CFD Optimal Analysis Of Hydro-generator Stator Ventilation System Based On The Longitudinal Vortex Generator

In recent years,with the development of the hydropower industry,demand of hydroelectric generation gradually increased,the gross installed capacity of China's hydropower is continually growing.As an important equipment in the process of hydroelectric power generation,it draws more and more attention of the design and operation of hydro-generator.The over hot problem of hydro-generator is directly related to its operation reliability and service life.Therefore,ventilation and heat transfer has been one of the key problems in hydropower equipment research.As an important part of the cooling system of the turbine generator,whether the design of stator ventilation system is appropriate or not and the flow velocity and temperature distribution of the internal cooling gas are directly related to the normal working of the hydro-generator.Based on the basic theory of computational fluid dynamics and heat transfer,a multi-field coupling calculation model for the stator ventilation system of bulb tubular hydro-generators is established.The flow field and temperature field distribution of hydro-generator stator ventilation system and their coupling relation are deeply researched,what's more,longitudinal vortex generators are set in the stator vents to enhance the heat transfer effect of the stator ventilation system.In this paper,a three-dimensional model of the stator ventilation system is built with software UG,then meshed with the ICEM CFD.Using the interface between ICEM CFD and Fluent the three-dimensional model is imported into the fluid flow analysis software Fluent.The flow field and temperature field of the stator ventilation system were calculated and analyzed,besides,the temperature distribution of whole and local system and the location of the highest temperature region are researched.The influence of inlet wind speed to the stator ventilation system temperature rise is also analyzed.It has been shown that the highest temperature in the system located at the stator coil and that the high temperature of the fluid portion located at the yoke region behind the stator coil.When the inlet velocity increases to some extent,the temperature rise in the system will decrease rapidly.If the inlet velocity continues to increase after a certain range,the decrease of temperature rise is no longer obvious.Based on the theory of heat transfer,a longitudinal vortex generator is proposed to improve the cooling effect of the stator ventilation system in this paper.The way of how the longitudinal vortex generators set is introduced too.Besides,the mechanism of how the longitudinal vortex generators enhance the heat transfer and the impact factors,including the attack angle,height and radial location are researched.Two standards are proposed to compare the optimal design.Obvious longitudinal vortex formed in the downstream area when longitudinal vortex generators are set in the stator ventilation system.With the analysis of the optimal factors of the longitudinal vortex generators,it is found that when the longitudinal vortex generators of height of 5mm and the attack angle of 45° is set between the middle of stator teeth and the inlet,the enhancement of heat transfer is best,and the temperature distribution inside the system is relatively uniform.The research of this paper provides some reference for the design of the ventilation system of the hydro-generator,especially for the stator ventilation system.