Combustion processes with partially or fully premixed cylinder load combined with self-ignition provide high combustion efficiency and low emissions of Nitrogen Oxides (NOx) and particulate matter at the same time. Since the number of diesel operated passenger cars is still rising, it would be interesting, if such a combustion concept can be realized in an ordinary DI-Diesel engine which is operated with conventional diesel fuel.
In this study, the influence of nozzle geometry, Tintake, pTDC and injection timing on the functioning chain of combustion was analyzed in a transparent single-cylinder diesel engine equipped with a common rail injection system by means of optical measurement techniques.
Simultaneously, different optical diagnostics (laser-based and non laser-based) were used to study the fuel distribution, ignition and combustion in the combustion chamber of the optically accessible diesel engine. The liquid fuel was visualized by Mie scattering at 532nm. The frequency tripled wavelength (355nm) of the same Nd:YAG-laser was used to obtain the spatial distribution of the fuel vapor and to visualize the quality of mixture formation with laser-induced fluorescence. The ignition process and the following combustion were detected in the UV spectral range. In order to distinguish between premixed and non-premixed combustion also the visible range of the combustion-light was detected
The investigation shall demonstrate to what extent a premixed mixture can be reached and how the spatial distribution of the ignition locations as well as the combustion are affected.