Abstract: A method for operating a rotating detonation engine, having a radially outer wall extending along an axis; a radially inner wall extending along the axis, wherein the radially inner wall is positioned within the radially outer wall to define an annular detonation chamber having an inlet and an outlet, wherein the method includes flowing liquid phase fuel along at least one wall of the radially inner wall and the radially outer wall in a direction from the outlet toward the inlet to cool the at least one wall and heat the liquid fuel to provide a heated liquid fuel; flowing the heated liquid fuel to a mixer at the inlet to reduce pressure of the heated liquid fuel, flash vaporize the heated liquid fuel and mix flash vaporized fuel with oxidant to produce a vaporized fuel-oxidant mixture; and detonating the mixture in the annular detonation chamber.

Abstract: A method for operating a rotating detonation engine, having a radially outer wall extending along an axis; a radially inner wall extending along the axis, wherein the radially inner wall is positioned within the radially outer wall to define an annular detonation chamber having an inlet and an outlet, wherein the method includes flowing liquid phase fuel along at least one wall of the radially inner wall and the radially outer wall in a direction from the outlet toward the inlet to cool the at least one wall and heat the liquid fuel to provide a heated liquid fuel; flowing the heated liquid fuel to a mixer at the inlet to reduce pressure of the heated liquid fuel, flash vaporize the heated liquid fuel and mix flash vaporized fuel with oxidant to produce a vaporized fuel-oxidant mixture; and detonating the mixture in the annular detonation chamber.

Abstract: A combustor for a detonation engine includes a radially outer wall extending along an axis; a radially inner wall extending along the axis, wherein the radially inner wall is positioned at least partially within the radially outer wall to define an annular detonation chamber having an inlet for fuel and oxidant and an outlet; a cooling flow passage defined along at least one of the radially outer wall and the radially inner wall and comprising at least two axially spaced cooling flow passage sections, whereby a different cooling rate can be implemented in the at least two axially spaced cooling flow passage sections.

Abstract: Supercritical fluid systems and aircraft power systems are described. The systems include a compressor, a turbine, and a generator. A primary working fluid flow path has a primary working fluid that passes through the compressor, a separator, the turbine, and back to the compressor. A secondary working fluid flow path having a secondary working fluid that passes through the generator, the compressor, the separator, and back to the generator. The primary working fluid and the secondary working fluid are compressed and mixed within the compressor to form a mixture of the two fluids and the separator separates the mixture of the two fluids to direct the primary working fluid back to the turbine and the secondary working fluid to the generator.

Abstract: A diffuser may comprise an inlet and an outlet. The inlet may comprise an arcuate shape. The outlet may comprise an annular shape. The diffuser may transition from the arcuate shape at the inlet to the annular shape at the outlet. The diffuser may comprise a radially inner wall and a radially outer wall disposed opposite the radially inner wall. The radially inner wall and the radially outer wall may partially define a duct.

Abstract: A method for operating a rotating detonation engine, having a radially outer wall extending along an axis; a radially inner wall extending along the axis, wherein the radially inner wall is positioned within the radially outer wall to define an annular detonation chamber having an inlet and an outlet, wherein the method includes flowing liquid phase fuel along at least one wall of the radially inner wall and the radially outer wall in a direction from the outlet toward the inlet to cool the at least one wall and heat the liquid fuel to provide a heated liquid fuel; flowing the heated liquid fuel to a mixer at the inlet to reduce pressure of the heated liquid fuel, flash vaporize the heated liquid fuel and mix flash vaporized fuel with oxidant to produce a vaporized fuel-oxidant mixture; and detonating the mixture in the annular detonation chamber.

Abstract: A combustor for a rotating detonation engine includes an outer tapered wall extending along an axis; an inner tapered wall extending along the axis, wherein the inner tapered wall is positioned within the outer tapered wall to define an annular combustion chamber having an annular gap between the outer tapered wall and the inner tapered wall, wherein the outer tapered wall is moveable relative to the inner tapered wall along the axis, and wherein movement of the outer tapered wall relative to the inner tapered wall changes the annular gap of the annular combustion chamber. Obstacles can be positioned on either or both of inner and outer wall to enhance turbulence within the combustion chamber.

Abstract: A heat exchanger including a plurality of tubes, a header, and a plurality of flow voids. The plurality of tubes extends in a first direction through which a first fluid is configured to flow. Each of the plurality of tubes have waves that repeat at regular intervals along the first flow direction and are spaced from one another vertically and laterally in the second direction. The header extends in the first direction and is attached to each of the plurality of tubes. The header is configured to convey the first fluid to each of the plurality of tubes. The plurality of flow voids are formed between the plurality of tubes. The plurality of flow voids extend in a second direction through which a second fluid is configured to flow such that the second fluid is in thermal contact with the plurality of tubes.

Abstract: Supercritical fluid systems and aircraft power systems are described. The systems include a compressor, a turbine, and a generator. A primary working fluid flow path has a primary working fluid that passes through the compressor, a separator, the turbine, and back to the compressor. A secondary working fluid flow path having a secondary working fluid that passes through the generator, the compressor, the separator, and back to the generator. The primary working fluid and the secondary working fluid are compressed and mixed within the compressor to form a mixture of the two fluids and the separator separates the mixture of the two fluids to direct the primary working fluid back to the turbine and the secondary working fluid to the generator.

Abstract: A boost compressor assembly may comprise an outer annular structure and a plurality of blades. Each blade in the plurality of blades may be moveably coupled to the outer annular structure. The plurality of blades may be configured to deploy in response to the boost compressor assembly rotating. The plurality of blades may be configured to retract when the boost compressor assembly stops rotating.

Abstract: Supercritical fluid systems and aircraft power systems are described. The systems include a compressor, a turbine operably coupled to the compressor, a generator operably coupled to the turbine and configured to generate power, a primary working fluid flow path having a primary working fluid configured to pass through the compressor, a separator, the turbine, and back to the compressor, and a secondary working fluid flow path passing through the generator, the compressor, the separator, and back to the generator. The primary working fluid is supercritical carbon dioxide (sCO2) and the secondary working fluid is a fluid having at least one of a density less than the primary working fluid and a molecular size smaller than the primary working fluid.

Abstract: A boost compressor assembly may comprise an outer annular structure and a plurality of blades. Each blade in the plurality of blades may be moveably coupled to the outer annular structure. The plurality of blades may be configured to deploy in response to the boost compressor assembly rotating. The plurality of blades may be configured to retract when the boost compressor assembly stops rotating.

Abstract: A diffuser may comprise an inlet and an outlet. The inlet may comprise an arcuate shape. The outlet may comprise an annular shape. The diffuser may transition from the arcuate shape at the inlet to the annular shape at the outlet. The diffuser may comprise a radially inner wall and a radially outer wall disposed opposite the radially inner wall. The radially inner wall and the radially outer wall may partially define a duct.

Abstract: A heat exchanger including a plurality of tubes, a header, and a plurality of flow voids. The plurality of tubes extends in a first direction through which a first fluid is configured to flow. Each of the plurality of tubes have waves that repeat at regular intervals along the first flow direction and are spaced from one another vertically and laterally in the second direction. The header extends in the first direction and is attached to each of the plurality of tubes. The header is configured to convey the first fluid to each of the plurality of tubes. The plurality of flow voids are formed between the plurality of tubes. The plurality of flow voids extend in a second direction through which a second fluid is configured to flow such that the second fluid is in thermal contact with the plurality of tubes.

Abstract: A heat exchanger including a plurality of tubes, a header, and a plurality of flow voids. The plurality of tubes extends in a first direction through which a first fluid is configured to flow. Each of the plurality of tubes have waves that repeat at regular intervals along the first flow direction and are spaced from one another vertically and laterally in the second direction. The header extends in the first direction and is attached to each of the plurality of tubes. The header is configured to convey the first fluid to each of the plurality of tubes. The plurality of flow voids are formed between the plurality of tubes. The plurality of flow voids extend in a second direction through which a second fluid is configured to flow such that the second fluid is in thermal contact with the plurality of tubes.

Abstract: A heat exchanger including a plurality of tubes, a header, and a plurality of flow voids. The plurality of tubes extends in a first direction through which a first fluid is configured to flow. Each of the plurality of tubes have waves that repeat at regular intervals along the first flow direction and are spaced from one another vertically and laterally in the second direction. The header extends in the first direction and is attached to each of the plurality of tubes. The header is configured to convey the first fluid to each of the plurality of tubes. The plurality of flow voids are formed between the plurality of tubes. The plurality of flow voids extend in a second direction through which a second fluid is configured to flow such that the second fluid is in thermal contact with the plurality of tubes.

Abstract: A heat exchanger is disclosed herein that includes three walls that are each shaped in a wave pattern with the waves that extend in both a first lateral direction and a second lateral direction. A second wall is adjacent to and in contact with a first wall with the waves of the second wall being offset from the waves of the first wall by one-half wavelength in the first direction. The third wall is adjacent to and in contact with the second wall with the waves of the third wall being offset from the waves to the second wall by one-half wavelength in the second direction. The first wall and second wall form a first plurality of flow paths extending in the second direction, and the second wall and the third wall for a second plurality of flow paths extending in the first direction.

Abstract: A fuel mixer for mixing a fuel and an oxidizer prior to detonation in a rotating detonation engine includes a combustion channel configured to transport a final mixture of the fuel and the oxidizer for combustion. The fuel mixer also includes a mixture channel positioned upstream from the combustion channel and configured to transport a first mixture having at least some of the fuel and at least some of the oxidizer. The fuel mixer also includes a secondary outlet positioned upstream from the combustion channel and configured to output a supplemental mixture of the fuel and the oxidizer that includes at least one of the fuel or the oxidizer such that the first mixture and the supplemental mixture combine in the combustion channel to form the final mixture.

Abstract: A rotating detonation engine includes an annulus that defines a volume in which a mixture of an oxidizer and a fuel detonate in a rotating fashion, the volume defining a downstream outlet through which detonation exhaust flows. The rotating detonation engine further includes a wave arrestor positioned upstream from a location of detonation and configured to reduce a magnitude of a pressure wave traveling upstream from the location of detonation.

Abstract: A fuel mixer for mixing a fuel and an oxidizer prior to detonation in a rotating detonation engine includes a combustion channel configured to transport a final mixture of the fuel and the oxidizer for combustion. The fuel mixer also includes a mixture channel positioned upstream from the combustion channel and configured to transport a first mixture having at least some of the fuel and at least some of the oxidizer. The fuel mixer also includes a secondary outlet positioned upstream from the combustion channel and configured to output a supplemental mixture of the fuel and the oxidizer that includes at least one of the fuel or the oxidizer such that the first mixture and the supplemental mixture combine in the combustion channel to form the final mixture.