Modelling of low-speed magnetic gear with viscose ferrofluid

Abstract

PurposeIn this paper, a computational model of a coaxial magnetic gear (MG) design with viscose ferrofluid between rotors is proposed. Viscose ferrofluid is used to decrease the magnetic reluctance and therefore creates higher magnetic torque. However, viscose friction of ferrofluid is undesirable and must be minimised in this particular application. MG is supposed to operate under low rotational speeds, where the dynamic viscose friction is very low, and the effects of the viscose ferrofluid over the MG’s efficiency must be estimated. The paper aims to analyze the performance of MG with viscose ferrofluid and to estimate the MG efficiency by computational model using finite element method (FEM).Design/methodology/approachAn MG design with viscose ferrofluid between the outer low-speed rotor and modulating steel segments was modelled as a coupled transient magnetic field problem and a kinematic model with viscous friction coefficients derived from a previously computed fluid dynamics model.FindingsThe proposed computational implementation is suitable for homogeneous magnetic fluid modelling in electromagnetic actuators and rotational machines. The results regarding power and torque transmission of MG were obtained by coupled finite element modelling. The efficiency of MG significantly decreased due to ferrofluid friction.Originality/valueThe described MG design with viscose ferrofluid is a novel device with new operational characteristics, and new results for the effects of viscose ferrofluid friction in the outer magnetic field over the MG efficiency are estimated.