An unsteady aerodynamic modeling for turbomachinery based on system identification

This paper presents an efficient and fidelity-oriented unsteady aerodynamic modeling method that can investigate flutter for turbomachinery. A certain blade of multiple blade passages is specified vibrating at a swept-frequency signal instead of harmonic one, and forced aerodynamic responses of the blade row can first be calculated. Identify form the aerodynamic responses data, so that the frequency responses of the system for muti-passages are acquired, and the aerodynamic coefficient of every blade for different natural frequencies within swept-frequencies can be obtained immediately. Following the superposition principle of small disturbance flow, aerodynamic damping coefficients changing with inter blade phase angles as well as frequencies are acquired only by an unsteady computational fluid dynamics (CFD) computation. The aeroelastic characteristics of STCF4 (Standard Test Configuration 4) are analyzed by using this method. The results for different na-tural frequencies are agreed well with that of reduced order model (ROM) method as well as direct CFD method, and the computational efficiency is improved obviously, as a result, this method is useful to analyze stability during preliminary design of turbomachinery.