基于多尺度多物理场的油浸式变压器流动-传热数值研究

Numerical Study on Flow-Heat Transfer of Oil-Immersed Transformer Based on Multiple-Scale and Multiple-Physical Fields

为改善油浸式变压器的性能,探索变压器内部温度场-流场的工作特性,该文提出基于涡流-温度-流场多物理场耦合方法,建立油浸式变压器内部流动-传热计算模型。该模型采用有限元差分法(FDM)计算变压器内涡流场;采用格子玻耳兹曼方法(LBM)计算变压器内温度-流场。该计算方法在宏观上以开尔文为单位通过传热学第一类边界条件实现了固-液边界传热;在介观上以无量纲的格子玻耳兹曼方法中分子分布函数为单位对变压器内铁心绕组固体域与绝缘油流体域进行温度传递与油流流动的计算,完成基于宏观-介观单位尺度变化的流-固温度耦合传热计算。在此基础上分析油浸式变压器内部温度场与流场的工作特性。为验证计算模型的有效性,该文设计变压器流动-传热模拟实验平台,进行正常工作状况下变压器模型的流动-传热实验。实验结果表明,该计算方法由于格子玻耳兹曼算法迭代前期需要扩散格子密度覆盖计算区域,计算迭代前期温升状况不明显,无法有效地拟合油浸式变压器内部温度场与流场工作特性;在计算方法迭代一定次数后,计算误差在5%以内,能有效地拟合变压器工作特性。该算法模型对开展预防油浸式变压器内部故障工作,减少油浸式变压器内部过热事故有着一定的工程意义。

In order to improve the performance of oil-immersed transformer and explore working characteristics of internal temperature field and flow field,a multi-physical field coupling method based on eddy-temperature-flow field is proposed and an internal fluid-heat transfer calculation model of oil-immersed transformer is established in this paper.Finite difference method(FDM)is used to calculate eddy current field in transformer.Lattice boltzmann method(LBM)is used to calculate temperature-flow field of transformer.On the macro,the method realized solid-liquid boundary heat transfer with the units of kelvin.On the mesoscopic,the method was used to calculate the temperature transfer and oil flow in solid domain and insulating oil fluid domain with the units of dimensionless LBM molecular distribution function.By this method,fluid-solid temperature coupled heat transfer based on macroscopic-mesoscopic unit scale variation was calculated,and the operating characteristics of temperature field and flow field in oil-immersed transformer were analyzed.This paper designed a transformer flow-heat transfer simulation experiment to verify the proposed model.It is shown that since the iteration of LBM algorithm requires the diffusion lattice density to cover the calculation area,the temperature rise is not obvious at the early calculation stage and cannot effectively fit the operating characteristics of the internal temperature field and flow field of the oil-immersed transformer.After a certain number of iterations,the calculation error is within 5%and can effectively fit the transformer operating characteristics.This algorithm model has some engineering significance to prevent the internal fault of oil-immersed transformer and reduce the internal overheating accident of oil-immersed transformer.