Stator structure for a rotary machine

A stator structure for a rotary machine, the rotary machine having an annular flowpath for working medium gases, having a stator assembly which extends circumferentially to bound the flowpath for working medium gases, and having a rotor assembly having an axis of rotation A and an array of rotor blades which extend radially outwardly across the working medium flowpath into close proximity with the stator assembly, the stator structure comprising:

• an inner case which extends circumferentially about the working medium flowpath to bound the flowpath for working medium gases, the inner case having a first hoop strength characteristic and a flange which extends circumferentially about the case, the flange having a plurality of holes extending through the flange which adapt the flange to receive a plurality of nut and bolt means;
• an outer case spaced radially outwardly from the inner case, the outer case having a second hoop strength characteristic which is less than the first hoop strength characteristic over at least a portion of the outer case;
• a support assembly which extends between the outer case and the inner case, the support assembly including
• a bracket which extends circumferentially about the interior of the outer case, the bracket having
• a cylindrically shaped first section which extends axially inwardly of the outer case and which is integrally attached to the outer case,
• a plurality of tab-like projections which extend axially from the first section toward the flange of the inner case and which are circumferentially spaced one from the other leaving a first gap G.sub.1 therebetween, each projection having a first portion which extends axially and a second portion which extends radially inwardly and which has an axial thickness T.sub.b, each second portion having a pair of arms, each of which extend circumferentially from a side of the second portion toward the adjacent arm leaving a circumferential spline gap G.sub.2 therebetween which is smaller than the first gap G.sub.1 such that the arm has an outwardly facing surface which radially bounds the first gap,
• a plurality of spline type spacers, each spacer having a hole extending therethrough in the axial direction and being adapted by the hole to receive a bolt for integrally attaching the spacer to the flange, the spacer being disposed in an associated spline gap between a pair of projections on the bracket to form a spline type connection between the outer case and the inner case, the spacer having an axial thickness T.sub.s which is greater than the axial thickness T.sub.b of the projection, the spacer having a pair of arms disposed in the first gap G.sub.1 each spacer arm extending circumferentially in the gap G.sub.1 and having an inwardly facing surface which faces in the radial direction toward the outwardly facing surface on the second portion of the tab-like projection, the radial height R.sub.a of the arms being less than the radial height R.sub.g of the gap G.sub.1,
• a plurality of retainer plates, each retainer plate facing the flange and having at least two holes therethrough which are aligned with a pair of circumferentially spaced holes in the flange, the retainer plate and flange trapping the second portion of the bracket and the spline type spacer in the axial direction;
• a plurality of nut and bolt means, each having a shaft which passes through the associated holes in the spline type spacer and the flange for urging the spacer against the flange, trapping the second portion of the bracket between the flange and the retainer, and integrally attaching the spacer to the flange;
• wherein the spline type connection positions the outer case from the inner case and the difference in axial thickness between the spacer and the second portion of the bracket permits relative movement between the bracket and the spacer in the radial direction to accommodate radial growth of the inner case outwardly with respect to the outer case, wherein the engagement between the arms of the spline type spacer and the second portion of the bracket limits outward movement of the outer case with respect to the inner case under abnormal operative conditions such as a containment operative condition and permits load sharing between the outer case and the relatively strong inner case and wherein the first portion of each projection which extends axially has reduced stiffness in the radial direction in comparison to the second portion of the tab like projection which extends radially and is deflectable outwardly to accommodate a sudden movement outwardly during a containment operative condition.