On the Application of Particle Image Velocimetry for Turbofan Engine Flow Quantification

Given the robustness and maturity of contemporary particle image velocimetry (PIV) methods, detailed flow measurements are now possible in actual turbine engine environments. For instance, flow non-uniformity measurements are possible in fan outlet gas-paths by adapting PIV hardware to the restricted access afforded in such applications. In the present work, a framework is proposed and demonstrated for planning and executing stereoscopic PIV measurements in the fan outlet duct of a Pratt & Whitney Canada JT15D-1A research turbofan engine. Two case studies have been carried out by following this framework in order to demonstrate two different imaging methods — conventional lens/camera coupling and endoscopic imaging. A key step within the planning and execution framework is risk reduction, and this step resulted in considerable refinement of the methods in both cases. For instance, in endoscopic imaging, the risk reduction provided a new fluorescent paint application for obtaining near wall data not previously possible. The data obtained in the engine experiments have been used to quantify the uncertainty for both imaging methods, not surprisingly revealing 50% greater average uncertainties for endoscopic PIV versus conventional lens/camera imaging. The results from the case studies indicate that both imaging methods may be practically and economically implemented for detailed measurements in fan outlet ducts, and application demands may be carefully considered, and risks reduced, using the framework proposed.