Anti-Erosion Theory On Elastic Coating Of Hydraulic Turbine And Its Application

Erosion damage, caused by water current carrying sand grains and impacting the channel border of fluid-pass parts, is one of important reasons of early failure of hydraulic turbines. It is a concrete behavior of fluid grain abrasive and is regarded as a cosmopolitan technical problem. It is very important both in theoretical research and practical application to study the internal relations between the movement of particles near the channel border of fluid-pass parts and the response of material of channel border, and to investigate the general principle of anti-erosion design and the surface protection technology. With the development of the worldwide industrialization, vegetation is destroyed continually, resulting in aggravation of soil erosion and more rivers carrying considerable amount of sand grains. Therefore study on Erosion damage has been noticed widely by researchers in the world.On the basis of summarizing publications on erosion damage of hydraulic turbine, an anti-erosion theory is proposed in this thesis. According to this theory, the elastic coat can be adopted to realize the channel border synchronistic fluctuation with the perturbation of boundary layer, and to change the passive state that channel border bears particles' impacting into that the channel border parries contact with particles on its own initiative. Wet heat intensity, characteristics of erosion damage of elastic coat, and its manufacturing technology and engineering application, are studied. This thesis consists of seven chapters.The introduction is in Chapter one, which summarizes the research situation of erosion damage of hydraulic turbine in the world and illuminates the research aim, significance and main contents .In Chapter two, the differential equation of particles' movement in flow channel of hydraulic turbine is derived, and then the conditions of particle impacting the channel border and the correlative influence factors are analyzed.In chapter three, the corresponding relation of characteristic parameters between the perturbation wave of boundary layer and the surface erosion corrugation wave of fluid-pass section is analyzed, and the anti-erosion design idea is proposed, which can realize the synchronistic fluctuates of channel border with the perturbation of boundary layer by adopting the elastic coat. The conditions of synchronistic wave, the fluctuation displacement of elastic border and the fluctuation stress of bondinginterface are also analyzed. In addition, the displacement constant curve of border fluctuation is drawn out according to results of numerical calculation. The theoretical basis is established for the elastic coat to avoid erosion and the theoretical foundation is set for the dispensation design of elastic coat material.In chapter four, according to the theoretical analysis and experimental study, the solidification internal stress of elastic coat, wet heat characteristics, wet heat stress and the dynamic stress in the course of contact between the coat surface and particles, are analyzed. All these build a theoretical foundation for the general intensity calculation and reliability design of elastic coat.In chapter five, an erosion experiment is carried out, and the characteristic curves of erosion damage of elastic coat are drawn out according to the experimental results. And then the erosion model of the elastic coat is established on the basis of the dynamic analysis of contact procedure.In chapter six, the structure design and manufacturing technology of elastic coat used for hydraulic turbines are studied. Finally, the application effect of elastic coat in hydrodynamic power station is introduced.The conclusive part of the paper is in Chapter seven .