民用运输机着陆构型纵向失速特性改善研究

Study on improvement of longitudinal stalling characteristics in landing configuration of civil transport aircraft

采用经风洞试验验证的CFD计算方法和网格生成策略,研究某大型民用运输机着陆构型纵向失速特性的改善措施,将全机分为七大部件:机身、内翼段、中翼段、外翼段、翼梢、短舱和平尾,分别分析各部件的影响。研究结果表明:内中翼段对全机俯仰力矩曲线上拐的贡献为负,恶化其气动性能可以在一定程度上改善全机力矩特性,但是与此同时会降低最大升力系数和失速迎角;翼梢小翼在低速大迎角时发生大面积分离,对全机俯仰力矩曲线上拐的贡献为正,修形后构型的翼梢前缘产生很强的空间涡,很好地抑制分离区的产生和发展,改善了全机俯仰力矩特性,但是简单的翼梢修形会增大巡航时的诱导阻力,需要在高/低速之间进行权衡;平尾对全机俯仰力矩曲线上拐的贡献为正,其中内襟翼翼根涡对平尾当地来流的影响最为显著,通过修形整流包可以很好地解决这个问题,使全机俯仰力矩曲线上拐迎角增加4°。

In order to improve the longitudinal stalling characteristics of landing configuration, a certain large civil transport aircraft was investigated by computational mothed based on CFD tools and grid generation technique. The computational method was validated by wind tunnel results. The whole aircraft was divided in seven parts, which are the fuselage, inboard wing, middle wing, outboard wing, wingtip, nacelle, and horizontal tail. The results show that the contribution of the inboard and middle wing is negative to the inflexion of pitch moment curve. The stalling characteristics can be improved by worsening the aerodynamic characteristics of the inboard and middle wing, but this worsening procedure decreases the maximum lift coefficient and stalling angle of attack. At high angle o{ attack and low coming flow speed, there are massive separations in upper surface of the wingtip. The contribution of these separations is positive to the inflexion of pitch moment curve. The leading edge of modified wingtip may induce strong vortex, which can restrain the production and development of massive separation, therefore, the longitudinal stalling characteristics are improved. However, the cruise induced drag is increased due to the modification. A balanced choice needs to be executed for low and high incoming flow speed. The contribution of the horizontal tail is positive to the longitudinal stalling characteristics. The influence of the root vortex of inboard flap is extremely significant on local flow around the horizontal tail. By cowling modification, this influence can be restrained, and the angle of attack increases by 4° for the inflexion of pitch moment curve.