自带冠叶片碰撞减振过程阻尼特性实验研究

Experimental Research on Damping Characteristics for Vibration-impact Process of Steam Turbine Blades with Integral Shroud

自带冠技术是一种提高汽轮机叶片可靠性的先进技术。为了定量描述自带冠叶片碰撞减振过程的阻尼特性,在实验台上进行了一系列的叶片碰撞减振实验,在不同转速、不同载荷和不同叶冠间隙的情况下,测量叶片同一位置的应变大小,获得叶片在不同实验条件下的振动对数衰减率,通过比较对数衰减率的大小来比较不同工况下的叶片振动阻尼大小。通过实验,获得了不同参数下的碰撞减振效果,证明了叶片的自带冠是一种很好的碰撞减振阻尼结构。实验研究还表明,当相邻两个自带冠叶片的冠间间隙很小时,叶片动态应力对负荷大小不敏感;冠间间隙不对称能够改善减振效果。

Integral shroud is an advanced technique used to improve reliability of steam turbine blades. In this paper, a series of experiments are well performed on the platform of contracting and impacting of blades tips, and damping characteristics of vibration-impact process of steam turbine blades with integral shroud are studied. The dynamic strain data under different clearances, different loads and different rotating speeds are surveyed through which the log decrement at each condition is obtained, and the effects of vibration damping are obtained by comparing the log decrement. The results of experimental study show that the vibro-impact structure is a good vibration damper. The dynamic stress of the blade with integral shroud is insensitive to loads when the clearance between adjacent integral shrouds is small ,and the asymmetry gap has better damping effect than symmetry one.