Advances in Electric Aircraft Flashcards

Question

What is the difference between a Rectifier and an Inverter?

Answer 1

Rectifier AC -> DC (transistors and diodes) Inverter DC -> AC

Answer 2

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.

Answer 3

A circuit used to avoid voltage peaks when the current is reduced or interrupted.

Answer 4

Mostly losses due to Switching (Transistors changing from off to on). Also Conduction, Blocking (Diodes from on to off), Driving Losses.

Answer 5

These electrically isolate components in a short time in case of fault operation. (Fuse)

Answer 6

Mechanical, Solid-state, Hybrid, Fuse, Vacuum, With Arc Chamber.

Answer 7

Electro-Hydrostatic Actuator (EHA) : Fast response. Electro-Mechanical Actuator (EMA): Disadvantage of possible jamming of the actuator.

Answer 8

Auxiliary Power Unit.

Answer 9

More-Electric Aircraft. Aircraft for which the pneumatic and hydraulic systems are replaced by electric systems, but primary control surfaces are hydraulic or pneumatic.

Answer 10

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.

Answer 11

Take-off and Climb

Answer 12

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).

Answer 13

Less complexity (all power comes from electrical system) More complex electric power system

Answer 14

Propulsion System, Subsystems (Controls), Avionics

Answer 15

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).

Answer 16

Low Pressure: Reduces critical field strength (air doesnt insulate as good) Temperature: Conduction Properties. Humidity: Condensation, insulation aging. Radiation Lightning Electromagnetic Interference (EMI)

Answer 17

-Power/Torque -Operating RPM -Efficiency -Torque-speed characteristics -Power Density -Voltage Requirement -Current draw from battery -Heat rejection -Maintainability -Reliability -Cost

Answer 18

ω = K_v * U Where K_v is a constant

Answer 19

Q = K_t * I where K_t Or Q = P/ω

Answer 20

P_out = Q*ω = UI - P_loss = U I - I² R - U I₀ Which are the wire resistance losses and the magnetic losses respectively

Answer 21

η = P_out/ P_in = (U I - I² R - U I₀) / U I

Answer 22

____________ ............................ 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

Answer 23

T = ma = ΔV * (Δm/Δt)

Answer 24

P_prop = T * V

Answer 25

J = V/(n d) where n = propeller speed (rev/sec) d = propeller diameter (m)

Answer 26

η_prop = P_out/P_in = TV/P_in = (C_T/C_Q) * J

Answer 27

-Tractor: pull aircraft through air, mounted in front of engine, increases airspeed of wing, propeller rotates in clean air. -Pusher: mounted on rear end of the aircraft, propeller rotates in unclean air (it passed the wings/fuselage), reduces drag by preventing flow separation, higher probability of damage

Answer 28

η_pr,simple = 2 / (V/V_∞) + 1

Answer 29

C_P = P / (ρ n³ d⁵)

Answer 30

C_T = T / (ρ n² d⁴)

Answer 31

V_tip = sqrt ( V² + (n π d_p)²

Answer 32

Distributed Propulsion. Easier to place motors anywhere on the airframe, Structural benefits potential increase of Disk Area, Thrust Vector control possible. One Engine Inoperative requirements might be easier to meet.

Answer 33

Boundary Layer Ingestion. Aircraft configurations where the boundary layer around the aircraft is ingested by the propulsors. Leads to reduced Wake and Higher propulsive efficiency

Answer 34

Annular : Propulsors at rear of fuselage, rotationally symmetric inlet flow, can ingest large amount of BL Asymmetric: Propulsors on wings, asymmetric inlet flow, reduced efficiency

Answer 35

Hybrid Electric Aircraft. Higher efficiency than Conventional, Increased complexity, Better EMs scaling, Better flexibility in operation and design.

Answer 36

H_p = P_elec/P_tot

Answer 37

H_E = E_elec/E_tot

Answer 38

ICE produces power to drive generator, which drives an EM, which drives a propulsor. (H_P = 1, H_E = 0) + ICE decoupled from EM + ICE can be positioned strategically + No batteries - Added weight of generators and EM - Fuel-driven

Answer 39

EMs supply part of propulsive power while the rest is generated by ICE turbofans. (0 < H_P < 1, H_E = 0) - Additional weight (Generator, Em) + Electrical components can be smaller (total weight is lower)

Answer 40

ICE drives generator which in turn drives EMs. Electric system is supplemented by a battery. (H_P = 1, 0< H_E < 1) + Simple concept +Design freedom. + New configurations are possible. - Propulsors are driven by EMs alone - Less efficient powertrain compared to parallel, bigger batteries and EMs needed.

Answer 41

Power Management System

Answer 42

ICE and EMs are both connected to the propeller shaft, Generator isn't required. (0 < H_P < 1, 0 < H_E < 1) + Direct connection of ICE to propeller shaft, higher propulsive efficiency + No Generator + Propulsive power comes from both ICE and EMs - Extra mass due to mechanical coupling - More complex propulsion Control - ICE directly involved in thrust generation, reduced performance.

Answer 43

Propulsors fully driven by electric motors with energy provided by batteries. - Battery Specific Energy Limitations - High Weight

Answer 44

The ability to perform work [ kWh ]

Answer 45

Energy transfer per Unit Time. [kW]

Answer 46

Energy per unit mass [ J/kg]

Answer 47

Energy per Unit Volume [ J/m³]

Answer 48

LOW mass HIGH safety -Energy Density -N. of Recharge Cycles -Recharge Rate -Temperature Sensitivity -Insulation requirements -Fire hazard, safety -Cost

Answer 49

NiCd : Cd toxic, High Discharge Rates, Inexpensive NiMH: Slightly higher energy density Li-ion: Higher Energy density than Ni based, Expensive, Fire hazard LiPO: Relatively light, higher energy density than Li-ion, potential explosive hazard Li-S: Higher energy density than Li-ion batteries, Sulfur is cheap and abundant

Answer 50

-High peak power duration -High safety and reliability -High number of cycles - Fast Charging

Answer 51

As a compressed gas: Low Density, Heavy tanks, Low Storage efficiency, Safety Risks As cryogenic Liquid: Requires cryogenic cooling, cooling uses up to 45% of stored energy

Answer 52

Fuel tank, Fuel cell (converts chemical energy into electric), ESC, Electric Motor, Propeller/Fan

Answer 53

η = V_cell/V_ideal

Answer 54

Maximum Power Point

Answer 55

m_H2,used/Δt = M_H2 * (N I_stack) / 2F Where: M = Molar mass, N = number of cells, I = Current, F = Faraday constant

Answer 56

Air supply subsystem Hydrogen supply subsystem Cooling subsystem Electrical subsystem

Answer 57

+ Higher Energy Density than batteries + Quickly recharged + Twice as efficient as an ICE + Few moving parts + Direct conversion of chemical energy into electric energy. - Heavy tanks needed - Storage is challenging - Requires fuel - Waste heat is produced - Hydrogen is explosive and flammable

Answer 58

E_b [Wh] = e_b [Wh/kg] * m_b [Kg] = C_b [A h] U_b [V] = E_b,max(1 - SOC_min)

Answer 59

t = (η_tot e_B/ V*g) (C_L / C_D) ( m_B/m_TO)

Answer 60

R = (η_tot e_B/ g) (C_L / C_D) ( m_B/m_TO)

Answer 61

R = (η_tot e_f/ g) (C_L / C_D) ln( 1/(1-m_f/m_TO)

Answer 62

ε = C_D/C_L = C_D0/C_L + k*C_L

Answer 63

An Electrical Aircraft can achieve maximum range at higher speeds, shorter flight times They can also achieve maximum range at maximum speed and they have a higher service ceiling

Answer 64

T = D + W * sin(γ)

Answer 65

L = W * cos(γ)

Answer 66

h/Δt = V * sin(γ) = VT/W - VD/W

Answer 67

It is C_L when D is at its minimum. What is C^*_L = sqrt(C_D0/k) = C_L,Dmin

Answer 68

It is the Lift Coefficient necessary for maximum endurance C_{L,t_max} = sqrt(3C_D0/k) = C_{L, P_min}

Answer 69

Initially stored Fuel Energy E_0,f = (1-Φ)*E_0,tot

Answer 70

Initially stored Battery Energy E_0,b = Φ*E_0,tot

Answer 71

Power Ratio

Answer 72

R_hyb = η_prop e_f / g * (C_L/C_D) ( η_el Φ/(1-Φ) + η_th ) ln (m_TO /(m_TO - m_0,f))

Answer 73

Helicopter, Multi-rotor, Lift+Cruise, Tilt-rotor, Tilt-wing

Answer 74

+ Low design complexity + Simple construction and rotor system than helicopters +Good hover performance + Small rotors, lower motor weight compared to helicopters +Good VTOL performance - High power required for forward flight - Only good for short ranges at low speeds - Relatively slow - Inefficient energy consumption in cruise

Answer 75

+Faster and more efficient than multirotors + Good hover and VTOL performance - More complex than multirotors - Larger rotors - high power required for forward flight - inefficient energy consumption in cruise - short range and low speed

Answer 76

+ Good compromise between cruise and hover performance + Higher flight speed + Suitable for long distances + Less complex than vectored thrust - Performance is not optimal for ANY condition - Added weight and drag due to double propulsion system

Answer 77

+Good for high speeds and high ranges + Higher Lift-to-Drag ratio + Extra cruise efficienc thanks to the wing and multiple small propellers + Good performance for a variety of missions + Energy efficient cruise - Challenging transition - More complex control

Answer 78

+ Generally lighter than tiltwings + Well suited for long ranges and high speeds + Energy-efficient cruise - Challenging transition - More complex control - Lower cruise efficiency than tiltwings

Answer 79

Personal Air Vehicles

Answer 80

P_P,duct = 1/2 sqrt(T³ / (ρA_jet)

Answer 81

P_P,prop = 1/sqrt(2) * sqrt(T³ / (ρA_fan)

Answer 82

How much weight can be lifted per given mount of power

Answer 83

Weight to thrust area ratio σ = mg/A

Answer 84

Helicopter: Best for small range at moderate to high speeds Multirotor: Best for small range at low speeds Tiltrotor: Best for a moderate range at medium to high speeds. Tiltwing: Best for Long range at any speed Lift+Cruise: Best for low to moderate range at any speeds, and best for moderate/long range at low speeds.

Answer 85

Battery mass fraction. Mass of the batteries to the total mass of the aircraft

Answer 86

Semi-empirical weight estimation Graphical constraints analysis Optimization Mission-dependent analysis Performance-based analysis Combinations

Answer 87

Similar to Wing Loading, but regarding Power instead of Wing Surface. W/P It used similarly, to obtain a design space in a P/W to W/S graph

Answer 88

-Constraints analysis to specify W/S and W/P -From design point calculate wing area given the total weight -Estimate motor and battery weight -Estimate relation between empty weight and total weight considering battery and motor weight as well as the assumed payload

Answer 89

High lift-thrust efficiency Less power required to maintain rotor speed Smaller engine required to hover Large rotor required Autorotation performance increased.

Answer 90

Complex dynamics and actuation (control and modelling is difficult) Novelty factor (New configurations, little experience, missing regulations) Operation in urban environments (Take-off and landing constrained, Updrafts, High Risk)

Answer 91

Wing requires dedicated actuators in order to tilt Large exposed wing area during vertical flight (higher wind gust sensitivity)

Answer 92

Negative lift due to wing being in propeller wash Interference effects can be large Tilt actuation delays

Answer 93

mV/Δt = F_tot -m( ω x V) I ω/Δt = M_tot -ω x Iω where: F_tot = F_A + F_P + F_G and M_tot = M_A + M_P

Answer 94

1.- Yaw ψ 2.- Pitch θ 3.- Roll φ

Answer 95

Using Simplified analytical models, Semi-empirical models, Fully data-driven models, and CFD -based models.

Advances in Electric Aircraft Flashcards

(119 cards)