Particle image velocimetry measurement inside axial air test turbine – Effect of window

We measure the two dimensional instantaneous velocity fields inside an axial turbine by using the technique PIV (Particle Image Velocimetry). The measured plane is located just behind the rotor wheel and it is oriented in axial × tangential direction. We measured a single overloaded regime as well as the nominal one at tip radius. We discuss several technical difficulties appearing during this measurement, mainly with the seeding particles and with the optical access into a massive steel body. The glass dividing the channel past rotor and the empty space of diffusor has been dirtied by large oil droplets condensing at the blades and splashed to this window. We “solved” this trouble by removing the glass, because it anyway divides volumes with same static pressure. Best quality result was obtained without this glass, but its removal changes the geometry. In our contribution we focus to the effect of such rude change to the trustworthiness of the results.