US Patent 10501200 Engine assembly for an auxiliary power unit

An auxiliary power unit having internal combustion engine(s) in driving engagement with an engine shaft, a generator having a generator shaft drivingly engaged to the engine shaft, a compressor having an outlet in communication with the internal combustion engine inlet, and a turbine having an inlet in communication with the internal combustion engine outlet. The turbine may be a first stage turbine, and the assembly may include a second stage turbine having an inlet in communication with the first stage turbine outlet. A method of providing electrical power to an aircraft is also discussed.