Abstract
This paper focus on the wing shape related drag reduction measures of normal layout civil aircraft, through the drag reduction to improve the aircraft performance. Mainly by the laminar flow wing to reduce skin drag and weak shock wave wing to reduce shock drag, to keep a section of laminar zone on the wing leading edge to reduce skin drag, the wing profile's pressure distribution transit from the middle part's tonsure pressure zone to the trailing edge's inverse pressure gradient zone gentle to reduce the shock drag. The wing body junction plus the body belly fairing to increase the junction flow velocity, through increase flow velocity to weak the boundary layer stacked at the junction, improve the drag performance. The blended winglet to reduce the wing tip induced drag, study the shape parameters impact on the drag reduction, longitudinal moment and directional moment, attain the winglet model with drag reduction effect, suitable pitching moment and directional moment. For the wing body fairing have significant impact on the wing shape lower surface pressure distribution, the winglet have important impact on the wing tip flow, so the single part drag reduction measure is not feasible, need to carry out integrated drag reduction study on the wing related three drag reduction measures, and study the drag reduction measure's drag reduction decrement, put a reference for the normal layout civil aircraft's drag reduction. Through the above drag reduction measure's assessment attain the effect of drag reduction and rising the normal layout civil aircraft's cruise ratio, improving the cruise performance.
Highlights
This paper focus on the wing shape related drag reduction measures of normal layout civil aircraft, through the drag reduction to improve the aircraft performance
The wing body junction plus the body belly fairing to increase the junction flow velocity, through increase flow velocity to weak the boundary layer stacked at the junction, improve the drag performance
The blended winglet to reduce the wing tip induced drag, study the shape parameters impact on the drag reduction, longitudinal moment and directional moment, attain the winglet model with drag reduction effect, suitable pitching moment and directional moment
Summary
本文主 要对常规布局客机与机翼相关的减阻[9⁃10] 措施开展研究,进行了有层流流动机翼减小 摩阻和弱激波机翼减小波阻,在机翼表面前缘维持 一段层流区[11] 以减小摩阻,机翼剖面中部的顺压梯 度区域向后缘的逆压梯度区域和缓过渡,形成弱激 波或基本无激波以减小机翼激波阻力,翼身整流减 弱翼身结合处附面层堆积,增加翼身结合处流速,改 善阻力性能;融合式翼梢小翼[12] 外形参数对降低翼 尖诱导阻力的影响。 为验证本文转捩模型的有效性,对标模 DLR⁃F4 进行数值模拟,该模型为典型跨音速标准模型,机翼 前缘后掠角 27.1°,后缘后掠角为 18.9°,1 / 4 弦线后 掠角 25°,展弦比为 9.5。 图 1a) 为文献[19] DLR⁃F4 构型跨音速下不同雷诺数的转捩风洞试验。 转捩计 算采用 γ⁃Reθt 转捩模型,根据计算环境自动判断转 捩。 图 1b) 为与文献[19] 同模型同状态下计算的摩 阻分布,可以看到数值模拟结果与风洞试验现象基 本吻合。 在雷诺数 6×106 时机翼上表面均存在大面 积层流区,且内翼段的层流区长度明显小于外翼段, 随着雷诺数的提高,整个翼面的转捩位置前移。 在 雷诺数 1.7×107 下风洞试验与本文计算结果均在机 翼上表面前缘存在一段层流区,只是本文计算结果 在内翼段出现了层流区,这是由于本文转捩模型未 引入横流转捩修正,而横流效应在机翼 Kink 位置处 的内翼段更强,且外翼段转捩基本由二维不稳定性 主导,同时高雷诺数下层流区本身较短,因此采用本 文的转捩模型进行数值模拟对气动特性影响不大。 1.2 翼身整流减阻和翼梢小翼降低诱导阻力计算 基于建立的单通道飞机外形,机翼翼展 30 m, 参考面积 102 m2,后掠角 27°,机翼展向剖面形状如 图 3 所示。 同,带整流罩外形的网格分布如图 8 所示。 整流罩 减阻优化过程如图 9 所示,进行 CFD 数值模拟计 算,达到减阻效果则结束迭代,如没达到减阻效果, 返回对整流罩外形进行优化,生成网格并计算,直到 达到减阻效果为止。
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