LASER-INDUCED FLUORESCENCE AND FLAME PHOTOGRAPHY - TOOLS IN GASOLINE-ENGINE COMBUSTION ANALYSIS

The development of engine combustion systems aims at exploiting the ta rgets set by thermodynamics within the constraints of practical mechan ical systems. This, in particular, involves the supply of a combustibl e mixture, its ignition and combustion. The fluid dynamic and thermo-c hemical processes involved therein must be controlled in a way to prov ide: a temporal rate of heat release prescribed by thermodynamic, mech anic and acoustic requirements; the paths for 'clean combustion', i.e. the limitation of exhaust components such as nitric oxide, carbon mon oxide or unburned hydrocarbons at lowest possible levels; and the cycl e-to-cycle stability of the entire combustion process. The engineering tasks to influence and control these processes create the permanent n eed to provide and improve diagnostic tools in order to understand the fluid dynamic and thermo-chemical phenomena governing the combustion in engines. It is the purpose of this article to describe the applicat ion of optical methods such as laser-induced-fluorescence and combusti on photography for the investigation of cylinder filling, mixture form ation and flame propagation in gasoline engines. First, some diagnosti c requirements for combustion analysis will be addressed. Optical tech niques and experimental procedures are then derived and finally the ap plication of these techniques in the analysis and development of gasol ine engine combustion systems is demonstrated.