Development of the reliable engineering method of the quality estimation of the turbine axial-radial sealing
Keywords:
axial-radial sealing, massflow coefficient of the sealing, method of the quality estimation of the sealingAbstract
Loses associated with the leakages through the turbine radial sealing are usually considered while calculating efficiency of the whole turbine stage. Wherein, massflow coefficient of the sealing often is estimated with Stodola’s equations, which includes empirical coefficients substantially depending on the particular form of the sealing. In recent times, axial-radial sealing is increasingly being used in powerful steam turbines. However, there are no reliable equations for estimating massflow coefficient of the axial-radial sealing. The purpose of the research work presented in the paper was to develop the reliable engineering method for calculating axial-radial sealing, which allows to determine massflow coefficient in the sealing considering the influence of geometrical, working parameters and offset of the sealing due to the heat expansion. Axial-radial sealing of the third high pressure turbine stage was decided to be the object of study. 10 parameters were chosen to be varied: u/c speed ratio, flow angle α1 near the shroud, angular velocity u, number of knife edges in the left side of the sealing, number of knife edges in the right side of the sealing, step between the knife edges, height of the knife edges, radial gap, width of the middle chamber, sealing offset due to the heat expancion. According to goal of the research, experiment plan, which included 132 calculation points, was built. All simulations were performed using CFD. Calculations according to the plan of the experiment allowed to obtain accurate formal metamodel and to plot dependencies of the varied parameters on the massflow coefficient. Developed engineering method allows to define massflow coefficient of the axial-radial sealing depending on its geometrical and working characteristics, also considering rotor offset caused by the heat expansion. Interactive computer program “Clearance” was developed which make possible to define value of massflow coefficient in the axial-radial sealing.
References
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Copyright (c) 2015 А. В. Бойко, А. П. Усатый, Д. И. Максюта
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