A Numerical Investigation on the Characteristics of the Radial Force in a Cycloid Gerotor Pump

In order to improve the performances of a cycloid gerotor pump,the variations of the radial force induced by different rotating speeds and outlet pressures are analyzed numerically.Using the numerical simulations as a basis,an improved oil inlet and outlet groove structure is proposed.The results show that the radial force decreases with the decrease of the outlet pressure and of the rotor speed.Compared with the original model,the large-end oil inlet line and pressure line of the new oil groove are claw-shaped.This configuration can effectively weaken the pressure changes inside the gerotor pump and reduce accordingly the radial force on the inner rotor.

FEA-based Geometrical Modification of Switched Reluctance Motor for Radial Force Reduction

Switched reluctance motors(SRMs)are becoming increasingly popular in the automotive sector owing to their robust design.Moreover,SRMs are preferred particularly for EV applications owing to their fault tolerance,magnet-free structure,and high power/torque density.The main concerns of SRM compared to other machines include torque ripple and vibration.The primary cause of vibration is the radial force created by the SRM.A geometry-based modification of the SRM to reduce the radial force without significantly changing the average torque produced is proposed.The primary goal is to design a 4-phase,8/6 SRM with a lower radial force.Two possible geometrical alterations are proposed:one with square windows and the other with circular holes on the rotor core.The windows are sized and positioned to avoid flux saturation.General criteria are developed for the optimal window size and placement.Finite element analysis(FEA)modelling of the SRM is used to validate its performance.The FEA results are compared with the performance parameters obtained using the analytical method.Utilizes the multiphysics design tool ANSYS to obtain the natural frequencies and associated deformations through modal analysis.Compared to the conventional geometry,the radial force is significantly reduced by providing windows.

Harmonics in the Squirrel Cage Induction Motor,Analytic Calculation Part Ⅱ:Synchronous Parasitic Torques,Radial Magnetic Forces

The magnetic field generated in the air gap of the cage asynchronous machine and the harmonics of the magnetomotive forces creating that magnetic field,as well as the synchronous parasitic torques,radial magnetic forces have been discussed in great detail in the literature,but always separately,for a long time.However,systematization of the phenomenon still awaits.Therefore,it is worth summarizing the completeness of the phenomena in a single study–with a new approach at the same time-in order to reveal the relationships between them.The role of rotor slot number is emphasized much more than before.New formulas derived for both synchronous torques and radial magnetic forces are used for further investigation.It will be shown that both phenomena in subject must be treated together.Formulas will be provided to take into account attenuation.Design guide will be provided to avoid dangerous rotor slot numbers.It will be shown that the generation of synchronous torques and radial magnetic forces do not depend–in this new approach-on the slot combination,but on the rotor slot number itself.

Influence of Different Transition Modes on the Performances of a Hydraulic Turbine

In order to analyze the response of a hydraulic turbine to a variation in the operating conditions,different laws of variation in time of the massflow rate have been considered.After validating the overall numerical framework through comparison with relevant experiments,the performances of the considered turbine have been analyzed from afluid-dynamic point of view.The results show that different time profiles of the massflow rate(in this work,for simplicity,referred to as“transition functions”)have a varying influence on the transient behavior of the turbine.When a quadratic function is considered for the case of largeflow,the transient head and torque increase gradually with time,thefluctuation amplitude of the transient hydraulic efficiency at the main frequency is the largest,and thefluctuation amplitude of the radial force is the smallest.For the smallflow case,the time profile with exponential nature leads to the best results.The transient head and torque decrease gradually with time,the pulsation amplitude of the transient hydraulic efficiency is the largest at the main frequency,and the pulsation amplitude of the radial force is the smallest.

非设计工况下带分流叶片半开式离心叶轮内部流动特性数值研究

In order to investigate the complex flow characteristics inside an unshrouded centrifugal impeller with splitter blades at off-design conditions,and analyze its influence on pump operation stability,a numerical simulation study was carried on using the curvature-corrected SST-CC turbulence model;the head and efficiency accorded with experimental results.The pressure fluctuation,unsteady radial force and velocity were analyzed quantitatively and the numerical results indicate this:the peak to peak value of pressure fluctuation in the impeller channel gradually increases in the flow direction and at 0.49Qn,the slope of peak to peak value to normalized impeller channel behind the splitter blade is 8.57 times greater than that before the splitter blade.The greater the flow rate deviates from the design condition,the larger the peak to peak value of the pressure fluctuation and radial force;in particular at 0.27Qn,the maximum radial force is 194.29%greater than that of the design condition.When the operating flow rate is smaller than 0.83Qn,the stall occurs and the stall vortex could block the impeller discharge;as the flow rate decreases further,the pressure amplitude at rotational frequency gradually increases in the impeller channel and the prevailing frequency changes from the blade passage frequency(BPF)to the rotating stall frequency in the diffuser.The tip leakage vortex(TLV)is generated in the tip region and rotated move downstream in the impeller flow channel,and the backflows appear on the blade suction side and in the tip and the tongue regions;the smaller the flow rate,the more serious the TLV and backflow phenomenon.The rotating stall causes uneven flow in the impeller channel,increasing the pressure fluctuation and the radial force,and resulting in an imbalance of the impeller rotation.

A Design Method of the Rotor Auxiliary Slot for the Water-filled Submersible Induction Motors

Aiming at the problem of electromagnetic vibration of the water-filled submersible induction motor(WSIM),a method of opening auxiliary slots on the rotor side is proposed to weaken the air-gap field harmonics caused by the rotor slot permeance harmonics.By analyzing the research status of electromagnetic vibration of the WSIM and the composition of the air-gap magnetic field of the motor,the idea that the auxiliary slots mainly affect the air-gap field harmonics by changing the air-gap permeance of the motor is put forward.The mathematical model of air-gap permeance of WSIM is established to simulate the influence of auxiliary slots on the air-gap permeance.Through the parametric analysis of the mathematical model,the change of auxiliary slot size is simulated.The air-gap permeance waveform is decomposed by the two-dimensional Fourier transform,and then the variation of the air-gap permeance harmonics with the size of the auxiliary slot is analyzed.Finally,the finite element simulation model of the WSIM with the auxiliary slots is established,and the waveform of the air-gap flux density of the motor is analyzed to verify the effectiveness of the mathematical model.Meanwhile,the results show that after opening the auxiliary slot,the radial electromagnetic force of the motor was reduced by 28.4%.

A glance on the effects of temperature on axisymmetric dynamic behavior of multiwall carbon nanotubes

In this paper the effects of temperature on the radial breathing modes （RBMs） and radial wave propaga- tion in multiwall carbon nanotubes （MWCNTs） are inves- tigated using a continuum model of multiple elastic isotropic shells. The van der Waals forces between tubes are simulated as a nonlinear function of interlayer spacing of MWCNTs. The governing equations are solved using a finite element method. A wide range of innermost radius-to-thickness ratio of MWCNTs is considered to enhance the investigation. The presented solution is verified by comparing the results with those reported in the literature. The effects of temperature on the van der Waals interaction coefficient between layers of MWCNTs are examined. It is found that the variation of the van der Waals interaction coefficient at high temperature is sensible. Subsequently, variations of RBM frequencies and radial wave propagation in MWCNTs with temperatures up to 1 600 K are illustrated. It is shown that the thick MWC- NTs are more sensible to temperature than the thin ones.

Cutting force prediction for circular end milling process

A deduced cutting force prediction model for circular end milling process is presented in this paper. Traditional researches on cutting force model usually focus on linear milling process which does not meet other cutting conditions, especially for circular milling process. This paper presents an improved cutting force model for circular end milling process based on the typical linear milling force model. The curvature effects of tool path on chip thickness as well as entry and exit angles are analyzed, and the cutting force model of linear milling process is then corrected to fit circular end milling processes. Instantaneous cutting forces during circular end milling process are predicted according to the proposed model. The deduced cutting force model can be used for both linear and circular end milling processes. Finally, circular end milling experiments with constant and variable radial depth were carried out to verify the availability of the proposed method. Experiment results show that measured results and simulated results corresponds well with each other.

NUMERICAL SI MULATION OF STEADY FLOWFOR VISCOELASTIC FLUID IN AN ECCENTRIC ANNULUS WITHINNER ROD MOVING AXIALLY

The governing equation about steady flow of viscoelastic fluids in an eccentric annulus with inner rod moving axially is established by using common conversion Maxwell constitutive model. The numerical solutions of the flow are obtained by control volume and ADI methods. The influence of the eccentricity, velocity of inner rod and elasticity of fluid to the velocity distribution, flow rate and radial force on the inner rod is obtained, and the reason for the severe eccentric wear of the sucker rod of polymer flood well is analyzed.

Development of new endovascular stent-graft system for type B thoracic aortic dissection with finite element analysis and experimental verification

Endovascular repair of the thoracic aorta with self-expanding stent-grafts has been emerging as a less invasive alternative treatment compared with conventional open surgeries.Despite the promising efficacy and safety of endovascular stent grafting,the stent-graft failure remains a major concern in terms of stent migration,device fatigue,and the risk of endoleaks.Challenges associated with the stent-grafts involve optimized geometrical structure,lifetime fatigue resistance,and adequate radial support.In this work,a novel endovascular stent-graft system is developed specially for the treatment of Stanford type B thoracic aortic dissections(TAD).Numerical study with finite element analysis(FEA)was utilized to evaluate the mechanical behaviors of the individual stent component.Results of the simulation were validated by experimental tests.Based on the systematic analysis of the parametric variations,a final stent-graft system was developed by the selection and arrangement of the individual stent components,targeting an optimal performance for treatment of TAD.The optimized solution of the stent-graft system was tested in clinical trials,showing advantageous therapeutic efficacy.

Fabrication of Intracranial Vascular Nitinol Alloy Stents with Improved Mechanical Property and Endothelialization Function

Intracranial vascular stenting has been widely used for ischemic stroke.However,there are complication risks with stent implantation,such as poor wall apposition,stent migration,thromboembolism and stent restenosis,due to the mismatched radial force and conformability of the stents."Therefore,a novel intracranial vascular nitinol stent was fabricated in order to improve mechanical property and endothelialization function.The bending moment of the stents was calculated to be 0.346 N mm,which shows improved conformability.The radial force of the stents evaluated by the flat plate test was0.0112 N/mm,within the range of the commercially available stent force(0.0065-0.0116 N/mm).Furthermore,the TyrIle-Gly-Ser-Arg(YIGSR)peptide derived from laminin was grafted onto the stent surfaces to promote endothelialization on vascular stents evaluated by the proliferation,adhesion and migration of human umbilical vein endothelial cells in vitro.The nitinol stents with improved mechanical property and endothelialization function are expected to reduce the recurrence risk of ischemic stroke after implantation.

Analysis and Optimization of Unsteady Flow in a Double-Suction Centrifugal Pump for a Cooling-Water Supply System in a Nuclear Reactor

The management of a cooling-water supply system in a nuclear reactor is performed by valve and reactor coolant pump(RCP)control,which regulates both the pressure and the discharge between certain limits.However,the RCP has a significant unsteady flow when operating at different conditions.The unsteady pressure pulsation and radial force vector are difficult to calculate because these are affected by the transient properties of the unsteady flow.This study explores the use of a commercial Computational Fluid Dynamics(CFD)code to comprehensively estimate the unsteady flow of the RCP.The full 3D-URANS equations were solved for different flow rates,and some optimised cases for the unsteady flow were proposed.The results showed that the numerical predictions were validated with the experimental data of a model pump.The code was used to estimate the velocity streamlines,pressure pulsation and radial force vector in the steady and transient conditions.The flow rates were not equal for the inner and outer passage in the double volute casing.Additionally,the pulsation of the pressure and radial force was effectively reduced by optimising the staggered angleα.An optimal case was observed whenα=30°.