Systems relating to axial positioning turbine casings and blade tip clearance in gas turbine engines

A gas turbine engine comprising:

• a compressor through which a flowpath is defined, the flowpath having a downstream and an upstream direction relative to a flow of working fluid therethrough;
• an inner casing defining an outboard boundary of the flowpath having an axially tilted profile so that, along the outboard boundary, the flowpath has a conical taper in the downstream direction;
• a row of circumferentially spaced rotor blades positioned in the flowpath, the rotor blades having outer tips that oppose the outboard boundary across a gap clearance defined therebetween;
• an outer casing concentrically arranged about the inner casing so to form an annulus therebetween;
• and
• a connection assembly that slidably connects the inner casing to the outer casing for axial movement between a downstream position and an upstream position;
• wherein the connection assembly includes a compression spring that axially preloads the inner casing toward the downstream position;
• wherein the inner casing includes at lease one receiving surface that defines a boundary of the annulus, the at lease one receiving surface configured to produce a net axial load on the inner casing toward the upstream position so to oppose the axial preload of the compression spring;
• wherein the connection assembly axially divides the annulus into an axially stacked downstream annulus and an upstream annulus, and wherein the connection assembly includes a seal configured to fluidly seal the downstream annulus from the upstream annulus so to maintain a pressure differential therebetween;
• and
• wherein the downstream annulus comprises an extraction passage that fluidly communicates with a downstream extraction point for producing a pressure therein that is proportional to a pressure at the downstream extraction point, and the upstream annulus comprises an extraction passage that fluidly communicates with an upstream extraction point in the flowpath for producing a pressure therein that is proportional to a pressure at the upstream extraction point.