Rotor blade for a rotary machine

A rotor blade for a rotary machine having a flowpath for working medium gases, the rotor blade having an inner end which includes a base which adapts the rotor blade to be joined to a rotatable structure, an outer end having a laterally extending, outwardly facing surface which is disposed circumferentially about an axis Ar and having a radius of curvature about the axis Ar, an airfoil having a leading edge, a trailing edge, and a suction side and a pressure side which each extend chordwise from the leading edge to the trailing edge, and a tip region which includes the outer end, which comprises:

• a plurality of airfoil sections disposed spanwise about and perpendicular to a stacking line for defining the surfaces of the airfoil, the stacking line of the airfoil extending spanwise in a radial direction, and each airfoil section having
• a leading edge,
• a trailing edge spaced chordwise from the section leading edge,
• a suction side extending from the section leading edge to the section trailing edge, and
• a pressure side extending from the section leading edge to the section trailing edge;
• a tip shroud for the rotor blade disposed in the tip region, the tip shroud including wings which extend from the sides of the airfoil, the wings including
• a pressure side wing extending from the pressure side of the airfoil having a front portion and a rear portion, having a laterally facing pressure side, and having a portion of a transition zone which extends from the pressure side of the airfoil,
• a suction side wing that extends from the suction side of the airfoil having a front portion and a rear portion, having a laterally facing suction side, and having a portion of a transition zone which extends from the suction side of the airfoil,
• a beam integral with the wings which extends laterally between the wings to divide each wing into the front portion and the rear portion, the beam further having
• a pressure side region extending laterally past the pressure side of the airfoil in the tip region of the airfoil, having a laterally facing pressure side which adapts the beam to engage a suction side of a beam of an adjacent airfoil, and having an inwardly facing surface which extends to the pressure side of the beam,
• a portion of a transition zone which extends from the pressure side of the airfoil,
• a suction side region extending laterally past the suction side of the airfoil in the tip region of the airfoil, having a laterally facing suction side which adapts the suction side of the beam to engage a pressure side of the beam of the adjacent airfoil, and having an inwardly facing surface which extends to the pressure side of the beam,
• a portion of a transition zone which extends from the suction side of the airfoil,
• a seal land extending radially outwardly from the beam, the seal land extending past the sides of the airfoil between the front and rear portions of the suction side wing and the pressure side wing and having said outwardly facing surface which extends circumferentially with respect the axis Ar and which adapts the seal land to block the leakage of working medium gases past the tip region of the rotor blade;
• and
• a transition zone formed from said transition zone portions of the wings and of the beam, the transition zone extending from a junction with the suction side of the airfoil and a junction with the pressure side of the airfoil to provide a flow path surface of the shroud which has a smooth contour;
• wherein the rotor blade has a reference normal sectioning plane P passing through a point at the junction of the transition zone to the airfoil that contains a first line perpendicular to the side of the airfoil section at that junction point and a second line passing through that junction point that is perpendicular to the first line and parallel to the stacking line of the airfoil;
• wherein a transition line is the line of intersection of the plane P with the transition zone at a junction point and defines the surface contour of the transition zone at a particular location;
• wherein each transition line has an offset distance A from the airfoil which is the distance of the projection of the transition line along the first line of the plane P perpendicular to the side of the airfoil section, has an offset distance B from the shroud which is the distance of the projection of the transition line along the second line of the sectioning plane parallel to the stacking line, and has an offset ratio which is the ratio of the offset distance A from the airfoil divided by the offset distance B from the shroud;
• wherein each transition line has a first end at the junction point and a second end at the point the transition zone terminates, the transition lines being smoothly recessed from a straight line connecting the ends of each transition line;
• wherein on at least one of said sides of the airfoil those transition lines that extend under the beam have greater bending away from the airfoil at a region closer to the airfoil on the transition line than at a region closer to the side of the shroud such that the average of offset ratios Rb of transition lines that extend under the beam are greater than one and are greater than the average of offset ratios Rw of transition lines that extend only under the rear portion of the wings.