TREATMENT OF L2F ANEMOMETER MEASUREMENT VOLUME DISTORTIONS CREATED BYCURVED WINDOWS FOR TURBOMACHINERY APPLICATIONS

In turbomachinery applications, optical access needed for laser anemom etry (L2F) measurements must be provided by curved glass windows to av oid introducing disturbances into the flow. However, the curvatures le ad to optical distortions of the laser beams which prevent the creatio n of acceptable foci. These distortions can be eliminated by inserting a simple and inexpensive corrective window between the frontal lens o f the anemometer assembly and the shroud window. First, a simplified a nalytical method is presented to determine the geometric characteristi cs and the position of this corrective window. Then, a more sophistica ted numerical method is described and applied to the case of an axial transonic compressor currently under investigation.