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为了快速获得不同刚度的叶轮机叶片颤振特性,提出了一种基于系统辨识技术的叶片排非定常气动力建模方法,分析了叶片气动阻尼随叶间相角差和固有频率的变化特性。该方法通过对多叶片通道的某一叶片单独施加一个扫频振动信号,求解一次非定常流场,得到叶片排上每个叶片的气动力响应,通过系统辨识,获得每个叶片的气动力频率响应。根据小扰动流的叠加原理,得到扫频范围内各固有频率下的叶片排所有叶片共同激励的气动力模型,由此进一步得到各个不同固有频率的所有叶间相角差下的气动阻尼。针对STCF4(Standard Test Configuration 4)算例,该方法的计算结果与直接采用计算流体力学(CFD)方法和直接采用谐振信号的降阶方法(ROM)得到的气动阻尼系数吻合得很好。该方法只需进行一次非定常CFD计算就能得到扫频范围内不同固有频率下的气动阻尼特性曲线,极大地提高了计算效率,方便了叶轮机设计初期的气动弹性稳定性参数分析。
In order to quickly obtain the flutter characteristics of blade with different stiffness, a method of unsteady aerodynamic modeling of blade row based on system identification technology is proposed. The variation characteristics of aerodynamic damping with leaf phase angle difference and natural frequency are analyzed. In the method, a swept-frequency vibration signal is applied to a blade of a multi-blade passage to solve an unsteady flow field to obtain the aerodynamic response of each blade on the blade row. The aerodynamic frequency of each blade is obtained through system identification response. According to the principle of superposition of small perturbation flow, the aerodynamic model of all blades in the blade row at each natural frequency in the swept frequency range is obtained, and the aerodynamic damping of all the inter-leaf phase angles with different natural frequencies is further obtained. For the STCF4 example, the calculated results agree well with the aerodynamic damping coefficients obtained directly from the Computational Fluid Dynamics (CFD) method and the reduced-order method (ROM) using the resonant signals directly. The method can obtain the aerodynamic damping curve under different natural frequencies within the swept frequency range by only one unsteady CFD calculation, which greatly improves the computational efficiency and facilitates the analysis of aeroelastic stability parameters during the initial stage of the turbine design.