Aerodynamic damping of the vibrations of the vanes in turbines as a function of the spacing and the marginal angle of the grid

The density and the marginal angle of a grid are the dimensionless numbers which determine the overall characteristics of grids exposed to a nonstationary flow, which is of practical importance in the determination of the aerodynamic damping forces. The GD-1 equipment at the Academy of Sciences of the Ukrainian SSR was used. The system for generating vibrations in the equipment is described. The investigations show that the dependence of the aerodynamic damping on the Strouhal number is qualitatively the same for the flow in grids with different spacings and for the vibrations of a single vane in a current. The logarithmic decrement of the vibrations, which characterizes the aerodynamic damping, is proportional to the dimensionless ratio between the mass criterion and the Strouhal number. The character of the effect of the Strouhal number on the aerodynamic damping does not depend on the relative spacing, and the effect of the latter on the aerodynamic damping does not depend on the Strouhal number at k > l. The causes of the aerodynamic damping increasing as the spacing of the grid decreases are discussed.