Aerodynamics and Design for Ultra-Low Reynolds Number Flight

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Chapter 6 6.3.3 Two-Blade Ten Inch Diameter Rotor The two-blade ten inch diameter rotor is a design based on the WES-Technik Carbon 25/ 12 propeller [41]. This carbon fiber prop is intended for slow-flight remote control aircraft but exhibits performance that makes it marginally suitable for use in a prototype rotor craft. This vehicle was intended originally as a systems integration and control test-bed, making the selection of an off-the-shelf rotor expedient. Initially it had been intended to simply manufacture identical mirror image props necessary for reverse rotation, but analysis of the rotor showed that a re-design could achieve significant gains for the static thrust hover case. Based on the results of Chapter 3, the airfoil section is specified as a NACA 4703. The two-blade geometry was maintained to simplify the composite tooling. The resulting chord distribution from a full re-design proved to be very close to the WES-Technik rotor, so the planform of the original rotor was maintained. This allowed for a more direct evaluation of any performance gains. The incidence-only design with the new airfoil is shown in Figure 6.9. For this rotor, the quarter-chord line is unswept. The manufactured carbon-fiber composite blade is presented as Figure 6.10. The design maximum thrust operating point is 1850 RPM. 104 c/R 0.4 0.3 0.2 0.1 5 inch Rotor Radius Incidence c/R 0.0 0.0 0.2 0.4 0.6 0.8 1.0 r/R FIGURE 6.9 Chord and incidence distributions for the two-blade ten inch diameter rotor. 25 20 15 10 5 Incidence (deg.)
FIGURE 6.10 Carbon-fiber two-blade rotors, inch scale. 6.4 Comparison of Total Thrust and Power 6.4.1 Two-Blade Ten Inch Diameter Rotor Chapter 6 Global metrics, the total rotor thrust and power required, are both the principal points of interest in design and the simplest to obtain experimentally. Whether or not they form a concrete and comprehensive measure of accuracy will be a topic of later discussion. The first comparison of analysis and experiment is for the ten inch two-blade rotor. The larger scale greatly increases the confidence in the as-built geometry and the lower rotational speeds, typically around 2000 RPM, diminish the likelihood of structural deflection. The measured forces and torques increase by a factor of ten, reducing the effect of approximately constant magnitude measurement errors. Close agreement is obtained in both thrust and rotor power required for this design. The maximum difference in thrust is approximately 10% at the highest tested RPM, corresponding to a less than 5% difference in power required. One point of note to be expanded on later is the indication of stalled tips when analyzed with the contracting wake model. The rotor was designed with the Prandtl tip loss model and at that point had no indication of stall. The thrust comparison for three rotor samples and the rapid 105
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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
Page 77 and 78: 4.2.3 Elimination of Trigonometric
Page 79 and 80: Chapter 4 applications of interest
Page 81 and 82: 4.2.7 The Distinction Between the A
Page 83 and 84: Chapter 4 Two input parameters dete
Page 85 and 86: Chapter 4 simplification, particula
Page 87 and 88: 4.3.3 Conservation of Angular Momen
Page 89 and 90: Chapter 4 moves downstream is less
Page 91 and 92: Chapter 4 of the pitch angle at the
Page 93 and 94: FIGURE 4.6 Converged wake streamlin
Page 95 and 96: Chapter 4 idealized models. The met
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Page 99 and 100: Chapter 5 Overview of Experimental
Page 101 and 102: 1. Substrate Preparation 2. Polymer
Page 103 and 104: Chapter 5 surface finish and aids i
Page 105 and 106: FIGURE 5.5 Small test fixture in th
Page 107 and 108: Chapter 5 The direct influence of t
Page 109 and 110: FIGURE 5.9 Large test fixture in th
Page 111 and 112: 5.4.1 Motor Power Supply All tests
Page 113 and 114: Chapter 5 or roughly (+/-) 25% of t
Page 115 and 116: Chapter 5 newly forming blade tip v
Page 117 and 118: FIGURE 5.14 Near-body grid geometry
Page 119 and 120: Chapter 6 Design Examples and Compa
Page 121 and 122: Chapter 6 capable of speeds up to 1
Page 123 and 124: FIGURE 6.2 The Astro Flight Firefly
Page 125 and 126: t/c 0.5 0.4 0.3 0.2 0.1 0.0 FIGURE
Page 127: c/R 0.0 0.2 0.4 0.6 0.8 1.0 r/R Cha
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
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FIGURE 7.2 The 65g prototype electr
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7.4 The 150g Prototype Chapter 7 Th
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At hover, with a mass of 153g, the
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Using the 150g prototype as an exam
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Chapter 7 Basic rotor theory has be
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most of the blade. These values are
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Chapter 7 For large scale helicopte
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Chapter 8 Conclusions and Recommend
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the significant performance gains a
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Chapter 8 are also opportunities to
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Chapter 8 formation flight, and man
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References [1] Spedding, G.R., Liss
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[28] Lamb, Sir Horace, Hydrodynamic
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Aerodynamics and Design for Ultra-Low Reynolds Number Flight

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