Fan containment structure having contoured shroud for optimized tip clearance

A fan containment structure comprising:

• an annular inner fan casing with a leading edge, a trailing edge, and having an inner annular surface, the inner annular surface being formed of an abradable material, the inner annular surface of the abradable material having a contour that has at least two different linear slopes in opposite directions between the leading edge and the trailing edge wherein, the abradable material further comprises a contoured surface characterized by a substantially triangular shape.

An abradable fan containment structure within a fan section of a turbofan engine, the fan section of the turbofan engine having fan blades with blade tips and an abradable fan shroud, the abradable shroud assembly comprising:

• an inner fan casing including an abradable material, the abradable material having an inner annular surface that is substantially triangular in cross-section along the axial length, the inner fan casing circumscribing the fan blades and the inner annular surface being disposed adjacent to the blade tips of the fan blades within the fan section wherein, the abradable material further comprises a contoured surface characterized by a substantially trapezoidal shape during operation of the engine.