JAXA's electric propulsion systems Akira Nishizawa Emission free aircraft section Innovative Aircraft Systems Research Aircraft Systems Research Team Next Generation Aeronautical Innovation Hub Center Japan Aerospace Exploration Agency(JAXA) 1
Motivations of R&D 1. FEATHER project 2. Study of FC GT hybrid aircraft Motivations Motivations Low operating cost Higher safety Airliner Fuel saving CO Simplified operation 2 reduction Air Taxi Commuter Electric propulsion system is a goal of MEA 2020 2030 2040+ Step by step development of electrc aircraft 2
Outline of FEATHER project Mission Development of JAXA s unique electric propulsion systems FY2012 Design FY2013 Fabrication FY2014 Integration and flight test 1. Multiplexed motor 2. Regenerative air brake 3
Overview of the demonstrator Original aircraft: Diamond aircraft type HK36TTC-ECO MTOW=850kg Reduction gear Electric motor Power lever Display Monitoring unit Battery pack Under wing container 1Multiplexed motor 2Pilot interface 3Li-ion battery 4
Specification of power train Types of electric motor and inverter Motor control method Maximum total shaft power (at RPM) Maximum motor efficiency Maximum inverter efficiency Cooling Types of propeller and reduction gear Motor and inverter weight (total) Power weight ratio of electric motor Reduction gear and prop. weight Specifications Permanent magnet type synchronous motor (three phase) and IGBT inverter FOC (Field-oriented control) 60kW (2.5min. at 6586RPM), 63kW(proven at flight) 95%(94% at cruise) 93%(90% at cruise) Water cooling (motors and inverters) MT propeller of type MTV-1 and HIRTH G50(1:3.16) Motor:29.0kg (=7.24kg*4), Inverter:14.3kg(=3.56kg*4) 2.17kW/kg (w/o reduction gear) Reduction gear:8.5kg, Propeller:10.6kg 5
Multiplexed electric motor system(1/3) Our motivations 1. Avoidance of loss of engine power for single piston engine aircraft. 2. Redundancy of electric motors. Other researches 1. Distributed motors and fans for VTOL (Alex M. Stoll et al. of Joby Aviation, 14 th AIAA Aviation Technology, Integration and Operations Conference 2014, AIAA2014-2407) 2. Electric Propulsion for Vertical Flight (Michael Ricci of LaunchPoint Technologies; AHS Transformative Vertical Flight Workshop 2014, Arlington, VA ) Our selection of approach Putting multiplexed motor on a propeller shaft 6
Multiplexed electric motor system(2/3) Technical issues for us Our solutions 1. Reduction of the size and weight 2. Optimization of the number of motors 3. Isolation of failures 1. Directly coupling with each motor (additional joint parts are unnecessary) 2. Quadruplex motor based on the trade-off analysis 3. Individual contactors motor axis #1 #2 #3 #4 motor housing 7
Multiplexed electric motor system(3/3) Characteristics Compact Light weight(2.17kw/kg) High efficiency(95%) High strength of structure 220mm 3.75 kg 1 232mm 2 3 4 inverters 8
Technical challenges of multiplexed electric motor system Avoidance of complete loss of thrust at engine failure 1. Avoidance of yaw moment imbalance at one engine failure 2. Automatic detection of engine failure in the early stages Safety improvement FEATHER project Single eingine pilot license available for multi engine plane Future potencial (Thechnical challenges) 9
Regenerative air brake system(1/4) Our motivations 1. Elimination of conventional systems by multifunctionality of electric motor. 2. Regeneration of electricity by electric motor. Other researches Our selection of approach Regenerative air brake system 1. Feasibility study of regenerative soaring (J.Philip Barnes, Perican Aero Group, SAE Tech. Paper 2006-01-2422, 2006) 2. WATTsUP can recuperate 13% of energy on every approach and reduce the field length of landing(pipistrel, Aircraft News,31 Mar 2015) 1. Utilization of aerodynamic drag on the prop. due to regeneration 2. Simultaneously harvesting a certain amount of energy 10
Regenerative air brake system(2/4) Technical issues for us 1. Simplify the control of descent rate 2. Avoidance of weight penalty and hardware complexity 3. Maximization of the regenerative electricity Our solutions 1. Augmentation of descent rate by pulling the power lever 2. The simplest system configuration based on the field-oriented control method 3. Formulation of control algorithm based on the aerodynamic features Power lever Motor Generator Inverter Rectifier Capacitor Battery DC/DC Conventional Motor / Generator Inverter Battery Field-oriented control 11
Regenerative air brake system(3/4) Motor/ Generator Inverter Battery Specially designed power lever to facilitate the control of descent rate and regeneration Propeller Pitot tube N p V air System control unit Target Torque displacement Regenerative power Power lever Display V air is not necessary as the feedback parameter to maximize the regenerative power in this system. Block diagram of the regenerative air brake system 12
Technical challenges of regenerative airbrake system Windmilling propeller Lower airspeed Lower altitude descent Windmilling fan Higher airspeed Higher altitude descent Simplification of airbrake mechanism FEATHER project Efficiency improvement Future potencial (Thechnical challenges) 13
Other topics of JAXA oriented technologies for EPS 1. Development of Electric Aviation Motor Coil Using Thermal Conductive Heatresistant Insulating Material http://global.jaxa.jp/press/2013/05/20130 514_motor_coil_e.html Collaboration with Nippon Kayaku Co., LTD 2. Estimate of Airspeed w/o Pitot tube Collaboration with Tokyo University The airspeed estimate system can approximately calcurate airspeed by using the motor current and rotational number only. 14
Distributed electric fans Hybrid Propulsion System High-efficiency, ultra low emission core engine 150pax electric hybrid aircraft Electric fan Hybrid propulsion system SOFC /GT core engine Hybrid Propulsion System Technological issues to be pursued Light-weight and robust (distributed) electric fan Electric generator system (FC-GT hybrid ) Fuel and power feed distribution control 15
Thank you http://www.aero.jaxa.jp/eng/research/frontier/feather/ 16