Aerodynamics and Design for Ultra-Low Reynolds Number Flight

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Chapter 7 158 TABLE 7.3 Mass allocation and payload estimate for the 150g prototype electric rotorcraft. Improved aerodynamic efficiency and novel structural and systems integration translates to increased payload and/or efficiency relative to the commercially available examples. Payload mass can effectively be traded with battery mass, trading endurance for additional payload. The end result is a vehicle capable of carrying up to 20 grams of payload with an endurance of five to 20 minutes depending on the battery size and chemistry. The integrated sensors, microprocessor, and transceiver currently allow augmented stability control with a near term goal of achieving autonomous flight. It also creates a flexible system, reprogrammable for varying conditions and missions. To date, the vehicle has been successfully remotely piloted with augmented stability, both tethered and in free flight. Power is currently supplied by a 12.0 Volt Tadiran [46] lithium / manganese-dioxide power pack consisting of four cells in series of either 430mAh or 780mAh capacity. Thrust is provided by four of the two-blade 10cm diameter rotors and the Astroflight Firefly motor with 16:1 gearing, both described in Chapter 6. High frequency PWM motor controllers provide the connection between the receiver or microprocessor and each powerplant. ��
At hover, with a mass of 153g, the entire system consumes ten Watts of power. The Chapter 7 predicted and experimental results indicate 1.3 Watts of power required per rotor at this thrust level indicating a total electro-mechanical efficiency of roughly 52%. This is a tremendous increase over the performance of the 15g prototype and once again demonstrates a key issue with developing electrically powered micro-rotorcraft: the rapid degradation of electro-mechanical efficiencies at reduced physical scales. 7.5 Insights Gained, Limiting Technologies, and the Potential for Future Development With the goal of self-powered autonomous micro rotorcraft, the three prototypes span the design space from 15g (considered infeasible with current technology), up to 65g (that with further design refinement would represent the state-of the-art), finally increasing to 150g. The largest is a design that poses challenges in system integration and automated flight control, but otherwise represents what can be accomplished with current consumer level technology and hardware. Experience with these three prototypes indicates that the cost of reduced scale on the overall power requirements is severe. A summary of key sizing parameters and hover power requirements for these rotorcraft is provided in Table 7.4. The data without battery mass is included to indicate the lower bound on hover power required. 159
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AERODYNAMICS AND DESIGN FOR ULTRA-L
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I certify that I have read this dis
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Abstract Growing interest in micro-
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Nomenclature A Rotor disk area B Nu
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τ Shear stress ω, Ω Rotor angul
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Contents Acknowledgments...........
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Chapter 5..........................
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List of Tables 3.1 Effect of Airfoi
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List of Figures 2.1 Comparison of I
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5.6 Small test fixture in the large
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6.38 Predicted spanwise thrust dist
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Chapter 1 Introduction 1.1 Looking
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Chapter 1 wind-tunnel facilities an
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1.3 Summary of Contributions Chapte
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Chapter 2 Two-Dimensional Computati
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Chapter 2 The artificial compressib
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Chapter 2 The control volume method
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2.2.4 Comparison with Experiment Th
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Chapter 2 to diverge if significant
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2.4 Flow Field Assumptions The INS2
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Chapter 2 The results of these time
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Chapter 3 Analysis and Design of Ai
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Chapter 3 adverse gradient in the p
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The canonical pressure coefficient
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Chapter 3 reaches α=5.0 and a lift
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��
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Cl 0.50 0.40 0.30 0.20 0.10 0.00 -0
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Re=6000 result due to Reynolds numb
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FIGURE 3.10 NACA 0002 and NACA 0008
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C l C l 0.8 0.7 0.6 0.5 0.4 0.3 0.2
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Chapter 3 The maximum L/D for all n
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3.5 Effect of Leading Edge Shape an
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C l 0.60 0.50 0.40 0.30 0.20 0.10 0
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Chapter 3 prominent droop near the
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Chapter 3 Small improvements in lif
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Chapter 4 Hybrid Method for Rotor D
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Q/r D L Chapter 4 FIGURE 4.1 Typica
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4.2.3 Elimination of Trigonometric
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Chapter 4 applications of interest
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4.2.7 The Distinction Between the A
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Chapter 4 Two input parameters dete
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Chapter 4 simplification, particula
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4.3.3 Conservation of Angular Momen
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Chapter 4 moves downstream is less
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Chapter 4 of the pitch angle at the
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FIGURE 4.6 Converged wake streamlin
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Chapter 4 idealized models. The met
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��
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Chapter 5 Overview of Experimental
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1. Substrate Preparation 2. Polymer
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Chapter 5 surface finish and aids i
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FIGURE 5.5 Small test fixture in th
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Chapter 5 The direct influence of t
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FIGURE 5.9 Large test fixture in th
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5.4.1 Motor Power Supply All tests
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Chapter 5 or roughly (+/-) 25% of t
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Chapter 5 newly forming blade tip v
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FIGURE 5.14 Near-body grid geometry
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Chapter 6 Design Examples and Compa
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Chapter 6 capable of speeds up to 1
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FIGURE 6.2 The Astro Flight Firefly
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t/c 0.5 0.4 0.3 0.2 0.1 0.0 FIGURE
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c/R 0.0 0.2 0.4 0.6 0.8 1.0 r/R Cha
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FIGURE 6.10 Carbon-fiber two-blade
Page 131 and 132: Power Req. (W) 3.5 3.0 2.5 2.0 1.5
Page 133 and 134: Chapter 6 TABLE 6.1 Comparison of p
Page 135 and 136: Electro-mechanical Efficiency 0.20
Page 137 and 138: these variations and possible solut
Page 139 and 140: upper and lower surface corners of
Page 141 and 142: Chapter 6 The Sample-1 rotor exhibi
Page 143 and 144: The static deformations described i
Page 145 and 146: Q( r) This problem is solved as a l
Page 147 and 148: Structural Analyses Chapter 6 The m
Page 149 and 150: Aero-Structural Twist (deg.) 0.00 -
Page 151 and 152: Thrust (g) 5 4 3 2 1 0 10000 20000
Page 153 and 154: Thrust (g) 4.5 4.0 3.5 3.0 2.5 2.0
Page 155 and 156: Torque per unit span (g cm) 0.75 0.
Page 157 and 158: Thrust per unit span (g) 3.5 3.0 2.
Page 159 and 160: V total / ωr 1.0 0.9 0.8 Classical
Page 161 and 162: Torque per unit span (g cm) 0.75 0.
Page 163 and 164: Chapter 6 Recall that this rotor wa
Page 165 and 166: Incidence (deg.) 30 25 20 15 10 5 0
Page 167 and 168: Thrust (g) 9 8 7 6 5 4 3 2 38000 40
Page 169 and 170: x/R 0.4 0.2 0.0 -0.2 Chapter 6 FIGU
Page 171 and 172: Cl 0.64 0.62 0.60 0.58 0.0 0.2 0.4
Page 173 and 174: C f 0.125 0.100 0.075 0.050 0.025 0
Page 175 and 176: Chapter 7 Micro-Rotorcraft Prototyp
Page 177 and 178: This vehicle does not currently inc
Page 179 and 180: FIGURE 7.2 The 65g prototype electr
Page 181: 7.4 The 150g Prototype Chapter 7 Th
Page 185 and 186: Using the 150g prototype as an exam
Page 187 and 188: Chapter 7 Basic rotor theory has be
Page 189 and 190: most of the blade. These values are
Page 191 and 192: Chapter 7 For large scale helicopte
Page 193 and 194: Chapter 8 Conclusions and Recommend
Page 195 and 196: the significant performance gains a
Page 197 and 198: Chapter 8 are also opportunities to
Page 199 and 200: Chapter 8 formation flight, and man
Page 201 and 202: References [1] Spedding, G.R., Liss
Page 203 and 204: [28] Lamb, Sir Horace, Hydrodynamic
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Aerodynamics and Design for Ultra-Low Reynolds Number Flight

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