零质量射流下波浪前缘叶片气动性能数值研究
NUMERICAL STUDY ON THE AERODYNAMIC PERFORMANCE OF THE WAVY LEADING- EDGE BLADE UNDER ZERO-NET-MASS-FLUX JET
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摘要: 针对垂直轴风机叶片大攻角工况下因流动分离导致的失速及颤振抖振问题, 引入零质量射流激励对波浪型前缘叶片进行流动分离控制. 采用大涡模拟方法建立了波浪前缘叶片绕流数值模型, 探究了主/被动耦合控制下叶片升阻力特性及其流动分离机理, 分析了射流参数(射流位置、动量系数)对波浪前缘叶片气动性能及失速特性的影响机制, 研究发现: 受控前后大攻角下波浪型前缘能诱导产生较小尺度流向涡, 降低后方大分离涡尺度, 波浪前缘与零质量射流耦合控制对于大攻角下流动分离抑制较单一控制更优; 零质量射流吹气时使前缘流向涡有更高的动能抵抗逆压梯度从而延迟流动分离, 吸气时会吸走流向涡的低动量流体, 抑制流向涡发展成大分离涡; 射流布置在距基准前缘0.033c处, 即位于前缘流向涡最前端, 能最大程度地参与前缘流向涡的生成, 升阻比的提升效果最好; 且升阻比提升量随着动量系数增大而增大, 但控制经济性在动量系数0.018时最优, 研究结果为垂直轴风力机失速控制提供了有益参考.Abstract: Aiming at the problem of stalling and flutter buffeting caused by the flow separation of vertical axis fan blades under the condition of high attack angle, zero-net-mass-flux jet excitation is introduced to control the flow separation of wavy leading edge blades. The numerical model of the flow around the static wavy leading-edge blade was established by the large eddy simulation method, the lift and drag characteristics and the flow separation mechanism of the wavy leading-edge blade was analyzed after adding the zero-net-mass-flux jet, and the influence of the change of jet parameters (jet position and momentum coefficient) on the stall characteristics of the wavy leading-edge blade was explored. It is found that the wavy leading-edge under the controlled and uncontrolled condition at large attack can induce the generation of small-scale streamwise vortex, and reduce the size of the rear large separation vortex, so that the coupling effect between the wavy leading-edge and the jet is better than that under the control of the jet or wavy leading-edge. Blowing of the zero-net-mass-flux jet makes the leading-edge flow-to-vortex have higher kinetic energy resistance to inverse pressure gradient, thus delaying flow separation. Inhaling will suck away the low momentum fluid of streamwise vortex, thus inhibiting the development of streamwise vortex into large separation vortex. The jet is located at a distance of 0.033c from the baseline leading edge, which is at the forefront of the leading edge streamwise vortex, allowing it to participate most effectively in the generation of the leading edge streamwise vortex, resulting in the best improvement in lift-to-drag ratio. Moreover, the increase in lift-to-drag ratio enhancement is proportional to the increase in momentum coefficient. However, the control economy is optimal when the momentum coefficient is 0.018. It provides useful support for the stall control of vertical axis wind turbines.