跨音速风扇全环叶片颤振特性的流固耦合分析

发展了求解叶片颤振问题的流固耦合计算方法和全环叶片振动的气动弹性模型,在每一时间步同步求解流体运动方程和叶片振动方程并交换边界信息;流体域求解了非定常雷诺平均N-S方程,得到每一步由于叶片变形而引起的流场变化;叶片变形则由积分叶片表面受到的气动力并求解结构动力学方程得到.颤振分析是在全环叶片模型上进行的,并解除了预先设定叶片间相位角的限制.此方法的显著特征是在一次气动弹性计算过程中,可同时分析叶片多个固有模态、多个节径下的气动弹性稳定性,大大提高了使用时域法进行叶片排气弹分析的计算效率.考察了NASA rotor 67风扇全环模型在堵塞点、最高效率点和近喘点3个气动工况下,节径变化对叶片气动弹性稳定性的影响,给出了不同模态下气弹最不稳定状态对应的叶片振动节径形式.结果表明,振动形式对于叶片气动弹性稳定性的影响很大.

Full assembly fluid/structured flutter analysis of a transonic fan

Numeric method for blade flutter with coupled fluid'structured approach and aeroelastic model of full assembly fan blade vibration were developed. The coupling was achieved by solving governing equations for fluids and the blade vibration simultaneously and exchanging boundary condition at each time step. In the fluid domain, the unsteady Navier-Stokes equations are solved numerically to assess the effects of the deforming blades on the flowfield. The blade motion was calculated by integration of aerodynamic forces on the blades and solving structured dynamic equations. The blade flutter was conducted on a full assembly model in order to avoid pre-defined Inter-Blade-Phase-Angle. This method is capable performing aeroelastic stability analysis of multiple modes/nodal diameter in an unsteady computation, thus the efficiency of time domain aeroelasticity approach was improved. Detailed fluid/structured interaction analysis of NASA rotor 67 were conducted at choked, peak efficiency and near stall operation points to assess the effect of nodal diameter on the aeroelastic stability, the least stable blade vibration mode and nodal diameter was presented. The result indicates that nodal diameter of blade-row vibration is the most influential factor to the aeroelasticity.