Simultaneous Measurements Of 3D Temperature And Velocity Fields In Gas Flows Using Thermographic Phosphor Tracer Particles

Abstract

A concept for joined three-dimensional temperature and velocity measurements in turbulent gas flows using sub-micron sized thermographic phosphor tracer particles is presented. Such measurements are needed to resolve flow structures commonly encountered in turbulent flows of scientific and industrial interest. While available techniques for simultaneous 3D thermometry and velocimetry are suitable for microfluidic applications or slow liquid flows, the present concept is applicable to macroscopic turbulent gas flows. The feasibility of these measurements is demonstrated using two turbulent heated gas jets. The concept utilizes two sub-systems: a four-view 3D particle tracking velocimetry system combined with a two-view ratiometric phosphor thermometry system. A double-pulse green laser and a single-pulse UV laser are used for illumination and excitation of phosphor luminescence, respectively. Upon imaging the particle-laden flow using the joined camera system, 3D particle positions and velocities are computed from four double-frame Mie-scattering recordings, while the temperature is inferred from two single-frame luminescence-emission recordings. Measurement results using low particle seeding densities successfully retrieve the expected temperature and velocity distributions. This proof-of-concept is a first step towards the ability of resolving 3D turbulent flow structures from individual single-shot recordings using higher particle seeding densities.