Aircraft propulsion system with intermittent combustion engine, hydraulic motor, and cooling system

An aircraft propulsion system, comprising:

• at least one hydraulic pump;
• at least one intermittent internal combustion (IC) engine configured to drive the at least one hydraulic pump;
• at least one hydraulic motor in communication with the at least one hydraulic pump and configured to drive at least one propulsor fan;
• at least one engine oil pump configured to pump an engine oil;
• and
• a cooling system that includes:
• a fluid-air heat exchanger (AIR-EO HEX) configured to transfer thermal energy between the engine oil and a flow of ambient air;
• a first fluid-to-fluid heat exchanger (EO-HF HEX) configured to transfer thermal energy between the engine oil and a flow of a hydraulic fluid;
• a second fluid-to-fluid heat exchanger (EO-EC HEX) configured to transfer thermal energy between the engine oil and a flow of an engine coolant;
• wherein the at least one hydraulic pump is configured to provide the hydraulic oil to the at least one hydraulic motor sufficient to drive the at least one hydraulic motor, and to provide sufficient motive force to the hydraulic oil to cause the hydraulic oil to pass through the at least one hydraulic motor and at least one EO-HF HEX and back to the at least one hydraulic pump;
• and
• wherein the cooling system is configured such that a flow of the engine oil passes through the AIR-EO HEX, and a first portion of the engine oil flow selectively passes through the intermittent IC engine, wherein the first portion of the engine oil flow is less than the engine oil flow.

A method of cooling components within an aircraft propulsion system, the aircraft propulsion system having a hydraulic pump, an intermittent internal combustion (IC) engine configured to drive the hydraulic pump, a hydraulic motor in communication with the hydraulic pump and configured to drive at least one propulsor fan, and at least one engine oil pump, the method comprising:

• using the at least engine oil pump to pump a flow of engine oil through a fluid-air heat exchanger (AIR-EO HEX) and a fluid-to-fluid heat exchanger (EO-HF HEX), wherein the AIR-EO HEX is configured to transfer thermal energy from the flow of engine oil to a flow of ambient air in communication with the AIR-EO HEX, and wherein the EO-HF HEX is configured to transfer thermal energy from a flow of a hydraulic fluid to the flow of engine oil;
• and using the hydraulic pump to power the hydraulic motor using the flow of hydraulic oil, and to pump the hydraulic oil through the EO-HF HEX and back to the hydraulic pump;
• and using the at least one engine coolant pump to pump engine coolant to and through a second fluid-to-fluid heat exchanger (EO-EC HEX) configured to transfer thermal energy between the flow of the engine oil and a flow of an engine coolant, and at least one engine coolant pump, and to and through the intermittent IC engine;
• and wherein the motive force provided to the engine oil produced by the at least one engine oil pump is sufficient to pass the engine oil to and through the EO-EC HEX, and thereafter to pass the engine oil to and through the intermittent IC engine.