Numerical Calculation And Performance Optimization Of Fluid Field Of End Fan Of Large Air-Cooled Turbo Generator

With the rapid development of China’s national economy,increasing attention has been paid to ecological environment as well as problems regarding energy conservation and emission reduction.The development of turbine is moving towards large-capacity,high efficiency direction.The improvement of motor capacity means the increase of the heat,which is not conducive to the reliability of the motor.As one of the most important equipment in an turbo generator,the temperature rise of the generator affected by axial fan directly.Therefore,it is of great significance to analyze the fluid field inside the fan as well as to improve its performance and increase the efficiency of the fan by optimization.A 350 MW air-cooled turbo generator’s single stage axial fan was taken as an example in this paper,a three dimensional physical model of end fan was established on the basis of the basic assumptions considering the structure feature of the model and the fluid dynamics,and the solution conditions were given.The characteristics of fluid flow inside the fan was detected through the numerical calculation and analysis,witch lay the foundation for the following optimization of the structure of the fan.Factors that influence the efficiency of the fan were found out according to the analysis and numerical calculations of the flow field of the fan under the original structure.At the same time,three optimization schemes were proposed in view of the structure of the fan.Relationship between characteristics of fan and those parameters were obtained and the optimal structural parameters of the fan were found out by adding the guide vane at the inlet and outlet as well as changing the installation angle of blades and the hub ratio of the fan.The results indicate that: the area of back-flow in the fan was decreased and the performance of fluid flow has been greatly improved after the guide vane was put in;In a certain range,total pressure and static pressure of the fan are proportional to the installation angle and the hub ratio,while the fan has the highest efficiency at a certain installation angle and hub ratio.The conclusions provide a theoretical basis for the structural optimization of the axial fan,and have a certain practical significance and practical engineering value.