Laser Anemometry Techniques for Turbine Applications

Laser anemometry offers a nonintrusive means for obtaining flow field information. Our current research efforts at NASA Lewis Research Center are focused on instrumenting a warm turbine facility with a laser anemometer system. In an effort to determine the laser anemometer system best qualified for the warm turbine environment, we compared the performance of a conventional laser fringe anemometer and a two spot time-of-flight system with a new, modified time-of-flight system, called a Four Spot laser anemometer. The comparison measurements were made in highly turbulent flows near walls. The Four Spot anemometer uses elliptical spots to increase the flow acceptance angle to be comparable to that of a Laser Fringe Anemometer. Also, the Four Spot uses an optical code that vastly simplifies the pulse detection processor. The results of the comparison measurements will exemplify which laser anemometer system is best suited to the hostile environment typically encountered in warm rotating turbomachinery.