Engineering Method for Air-Cooling Design of Two-Seat Propeller-Driven Aircraft Powered by Fuel Cells

Abstract

The application of fuel-cell technology to aircraft propulsion and/or energy supply is becoming of great interest for undoubted advantages in terms of pollution emissions and noise, features particularly important for commuter airplanes that usually take off and land from and in urban areas. The conversion of conventional aircraft into more/all-electric one tends to be based on the installation of such innovative systems. A better understanding of problems related to fuel cells applied to aeronautics is sought by the European Commission funded project environmentally friendly intercity aircraft powered by fuel cells (ENFICA-FC). The main objective of the ENFICA-FC project is to develop and to validate the use of a fuel-cell based power system for propulsion of an all-electric aircraft. The fuel-cell system will be installed in a light sport aircraft (Rapid 200) that will be flown and performance tested as a proof of functionality and future applicability. Specific aspects have to be investigated in the onboard installation of the innovative system and new design indications have to be pointed out in order to fulfill the conversion. One of the key items under investigation is the simulation of existing cooling system and the evaluation of motor and fuel-cell temperature; the temperature has to be maintained within the limits established by manufacturers of critical systems during all likely operating conditions as indicated by aeronautic regulations for general aviation. The computational problem addressed in this paper is the numerical computational fluid dynamics (CFD) simulation of the existing air-cooling system that satisfies air request for cooling and venting. An engineering model has been developed and it is used to support air inlet and outlet design. The flow is reasonably approximated by a potential flow plus boundary layer; hence, total upstream pressure losses are neglected except for those within the thin boundary layer. Pressure recovery of incoming cooling air and pressure coefficient distribution have been studied by using VSAERO panel code, and the optimal position of cooling and venting intakes is defined according to aerodynamic results. Propeller effects are included by referring to an optimal propeller specifically designed for the ENFICA-FC project. Propeller slip-stream wake is modeled by an actuator disk plus a swirl membrane and used to study the problem of motor, electronic, and fuel cells’ cooling during takeoff.