OPTICAL SYSTEMS AND METHODS FOR MEASURING TURBINE BLADE TIP CLEARANCE

摘要

A blade tip measurement system includes a case and a blade that rotates within the case, the blade having an outer blade tip surface that has a clearance distance from an inner surface of the case. A light source emits light along an optical path that is directed toward the outer blade tip surface by a lens, and the outer blade tip surface reflects the light back along the optical path. An optical interferometer generates an interference pattern using the reflected light, and a photoreceiver receives the interference pattern. A complex logic device determines the clearance distance of the blade tip surface from the inner surface of the case based on the interference pattern. The interferometer may be a Fabry-Perot optical interferometer formed using a window positioned between the lens and the blade tip surface, or a Michelson interferometer formed using a reference optical path. The system may alternatively include an optical time of flight measurement of the blade tip clearance. The system further may include an abradable substrate having an optical fiber array of optical fibers at different depths, whereby the blade tip clearance is determinable based on which of the optical fibers are abraded as the blade tip rotates.