Establishment of an Accurate Thermal Source Partition Mapping Method Based on Electromagnetic Properties and Loss Distribution

In the research and design of the compact structure of the bulb tubular turbine generator cooling system, the accuracy of heat source distribution significantly affects the rationality and effectiveness of the final temperature numerical calculation results. Specifically, due to the differences in the iron loss curves of different magnetically conductive materials, the inevitability of harmonics in the magnetic field, and the diversity of magnetization modes in different positions, the combined action of these three factors makes the calculation of core losses more complex. In addition, current numerical calculations of fluid-thermal fields often treat heat sources as uniform heating, which leads to numerical temperature calculation results deviating from reality. Therefore, this paper proposes a precise heat source zoning mapping method through electromagnetic-thermal coupling analysis of a 24MW bulb tubular turbine generator. Firstly, Maxwell's numerical calculation of the electromagnetic field of the generator is used to obtain the electromagnetic characteristics and distribution of iron losses, and the thermal source area is divided based on the gradient changes of both. Secondly, considering the effect of harmonics in the generator on iron core losses, a variable-coefficient iron core loss calculation method based on equivalent frequency is proposed, and Matlab is used to perform secondary calculations on the magnetic flux density results of the electromagnetic field to obtain the iron core loss values as heat source quantities. Finally, Flunet is used for numerical calculation of fluid-thermal coupling, and experimental verification is conducted. The results show that the heat source zoning mapping method is more accurate in temperature distribution calculation results compared to the original uniform heat source distribution method.