【作者】 刘小雷；

【导师】 施卫平；

【作者基本信息】 吉林大学 ， 流体力学， 2010， 硕士

【摘要】 减小诱导阻力是实现飞机减阻的一个重要途径,人们从鹰和隼向上偏折翅尖羽毛进行远距离滑翔中得到启示,发明了多种翼尖减阻装置。本文以RAE2822超临界翼型为剖面,参考ARJ-21机翼尺寸建立的机翼为基本翼,借鉴国内外的翼尖小翼设计和相关的资料,设计了一种全新的翼尖小翼。使用Fluent软件,按照相同数值模拟方法和边界条件分别对平直翼和加装翼尖小翼的机翼进行三维数值模拟。对比结果,得到加装翼尖小翼后阻力减小、气动性能提升的结论:在同一马赫数和攻角条件下,加装翼尖小翼的机翼升力系数都增大了。0.65M条件下,最大增升率为3.1%,平均增升率为2.0%;0.7M条件下,最大增升率为4.2%,平均增升率为2.8%。阻力系数在各马赫数、各攻角计算条件下都有不同程度减小。其中0.65M条件下,最大减阻率达到14.4%,平均减阻率11.8%;0.7M条件下,最大减阻率11.2%,平均减阻率为10.2%。加装翼尖小翼以后,模拟计算条件下升阻比最大提升了18.7%,马赫数0.65,平均升阻比增加率为16.8%;马赫数0.7,平均升阻比增加率为15.4%。本文对加装翼尖小翼后机翼的气动特性以及减阻机理进行了分析。翼尖小翼对下翼面空气向上绕流的端板作用,以及对翼尖涡的能量耗散作用使翼展范围内下洗角和下洗速度减小,是使得机翼阻力减小的主要原因。更多还原

【Abstract】 With the deterioration of the energy shortage and people’s increasing concern about environmental issue, efficient, energy-saving, environmental friendly mode of economic development has become the major theme of the world economic development in the contemporary era. Airplane is a kind of efficient and fast means of transportation, it need to consume a large amount of fuel. Therefore, how to reduce fuel consumption and improve flight efficiency is increasingly concerned by the aircraft designers. The key of achieving this goal is to reduce the drag and increase the lift. Particularly, reducing the drag in flight is an important aspect to improve the characteristics of a large transport airplane. The drag of large-scale long-range transport airplane is mainly consist of induced drag, pressure drag and friction drag. It is noteworthy that the induced drag accounts for about 40% of the total drag during cruising flight, so reducing the induced drag is an important way for drag reduction, which is also the goal for the aircraft designers to make a concerted effort to solve.By the long-term observation of the large birds (such as eagles and falcons), it is discovered that they deflect their wings upward in flight to reduce the drag for gliding farther. The vortex was formed at the wing tip and resulted in the induced drag. Hindering the formation of wing tip vortex or destroying the structure of the vortex are the fundamental way to reduce the induced drag. So wing tip drag-reducing device such as cut tip, wing tip sails, wing tip winglet were invented. Currently, equipped winglets on large transport aircraft in the civilian has been concern widely by the airplane designers. It has become a necessary equipment of the new airplanes. Many countries put into a lot of manpower and financial resources to conduct relevant researches.Many shape parameters of winglet, such as the tilt angle, the installation angle, the airfoil of winglet, the height and the area of winglet, and so on, affect the drag reduction. Therefore, the drag reduction effects of different winglets are reported in many articles. In our country, the research is relatively weak because the design of large transport aircraft has just begun. In this thesis, a basic wing shape was created by selecting standard RAE2822 supercritical airfoil as the aerofoil of wing and referring to ARJ-21 wing size. On the basis of that, a new wing tip winglet was designed. The 3-D airflow over the wing is simulated by Fluent software, and the related theoretical analysis was done about the wing drag reduction effect.In order to provide a reference for comparing the drag reduction effect of the winglets, the 3-D numerical simulation of basic wing created by using standard RAE2822 supercritical airfoil as aerofoil of wing and referring to ARJ-21 wing size was simulated at first. Independent of mesh topology and the reliability of turbulence model were demonstrated numerically and it shows that numerical simulation is reliable. The numerical results are compared with the experimental data, and the results is proved to be reliable.Based on the simulation for the basic wing, the same simulation method and boundary condition are applied on 3-D numerical simulations for the wing with winglet. Comparing to the results of two wings, a conclusion about drag-reducing properties can be drawn. At the same Mach numbers and attack angles of attack, all the lift coefficients of the wings with winglet increased. When the Mach number is 0.65, the maximum of increment is 3.1%, the average increment is 2.0%. At Mach number of 0.7, the maximum of increment is 4.2%, the average increment is 2.8%. The drag coefficients of the wing with winglet decrease to the different degree. At Mach number of 0.65, the maximum of drag reduction rate is 14.4%, the average drag reduction rate is 11.8%. At Mach number of 0.7, the maximum of drag reduction rate is 11.2%, the average drag reduction rate is 10.2%. The maximum of increment is 18.7% in lift-drag ratio of wing, the increment is 16.8% at Mach number of 0.65, and the increment is 15.4% at Mach number of 0.7. Thus, aerodynamic performance of wing with winglet has been greatly enhanced.Comparing the two results of calculation, the aerodynamic characteristics and the drag-reducing mechanism of wing with winglet were analyzed in this thesis. Blocking air flow upward, dissipating energy of wing tip vortex, reducing downwash angle and downwash velocity within entire wing span, are the main reasons of winglet drag reduction.更多还原