An engine that uses detonation for generating energy includes a housing; an inlet configured to inject a fuel mixture into an ignition region of the housing, the inlet being attached to the housing; an ignitor located in the ignition region and configured to ignite the fuel mixture; a deflagration to detonation, DDT, region in fluid communication and downstream from the ignition region; a pair of electrodes located in the DDT region and configured to apply nanosecond repetitive voltage pulses to the DDT region; and a detonation region, within the housing, in fluid communication and downstream from the DDT region. The nanosecond repetitive voltage pulses generate a non-thermal plasma that transition a combustion front propagation through the housing from a deflagration mode to a detonation mode.

An engine that uses detonation for generating energy includes a housing; an inlet configured to inject a fuel mixture into an ignition region of the housing, the inlet being attached to the housing; an ignitor located in the ignition region and configured to ignite the fuel mixture; a deflagration to detonation, DDT, region in fluid communication and downstream from the ignition region; a pair of electrodes located in the DDT region and configured to apply nanosecond repetitive voltage pulses to the DDT region; and a detonation region, within the housing, in fluid communication and downstream from the DDT region. The nanosecond repetitive voltage pulses generate a non-thermal plasma that transition a combustion front propagation through the housing from a deflagration mode to a detonation mode.

A computer-implemented method for multi-mode operation of a combustion system, a combustion system, and a heat engine are provided. The method includes initializing combustion of a fuel/oxidizer mixture, determining whether conditions at the combustion system meet or exceed a first threshold operating parameter, transitioning to detonation combustion of the fuel/oxidizer mixture if conditions at the combustion system meet or exceed the first threshold operating parameter, and maintaining or increasing fuel flow through a deflagrative fuel circuit if conditions at the combustion system do not meet or exceed the first threshold operating parameter.

A computer-implemented method for multi-mode operation of a combustion system, a combustion system, and a heat engine are provided. The method includes initializing combustion of a fuel/oxidizer mixture, determining whether conditions at the combustion system meet or exceed a first threshold operating parameter, transitioning to detonation combustion of the fuel/oxidizer mixture if conditions at the combustion system meet or exceed the first threshold operating parameter, and maintaining or increasing fuel flow through a deflagrative fuel circuit if conditions at the combustion system do not meet or exceed the first threshold operating parameter.

Aircraft power plants including combustion engines, and associated methods for recuperating waste heat from such aircraft power plants are described. A method includes transferring the heat rejected by the internal combustion engine to supercritical CO.sub.2 (sCO.sub.2) used as a working fluid in a heat engine. The heat engine converts at least some the heat transferred to the sCO.sub.2 to mechanical energy to perform useful work onboard the aircraft.

Aircraft power plants including combustion engines, and associated methods for recuperating waste heat from such aircraft power plants are described. A method includes transferring the heat rejected by the internal combustion engine to supercritical CO.sub.2 (sCO.sub.2) used as a working fluid in a heat engine. The heat engine converts at least some the heat transferred to the sCO.sub.2 to mechanical energy to perform useful work onboard the aircraft.

Aircraft power plants and associated methods are provided. A method for driving a load on an aircraft includes: transferring motive power from an internal combustion (IC) engine to the load; discharging a flow of first exhaust gas from the IC engine when transferring motive power from the IC engine to the load; receiving the flow of first exhaust gas from the IC engine into a combustor; mixing fuel with the first exhaust gas in the combustor and igniting the fuel to generate a flow of second exhaust gas; receiving the flow of second exhaust gas at a turbine and driving the turbine with the flow of second exhaust gas from the combustor; and transferring motive power from the turbine to the load.

A rotating detonation engine can include an annular combustion chamber, an adjustable exhaust nozzle, and a nozzle actuator arrangement. The annular combustion chamber can have repetitive high frequency combustion and can include an outlet. The nozzle can be coupled to that outlet to receive exhaust reactants expelled therefrom. The nozzle can include elongated fins arranged in a conical shape having inner surfaces, outer surfaces, and distal ends. The fins can include outer and inner sets of fins, can contract toward a closed position, and can expand toward an open position. Distal ends of the fins can define a nozzle outlet having variable diameters. The nozzle actuator arrangement can have fin adjusters that adjust the fins between the closed and open positions when power is applied to a power transmitter coupled to the fin adjusters during engine operations.

A rotating detonation engine can include an annular combustion chamber, an adjustable exhaust nozzle, and a nozzle actuator arrangement. The annular combustion chamber can have repetitive high frequency combustion and can include an outlet. The nozzle can be coupled to that outlet to receive exhaust reactants expelled therefrom. The nozzle can include elongated fins arranged in a conical shape having inner surfaces, outer surfaces, and distal ends. The fins can include outer and inner sets of fins, can contract toward a closed position, and can expand toward an open position. Distal ends of the fins can define a nozzle outlet having variable diameters. The nozzle actuator arrangement can have fin adjusters that adjust the fins between the closed and open positions when power is applied to a power transmitter coupled to the fin adjusters during engine operations.

A combustor for a rotating detonation engine includes a radially outer wall extending along an axis (A); a radially inner wall extending along the axis (A), wherein the radially inner wall is positioned within the radially outer wall to define an annular detonation chamber having an inlet for fuel and oxidant and an outlet; a first passage for feeding at least one of the fuel and the oxidant along a first passage axis (a.sub.1) to the inlet; a second passage for feeding at least one of the fuel and the oxidant along a second passage axis (a.sub.2) to the inlet, wherein the second passage axis is arranged at an angle (α) relative to the first passage axis whereby mixing of flow from the first passage and the second passage is induced.