The Numerical Simulation of Moisture-Removal Groove in the Last Stages of Steam Turbine Blades
|School||Harbin Institute of Technology|
|Course||Power Machinery and Engineering|
|Keywords||steam turbine wet steam condensing flow steady moisture removal|
With the rapid development of high-power steam turbine, nuclear steam turbine and nuclear-powered marine steam turbine, droplet erosion problems of the last and penultimate stages of steam turbine blades are more and more serious. which would not only increase the loss of the stages, but also lead to blade erosion. Wet steam environment would not only increase the loss of the stages, but also lead to blade erosion.The hollow stationary-blade groove moisture-removal method is the one most direct and effective method of moisture-removal method to prevent or minimize droplet erosion. If the design of the suction aperture structure is reasonable, it can remove most moisture which is harm to rotor blades, not only can reduce or eliminate the droplet erosion of rotor blades, but also can reduce the loss caused by droplet brake and friction.The development of the two-phase theory on wet steam and the current situation of this investigation field in domestic and abroad are all summarized in this thesis.It also introduces the application and investigation of internal moisture removal techniques on steam turbines, and briefly analyses the advantages and disadvantages of various methods.Through flow field analysis of the prototype Steam Turbine Blade Cascade, the appropriate location of slit of the pressure side and suction side is given, then blade four double-slit pumping scheme with the two same geometry suction slot is contrived. Eulerian/Eulerian numerical model for computation of condensing flow, based on the three-dimensional Reynolds averaged Navier-Stokes equations, is employed to establish two-phase homogenous flow model equations to investigate the two-phase flow problem. A computer program is exploited to involve the actual water steam thermophysical properties on the basis of the equilibrium phase change model. In virtue of a CFD solver tool named CFX software, and the homogeneous multiphase model, the numerical method has been established for the simulation of wet steam transonic flow in the blade cascades and the corresponding numerical results are analysed.The computation results show that for a single scheme the suction mass flow and mass-averaged static pressure of slot outlet from PS are bigger than that from SS. Comparison of two schemes points out that the decrease in static pressure of slot outlet and the increase in the width of slot inlet are favorable to enhance the suction mass flow for a slot at the same site.The pump effect of suction slot could improve though smaller imports angle and appropriate fillet angle. At the same time, suction slot give an impact on the flow parameter near the suction slot, which is proportional to the suction slot, the amount of current pumped by suction slot is much, the influence to cascades current parameter is greater. Therefore, The congruous design is a compromise between the aerodynamic efficiency of the stage and the dewatering efficiency of the slots.