Turbomachinery Blade Vibration and Dynamic Stress Measurements Utilizing Nonintrusive Techniques

The vibration of large turbomachinery blading is well known to be one of the most important design factors in modern turbomachinery. Typically, blade vibration is dominated by the unsteady flow phenomena and the interaction effects set up by vibration of blades within a high-velocity compressible fluid medium. This paper addresses the feasibility of developing an in-service noninterference measuring/monitoring system for steam turbine and gas turbine jet engine blade vibrations and stresses. The major purpose of such a measurement system is to provide a technically feasible, cost-effective means to isolate potential turbine and fan blade failures before they occur; thus minimizing costly machinery failure and risk of injury. The techniques that are examined include magnetic, inductive, optical, and laser and acoustic Doppler measurement methods. It appears likely that the most feasible and promising approach would include use of a few properly chosen measurement points on the blading in combination with use of advanced finite-element computational techniques and vibration modal methods. The modal analysis, performed experimentally and/or computationally, is especially useful in converting vibration measurements to the desired dynamic stresses.