Rotary machine

An axial flow gas turbine engine having an axis of rotation Ar which includes a compressor having a flow path for working medium gases, the flow path having a mean flow line in the compressor which converges radially inwardly with a negative slope whose absolute value is greater at the aft region of the compressor than the mid-region of the compressor, and a bearing for supporting a rotor assembly, which comprises:

• a rotor assembly having
• a rotor shaft which engages the bearing,
• a fan rotor disk rotatable with the shaft and supported from the bearing, the fan rotor disk having a rim, a web and a bore,
• a plurality of fan rotor blades extending outwardly from the rotor disk, and
• a drum rotor extending rearwardly from the fan rotor disk, the drum rotor assembly having a
• A. first end which is attached to the fan rotor disk to support the drum rotor from the fan rotor disk,
• B. a second end spaced rearwardly from the first end having a rearmost rotor disk and blade assembly, the rotor disk including a rim, a web and a bore which is spaced radially from the rim by the web,
• C. at least three arrays of rotor blades, the arrays being spaced axially one from the other and extending outwardly in a generally radial direction from the drum rotor, at least one of the arrays of rotor blades being a first array of rotor blade having a tip at each rotor blade which is angled toward the axis Ar in the rearward direction with an angle greater than fifteen degrees (15°) as measured from a reference line parallel to the axis Ar and passing through the top of the airfoil at a first axial location,
• D. at least one knife edge seal element disposed between each pair of arrays of rotor blades, each element extending circumferentially about the drum rotor and extending outwardly from the drum rotor;
• a stator assembly which extends circumferentially about the rotor assembly which includes,
• at least one circumferentially extending seal land disposed radially outward of each of said knife edge elements and at least one circumferentially extending rubstrip disposed radially outwardly of each of said arrays of rotor blades in the low pressure compressor, the first rubstrip being disposed outwardly of the first array of rotor blades and being formed of an elastomeric material, the rubstrip having an average diameter Dav in the non-operative condition at the first axial location, the rubstrip being disposed about said array of rotor blades and extending rearwardly at about the same angle as the tip of the rotor blade and being radially oriented with respect to the airfoil tip with a nominal clearance dimension and a tolerance band having a minimum clearance dimension and a maximum clearance dimension,
• an outer case formed from a circumferentially continuous structure which is split longitudinally into at least two axially and circumferentially extending portions, the circumferentially extending portions being joined together in the assembled condition and supporting and positioning the rubstrip such that the rubstrip is not a perfect circle at the first axial location;
• wherein the rotor blade has a stacking line S and the first axial location is axially aligned with the intersection of the stacking line S with the tip of the rotor blade and wherein the rotor blade and the rubstrip at the average diameter Dav have an interference fit at the minimum clearance dimension with the average diameter Dav of the rubstrip in the non-operative condition;
• wherein the clearance between said rotor blade and said rubstrip of the outer air seal increases under operative conditions as the midportion of the rotor assembly deflects radially outwardly and the arrays of rotor blades move axially forwardly toward the bearing and away from the frustoconical outer air seal;
• and,
• wherein the clearance is smaller than if the same tolerance band were used and the minimum clearance was not an interference fit at said first axial location.