Rotary internal combustion engine with exhaust purge

A compound engine system comprising a compressor, a turbine and a rotary engine, the rotary engine having a stator body having walls defining an internal cavity and a rotor body mounted for eccentric revolutions within the cavity, the rotor and stator bodies cooperating to provide rotating chambers of variable volume when the rotor moves relative to the stator, the system comprising spaced apart primary and secondary inlet ports and an exhaust port defined in the stator body and communicating with the cavity, the primary and secondary inlet ports communicating with the compressor and the exhaust port communicating with the turbine, the secondary inlet port being located rearwardly of the primary inlet port and forwardly of the exhaust port relative to a direction of the revolutions, the primary inlet port and the exhaust port being positioned to define a volumetric compression ratio of the engine lower than a volumetric expansion ratio of the engine, and wherein for each of the chambers, each revolution of the rotor includes an exhaust portion where the chamber contains the exhaust port, a purge portion being part of the exhaust portion where the chamber contains both the secondary inlet port and the exhaust port, and a primary intake portion where the chamber contains the primary inlet port, the exhaust portion and the primary intake portion being non-overlapping such that the rotor body prevents communication between the primary inlet and exhaust ports through the rotating chambers in any rotor position.

A method of operating a rotary engine, the method comprising, through each orbital revolution and rotary motion of a rotor of the engine and for each chamber thereof:

• filling the chamber with air through an inlet port;
• compressing the air by reducing a volume of the chamber according to a volumetric compression ratio;
• mixing the compressed air with fuel and combusting a resulting air-fuel mixture;
• expanding combustion gases from the combustion by increasing a volume of the chamber according to a volumetric expansion ratio higher than the volumetric compression ratio;
• expulsing the combustion gases through a primary exhaust port;
• closing a communication of the chamber with the primary exhaust port;
• and
• purging the combustion gases through a secondary exhaust port distinct from the primary exhaust port with air entering the chamber through a purge port distinct and spaced apart from the inlet port.