仿鲸鱼鳍凹凸前缘翼型流动分离控制及应用研究

发布时间：2019-03-19 17:34

【摘要】：座头鲸具有的前缘突起的肢状胸鳍,为其扑食回转提供强大的动力。受此生物学特性启发。本文作者开展了以NACA634-021为基本翼型和相应的仿生凹凸前缘翼型的气动特性、流场特性以及凹凸前缘流动控制机理研究。在此基础上,对典型的风力机翼型DU40、DU18的仿生凹凸前缘流动控制进行了实验研究和数值计算研究；同时对仿生凹凸前缘叶片和光滑叶片进行实验研究。针对以NACA634-021翼型为基型的光滑翼段和凹凸前缘翼段模型,在0。～90°攻角,采用三分量测力天平和粒子图像测速仪(PIV)于直流风洞中分别测量升力、阻力、俯仰力矩等翼型气动特性和流速、涡量、边界层等流场特性,开展仿生凹凸前缘流动控制的有效性和作用机理的实验研究。实验结果表明：与光滑翼段相比,凹凸前缘翼段的失速特性更为平缓,失速后气动特性有明显改善,其中升力系数提高可达18%,升阻比可增加12%,阻力系数减小10%,在30°～80°高攻角区内凹凸前缘仍然具有一定的效果；通过分析,凹凸前缘翼型对失速控制的作用机理在于：当气流绕过凹凸前缘后,气流被引导环绕凸峰运动,在每个凸包的两侧产生一对反向旋转的流向涡结构,该涡结构作用范围不仅仅局限在边界层内,加强了边界层内部和外部势流的动量交换,进而增强了翼型抵御逆压梯度的能力,降低了吸力面的负压梯度,推迟了流动分离,失速得以延缓。同时分析了流向涡环量的变化趋势,在攻角17°～25°之间其环量值在变化很小,使得翼型失速平缓。依据凹凸前缘流动控制机理,对凹凸前缘的有效高度与边界层heffc/δ的比值进一步分析,发现heffc/δ小于1,其范围在0.1-0.5之间能有效改变翼型的失速特性与微小涡流发生器作用相似。通过DU40和仿生凹凸前缘DU40-25wavy、DU40-11wavy和1DU18和仿生凹凸前缘DU18-25wavy、DU18-11wavy的气动力特性实验研究表明,在高攻角区域凹凸前缘翼型都能提高升力系数,在低攻角区域11wavy翼型更有优势气动升力相比光滑减小幅度较小。通过计算DU40和仿生凹凸前缘DU40-25wavy、DU40-11wavy和DU18和仿生凹凸前缘DU18-25wavy、DU18-11wavy在低攻角区域和高攻角区域的流场和压力系数分布表明,凹凸凸起对于压力系数的分布有较大的影响,在低攻角区域由于凹凸前缘的影响较弱压力差提高幅度较小,在高攻角区域由于凹凸前缘引起的流向涡强度增大,压力系数在翼型的前缘差值增大,提高了升力系数。另夕11wavy翼型提高幅度较大,表现了更优异的气动性能。在双叶片风机实验台上进行了光滑叶片和凹凸前缘叶片的风洞试验,结果表明：对于凹凸前缘叶片,在来流风速和尖速比分别与光滑叶片保持相同的情况下,凹凸前缘叶片扭矩增大15.6%,推力减小9.7%,功率系数提高可达到22%。
[Abstract]:Humpback whales have a protuberant limb-shaped pectoral fin that provides a powerful force for flapping and turning. Inspired by this biological characteristic. In this paper, the aerodynamic characteristics, flow field characteristics and flow control mechanism of NACA634-021-based airfoils and corresponding bionic concave-convex front airfoils are studied. On this basis, the flow control of bionic concave-convex leading edge of typical wind turbine airfoil DU40,DU18 is studied experimentally and numerically, and the bionic concave-convex front blade and smooth blade are also studied experimentally. For the smooth airfoil and concave-convex front wing models based on NACA634-021 airfoil, the lift and resistance were measured in a DC wind tunnel using a three-component force balance and a particle image velocimeter (PIV) at an angle of attack of 0. 0 掳and a particle image velocimeter (PIV), respectively, at an angle of attack of 0. 0. 90 掳. The aerodynamic characteristics, velocity, vorticity and boundary layer characteristics of pitching moment equal airfoil are studied. The effectiveness and mechanism of flow control of bionic concave and convex leading edge are studied experimentally. The experimental results show that the stall characteristics of concave and convex front flanks are more smooth than that of smooth airfoils, and the aerodynamic characteristics are obviously improved after stall. The lift coefficient increases by 18%, the lift-drag ratio increases by 12%, and the drag coefficient decreases by 10%. In the area of 30 掳~ 80 掳high angle of attack, the concave and convex leading edge still has certain effect. According to the analysis, the mechanism of the airfoil acting on the stall control is that when the air flows around the convex front, the air flow is guided around the convex peak, and a pair of reverse rotating flow vortices are produced on both sides of each convex envelope. The scope of the vortex structure is not only confined to the boundary layer, but also enhances the momentum exchange between the inner and outer potential flows in the boundary layer, and then enhances the airfoil's ability to resist the inverse pressure gradient, reduces the negative pressure gradient on the suction surface, and delays the flow separation. The stall was delayed. At the same time, the variation trend of the flow vorticity is analyzed. The value of the torus varies little between the angle of attack 17 掳~ 25 掳, which makes the airfoil stall smooth. Based on the flow control mechanism of the bump front, the ratio of the effective height of the bump front to the boundary layer heffc/ 未 is further analyzed. It is found that the heffc/ 未 is less than 1, The range between 0.1 and 0.5 can effectively change the stall characteristics of airfoils, which is similar to the action of micro eddy current generator. The aerodynamic characteristics of DU40, bionic bump leading edge DU40-25wavy,DU40-11wavy and 1DU18 and bionic bump leading edge DU18-25wavy,DU18-11wavy are experimentally studied. The results show that the lift coefficient of the airfoil can be improved in the high angle of attack region. In the low angle of attack region, the aerodynamic lift of the 11wavy airfoil is more dominant than that of the smooth reduction of aerodynamic lift. The distributions of flow field and pressure coefficient of DU40 and bionic bump leading edge DU40-25wavy,DU40-11wavy and DU18 and bionic bump leading edge DU18-25wavy,DU18-11wavy in low angle of attack region and high angle of attack region are calculated. The bump has a great influence on the distribution of pressure coefficient. In the low angle of attack region, the pressure difference increases slightly due to the weak influence of the front edge of bump, and in the region of high angle of attack, the intensity of flow vorticity increases due to the leading edge of bump. The pressure coefficient increases at the leading edge of the airfoil and increases the lift coefficient. On the other hand, the improvement range of 11wavy airfoil is larger, and it shows better aerodynamic performance. Wind tunnel tests of smooth blades and concave-convex front blades were carried out on a two-blade fan test rig. The results show that for concave-convex front blades, the inlet wind speed and tip-velocity ratio are the same as those of smooth blades, respectively. The torque of the front blade increases by 15.6%, the thrust decreases by 9.7%, and the power coefficient increases by 22%.
【学位授予单位】：中国科学院研究生院(工程热物理研究所)
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TK83;TB17

【共引文献】