctuation amplitude at specific staggered angle. For a point of the volute far from the exit volute, in comparison of case 0, the maximum amplitudes of pressure fluctuation for case 10, case 20, and case 30 are reduced by 13.1%, 49.8%, and 93.3%.

Three-objective optimization of a centrifugal pump with double volute to minimize radial thrust at off-design conditions

Optimization of a centrifugal pump with double volute was performed using surrogate modeling and a multi-objective genetic algorithm to minimize the radial thrust at off-design conditions with minimal loss in hydraulic efficiency. Both steady and unsteady numerical analyses were conducted using three-dimensional Reynolds-averaged Navier–Stokes equations with a shear stress transport turbulent model. The three objective functions are hydraulic efficiency at the design flow rate, and radial thrust coefficient at 70% and 120% of the design flow rate. In addition, three geometric parameters related to the surface curve and the locations of both ends of the rib structure were selected as the design variables for optimization. The Latin hypercube sampling method was used to choose the design points in the design space. The three objective functions were approximated using response surface approximation models. Pareto-optimal solutions representing the trade-off between the objective functions were obtained using a genetic algorithm. Representative optimal designs show that the optimized double volutes significantly reduce both the radial force and the amplitude of the radial force fluctuation with small loss in hydraulic efficiency.

Characteristics of Unsteady Excitation Induced by Cavitating Flow in Centrifugal Pumps

Unsteady excitation induced by cavitating flow is one of the main factors causing the vibration and noise of the pump.In order to study the characteristics of unsteady excitation,the unsteady numerical simulation of the cavitating flow in the flow-passage of a centrifugal pumps is carried out by using the full cavitation model and the mixed two-phase flow model.Simulation results indicates that the cavitation bubbles generate at the suction side of blades near the leading edge,the region of bubbles extends with the reduction of inlet total pressure.When cavitation becomes serious,low-speed vortex is observed in the flow-passage.The frequency of the pressure fluctuations has the obvious discrete characteristics and the blade passing frequency dominates the pressure fluctuations.Along with the development of cavitation,cavitating flow can induce the increase of pressure fluctuation amplitude in the flow-passage,and there is a corresponding relationship between them.The cavitation can also induce the increase of unsteady radial force fluctuation amplitude and substantial increase of axial force.So cavitation affects operation stability and reliability of pumps.

Investigation on impeller radial force for double-suction centrifugal pump with staggered blade arrangement

In order to find the effects of blade arrangement on impeller radial force, a double-suction centrifugal pump with two impeller configurations is investigated by using CFD approach. The two impeller have same geometry, same blade number, and different blade arrangement. One is staggered impeller in which the blades are arranged with half of blade phase angle staggered in circular direction, another is traditional symmetrical impeller with symmetrical blade arrangement. Results show that the radial force vector diagram for symmetrical impeller is a hexagonal, while it is nearly a circle for staggered impeller. The staggered impeller results no radial force saltation which exists in symmetrical impeller. The blade passing frequency dominates the radial force fluctuation in symmetrical impeller, while this frequency is almost not existed in staggered impeller. The results indicate that staggered blade arrangement can significantly reduce radial force fluctuation in double-suction centrifugal pump.

Numerical simulation of pressure fluctuation in 1000MW Francis turbine under small opening condition

In order to study the cause of abnormal vibration in large Francis turbine under small opening condition, CFD method was adopted to analyze the flow filed and pressure fluctuation. Numerical simulation was performed on the commercial CFD code Ansys FLUENT 12, using DES method. After an effective validation of the computation result, the flow behaviour of internal flow field under small opening condition is analyzed. Pressure fluctuation in different working mode is obtained by unsteady CFD simulation, and results is compared to study its change. Radial force fluctuation is also analyzed. The result shows that the unstable flow under small opening condition leads to an increase of turbine instability in reverse pump mode, and is one possible reason of the abnormal oscillation.

Characteristics of Radial Force Fluctuations on Runners of Francis-type Pump-turbines : Report 1 : Experiments on General Characteristics of Radial Force Fluctuations and Effects of Structural Factors

The hydraulic, radial force fluctuation acting on the runner of a Francis-type pump-turbine was investigated experimentally. Five model pump-turbines of different specific speeds were tested. In pumping operation, the amplitude of the fluctuation increases as discharge decreases. In generating operation, the maximum amplitude appears with the draft surge frequency during partial load operation. The runner speed frequency component always appears. Components with 0.5 to 1.0 times the runner speed frequency become dominant when maximum amplitude fluctuation occurs during transient operations.