CFD Numerical Simulation On Thermal And Flow Fields Of Multi-Scheme Brushless Exciter

The brushless exciter is a rotating motor providing the excitation current to establish the magnetic field for the synchronous motor.Its structure is relatively complex.The two rotating parts,rectifier plate and the rotor,are connected through a rotating shaft.The important issues for the design and study researchers are whether the internal insulation and diodes of the brushless exciter are over temperature which directly affect the safe and stable operation of equipment.Due to the existence of the rotating parts,the flow inside the brushless exciter is complex.It is certainly difficult to measure the inner flow field and temperature field.Appling CFD numerical simulation method can not only get brushless exciter internal flow field,temperature field distribution,but also locate peak temperature of different parts.It provides theoretical guidance for cooling ventilation design of brushless exciter.At present,the brushless exciter in this paper is running on west-east gas transmission 20 MW motor which is domestic research and development.The temperature of the rectifying plate part of the brushless exciter is too high,which affects the service life of diodes via field test.In order to solve this problem,the same type brushless exciter which has introduced before by some company was taken as the prototype,multi-schemes ventilation cooling system of brushless exciter were numerically simulated based on CFD principle.First of all,based on the introducted structure ventilation solutions(scheme A)changed the inlet position to get another project(scheme B).Based on CFD and finite volume method,the thermal and flow fields of the two schemes were simulated at the rotational speed 3120r/min according to the computational conditions given by the factory.The influences of the position of inlet on thermal and flow fields of brushless exciter were analyzed.Meanwhile,the flow and temperature field distribution characteristics were obtained and better scheme of cooling system was gained.Then,for the origin scheme with better cooling effects and running operation scheme,with which the brushless exciter supports the use of west-east gas 20 MW motor,the three-dimensional thermal and flow fields were simulated numerically and the flow and temperature field distribution characteristics of two schemes were analyzed and contrasted at the rated speed 4800 r/min.Based on the above research,distribution characteristics of three-dimensional thermal and flow fields of different schemes inside brushless exciter were analyzed and the interaction of two rotational flow field and mutual influence between flow field and temperature field were explored and completed.This paper can provide a theoretical basis for the development of ventilation and cooling design of brushless exciter for synchronous motor.