Concentration fields in a confined two-gas mixture and engine in-cylinder flow: laser tomography measurement by Mie scattering

Abstract

Gaseous mixture concentration characterisation by Mie scatter laser tomography has been widely used, except when experimental conditions turn out to be difficult especially in confined flow. This paper describes a complete formulation of the image processing required for a confined flow including effects from wall reflection, quality of the seeding, thermodynamic flow characteristics and instantaneous laser profile disparity. Two applications are described; the first one on a free and confined jet (turbulent, isothermal, isobaric flow) which shows the potential of the technique and the processing needed to reconstitute the mean concentration field, thus demonstrating the reliability of the processing. Second, an in-cylinder engine concentration measurement is put forward. Normal running and a stratified concept are given as examples. The results show the excellent potential of the technique to help engine developers. Thus, this paper presents the problems connected with measurement of concentration fields by laser tomography and Mie scattering from a theoretical and experimental approach.