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Drag Reduction of MAV by Biplane Effect Chinnapat THIPYOPAS Graduate student, Department of Aerodynamics and Jean-Marc MOSCHETTA Associate Professor of Aerodynamics, Department of Aerodynamics Ecole Nationale Supérieure de l’Aéronautique et de l’Espace (SUPAERO) 10 Av. Ed. Belin, Toulouse, France P1/29

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Contents Introduction Part 1 Optimization - (Experimental) - (Numerical) Part 2 Biplane Combinations Part 3 Propeller Influence Conclusions Department of Aerodynamics SUPAERO P2/29

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Contents Introduction Part 1 Optimization - (Experimental) - (Numerical) Part 2 Biplane Combinations Part 3 Propeller Influence Conclusions Department of Aerodynamics SUPAERO P3/29

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Monoplane MAV concepts Minus-Kiool 57g cm Plaster 64g - 23 cm Department of Aerodynamics SUPAERO P4/29

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Monoplane-MAVs Total Drag = Parasite Drag + Induced drag 100 % % % Plaster, SUPAERO Drenalyne, SUPAERO Biplane Concept !! Maxi-Kiool, SUPAERO Induced Drag 76%* * J.L ’ HENAFF, SUPAERO 2004 Department of Aerodynamics SUPAERO P5/29

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Monoplane vs. biplane Constant lift, speed & overall dimension wing drag = Parasite Drag + Induced Drag Parasite drag is a function of Skin-Friction which depends on Wing Chord Induced Drag is very strongly effected by Aspect Ratio Department of Aerodynamics SUPAERO P6/29

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Contents Introduction Part 1 Optimization - (Experimental) - (Numerical) Part 2 Biplane Combinations Part 3 Propeller Influence Conclusions Department of Aerodynamics SUPAERO P7/29

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Design Constraints Maximum overall dimension : 20 cm Lift at 10 m/s = Weight = 80 grams Manoeuvrability : Cost function Minimum Drag at cruise condition Optimization process Department of Aerodynamics SUPAERO 20 grams min. for payload P8/29

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Experimental setup Wind tunnel –Test Section 45cm x 45cm –Velocity 10 m/s Measurement –3-component balance Models –16 flat-plate wing models Aspect ratio 1 – 4 Taper ratio 0.2 – 1.0 Sweep angle ° Reference surface/length –For comparison, every model is referenced by same area, length Strut AR1, Taper 1, No Swept 20cm. AR2.5, Taper0.6, Swept25° Department of Aerodynamics SUPAERO P9/29

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Model’s Drag Correction Model Strut Model is not attached to strut Department of Aerodynamics SUPAERO P10/29

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Results No. A4S50T1 A4S50T0.6 A4S50T0.2 A4S25T0.6 A4S0T1 A4S0T0.2 A2,5S50T1 A2,5S25T1 A2,5S25T0.6 A2,5S0T1 A2,5S0T0.6 A1S50T1 A1S50T0.2 A1S25T0.6 A1S0T1 A1S0T0.2 Disc Model Name (cm.) ***Area Red color is a value referenced by wing’s area Department of Aerodynamics SUPAERO P11/29

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Numerical method Vortex lattice method : code TORNADO v126b [T. Melin; KTH] Drag evaluation Parasite Drag = 1.5 of equivalent flat plate skin friction drag (Blasius Eq. + Thwaites formula) + Induced drag (TORNADO) Various models : –aspect ratio –taper ratio –sweep angle Department of Aerodynamics SUPAERO P12/29

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Results Monoplane Triplane An approximate stall angle curve Biplane L/D at cruise cond. increases with AR Poor manoeuvrability of monoplane wings with AR 2 and higher greater L/D for biplanes L/D of Triplane AR4 is smaller than biplane because of high parasite drag. Biplane AR2-3 is suitable for flight Department of Aerodynamics SUPAERO P13/29

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,050,10,150,20,250,30,350,4 Drag Mass Monoplane Biplane 60 grams Monoplane Biplane Biplane vs. monoplane Department of Aerodynamics SUPAERO 80 P14/29

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Contents Introduction Part 1 Optimization - (Experimental) - (Numerical) Part 2 Biplane Combinations Part 3 Propeller Influence Conclusions Department of Aerodynamics SUPAERO P15/29

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Zimmerman PlanformArea (m 2 )CL (max) CD (min) L/D (max) Zim Zim Zim1Inv Zim2Inv Plaster Plaster Drenalyne Drenalyne Plaster Other planforms Drenalyne Department of Aerodynamics SUPAERO P16/29

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Inverse Zimmerman Torres et al., Univ. Florida, 1999 Plaster wing Reyes et al., SUPAERO, 2001 Calculation Department of Aerodynamics SUPAERO P17/29

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Scale 1 (SUPAERO) Parameters Gap Stagger Decalage angle Side View U Lower Wing Gap Stagger Upper Wing Decalage angle End-plates Scale 3 (S4, ENSICA) Department of Aerodynamics SUPAERO P18/29

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Gap Reduced an influence between both wings Increase lift slope and maximum lift Not change position of aerodynamics center Increase drag from the structure L/D not change Department of Aerodynamics SUPAERO P19/29

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Stagger Increase lift slope and maximum lift Aerodynamics center is between two wing No stagger has more L/D Local AoA of fore-wing is bigger Department of Aerodynamics SUPAERO P20/29

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Decalage Angle Done with positive stagger model Strongly effect to stall angle and L/D Negative decalage give highest wing performance Department of Aerodynamics SUPAERO P21/29

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Visualisation S4, ENSICA Department of Aerodynamics SUPAERO P22/29

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Contents Introduction Part 1 Optimization - (Experimental) - (Numerical) Part 2 Biplane Combinations Part 3 Propeller Influence Conclusions Department of Aerodynamics SUPAERO P23/29

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Propeller Effect (S4) Motor & propeller Test section Power supply Moveable system Tube Test section Upper Wing Lower Wing UMotor Side View Front View Half Span Center line Upper wing Lower Wing 7 motor positions were observed. Upper wing stalls At pre-stall regime, lift is increased due to propeller. Lift increases Lower wing stall at 22° Lower wing not stalled The stall angle is delayed, lower wing is still not stall at AoA 22° Lift, maximum lift and L/D are increased. Department of Aerodynamics SUPAERO P24/29

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Propeller Effect (Scale 1) Zim2 wing planform scale 1 (20cm. Max dim.) Motor in front of wing gives highest performance. The motor countering / encountering wingtip vortex effects are very small. Monoplane Wing P25/29

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Propeller Effect Incidence B = mid position R = upper wing G = lower wing L/D 155 Motor on upper and lower wing have the same effect Middle position is poorest Attached on upper and lower wing Same efficiency Delay stall phenomena, increase maximum lift Attach Motor to the model Motor sting Model struts Effect of induced flow to model P26/29

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Contents Introduction Part 1 Optimization - (Experimental) - (Numerical) Part 2 Biplane Combinations Part 3 Propeller Influence Conclusions Department of Aerodynamics SUPAERO P27/29

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Conclusions Biplane is better than monoplane for this design criteria Wind tunnel measurements and numerical calculations confirm the interest for biplane MAV wings. AR 2.5 to 3 are appropriate for biplane MAV concepts. On-going developments More accuracy measurement Further optimization of motor position (wingtip) Optimizing biplane-connecting structure Pototype of Biplane MAV Department of Aerodynamics SUPAERO P28/29

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Thank you for your attention P29/29

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Drag Reduction of MAV by Biplane Effect Chinnapat THIPYOPAS Graduate student, Department of Aerodynamics and Jean-Marc MOSCHETTA Associate Professor of Aerodynamics, Department of Aerodynamics Ecole Nationale Supérieure de l’Aéronautique et de l’Espace (SUPAERO) 10 Av. Ed. Belin, Toulouse, France

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Parasite and Induced Drag The zone which biplane has total drag less than monoplane configuration (when Induced drag > 45% total drag) 55 Department of Aerodynamics SUPAERO

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Parasite and Induced Drag casea.) AR1 b.) AR2 c.) 2 x AR2 total Surface SS/2 Lift for each wing WWW/2 Max. Lift LL/2 L Lift coef. CLCL 2C L CLCL Skin friction drag DfDf D f / D f Induced drag coef. C Di 2C Di C Di /2 Induced drag DiDi DiDi D i /4D i /2 Total drag 1.5D f + D i 1.5D f / D i 1.5*1.414D f + D i /2 Airplane drag = Parasite Drag + Induced Drag Parasite drag is a function of Skin-Friction which depends on Wing Chord Induced Drag is very strongly effected by Aspect Ratio The zone which biplane has total drag less than monoplane configuration (when Induced drag > 45% total drag) 55

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Results Reynolds number effect on L/D Winglet can improve wing performance Gap increases the lift slope and maximum lift L/D increased by positive stagger Stall angle and maximum lift changed by decalage angle Parasite drag from the strut between two wing is very important

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Propeller-induced lift Increasing in lift

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Why are these 16 models ? The Taguchi method was used in the first experimental design table. But an interaction between each parameters is very strong. To determine the optimizing model, some interpolation was formed to complete the experimental table.

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Gap effect

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Stagger effect

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Decalage effect

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Scale 1 Sweptm Plaster and Inv-Zim planeform Connected with strut Biplane –parameters Gap Stagger Decalage angle

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Swept Planform

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Inverse-Zimmerman

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Visualisation Tuft method Smoke generation

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Motor-Propeller Effect Attached on upper and lower wing Same efficiency Delay stall phenomena, increase maximum lift

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GEOBAT

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