A new magnetic modeling method for magnetic levitation rotary table

Precision machining fields require the worktable to have a large-scale multi-degree-of-freedom motion capability. In order to provide a more accurate magnetic model for the control strategy decoupling process and the size parameter optimization design process of the maglev rotary table. This paper proposes a new magnetic modeling method based on the Two-Dimensional Harmonic method. Different from the existing harmonic method, this method simultaneously considers the tangential and radial magnetic field changes of circumferential magnetic array. And it eliminates the edge effect of the magnetic flux density distribution in the radial aperiodic direction. The magnetic force and torque are solved by the Lorenz integral formula and the Gaussian quadrature method. In order to verify the accuracy of the TDH method, the boundary element software RadiaTM is used for simulation, and a prototype is made for measurement. The experimental results shown that this method reduced the maximum error of the radial edge magnetic field from 104.19% to 3.29%. And it improved the calculation accuracy of magnetic force and torque by 60.74% and 84.39% respectively. This method does not rely on special example, and is beneficial to cross-platform applications. It is more suitable for realizing the magnetic modeling of the maglev rotary table with both rotational motion and large-stroke translational motion.

NUMERICAL INVESTIGATION OF A TONE NOISE OF THE FAN WITH CASING TREATMENT

Numerical investigation of influence of a slot-type casing treatment on acoustic and aerodynamic characteristics of the fan of ultra-high bypass ratio turbofan is presented. The investigation was performed using NUMECA FINE/Turbo solver. NLH harmonic method was used to simulate the effect of casing treatment on unsteady flow field in the turbomachine. Two operational conditions were investigated – “sideline” and “approach”. The attention for the first operational condition was paid for aerodynamic characteristics. Significant influence of casing treatment on them was found especially near the surge line. At the “approach” operational conditions the attention was paid for the proper calculation of tone noise. It was shown that the installation of casing treatment leads to decrease of power of tone noise radiated through the inlet. However the power of the tone noise, radiated through the nozzle, and also the overall power of tone noise increase.

Flutter analysis of a one-and-a-half-stage fan at low speed using nonlinear harmonic method

Multirow effects on flutter stability of a 1.5-stage fan at low speed are investigated using nonlinear harmonic method in a one-way coupled fashion. In the first part, the mesh-independence verification and validation of nonlinear harmonic method to simulate multirow effects are performed. In the second part, multirow effects are separated into two parts including acoustic reflection and rotor–stator interaction induced by relative motion between rotor and stators with each part investigated individually. Effect of acoustic reflection from upstream and downstream blade rows is investigated separately using a harmonic truncation method to avoid the change of time-mean flow. The results show that acoustic reflection can have a large effect on flutter stability of rotor blade. The simulation of the rotor–stator interaction effect indicates that the rotor–stator interaction does not significantly affect the flutter stability of rotor blade in this case. Lastly, the variation of aerodynamic modal damping ratio with the size of gap between inlet guide vane and rotor is investigated. Aerodynamic modal damping ratio at a nodal diameter whose fundamental mode is cut-on varies periodically with gap size. Wave splitting method is employed to further investigate the relation between the phase difference between incoming and outgoing wave and aero damping, which can be used to improve the flutter stability at the design stage.