Mistuning Effects on Aero-elastic Stability of Contra-Rotating Turbine Blades

The aero-elasticity of contra-rotating turbine blades has been evaluated by employing the energy method and the aero-elastic eigenvalue method, which is different from the normal turbine blades with HPT wake impinging on the LPT directly. The effects of two different intentional mistuning patterns and random mistuning with standard deviation from 0.1 to 1% on aero-elastic stability of the low-pressure turbine (LPT) blades have been investigated by use of the eigenvalue method. Studies show that the best stabilized effect can be obtained with a specific distribution of mistuning amount for alternate and sinusoidal patterns. The random mistuning can improve the stability of tuned system with the increase of the standard deviation. But when the standard deviation is greater than 0.6%, the improving effect is invariable. For the mistuned system, the random mistuning decreases the stability of the intentional mistuned system and the optimal mistuning pattern has been changed. Additionally, when the standard deviation of the random mistuning is fixed, the mistuning amount has a more significant effect on the alternate mistuning than the sinusoidal mistuning.