Resonance behavior of steam turbine blades with zigzag lacing pins

Abstract

The paper highlights the contribution of zigzag lacing pins, which are assembled in LP stages of some of the steam turbines. The result of experimental investigations on a prototype rotor establishes that these zigzag pins play a major role in forming a disk-like structure at high speeds. For such blades, conventional Campbell diagram does not give the complete dynamic behavior and hence SAFE diagram/Impulse diagram need to be generated. Due to the complex fixity conditions, analytical modeling is not very accurate and hence experimental investigation is a must to determine the exact behavior of the bladed disk. The paper describes the details of telemetry instrumentation used during the test. Detailed analysis procedure has been highlighted to retrieve and interpret the recorded data for generation of SAFE diagram.