Auxiliary power unit with combined cooling of generator

Abstract

An auxiliary power unit for an aircraft, including an internal combustion engine having a liquid coolant system, a generator drivingly engaged to the internal combustion engine and having a liquid coolant system distinct from the liquid coolant system of the internal combustion engine, a first heat exchanger in fluid communication with the liquid coolant system of the internal combustion engine, a second heat exchanger in fluid communication with the liquid coolant system of the generator, an exhaust duct in fluid communication with air passages of the heat exchangers, and a fan received in the exhaust duct and rotatable by the internal combustion engine for driving a cooling air flow through the air passages. The liquid coolant system of the engine may be distinct from fuel and lubricating systems of the auxiliary power unit. A method of cooling a generator and an internal combustion engine is also discussed.

1 . A method of cooling a generator and an internal combustion engine of an auxiliary power unit for an aircraft, the method comprising:
 circulating a first liquid coolant through the internal combustion engine;   circulating a second liquid coolant through the generator; and   driving a cooling air flow in heat exchange relationship with the first and second liquid coolants using a fan driven by the internal combustion engine.   
     
     
         2 . The method as defined in  claim 1 , wherein the first coolant is distinct from any fuel and lubricating system of the auxiliary power unit. 
     
     
         3 . The method as defined in  claim 1 , wherein the internal combustion engine is a Wankel rotary engine including a rotor having three apex portions mounted for eccentric revolutions within an internal cavity defined in a housing, the internal cavity having an epitrochoid shape with two lobes. 
     
     
         4 . The method as defined in  claim 1 , wherein the fan is driven by the internal combustion engine through a mechanical engagement between the fan and the internal combustion engine.