Investigation of Differential Evolution Algorithm for a Tandem Cascade Optimization

Due to the fact that there are numerous factors and parameters associated to tandem cascade, and upstream and downstream blades have intensive interference and unknown matching correlation, it is difficult to create tandem blades with high performance based on conventional optimization design method. Therefore, developing an optimization strategy that can take into account key parameters of tandem blades is a feasible way to get optimal design of tandem cascade. In the present work, the Sphere and Rastrigin test functions were adopted to compare and analyze five differential evolution modes, and the DE/r2b/2 evolution mode was then obtained, which can be applied to engineering practice. Based on the present evolutionary pattern, the combination the effects of axial overlap (AO), percent pitch (PP), camber ratio (TR), chord ratio (CR) and approximate incidence angle of the rear blade ( K b-b ) are considered comprehensively. Thus, the optimization process and strategy are designed, and the optimization objective function is determined. The optimization results show that under the condition of designed Mach number and large angle of attack (AOA), comparing with the original blades, the optimization makes the static pressure ratio of the tandem blades increased by 1.14%, and the total pressure loss coefficient decreased by 6.57%. 串列叶型可调参数多，上下游叶片有强烈的干涉效应和某种未知的匹配关联，基于传统的叶片优化设计方法难以获得高性能串列叶片。应用Sphere和Rastrigin测试函数对比分析了DE/b/1、DE/b/2、DE/r/1、DE/r/2和DE/r2b/2差分进化模式，从中选取可工程实用的DE/r2b/2进化模式。应用该差分进化模式，综合考虑轴向重合度、节距系数、弯角比、弦长比以及后排来流近似攻角5种参数的共同作用，设计了优化流程、优化策略，确定了优化目标函数，对初始设计的串列叶型进行了优化研究，提出了一种可以考虑串列叶片关键参数的优化策略和方法。优化结果表明，在设计马赫数，大攻角工况下，较原始叶片，优化使得串列叶型静压比增加1.14%，总压损失系数降低6.57%。