Aero-mechanical modal approach

Aero-mechanical Modal Approach to Aerodynamic Performance Optimization

A blading design optimization system has been developed using an aeromechanical approach and harmonic perturbation method. The developed system has the capability to optimize aero-thermal performance with constraints of mechanical and aeromechanical integrity at the same time. ‘Aerodynamic mode shape’ is introduced to describe geometry deformation so that both blade shape change perturbations for both the gradient sensitivity and the structural vibration analysis can be dealt with within an unified solver.  A redesign practice of the NASA rotor-67 at the peak efficiency point shows that the aero thermal efficiency can be improved by 0.4%, whilst the maximum static stress has been increased by 33%. Aeromechanical analysis of the optimized blade shows that the aerodynamic damping of the least stable first flap mode is still well above the critical value though the natural frequencies of the first 5 modes have been reduced by 1-4%. The present finding highlights the need for more concurrent integrations of mechanics, aerodynamics and aeromechanics design optimization.

 Examples of 3D "Aerodynamic Modes"

Reference:

-H-D. Li, L. He, Y-S Li and R G Wells, “Blading aerodynamics design optimization with mechanical and aeromechanical constraints”, ASME Paper, GT- 2006-90503.
-H-D. Li and L. He, “Aerodynamic and Aeromechanic Blading Design Optimization Using Harmonic Perturbation Methods”, AIAA Paper 2005-1256.  Proc of the 15th International Symposium on Air-breathing Engines, Munich, Germany, Sept., 2005.