Planar Concentration Field Measurement In A Transient Jet Using Mie Scattering

An experimental method for time resolved concentration measurements in the near field of a transient starting turbulent air jet is presented. Planar Laser Mie Scattering (PLMS) using DEHS droplets produced by a Laskin nozzle as tracers of concentration is applied on an air jet with Reynolds number of 62.000 and is recorded with 10.000 frames per second. A jet penetration of about 20 nozzle diameters into the ambient environment is resolved with more than 100 frames. A linear response between grey scale values and concentration is found for mixtures up to 13% of the air-particle flow from the Laskin nozzle mixed with clean air. The calibration is based on images with no particles and images with a homogeneous particle concentration. A correction for light scattered by particles outside the laser sheet is proposed. The experimental results agree well with mean concentration measured with other techniques.