Inter and Intrablade Row Laser Velocimetry Studies of Gas Turbine Compressor Flows

Characterization of the aerodynamics of the flows within gas turbine intrablade passages requires the development of sensitive laser-Doppler velocimeters, a data acquisition system capable of efficiently and accurately handling substantial quantities of data, and appropriate methods of posttest data analysis and display to maximize the value of the recorded data. Pratt & Whitney developed a confocal LDV and data acquisition system that were first employed in the mid-1970s for gas turbine intrablade fan studies. Experience gained through use of the instruments in several aerodynamic studies has provided the basis for the development of a second generation system. The performance of the recently enhanced instrument configured as a single-component LDV has been demonstrated by a NASA-sponsored fan study in which approximately 200 million valid velocity signals were rapidly acquired. The high resolution and data rates achieved permitted detailed mappings of the flow at a variety of conditions and locations. Following this successful study, a second NASA-sponsored program was initiated to assess the feasibility of utilizing this LDV capability to perform detailed stator–rotor interaction studies in a multistage compressor. The equipment employed in these studies will be described and data typical of the findings will be presented.