A compound engine assembly for use as an auxiliary power unit for an aircraft and including an engine core with internal combustion engine(s), a compressor having an outlet in fluid communication with an engine core inlet, a bleed conduit in fluid communication with the compressor outlet through a bleed air valve, and a turbine section having an inlet in fluid communication with the engine core outlet and configured to compound power with the engine core. The turbine section may include a first stage turbine having an inlet in fluid communication with the engine core outlet and a second stage turbine having an inlet in fluid communication the first stage turbine outlet. A method of providing compressed air and electrical power to an aircraft is also discussed.

A method of operating a rotary engine including a rotor engaged to a shaft and rotationally received in a housing to define a plurality of working chambers of variable volume, including delivering a pilot quantity of fuel into a pilot cavity in successive communication with the working chambers, igniting the pilot quantity of fuel within the pilot cavity, and delivering a main quantity of fuel into the working chambers downstream of the successive communication of the pilot cavity with the working chambers, where at least one of the pilot quantity and the main quantity is varied between successive rotations of the shaft.

A method of operating an engine assembly receiving fuel, including admitting atmospheric air at a temperature T.sub.1 through an inlet of a compressor having a pressure ratio of PR.sub.GT, compressing the air in the compressor, cooling the compressed air from the compressor through an intercooler to cool the air from a temperature T.sub.BIC to a temperature T.sub.AIC, delivering the cooled compressed air from the intercooler to an inlet of an intermittent internal combustion engine having an effective volumetric compression ratio r.sub.VC, and further compressing the air in the intermittent internal combustion engine before igniting the fuel, where ${\left({\mathrm{PR}}_{\mathrm{GT}}\right)}^a{\left(r_{\mathrm{VC}}\right)}^b\left(\frac{T_{\mathrm{AIC}}}{T_{\mathrm{BIC}}}\right)\left(\frac{T_1}{T_A}\right)<1.$
An engine assembly is also discussed.

A rotary engine that starts and operates on compression-ignition of a heavy fuel without a secondary ignition source. The rotary engine includes a rotor housing that forms an epitrochoidal-shaped chamber having linear side portions extending between rounded end portions. A three-flanked rotor is disposed in the chamber to rotate and operate in a manner similar to that of a common Wankel-style rotary engine. The rotor and chamber are configured to provide a compression ratio sufficient to produce compression-ignition of a heavy fuel. The rotor includes apex seal and side seal mounting blocks formed from hardened materials and that are simply removable from the rotor for replacing apex and side seals. The apex seals may include multiple non-parallel seal members at each apex and the apex seals and the side seals may overlap or intersect a corner seal to increase sealing under high compression loads produced by the rotor/chamber configuration.

A rotary internal combustion engine (ICE) has: a housing defining a rotor cavity; a rotor received within the rotor cavity to define working chambers of variable volume around the rotor, the rotor having circumferentially spaced peripheral apex seals biased radially outwardly in sliding engagement against a peripheral wall of the housing to separate the working chambers from one another, the housing having a fluid passage defined therethrough and opening into an inner surface of the peripheral wall; and an injector having a lubricant inlet hydraulically connected to a lubricant source, an actuation inlet hydraulically connected to a source of an actuation fluid, and a lubricant outlet, the injector having an open state in which the lubricant outlet is in fluid flow communication with the fluid passage upon the actuation fluid received within the injector and a closed state in which the lubricant outlet is disconnected from the fluid passage.

A method of combusting fuel, e.g. heavy fuel, in a rotary engine, including injecting a main quantity of fuel directly into a combustion chamber to form a first fuel-air mixture having a first air-fuel equivalence ratio λ higher than 1, injecting a pilot quantity of fuel into a pilot subchamber to form a second fuel-air mixture having a second air-fuel equivalence ratio λ smaller than the first air-fuel equivalence ratio, igniting the second fuel-air mixture within the pilot subchamber, using the ignited second fuel-air mixture from the pilot subchamber to ignite the first fuel-air mixture, and injecting a supplemental quantity of fuel directly into the combustion chamber after igniting the first fuel-air mixture, upstream of an exhaust port of the rotary engine with respect to a direction of rotation of the rotor. A rotary engine with interburner fuel injector is also discussed.

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.

Sealing in rotary positive displacement machines based on trochoidal geometry that comprise a helical rotor that undergoes planetary motion within a helical stator is described. Seals can be mounted on the rotor, the stator, or both. The rotor can have a hypotrochoidal cross-section, with the corresponding stator cavity profile being the outer envelope of the rotor as it undergoes planetary motion, or the stator cavity can have an epitrochoidal cross-section with the corresponding rotor profile being the inner envelope of the trochoid as it undergoes planetary motion. In some embodiments, the geometry is offset in a manner that provides advantages with respect to sealing in the rotary machine. In multi-stage embodiments, the rotor-stator geometry remains substantially constant or varies along the axis of the rotary machine.

A rotary combustion engine, such as a Wankel engine has a rotor with a rotor pocket for receiving air-fuel mixture that is combusted therein to propel the rotor within the housing. Rotor air channels extend from an inlet that is configured in the compression chamber to an outlet configured in the rotor pocket to deliver compressed air-fuel mixture to said rotor pocket. The rotor air channels have an open portion, open on the face of the rotor and a closed portion extending as a conduit into the rotor to the rotor pocket. Fuel may be delivered to the rotor air channel from a rotor-gear fuel conduit that receives fuel from the fixed gear or a side-wall fuel conduit that receives fuel from a housing side-wall injector through a side-wall fuel transfer port. Rotor air channels may be configured to direct air-fuel streams to intercept one another to enhance combustion.

A rotary combustion engine, such as a Wankel engine has a rotor with a rotor pocket for receiving air-fuel mixture that is combusted therein to propel the rotor within the housing. Rotor air channels extend from an inlet that is configured in the compression chamber to an outlet configured in the rotor pocket to deliver compressed air-fuel mixture to said rotor pocket. The rotor air channels have an open portion, open on the face of the rotor and a closed portion extending as a conduit into the rotor to the rotor pocket. Fuel may be delivered to the rotor air channel from a rotor-gear fuel conduit that receives fuel from the fixed gear or a side-wall fuel conduit that receives fuel from a housing side-wall injector through a side-wall fuel transfer port. Rotor air channels may be configured to direct air-fuel streams to intercept one another to enhance combustion.