Research On Fluid Flow State And Heat Exchange Mechanism In Large Turbogenerator End Region

Energy production is usually made use of power device which convertsprimary energy or other forms of energy into electrical energy. Energy wayincludes mainly wind power generation, nuclear power generation, hydropowergeneration, thermal power generation, fuel cell power generation, biomass powergeneration and solar power generation, ect. Nuclear power and thermal power areprovided by turbogenerator which converts mechanical energy into electricalenergy and supplied to the power grid. At present, about80%of electrical energyis produced by the turbogenerator. It is visible that turbogenerator occupies acrucial position in the power system and its development and applicationprospect are more and more wide. However, with the growth of the largeturbogenerator unit capacity, the flux density and eddy current losses of end partshas been increasing correspondingly. Temperature rise of end parts increasesobviously. It results in overheating problem at the certain location of end region.They affect seriously the safety and reliability of the turbogenerator. Therefore,researching on influence of different complex structures and material propertieson fluid flow state and temperature distribution and revealing fluid evolutionmechanism in the multistage fan in the turbogenerator end region have importantsignificance to improve stability of turbogenerator.In this thesis, influence of different ventilation structures and differentmaterial properties on the distributions of fluid velocity and end part temperatureis researched in the stator end region of large turbogenerator. Fluid distributionlaw is analyzed in the multistage fan in the turbogenerator end region. Thecalculated results of the3-D fluid-thermal coupling field are verified by the testvalues, which verify the correctness and reliability of the calculation method andcalculation results.According to the characteristics of complex ventilation structure in theturbogenerator, flow network of the turbogenerator with multipath ventilation inthe half-axial segment is established. It reveals the flow rate distribution,pressure distribution, and ventilation losses in the turbogenerator. Taking the3-Dbasket end winding and complex structures of end parts into account,3-D fluid- thermal coupling analysis model of the end region is established. The flowvelocity and pressure values from the flow network calculations are applied tothe end region as boundary conditions and the losses obtained from3-D transientelectromagnetic field calculations are applied to the end parts as heat sources inthe fluid and thermal coupling analysis. The fluid and thermal equations of fluid–solid conjugated heat transfer are calculated. It reveals the distribution law ofcomplex fluid velocity, fluid temperature, fluid velocity around end parts, andend part temperature in the turbogenerator end region. The calculatedtemperature from the fluid-thermal coupling analysis model of end region andmeasured temperature of copper shield are compared. The error meets projectrequirements. It verifies rationality of the boundary conditions and accuracy ofcalculation method.Based on the theories of numerical heat transfer and computational fluiddynamics, surface heat-transfer coefficient distribution law of stator end windinginsulation and end parts is studied. It reveals influence of changes in coolingfluid parameter in the stator end winding pipe on end part temperature in the endregion. A reasonable value of water velocity in the stator end winding pipe isgiven. Influence of changes in cooling fluid rate and fluid temperature of the faninlet on fluid velocity, the highest temperature and average temperature of endparts is studied in the turbogenerator end region.Influence of changes in the end ventilation structure on fluid rate and fluidpressure of end region outlet, fluid velocity and end part temperature is studied inthe end region. It reveals influence of change in air gap spacer height on thesurface heat-transfer coefficient distribution law of copper shield inner circlezone. In order to decrease effectively end part temperature, the reasonable valuesof the air gap spacer height and shelter board width are given. Influence of thedifferent empty solid copper shield structures on fluid velocity and fluidtemperature is studied in the end region. The influence degree of optimizedempty solid copper shield structure on decreasing the temperature rise of thecopper shield is given. Influence of change in the press plate permeability ontemperature change law of copper shield, press plate, press finger and stator endwinding is researched in the turbogenerator end region.Based on the theory of computational fluid dynamics, the mathematical model of multistage fan is established in the turbogenerator end region.Characteristic curve of pressure and fluid rate about the multistage fan is given.It reveals static pressure distribution law of dynamic and static fan blade surfacesand fluid velocity vector distribution law around dynamic and static fan bladesurfaces. In addition, the distribution law of radial-direction, circumferential-direction, and axial-direction fluid velocities between the dynamic and static fanblades is discussed. After passing the dynamic and static fan blades, evolutionmechanisms of fluid static pressure and fluid total pressure are researched indepth.