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無人飛機長滯空高升力翼型設計及積冰對於翼型氣動力特性影響
Ice Accretion Effect on the Aerodynamic Characteristics of Long-Endurance, High-Lift Airfoil Design for UAV
摘要
本文以數值方法探討機翼翼前緣積冰對於無人飛機長滯空高升力翼型設計氣動力特性影響評估。探討參數將包括結冰的厚度，結冰的長度、機翼型狀及機翼結冰位置。在本文所選定的三種適用於UAV的翼型所得結果顯示，當結冰厚度增加時，翼型的升力及失速角有隨著減小的趨勢的影響；此外其最大升阻力係數比也明顯大幅下降。在結冰長度方面，發現若結冰長度增加，翼型的升力及失速角有隨著減小的趨勢；此外其最大升阻力係數比方面，愈集中在翼前緣情況較整個翼型前段結冰時的影響更明顯。三種翼型氣動力特性係數下降的趨勢相似，但GA-17與NLF-1015受結冰影響較TYPE A?輕。與NLF-1015及TYPE A兩種翼型比較，以基因演算法優化的翼型GA-17受到結冰影響後其C(下標 l)/C(下標 d))(下標 max)及ΔC(下標 l)/C(下標 d))(下標 max)仍然能維持最高，顯示該翼型受結冰後仍然可以維持較佳的氣動力特性。此外GA-17該翼型在上下表面結冰後兩種結冰位置相較之下又以翼型在上表面對結冰後容忍度明顯較差。結果說明適當翼型設計有助於增加機翼結冰的忍受程度，而所得結果可作?日後機翼最佳化之設計參考。對於低雷諾數下長滯空的UAV來講，優秀的機翼不僅是高升力及低阻力，也必需適合在不同高度及環境條件下，在高空有好的抗失速能力，才能確保UAV安全完成任務。
並列摘要
This research utilizes numerical methods to evaluate ice accretion effects on the aerodynamic characteristics of airfoils designed for UAV application, especially on the effects of leading edge ice accretion. The thickness, length, and position of ice accretion and basic airfoil shapes are the parameters to be studied. The results show that when the ice thickness increases the lift coefficient, stalling angle, and maximum lift coefficient are seriously impaired for the three UAV airfoils used in this study. The lift coefficient and stalling angle decrease when the length of ice accretion increases. On the icing position, if ice accretion concentrates more on the leading edge its effect on the maximum lift coefficient is more pronounced than the case that ice spreads more evenly on the fore part of the airfoils. All three airfoils calculated show similar trend of performance deterioration, but the airfoils, GA-17 and NLF-1015, are less influence by ice accretion than the airfoil, TYPE A. When compared with the airfoils, NLF-1015 and TYPE A, the GA-17 airfoil designed by using genetic algorithm still have maximum C(subscript l)/C(subscript d))(subscript max) and ΔC(subscript l)/C(subscript d))(subscript max) under icing conditions. Ice formed on the upper leading edge has more detrimental effects than that formed on lower leading edge. This research results indicate that the icing effects can be minimized if it is taken into consideration during the airfoil design stage. The results of the paper can be used in future airfoil optimization work. For the UAVs designed to loiter under low Reynolds number conditions, their wings must not only have high lift and low drag coefficients but maintain high maximum lift coefficients under all weather conditions to safeguard their mission success.