Optical Methods for Data Processing in Heat and Fluid Flow

19

Gas/Liquid Mixing: Simultaneous PIV Measurements of Two Phases Mixing Together; High-pressure Spray Application

T Boëdec and S Simoëns

Abstract

The aim of this work is to provide an efficient tool to describe the mixing between liquid and gas phases like, for example, high pressure spray atomization in quiet ambient gas. Out of the basic research interest this is of very high importance for car engine or agricultural spray manufactories. We describe a new planar visualization technique which allows simultaneous measurements of droplet and ambient gas velocity. It combines planar Mie scattering diffusion and planar laser induced fluorescence. Digital image treatment and analysis are used to discriminate the two phase flow information necessary to apply PIV. The basic principle is to seed the ambient gas and to tag the liquid with fluorescent. A synchronized system combining two different CCD cameras (one mounted with a filter) and two Yag lasers, respectively used to record images and to generate light sheets, was designed. We show the steps involved in discriminate gas from liquid information. This technique is efficient independently from the droplet shape. Furthermore this technique furnishes some instantaneous results (velocity field and droplet apparent diameter) which is of high importance for gas/liquid mixing. Instantaneous liquid and ambient gas velocity field examples are given in case of 6 MPa pressure spray.

19.1 Introduction

In the past twenty years, some optical ...