以跨声速机翼设计中权衡气动性能和总体设计要求的工程应用为出发点,在保证机翼结构重量和容积不变的约束下,提出了平面形状优化与剖面翼型优化结合的两步优化设计策略。应用神经网络和遗传算法,建立了相应的设计方法。采用两步优化方法进行跨声速机翼设计,第一步设计中,通过平面形状优化,增大机翼展弦比、减小诱导阻力是机翼气动性能改善的主要原因,但由于结构重量约束,平面形状变化不大,对机翼气动性能改善有限;第二步设计中,以第一步设计所优化的机翼平面形状为基础,并以机翼容积为约束,通过机翼剖面翼型优化,弱化较大马赫数下的激波、减小激波阻力是机翼气动性能改善的主要原因。经过这两步优化设计,机翼在两个设计点下的升阻比分别提高了3.02%和9.96%,阻力发散马赫数由0.854 0推迟到0.865 3,表明两步优化设计方法适合于工程应用。在无结构重量和容积约束下,采用单纯气动最优的平面形状和剖面翼型优化两种设计方法均可明显改善机翼气动性能,但不能满足机翼结构重量和容积不变的设计要求。
This paper starts with the engineering application of a trade-off between the aerodynamic characteristics and aircraft design requirements in transonic wing design, and proposes a two-step design strategy which combines the wing planform optimization and wing section optimization based on the constraints of constant structure weight and volume. Using the neural network and genetic algorithm, a corresponding design method is set up. For the transonic wing design using the two-step optimization method, improvement of the wing aerodynamic characteristics in the first design step mainly depends on the optimization of the wing planform, which can increase the wing aspect ratio and reduce induced drag. However, the improvement is very limited because the structure weight constraint just allows very little change in the wing planform. In the second design step, based on the wing planform optimized in the first design step and wing volume constraint, improvement of the wing aerodynamic characteristics mainly depends on the optimization of the wing sections which can weaken the shock wave and reduce wave drag at high Mach numbers. By using the two-step optimization method, the lift-drag ratio increments of the two design points can reach 3.02% and 9.96% respectively, and the drag divergence Mach number can be postponed from 0.854 to 0.8653. Moreover, the two-step optimization design method is suitable for engineering application. The pure aerodynamic optimization methods are also applicable to transonic wing design without the constraints of structure weight and volume. The results show that the improvement in aerodynamic characteristics is significant though the method will not then satisfy the design requirements of constant structure weight and volume.
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