面向高超声速飞行器的宽速域翼型优化设计

Aerodynamic design optimization of wide-Mach-number-range airfoils for hypersonic vehicles

宽速域气动设计是水平起降高超声速飞行器研制的瓶颈问题之一。水平起降高超声速飞行器在飞行过程中需要经历亚、跨、超和高超声速多个速域,而适应不同速域的最佳气动外形相互矛盾,使得实现良好的宽速域气动设计面临极大挑战。首先,针对高超声速飞行器宽速域翼型气动设计问题,发展了基于代理模型的高效全局气动优化设计方法,并设计出一种相对厚度为4%、有一定弯度、下表面具有双“S”形特征的宽速域翼型。将新翼型与常规四边形和双弧形翼型进行了气动特性对比,并进行了流动机理分析,结果表明新翼型的宽速域综合气动特性显著优于常规翼型,从而证明发展兼顾亚、跨、超和高超声速气动性能的宽速域翼型是可行的。其次,开展了宽速域翼型的多目标优化设计,通过分析Pareto解集中翼型的宽速域气动性能随几何外形变化的演化规律,进一步解释了有一定弯度、下表面呈双“S”形的薄翼型能够协调亚、跨、超声速与高超声速气动性能的原理。最后,采用平面外形为梯形的机翼,进行了三维机翼构型下的宽速域翼型多目标优化设计。三维优化设计结果与二维结果具有相似的几何特征和压力分布,说明这种通过下表面双“S”形小弯度薄翼型来兼顾亚、跨、超和高超声速气动性能的宽速域流动机理同样适用于三维情况,也证实了翼型设计对于宽速域高超声速飞行器仍然具有重要意义。

Wide-Mach-number-range aerodynamic design is one of the bottlenecks in the development of horizontal take-off and landing hypersonic vehicles which experience subsonic,transonic,supersonic,and hypersonic regimes during their flights.However,optimized airfoil profiles for different speed regimes are often contradictory,which presents a great challenge to obtain satisfactory wide-Mach-number-range aerodynamic performance by a single configuration.Consequently,this article is aimed at the design of wide-Mach-number-range airfoils via an efficient global aerodynamic optimization design method based on surrogate models.First,a new wide-Mach-number-range airfoil is designed by taking both the hypersonic and transonic aerodynamic performance into account.The thickness of the optimal airfoil is 4%,and its lower surface features a double-"S"shape.Flow-field analyses indicate that the optimal airfoil compromises aerodynamic performance over a wide speed range,which has not been observed before.Second,a multi-objective optimization design of airfoils is further carried out,and a Pareto front of the lift-to-drag ratios from the transonic to hypersonic states is obtained.By analyzing the optimal results,the design principle of airfoils that compromises transonic and hypersonic aerodynamic performance is explained.Finally,the multi-objective optimization design of airfoils for three-dimensional wings is carried out.It is shown that the optimized airfoil for three-dimensional configurations has geometric characteristics similar to those obtained by two-dimensional optimization design,indicating that the flow mechanism around airfoils with small chambers and double-"S"lower surfaces also applies to three-dimensional situations and that the airfoil design is still of significance for wide-Mach-number-range hypersonic vehicles.