Advances in Electric Aircraft Flashcards
What is the formula for Pressure (Using ideal gas eq)?
p = ρRT
What are some benefits of electric flight?
More Sustainable, Reduced Environmental Impact, Less Noise, Easier Maintenance, Lower Operational Cost, Potential Performance Benefits,
What is the main challenge for making Electric Aircraft Feasible?
Energy Density: Considering the power-to-weight ratio of both fuel and batteries, 1 kg of fuel = 25…30 kg of batteries.
What percentage of the total weight do batteries represent in an electric aircraft?
Almost 45%
What are some challenges in addition to the technological?
Certifications and Regulations, Infrastructure and Airports, Air traffic management, Maintenance and Servicing, Industry processes.
What is a UAM?
Urban Air Mobility
What is a UAV?
Unmanned Aerial Vehicle.
What is TRL?
Technology Readiness Level
Energy/power sources of electric aircraft?
Battery Powered
Solar Powered
Fuel Cell Powered (Hydrogen Cells)
Hybrid Powered (Combination Fuel and Electricity)
What are Hybrid Aircraft? What are some disadvantages?
A fuel engine drives a generator that charges the batteries in flight. Problems surge from: Size of generator, Efficiency, Power Distribution.
What types of hybrid electric drive architectures are there?
Parallel hybrid electrical (Both the Batteries and the Fuel engine drive the propeller)
Serial hybrid electrical (The engine recharges the batteries, which then power drive the propeller)
Partial Electrical (The batteries only provide additional power when needed)
Turbo-Electric (Similar to Serial-hybrid, but the electric motor is decoupled from the generator)
Whats HEP?
Hybrid Electric Propulsion.
Definition of “System”?
An assembly of electronic, electrical or mechanical components with interdependent functions forming a self-contained unit.
What are the different types of systems in an aircraft?
Aiframe/structure, Vehicle systems (Propulsion, Flight Controls, etc.), Avionic Systems (Navigation, Controls, Displays).
What is the aircraft electric system constructed of?
-Energy Sources
-Control Devices
-Conversion Devices.
-Protection devices and switches
-Electric wiring interconnection systems
-Electrical loads.
What is the main objective of Electric Power Systems?
Generate, convert, and distribute power safely and efficiently to aircraft loads. While also providing fault protection in the event of failure.
What is EPS?
Electric Power System
What are some of the regulated elements of EPS?
-Backup Power Sources
-Power Quality
-Failures are independent of different systems
-Electrical Wiring Interconnection System (EWIS) must have adequate physical separation.
-Power Management System ensures safety, power quality, stability, and effective function of the EPS for all conditions.
Whats a three channel electrical system in an aircraft?
The electrical system has 3 independent electrical circuits that distribute electrical power to the aircraft’s electrical systems and components. It exists so that there is redundancy in the system.
What is Power Quality?
Is a measure of the reliability and efficiency of the electrical system, which implies a steady and consistent power supply.
What is Ohms Law?
V = R * I
How is electrical power calculated?
P = I * V
How is Electrical Work calculated?
W = P * t = V * Q = U * I * t
How is electrical Resistance of a wire/conductor calculated?
R = ρ * l / A
where:
ρ = specific resistance (Material)
A = Transversal Area of the conductor
l = length of the conductor
What is the difference between a Rectifier and an Inverter?
Rectifier AC -> DC (transistors and diodes)
Inverter DC -> AC
What does an H-Bridge do? What does it consist of?
It controls both the direction of the current flowing through a Load (Motor) as well as the amount of power supplied to it.
It consists of 4 switches connected to a load, arranged in the shape of an H with the load in the middle.
What is a Flyback Diode?
A circuit used to avoid voltage peaks when the current is reduced or interrupted.
What causes Electric Component Power Losses in power electronics?
Mostly losses due to Switching (Transistors changing from off to on).
Also Conduction, Blocking (Diodes from on to off), Driving Losses.
What are Circuit Breakers?
These electrically isolate components in a short time in case of fault operation. (Fuse)
What types of Circuit Breakers are there?
Mechanical, Solid-state, Hybrid, Fuse, Vacuum, With Arc Chamber.
What are the different types of electrical actuation?
Electro-Hydrostatic Actuator (EHA) : Fast response.
Electro-Mechanical Actuator (EMA):
Disadvantage of possible jamming of the actuator.
What is APU?
Auxiliary Power Unit.
What is MEA?
More-Electric Aircraft. Aircraft for which the pneumatic and hydraulic systems are replaced by electric systems, but primary control surfaces are hydraulic or pneumatic.
Why use Electrical systems as opposed to Pneumatic or Hydraulic?
Air compression process is eliminated, Less components and complexity, Fewer risks (Oil contamination of cabin air supply), Improved aerodynamics (No bleed air vents), Easier Maintenance.
When is the most power-intensive flight phase?
Take-off and Climb
What are Remotely Distributed Electrical Power Systems?
It is an electrical Power system where the distribution isnt centralized, so distribution centers can be placed closer to loads, making it so that the systems are more reliable, and with less weight (less wiring).
Advantages of All-electric aircraft
Less complexity (all power comes from electrical system)
More complex electric power system
What re the 3 main electrical systems of a transport aircraft (All electric)?
Propulsion System, Subsystems (Controls), Avionics
Differences in Power Type between All electric and More electric aircraft?
All Electric: sources usually deliver DC. (Reduced system complexity, low voltage drop, reduced EMI)
More electric: Generator delivers AC (Challenges for parallel operation, No need for synchronization of AC generator to AC distribution system, Additional components needed).
What considerations of environmental influences must be taken into count for the electrical systems?
Low Pressure: Reduces critical field strength (air doesnt insulate as good)
Temperature: Conduction Properties.
Humidity: Condensation, insulation aging.
Radiation
Lightning
Electromagnetic Interference (EMI)
What to consider when selecting a motor?
-Power/Torque
-Operating RPM
-Efficiency
-Torque-speed characteristics
-Power Density
-Voltage Requirement
-Current draw from battery
-Heat rejection
-Maintainability
-Reliability
-Cost
How is Motor Speed calculated?
ω = Kv * U
Where Kv is a constant
How is Motor Torque Calculated?
Q = Kt * I
where Kt
Or Q = P/ω
How is Motor Output Mechanical Power calculated?
Pout = Q*ω = UI - Ploss = U I - I2 R - U I0
Which are the wire resistance losses and the magnetic losses respectively
How is Motor Efficiency Calculated?
η = Pout/ Pin = (U I - I2 R - U I0) / U I
How do Electric Motors compare to Combustion Engines in the following areas?
Efficiency, Reliability, Power Density, Torque Power Production at standstill, Number of Moving parts, Exhaust emissions, Noise/Vibrations, Bi-Directional?
____________ ………………………. Combustion. …….Electric
Efficiency ………………………………. Low ……………. High
Reliability ……………………………. Medium ……… High
Power Density ……………………….. Low …………. High
Torque production at standstill .. No …………… Yes
Number of Moving Parts ……….. Very High …… None
Exhaust Emissions ……………………. High ………… Low
Noise/Vibrations ……………………… Medium ……… Low
Bi-directional? …………………………….. No …………… Yes
How is the Propulsion Thrust Calculated? (Thrust produced by the propulsion system)
T = ma = ΔV * (Δm/Δt)