The University of Nottingham - PDF Free Download

Power Electronics Research at the University of Nottingham The University of Nottingham Professor Pat Wheeler Power Electronics, Machines and Control (PEMC) Research Group UNIVERSITY OF NOTTINGHAM, UK Professor Pat Wheeler Email: pat.wheeler@nottingham.ac.uk Email: pat.wheeler@nottingham.ac.uk

Technology Development from the More Electric Aircraft to All Electric Flight UNIVERSITY OF NOTTINGHAM, UK Professor Pat Wheeler Email: pat.wheeler@nottingham.ac.uk

Introduction More Electric Aircraft: why and technology progress Aircraft electrical equipment, generators and power Systems All Electric Aircraft Technology requirements, Progress to date and future prospects Electromagnetically assisted aircraft take-off Technology and benefits

The More Electric Aircraft What is a More Electric Aircraft (MEA)? Why is there so much interest in MEA? Why is Power Electronics important?

Power Sources Conventional Aircraft Figures for a typical civil aircraft Jet Fuel Propulsion Thrust ( 40MW) Gearbox driven generators Electrical High pressure air bled from engine Pneumatic Gearbox driven hydraulic pump Hydraulic Total non-thrust power 1.7MW Fuel pumps and oil pumps on engine Mechanical 200kW 1.2MW 240kW 100kW

Power Sources More Electric Aircraft Rationalisation of power sources and networks Jet Fuel Bleedless engine Propulsion Thrust ( 40MW) Engine driven generators Expanded electrical network Existing electrical loads ELECTRICAL Cabin pressurisation Air conditioning Icing protection ELECTRICAL Flight control actuation Landing gear/ Braking Doors ELECTRICAL Fuel pumping Engine Ancillaries New electrical loads Total Electrical System Power 1MW

More Electric Aircraft Motivations Removal of hydraulic system reduced system weight ease maintenance Bleedless engine improved efficiency simplified design Desirable characteristics of electrical systems controllability power on demand re-configurability maintain functionality during faults advanced diagnostics and prognostics more intelligent maintenance increased aircraft availability

Electrical System Power (kw) The Most Electric Civil Aircraft Yet Boeing 787 Electric environmental control, cabin pressurisation and wing anti-icing Removes need for bleed air from engines Still retains a hydraulic system for primary actuation etc 1600 1400 1200 1000 800 600 400 200 0 0 200 400 600 800 Conventional aircraft B787 much more electric A380 slightly more electric Aircraft Weight (tons) Power, kw 1000 900 B787 800 700 600 A380 A350 500 B747 A340 400 300 200 VC10 Concorde B767 B757 A320 A330 B777 100 Caravelle B737 1950 1960 1970 1980 1990 2000 2010 2020 Year

AC Power Generation Mechanical Constant Frequency Generation Variable speed Engine Shaft Constant Speed Mechanical Drive [Gearbox] Constant Speed Shaft Generator 3-phase 400Hz, 115V Variable Speed generator /Constant Frequency Output Variable speed Engine Shaft Generator Power Converter [DC Link or Cycloconverter] 3-phase 400Hz, 115V Variable Frequency Output Variable speed Engine Shaft Generator 3-phase 320Hz to 800Hz 230V or 115V

Aircraft Actuation Systems

Flight Control Actuation Systems Leading Edge Slats High Lift (High angle of attack) Roll Spoilers supplement ailerons Ailerons Rudder Electronic Controllers Airbrakes lift dump + drag Elevators Thrust Reversers supplement to wheel brakes Trailing Edge Flaps High Lift / drag Trimming Tailplane pitch attitude influence stabilizer RH & LH Synchronisation PITCH Elevators YAW Rudder ROLL Ailerons Roll spoilers

Flight Control Primary Actuation Roll - Ailerons on trailing edges of wings Pitch - Elevators on trailing edge of tail-plane Yaw - Rudder Flight critical Secondary Actuation Flaps - Trailing edge of wing Used for take off and landing increase lift at low speed Slats - Leading edge of wing, used for same reason as Flaps Airbrakes - Spoilers and lift dumpers on wings to increase drag Not actually required for flight, but very useful!

Electrically Driven Actuators Electro Mechanical Actuator EMA 3-phase supply Power Converter Electric Motor Reduction gearbox Ball Screw Actuator is moved as motor spins Each turn of the motor moves the actuator a fixed amount Direct connection between motor and actuator arm EMA issues Direct drive solution Any potential jamming failure modes must be addressed Potentially the most compact solution

Electrically Driven Actuators Electro Hydrostatic Actuator EHA 3-phase supply Power Converter Electric Motor Fixed Displacement pump PEMC Research Group Hydraulic Ram Actuator is moved as motor spins using local Hydraulic system Each turn of the motor moves the actuator a fixed amount No direct connection between motor and actuator arm EHA Issues Benign failure modes Based on a familiar technology for aircraft component manufactures Hydraulic fluid may leak

Electrically Driven Actuators EMA Direct drive solution Any potential jamming failure modes must be addressed Potentially the most compact solution EHA Benign failure modes Based on a familiar technology for aircraft component manufactures Hydraulic fluid may leak

All Electric Aircraft

All Electric Aircraft Solar Impulse PV powered Aircraft Flew ½ way around the world in 30 days! Airbus Electric 2-seater flies for just 20 minutes

Hybrid and All Electric Propulsion Series Hybrid Propulsion Parallel Hybrid Propulsion All Electric Propulsion

Targets for Aircraft Propulsion Electrical Machines Short term (5-10 years) 7-10 kw/kg Mid Term (10 to 15 years) 10-20 kw/kg Long Term ( >>15 years) 20-50 kw/kg Power distribution network cables Short term (5-10 years) 1 kg/km/a Mid Term (10 to 15 years) 0,5 kg/km/a Long Term ( >>15 years) 0,1 kg/km/a Longer term goals may have to be achieved through superconducting or new technologies. Short-Medium term goals likely to be achieved using more conventional machines with a strong level of innovation.

State of the Art Enabling Technologies Drivetrain Integration Mechanical Power Electronics Materials (Devices, Magnetic, Electric, Thermal, Structural) Exciting improvement using nano materials Machine-drive topologies working at high frequency High poles/high speed Manufacturing automation, additive New structures Advanced thermal management Electrical and mechanical integration High frequency machines Thermal material integration 20kW/L, SiC converter

Performance Limits

Hybrid Propulsion Systems

Modern Trends in Aircraft Electric Power Systems and in Onboard Electric Power Generation Potential TeDP EPS architecture: - gas turbines drive generators, and optionally may act as direct propulsion devices - distributed electrical machines drive propulsion devices - energy storage devices can be used to buffer energy - overall EPS control/energy management Turbine Engine Propulsion Fuel Energy Storage Turbine Single-bus approach is employed! Electric Propulsion Electric Starter/Generators Electric Propulsion EM EM EM EM Power Electronic Converters EPS control and energy management Battery Electrical Energy Storage Fuel Cell Electrical Energy Storage Fast-Responce Electrical Energy Storage (SuperCap) Electric Loads (WIPS, EPS, EMA, etc)

Modern Trends in Aircraft Electric Power Systems and in Onboard Electric Power Generation High-power machine design for hybrid platforms - MW-class equipment - Efficiency/losses become a critical design factor Propulsors Generator Converter EM Gas Turbine EM - High speed gen-sets - Close Integration with GT - Very high power density requirement - Thermally/Mechanically challenged - Low-speed propulsion motors - Very high torque density - Electromagnetically/Thermally challenged

Case 1: Starter/Generator System

Aircraft Starter/Generator Overall drive system machine choice Slot-Pole Combination 36-6 6 pole to limit switching frequency loses distributed winding low rotor losses Solid rotor with a CF sleeve retention Stiff rotor Quasi Hallbach array Large airgap = low rotor loses & adoption of a stator sleeve motoring Selected Solution 8k rpm 19k rpm 32k rpm generating

Aircraft Starter/Generator Power Converter Selection Up to 1.6kHz electrical frequency at maximum speed Maximum current: 260Arms peak, 270V DC Low harmonic content to minimize rotor losses Air cooled significant impact on heat sink weight 2 Level, fs = 20kHz 3 Level, fs= 16kHz Same output current THD

High Power Density Starter Generator Rotor assembly and Low loss laminations E-machine 3-Level NPC drive Lightweight Housing Components

Helicopter Swash Plate Actuation

Design Concept Swashplate attachment and EMA arrangement Jam-tolerant design required due to the jamming risk in ball screw Redundant EMAs Requirement to replicate hydraulic system space envelope Arrangement of 2 EMAs side by side Hydraulic swashplate actuator arrangement 6 EMAs, each pair connected to output rods

Optimisation System Optimisation - models and tools Models needed for all the parts of the system Reliability Functional scalable

Optimisation Detailed Design Optimisation Optimisation with Particle Swarm Optimisation algorithm: Simulates behaviour of bird flocks to find optimum of non-linear functions Number of particles with random initial position and velocity At each iteration step velocity is updated with attraction to personal best particle position Efficient optimisation method for electromechanical problems Optimisation with 6 parameters applied for this design: Parameter Lower Boundary Upper Boundary Unit Airgap Diameter d 24 35 mm Split Ratio SR = d/d 0.4 0.6 - Tooth-width factor 0.5 0.7 - Fin extension 1 8 mm Fin thickness 1 3 mm Fin pitch/thickness 2 8 - D d L Particle Projection Evolution of Drive Weight

Hardware Construction Actuator, Motor and Power Converter Rotor Completed Motor Phase C2 Phase A1 Phase B2 Phase C1 Power Converter Phase B1 Stator Phase A2 Actuator with two motors, each motor has two independent stators Short Circuit Motor Current and Drag Torque

Electromagnetic Aircraft Launch Systems for Civil Aircraft

Electromagnetic Launch Systems Electromagnetic Launch (EML) system used to replace steam catapults on the deck of aircraft carrier. Steam catapult have a number of disadvantages Operate without feedback control Bulky and heavy Highly maintained Inefficient (4-6%) Adoption of EML in military application was slow Recently technical advances have been good for the technology: Pulsed power Power conditioning Energy storage devices Advanced controls Requirements Aircraft mass Take-off speed Acceleration Peak Thrust Runway length Take-off time Minimum cycle time Data 73500 kg 85.73 m/s 0.60 g 502.9 kn 624 m 14.57 s 90 s

Electromagnetic Launch Benefits 1 1) Runway length reduction An acceleration of 0.6G was chosen - compliance with the maximum axial acceleration that a human body can comfortably withstand. The runway length computed assuming a uniformly accelerated motion to the rotation speed VR plus a safety distance equal to the 25% of the acceleration path. V R = 1. 05 V 2 Τ1. 11

Electromagnetic Launch Benefits 2 2) Fuel consumption and exhaust emission reduction Assume all the energy required to accelerate the aircraft can be saved. Consider a CFM56-5B4 on the Airbus A320-200, the total fuel burnt during take-off can be computed as Fuel burnt = 2 engines 1.166 kg s 42 s = 97. 94 kg Considering an airport like Heathrow with 650 flights per day yields Fuel Burnt Daily = 97.94 kg take off 650 take off day = 63661 kg day HC CO NOx Emission indices (g/kg) 0.1 0.5 28.7 Daily emission reduction (kg) 6.37 31.83 1827.07 The NOx emission is equivalent of that of 80180 diesel car son daily base

Electromagnetic Launch Benefits 3 3) Noise Emission reduction Aircraft engines usually take 4-5 seconds to accelerate from idle to maximum power condition. The overall noise emission reduction at ground level is expected to be Noise reduction = 42 5 s 42 s 100 = 88. 1 % 4) Engine size reduction In the hypothesis of an EML system installation on a large number of airports, the engine rated thrust could be updated to that required during climbing or during emergency procedure (approximately 85% of the thrust required at take-off). This would lead to reduced aircraft drag and weight

EML System Requirements Comparison of launcher requirements for F-35C and for an A320-200. Requirements F-35C A320-200 Comments Take-off speed [m/s] 78 70 Aircraft mass [kg] 37000 73500 Acceleration [G] 3.3 0.6 Runway length [m] 94 535 Peak thrust [MN] 1.198 0.548 (0.455) Launch energy [MJ] 113 210 (182) Data taken from references F-35C launcher length is set by the dimensions of the aircraft carrier and the launch acceleration is function of it. The launcher acceleration for civil application is a requirement and its length is later determined. Peak Thrust and Launch Energy of military launcher are calculated considering only aircraft inertia, while those for the civil application consider the contributions of aerodynamic drag and ground friction. Inertia contribution is reported between brackets.

Motor Technologies Superconducting Permanent Magnet Induction Complex design, costly and significant additional equipment Linear Permanent Magnet has higher efficiency and simpler and cheaper. The mover is more robust and lighter. Expensive, efficiency savings not significant in this application Lacks robustness, may incur magnets demagnetization Lower efficiency, but this is a system with a low duty cycle Superconducting linear motor design Permanent magnet and induction motors Permanent magnet linear motor performance

EML? Introduction Electric Ground Aircraft Launch Systems Reduce engine requirements Extend maximum flight distances Save aviation fuel Increase payload A different way of thinking

Landing More Electric Aircraft: Still challenges to address Flying aircraft a good way to test technology All Electric Aircraft Technology requirements are demanding and not possible today Hybrid will be followed by true electric if we can address all issues Electromagnetically assisted aircraft take-off An out-of-the-box approach Advantages are many Infrastructure requirements are daunting!

Thank you!