Applications Of Thermographic Particle Image Velocimetry To Film Cooling Flow Experiments In A Closed Loop Wind Tunnel
C. Abram (1), M. Straußwald (2), T. Sander (2), L. Zigan (2), M. Pfitzner (2)
(1) Dept. of Mechanical and Aerospace Engineering, Princeton University, USA
(2) Institut für Thermodynamik, Fakultät für Luft‐ und Raumfahrttechnik, Universität der Bundeswehr München, Germany
A laser-imaging method based on thermographic phosphor tracer particles (thermographic particle image velocimetry) is used to simultaneously measure temperature and velocity fields in film cooling flows in wind tunnels, in order to compare novel film cooling configurations under conditions of realistic mainstream turbulence. Several important experimental factors that affect the measurement precision, accuracy, and ultimately the success of the technique in its application in these practical environments are identified: (1) the choice of phosphor particles, which affects the inherent temperature sensitivity and flow tracing accuracy; (2) the particle seeding and management of particle deposition, which affects control of the overall particle number density and seeding uniformity and temporal stability; (3) the setup of the excitation laser/detection cameras and the wind tunnel geometry, which influences background interference from deposited particles and potential influence of multiple scattering. This paper discusses these three factors, gathering and adding to information in prior journal publications, to provide guidance and future research directions for experimental researchers wishing to use these optical diagnostics in film cooling studies and similar enclosed geometries.