OPTICAL DIAGNOSTICS FOR IN-CYLINDER MIXTURE FORMATION MEASUREMENTS INIC ENGINES

In the last few years, there has been a very rapid increase in the num ber of applications of laser diagnostics in internal combustion (IC) e ngines, particularly the use of optical techniques for studying mixtur e preparation and in-cylinder mixture distribution. This is due to the importance of mixture formation in controlling the subsequent combust ion and pollutant formation in IC engines. This paper attempts to revi ew and discuss the current status of the applications of these optical techniques for in-cylinder mixture formation studies. The first half of this paper focuses on the three optical techniques used for the mea surements of fuel vapour concentrations in IC engines. These are Laser Rayleigh Scattering (LRS), Spontaneous Raman Scattering (SRS), and La ser Induced Fluorescence (LIF). The second half of this paper is devot ed to another two optical techniques, Laser Induced Exciplex Fluoresce nce (LIEF) and dual wavelength Laser Extinction/Absorption (LEA), whic h are capable of simultaneous measurements of fuel vapour and liquid d roplets in IC engines. Simple theoretical descriptions are used to int roduce the principle of each optical technique. Experimental considera tions are given for the application of these techniques to IC engines. Much attention is devoted to providing readers with appropriate refer ences to the technical literature, which will be of further assistance to readers interested in a particular application of each technique. (C) 1998 Elsevier Science Ltd. All rights reserved.