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Electric Aircraft Symposium May 23, 2007

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Presentation on theme: "Electric Aircraft Symposium May 23, 2007"— Presentation transcript:

1 Electric Aircraft Symposium May 23, 2007

2 Benefits of Electric Propulsion
Public Policy: Diversion from use of gasoline Reduced noise (radiated) Enhanced safety and performance Reduced air pollution Further increase efficiency of energy use

3

4 Concept Source: Don Galbraith, 1979

5 High Lift Technology - Wind Turbine Technology
C.P. (Case) van Dam Department of Mechanical and Aeronautical Engineering UC Davis

6 Outline Introduction High-Lift Technology Wind Turbine Technology
Concluding Remarks

7 Historical Jet Fuel Prices
Price information as of May 2007: NY Harbor $2.0904 US Gulf Coast $2.0479 LA $2.1179 Rotterdam $1.9919 Singapore $1.9321

8 Fuel Share of Direct Operating Cost Schrauf (2006)
Trip length = 6000nm, Fuel: $0.60/US gallon Fuel: $1.80/US gallon

9 Impact of Fuel Efficiency
Impact of fuel on aircraft operating cost is significant and is main component of DOC for long missions at current fuel prices Reduction of fuel usage also has beneficial on air pollution with X% reduction of fuel burn for a given mission resulting in X% reduction in emissions European Aeronautics Vision 2020 includes: 50% reduction in fuel consumption (i.e., 50% reduction in CO2) 80% reduction in NOx 50% reduction in perceived noise

10 Potential Reduction in Fuel Consumption Szodruch&Hilbig (1998)
Time frame ~ 20 years Trip Fuel/Distance ~ W/(L/D)SFC/M∞ Conclusion: > 50% reduction in fuel consumption is feasible

11 Potential Improvement in Aerodynamic Efficiency Schrauf (2006)
Drag Decomposition Technologies Drag Reduction Potential Shock control Novel configurations Shape optimization Adaptive wing devices Wingtip devices Load control Laminar flow technology Turbulence control Flow separation control -3% -7% -15% Conclusion: Total improvement of 25% in L/D is feasible

12 Breguet Range Equation for Transport Jets
Range performance of a transport jet at constant lift coefficient and speed (cruise-climb cruise) is governed by: where: a∞ = speed of sound TSFC = thrust specific fuel consumption M∞ = Mach number L/D = airplane lift-to-drag ratio W0 = initial weight W1 = final weight = W0 - fuel weight

13 Performance Characteristics of Transport Jets in Cruise
Simple parabolic drag polar: Minimum required thrust condition: Note: Application of laminar flow reduces CD0 and, hence, CL(CDmin) Increase in aspect ratio, AR, or Oswald’s efficiency factor, e, increases CL(CDmin) Combined effect necessary in order to maximize beneficial effects of laminar flow and high AR for given cruise condition and wing loading

14 Aerodynamic Efficiency Evolution of Long-Range CTOL Airplanes Airplane range > 4,500 n.mi., Callaghan & Liebeck (1990)

15 Design Space for Long-Haul CTOL Transports Initial cruise conditions: M∞ = 0.80 at h = 30,000 ft (SA)

16 Design Space for Personal Air Vehicles Initial cruise conditions: h = 8,000 ft at 200 KTAS (SA)

17 Stall Speed and Maximum Lift for GA Aircraft Holmes (1982)

18 Modern PAV Design Lancair Legacy, Source: http://www. cafefoundation
(W/S)TO = lb/ft2 MTOW = 2,200 lb S = 82.5 ft2 CLmax,clean = 1.51 CLmax,flaps = 2.35 Vs = 56.9 kts

19 PAV Design Observations
To achieve higher performance plateaus, higher wing loadings are required. To maintain acceptable stall speeds (61-knot rule), higher maximum lift coefficients are required. Lower viscous drag (lower CDo) can significantly mitigate the negative impact of higher wing aspect ratio on wing loading.

20 Evolutionary Versus Revolutionary Progress
Technical progress for a product tends to occur along an S-curve The S-curve models the evolutionary changes in technology Leaps in technology are modeled in the form of jumps between S-curves These jumps model revolutionary changes in technology Leaps in technology are needed to extend the capabilities of the product to a new level

21 Circulation Control Wing (CCW) Concept Linton (1994)

22 Circulation Control Airfoils and Wings

23 Effect of Circulation Control on Lift t/c = 0
Effect of Circulation Control on Lift t/c = 0.17 supercritical airfoil, Englar et al (1993)

24 Modifications to A-6/CCW Airplane Nichols (1979)

25 Trimmed Lift Curves of A-6/CCW Airplane Nichols (1979)

26 Flight Test Results of A-6/CCW Airplane Nichols (1979)

27 CCW Concept Advantages and Disadvantages
Higher maximum lift than obtainable with conventional multi-element mechanical high-lift systems resulting in: Improved takeoff/landing performance Higher design wing loadings and, hence, improved cruise performance Reduced complexity of high-lift system Reduced complexity of control system by combining high-lift, direct-lift control and roll control into single multipurpose pneumatic surfaces Disadvantages Reduced efficiency due to (bleed-)air requirements Airplane trim requirements may significantly reduce attainable maximum lift coefficient

28 Wind Turbine Technology
Wind-based electric energy has become cost effective Cost effectiveness has spurred large companies (FPL, GE, Siemens, etc.) to enter the market Push to drive cost of energy down has resulted in much larger wind turbines Square-cube law (rotor power goes by diameter-squared, rotor mass goes by diameter-cubed) has resulted in significant lighter composite rotor structures Modern rotors have efficiency of approx. 52% vs. theoretical maximum of 59.7% Modern rotors use variable speed to maximize efficiency and variable pitch to control torque/power Technology developments are focused on lighter structures for given energy capture or increased energy capture through longer blades for unchanged rotor mass Technology is bifurcating: Land-based utility-scale wind turbines (blade length ≤ 45 m, P ≤ 3 MW) Off-shore wind turbines (P ≥ 5 MW) Wind turbines for residences and small businesses (P = kW)

29 Trend in Turbine Size and Power Output
S. Johnson

30 Innovations in Utility Scale Wind Turbines
Advanced Tower Designs Advanced Drive Trains Advanced Blades Jack-up concept Telescoping concept

31 Design Advancement Opportunities Source: Ashwill, SNL
Load alleviation Passive - twist coupling Sweep twist Active devices - microtabs Performance enhancement & control devices Pitch – collective & individual Flaperons, ailerons Active devices Variable diameter rotor Efficient internal blade architecture Anti-buckling concepts Slender blades Integrated structural/aerodynamic design Thickened airfoils Safety factor shakeouts

32 Conclusions It is timely to (re-)consider electric aircraft
In order for these vehicles to achieve acceptable flight performance, they must have high L/D, and capable of generating high lift coefficients Circulation control wing concept is proven technology to provide high lift performance As we move forward and reduce our oil dependency and emissions, wind power may be able to provide a large percentage (>20%?) of electric energy needs in USA Wind turbine technology is rapidly becoming very sophisticated


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