Gas turbine engine with partial inlet vane

A gas turbine engine comprising:

• a propulsive fan including an array of circumferentially spaced blades configured for rotation and extending radially between a root and a tip with a maximum radial dimension between the root and the tip defining a maximum blade span;
• an annular inlet including:
• an axially extending wall, the wall having an upstream wall portion extending axially upstream from the fan blades, the upstream wall portion defining an inlet flow path for directing air to the fan, and
• a plurality of vanes circumferentially spaced around the annular inlet and extending radially inwardly from the upstream wall portion, a maximum radial distance between a tip of the vanes and the upstream wall portion defining a maximum height of the vanes, the maximum height of the vanes being at most 50% of the maximum blade span, the vanes being oriented to swirl a flow upstream of the tip of the blades of the fan such that an exit angle induced in the flow by the vanes reduces a relative Mach number of the flow at the tip of the blades, wherein the height of the vanes varies between a leading edge and a trailing edge of the vanes.

A method of reducing a relative Mach number at tips of fan blades of a gas turbine engine, the method comprising:

• directing a flow of air to the fan blades through an inlet flow path having a downstream radial height adjacent the fan blades, including:
• swirling the flow of air upstream of the blade tips within an annular outer portion of the inlet flow path to change an angle of the flow within the annular outer portion such that the relative Mach number at the blade tips is reduced, the annular outer portion including a circumferential array of vanes extending a radial distance from a wall surrounding the inlet flow path, the radial distance defining a height of the vanes, the height being at most 50% of the downstream radial height, wherein the height of the vanes varies between a leading edge and a trailing edge of the vanes;
• and
• allowing the flow of air to flow freely within a remaining central portion of the inlet flow path.