Design and optimization of tandem cascade based on parallel differential evolution algorithm

A method of tandem airfoil geometry generation and an algorithm of master-slave parallel differential evolution are first developed for the later optimization. An initial tandem cascade is roughly designed and significantly outperforms the original conventional cascade. Based on the parallel differential evolution algorithm and a Navier-Stokes solver, five configuration variables of the initial tandem cascade are then numerically optimized at an inlet Mach number of 0.7 and an approximately minimum-loss incidence of 1.9°. The result shows that the total pressure loss coefficient of the optimum design decreases by 8.67%. The history data of the optimization is statistically analyzed, which reveals the influence levels of the five configuration variables on tandem performance. The performances of the initial and optimum designs at a range of incidence angles are then numerically calculated, showing that the optimum design outperforms the initial design at small or negative incidence angles and performs more poorly at high incidence angles. It is proposed and verified that the different front-rear distributions of camber and chord leads to this phenomenon. Finally, a new-defined variable is proposed to measure the distribution above.