某运输机加装失速条气动特性研究

Research on aerodynamic characteristics of transport aircraft with stall strips

为改善某运输机着陆襟翼构型失速急剧滚转问题,采用数值计算和风洞实验方法优选了机翼失速条的外形参数,并对气动力和流场特性进行了研究分析。以失速条高度H和安装位置距离前缘的长度S为设计变量,采用求解RANS方程的方法研究了失速条对着陆构型翼型二维特性的影响,表明S越小(即越靠近上翼面)失速迎角提前越多,H增大也能使失速迎角提前但敏感性小于S。失速条后方产生了分离气泡且随迎角增加而逐渐增大增长,在破裂后导致翼型失速提前,使升力线出现圆弧形的失速特征。设计了4种失速条在机翼上的平面布局方案,通过缩比模型风洞实验验证表明:40%半展长处展向长度2m,S=0的失速条使升力线由急剧失速变为平顶型失速并消除了失速后的不对称滚转力矩,将此失速条展长缩小一半的2种方案也不同程度地改善了失速形态,15%半展长处失速条对失速特性无明显改善,主要原因是气流分离从约40%半展长处开始发生,失速条安装在这一展向位置时才能发挥作用。

In order to alleviate the violent roll motion during stall of a transport aircraft with landing flap configuration, the geometric parameters of stall strips are optimized and selected by numerical simulations and wind tunnel tests, and the aerodynamic force and flow field characteristics are studied. The height H and the install distance S from the leading edge are selected as design parameters for stall strips, and are evaluated by solving Reynolds Averaged Navior-Stokes （RANS） equations for the airfoil section of the landing flap configuration. The calculation indicates that smaller S value （installed closer to the upper surface） promotes earlier stall, while the larger H has similar but weaker effect. Separation bubble emerges after the stall strips when the angle of attack （AOA） of the airfoil becomes large, which grows larger and longer with increasing AOA. The bubble bursts eventually and causes the airfoil to stall earlier, leading to the rounded shape of the lift curve. The effect of the stall strips installed on the wing is studied by scaled model in wind tunnel tests, which shows that its spanwise length and arrangement have significant impact on the performance besides the cross section geometry. Four planform arrangements of stall strips are advanced and evaluated. Keeping the S parameter equal to 0, the stall trips installed at 40% half span with spanwise length of 2m change the abrupt stall of the lift curve to a flat roof type one, and eliminate the asymmetric roll moment after stall. The spanwise length of the stall strips is halved to form 2 new arrangements, which also ameliorate the stall of the lift curve and roll moment to some extent. The stall trips installed at 15% half span have no obvious effects on the stall characteristics. The suggested explanation is that the flow separation starts at about 40% half span of the wing at landing configuration, where the stall strips have the best performance.