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高超声速钝前缘乘波构型优化设计研究

DESIGN AND OPTIMIZATION FOR HYPERSONIC CONE-DERIVED WAVERIDER WITH BLUNTED LEADING-EDGE

  • 摘要: 乘波体的高升阻比优势使其在高超声速飞行器设计中极具应用前景. 在实际工程应用中, 为了满足防热要求, 乘波体前缘必须进行钝化处理, 前缘钝化对乘波体气动性能会产生显著影响. 因此, 原始尖前缘最优乘波体并不能保证钝化后仍为最优. 针对这一问题, 首先研究了前缘钝化对不同构型升阻特性的影响程度和作用机理. 结果表明: 前缘钝化会造成乘波体升力小幅度降低, 阻力大幅增加, 升阻比显著降低; 其中钝前缘本身的波阻在阻力增量中起主导作用, 而钝前缘本身的摩阻增加量与物面的摩阻降低量十分接近. 基于上述结果, 提出了一种高效评估钝前缘乘波体气动力的方法, 并结合遗传算法, 开展了直接考虑前缘钝化影响的乘波构型优化设计研究, 获得了钝前缘最优构型. 通过CFD数值模拟对最优构型的气动力特性进行评估, 结果表明: 在不同飞行高度、不同升力和不同钝化半径约束下, 相比尖前缘最优构型, 钝前缘最优构型宽度变窄, 相同纵向位置处的后掠角增大, 且升阻比显著提升. 在M = 15, H = 50 km, CL = 0.3约束条件下, 钝化半径R = 10 mm的钝前缘最优构型设计点升阻比相比尖前缘最优构型提升量可达9.32%.

     

    Abstract: The waverider configuration has a broad application in hypersonic vehicles due to its high lift-to-drag ratio (L/D). In actuality, the sharp leading edge must be blunted because of the serious aerothermal heating problem, which can lead to significant loss of aerodynamic performance. Thus, the optimum configuration with sharp leading-edge cannot guarantee that it is still optimum after being blunted. To solve the problem, this paper first studies the influence and mechanism of leading-edge bluntness on the lift and drag characteristics of different configurations. The results show that the bluntness causes the lift to decrease slightly, the drag to increase greatly, and the L/D to decrease significantly. The wave drag of the blunted leading-edge plays a dominant role in the total drag increment, and the friction drag of the blunted leading-edge is very close to the friction drag reduction of the upper and lower surface. Based on the above results, this paper evaluates the wave drag of the blunted leading-edge by the modified Newton theory, and combines the aerodynamic models of sharp leading-edge waverider and genetic algorithm to obtain the optimum configurations with blunted leading-edge. The aerodynamic forces of the optimum configurations are evaluated via CFD simulation. The results show that under the constraints of different flight altitudes, different lift, and different blunt radii, compared with the optimum configurations with sharp leading-edge, the blunted optimized waveriders have the characteristics that the width is smaller, the sweep angle at the same longitudinal position is larger, and the L/D is higher. At the design condition of M = 15, H = 50 km and CL = 0.3, the L/D of the optimum blunted configuration with R = 10 mm can be improved by 9.32%. What’s more, as the constraint of the lift coefficient increases, blunt radius increases, and the flight altitude decreases, the advantage of L/D for the blunted optimized waveriders become more evident.

     

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