Abstract: A gas turbine engine is provided including a turbomachine having a compressor section, a combustion section, and a turbine section arranged in serial flow order; a rotor assembly driven by the turbomachine, the rotor assembly, the turbomachine, or both comprising a substantially annular duct relative to the centerline of the gas turbine engine, the annular duct defining a flowpath; a heat exchanger positioned within the annular duct and extending substantially continuously along the circumferential direction, the heat exchanger comprising a first material defining a heat exchange surface exposed to the flowpath, wherein the first material defines a heat exchange coefficient and wherein the heat exchange surface defines a surface area (A), and wherein the heat exchanger has an effective transmission loss (ETL) of between 5 decibels and 1 decibel for an operating condition.

Abstract: A lift fan apparatus includes: a rotor having at least one rotatable hub carrying at least one row of blades; a duct surrounding the rotor, the duct including spaced-apart peripheral walls extending between an inlet and an exit, the peripheral walls collectively defining a flow channel which includes a diffuser disposed downstream of the rotor, in which a flow area at the exit is greater than a flow area at the rotor; and a plurality of spaced-apart splitters disposed in the diffuser, each of the splitters having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the splitters divide the diffuser into a plurality of side-by-side flow passages.

Abstract: A ducted fan is provided including a fan casing surrounding a plurality of fan blades mounted to a rotating drive shaft. The plurality of blades define a tip stagger angle of greater than 68 degrees and the fan casing defines an annular recess defined by an inner wall of the fan casing, the annular recess extending about the circumferential direction proximate a blade tip of each of the plurality of blades. The annular recess may define an average recess depth greater than 10 percent of the tip chord length. The annular recess may also define a length ratio equal to a recess length over the tip axial chord length that is greater than 1.5.

Abstract: A heat exchanger apparatus includes: spaced-apart peripheral walls extending between an inlet and an outlet, the peripheral walls collectively defining a flow channel which includes a diverging portion downstream of the inlet, in which a flow area is greater than a flow area at the inlet; a plurality of spaced-apart fins disposed in the flow channel, each of the fins having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the fins divide at least the diverging portion of the flow channel into a plurality of side-by-side flow passages; and a heat transfer structure disposed within at least one of the fins.

Abstract: A ducted fan is provided including a fan casing surrounding a plurality of fan blades mounted to a rotating drive shaft. The plurality of blades define a tip stagger angle of greater than 68 degrees and the fan casing defines an annular recess defined by an inner wall of the fan casing, the annular recess extending about the circumferential direction proximate a blade tip of each of the plurality of blades. The annular recess may define an average recess depth greater than 10 percent of the tip chord length. The annular recess may also define a length ratio equal to a recess length over the tip axial chord length that is greater than 1.5.

Abstract: An open rotor airfoil apparatus includes: an airfoil body having pressure and suction sides extending in span from a root to a tip, and in chord between leading and trailing edges. A majority of the leading edge in an outer portion of the airfoil body has a sweep equal to or greater than a predetermined sweep profile, selected to produce a blade-relative velocity component perpendicular to the leading edge, at a tip radius, of Mach 0.75 or less, and to produce a blade-relative velocity component perpendicular to the leading edge, at 65% of tip radius, of Mach 0.87 or less, with the blade-relative velocity component perpendicular to the leading edge varying linearly between the two limits, in the presence of transonic or supersonic relative velocity conditions. Each of the blades has a leading edge thickness greater than 0.45% of the chord, measured at a 0.5% chordwise location.

Abstract: A lift fan apparatus includes: a rotor having at least one rotatable hub carrying at least one row of blades; a duct surrounding the rotor, the duct including spaced-apart peripheral walls extending between an inlet and an exit, the peripheral walls collectively defining a flow channel which includes a diffuser disposed downstream of the rotor, in which a flow area at the exit is greater than a flow area at the rotor; and a plurality of spaced-apart splitters disposed in the diffuser, each of the splitters having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the splitters divide the diffuser into a plurality of side-by-side flow passages.

Abstract: A variable-solidity propeller apparatus, comprising a propeller having at least one rotatable hub carrying at least one row of propeller blades, wherein the propeller has a first configuration in which the propeller has a first average solidity, and a second configuration in which the propeller has a second average solidity which is greater than the first average solidity.

Abstract: An unducted thrust producing system is provided that can include a rotating element having an axis of rotation about a central longitudinal axis and comprising a plurality of blades attached to a spinner; a stationary element positioned aft of the rotating element; and an inlet positioned between the rotating element and the stationary element such that the inlet passes radially inward of the stationary element. The rotating element defines an annular valley positioned between a first annular crown and a second annular crown, and the inlet defines an open area positioned aft of the second annular crown.

Abstract: An airfoil section of a blade for an open rotor includes: a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein a chord of the airfoil section is defined as a straight-line distance between the leading edge and the trailing edge; the airfoil section has a meanline defined midway between the pressure side and the suction side; and the meanline is shaped such that, in the presence of predetermined transonic or supersonic relative velocity conditions, maximum and minimum ideal Mach numbers on the suction side will lie within a 0.08 band, between 25% and 80% percent of the chord.

Abstract: A heat exchanger apparatus includes: spaced-apart peripheral walls extending between an inlet and an outlet, the peripheral walls collectively defining a flow channel which includes a diverging portion downstream of the inlet, in which a flow area is greater than a flow area at the inlet; a plurality of spaced-apart fins disposed in the flow channel, each of the fins having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the fins divide at least the diverging portion of the flow channel into a plurality of side-by-side flow passages; and a heat transfer structure disposed within at least one of the fins.

Abstract: An airfoil section of a blade for an open rotor includes: a pressure side and a suction side, the pressure side and the suction side intersecting at a leading edge and a trailing edge, wherein a chord of the airfoil section is defined as a straight-line distance between the leading edge and the trailing edge; the airfoil section has a meanline defined midway between the pressure side and the suction side; and the meanline is shaped such that, in the presence of predetermined transonic or supersonic relative velocity conditions, maximum and minimum ideal Mach numbers on the suction side will lie within a 0.08 band, between 25% and 80% percent of the chord.

Abstract: An open rotor airfoil apparatus includes: an airfoil body having pressure and suction sides extending in span from a root to a tip, and in chord between leading and trailing edges. A majority of the leading edge in an outer portion of the airfoil body has a sweep equal to or greater than a predetermined sweep profile, selected to produce a blade-relative velocity component perpendicular to the leading edge, at a tip radius, of Mach 0.75 or less, and to produce a blade-relative velocity component perpendicular to the leading edge, at 65% of tip radius, of Mach 0.87 or less, with the blade-relative velocity component perpendicular to the leading edge varying linearly between the two limits, in the presence of transonic or supersonic relative velocity conditions. Each of the blades has a leading edge thickness greater than 0.45% of the chord, measured at a 0.5% chordwise location.

Abstract: A variable-solidity propeller apparatus, comprising a propeller having at least one rotatable hub carrying at least one row of propeller blades, wherein the propeller has a first configuration in which the propeller has a first average solidity, and a second configuration in which the propeller has a second average solidity which is greater than the first average solidity.

Abstract: An unducted thrust producing system is provided that can include a rotating element having an axis of rotation about a central longitudinal axis and comprising a plurality of blades attached to a spinner; a stationary element positioned aft of the rotating element; and an inlet positioned between the rotating element and the stationary element such that the inlet passes radially inward of the stationary element. The rotating element defines an annular valley positioned between a first annular crown and a second annular crown, and the inlet defines an open area positioned aft of the second annular crown.