Flow field and convective heat transfer of smallscale Taylor-Couette flow induced by end leakage

More and more researchers have paid attention to Taylor-Couette flow whose axial dimension is much larger than other dimensions.However,featured by the limited axial length of the bearing,its flow field and convective heat transfer between the rotator and the stator are highly conglutinated with the leakage at the end of the clearance.An investigation was conducted on the flow field and convective heat transfer of small-scale Taylor-Couette flow induced by end leakage through means of numerical simulation and experimental measurement.The static pressure and temperature of the stator were captured by a micromanometer and a time-resolved infrared camera,respectively.Large Eddy Simulation(LES)was performed to reveal the instantaneous and mean flow field of the shearing flow.Results show that the flow field and convective heat transfer are tightly associated with the presence of end leakage.As approaching the end of the clearance,the flow is dominated by the axial flow induced by the end leakage,and then a series of Taylor vortices gradually distorts and tilts as moving downstream.Along the angular direction,the maximum and minimum static pressures take place near minimum clearance height,respectively.The static pressure along the angular direction and the axial velocity near the minimum clearance height as well as the Nusselt number increase with increases of the rotational Reynolds number and the eccentricity ratio while decreasing with an increase of the dimensionless clearance height.Both natural convection by buoyancy and forced convection by the shearing flow play a significant role in convective heat transfer.Compared with classic Taylor-Couette flow,the occurrence of leakage decreases the maximum static pressure while increasing the minimum static pressure.The formation and evolution of the Taylor vortex are dominated by the axial flow.

Multi-layer Quasi Three-dimensional Equivalent Model of Axial-Flux Permanent Magnet Synchronous Machine

Axial-flux permanent magnet synchronous machine(AFPMSM)enjoys the merits of high torque density and high efficiency,which make it one good candidate in the direct-drive application.The AFPMSM is usually analyzed based on the three-dimensional finite element method(3D FEM)due to its three-dimensional magnetic field distribution.However,the 3D FEM suffers large amount of calculation,time-consuming and is not suitable for the optimization of AFPMSM.Addressing this issue,a multi-layer quasi three-dimensional equivalent model of the AFPMSM is investigated in this paper,which could take the end leakage into consideration.Firstly,the multi-layer quasi three-dimensional equivalent model of the AFPMSM with single stator and single rotor is derived in details,including the equivalent processes and conversions of structure dimensions,motion conditions and electromagnetic parameters.Then,to consider the influence of end leakage on the performance,a correction factor is introduced in the multi-layer quasi three-dimensional equivalent model.Finally,the proposed multi-layer quasi three-dimensional equivalent model is verified by the 3D FEM based on an AFPMSM under different structure parameters.It demonstrates that the errors of flux linkage and average torque obtained by the multi-layer quasi three-dimensional equivalent model and 3D FEM are only around 2%although the structure parameters of the AFPMSM are varied.Besides,the computation time of one case based on the multi-layer quasi three-dimensional equivalent model is only 6 min,which is much less than that of the 3D FEM,1.8 h,under the same conditions.Thus,the proposed multi-layer quasi three-dimensional equivalent model could be used to optimize the AFPMSM and much time could be saved by this method compared with the 3D FEM.