| High-performance airfoils and planar cascades have important impact on the efficiency and performance of rotating machinery.In this paper,the numerical simulation calculation method is used to study the airfoil optimization under the constrained angle of attack method,the airfoil and plane cascade optimization under the unconstrained angle of attack method,and provide a reference for the research on the optimization method of airfoil and plane cascade.The airfoil profile is parametrically modeled by Bézier curve,combined with the multi-island genetic algorithm,the profile characteristics and aerodynamic characteristics of the optimized airfoils under different constrained angles of attack are studied.The research results show that at the constrained angle of attack,the lift-to-drag ratio of the optimized airfoils are higher than that of the comparative airfoils;the flow of the optimized airfoils is more reasonable and the aerodynamic performance is better;the maximum lift-to-drag ratio of the optimized airfoils does not necessarily appear in the constrained angle of attack;the position of maximum thickness of the optimized airfoils moves forward as the angle of attack increases.An unconstrained angle of attack optimization method is proposed,which takes the angle of attack as one of the optimization variables.The unconstrained angle of attack optimization airfoils under different Reynolds number conditions are studied,and their profile and aerodynamic characteristics are analyzed,and the results are compared with the optimized airfoils obtained by constrained angle of attack method.The research results show that the lift-to-drag ratio of the optimized airfoils obtained by the unconstrained angle of attack method is higher,the flow field distribution is more reasonable,and the aerodynamic performance is better;the optimized airfoils have good Reynolds number characteristics;The optimized airfoils obtained by unconstrained angle of attack method can maintain a higher lift-drag ratio in a wide range,while the optimized airfoils obtained by the constrained angle of attack method have a high lift-to-drag ratio only near the constrained angle of attack.Using the unconstrained angle of attack optimization method,combined with the Bézier curve and the NSGA II algorithm,the optimized cascade airfoils under different Reynolds numbers and different relative pitches were studied respectively,and their lift-to-drag characteristics and total pressure loss characteristics were analyzed.The research results show that within the range of the calculated angle of attack,the optimized cascade airfoils have a higher lift-to-drag ratio and a smaller total pressure loss coefficient;the optimized cascade airfoils have a larger angle of attack with a sharp increase in the total pressure loss coefficient,and the increase is smaller at large angles of attack;the optimized cascade airfoils have good Reynolds number characteristics and relative pitch characteristics. |
