Blade flutter and forced-response prediction

Blade Flutter and Forced-Response Prediction Method Development

The direct coupled solution method is suited for prediction of aeroelastic behaviour of blade at highly loaded flow conditions with large scale self-excited flow instabilities (e.g. rotating stall). The simultaneous strongly coupled solution for both the blade structural dynamics equations and the Navier-Stokes floe equations was obtained using a multi-stage Runge-Kutta integration (He, 1994, 1996). The results for a compressor blade row at a transonic flow condition with and without the structure coupling show a rotating flow instability of a limit cycle type can be locked to the blade torsional structural mode with a relatively large frequency shift, leading to stall flutter.  

For many turbomachinery applications, efficient and accurate predictions can be obtained by using a loosely coupled or decoupled approach, assuming the structural mode shapes and frequencies are not affected by aerodynamics. A prediction system for blade forced response and flutter has been developed (Moffatt et al, 2005) and its validity and effectiveness has been analyzed (Moffatt and He, 2005)

Blade forced response prediction system 



L. He, "Integration of 2-D Flow/Structure Coupled System for Calculations of Turbomachinery Aerodynamic/aeroelastic Instabilities", International Journal of Computational Fluid Dynamics, Vol.4, No.4, pp217-231, 1994.
L. He, "I. Modelling Issues in Computation of Unsteady Turbomachinery Flows; III. Flow-Structure Coupled Solution for Stall Flutter and Rotating-Stall", VKI Lecture Series "Unsteady Flows in Turbomachines" (ISSN 0377-8312), von Karman Institute for Fluid Dynamics, Brussels, March, 1996.
S. Moffatt, W. Ning, Y. Li, R. G. Wells and L. He, “Blade Forced Response Prediction for Industrial Gas Turbines”, AIAA Journal of Propulsion and Power, Vol.21, No.4, pp707-714, July-August, 2005.
S. Moffatt and L. He, “On Decoupled and Fully-Coupled Methods for Blade Forced Response Prediction”, Journal of Fluids and Structures. Vol. 20, No. 2, pp217-234, Feb, 2005.