Investigation of Mixture Formation in Diesel Sprays under Quiescent Conditions using Raman, Mie and LIF Diagnostics

Mixture formation plays an important role for combustion and pollution formation in Diesel sprays. In particular air/fuel ratio (AFR) and temperature of the mixture short before ignition are crucial for these processes. Thus, these two quantities were measured quantitatively using 1-d spontaneous Raman scattering in this work. In addition, 1-d and 2-d Mie scattering was applied to visualize the distribution of the fuel droplets. 1-d and 2-d laser induced fluorescence (LIF) was also used to measure oxygen and fuel in a qualitative way in this work. The common rail Diesel injector was installed in a combustion vessel, in order to provide nearly quiescent high-pressure and high-temperature conditions. N-decane was used as the fuel, because it is a commonly used model fuel for standard Diesel fuel. It was doped with three different tracers with different boiling points in consecutive experiments in the case of 2-d LIF measurements. The Diesel spray is analyzed by combining the qualitative 2-d Mie and LIF images with the quantitative 1-d air/fuel ratio and temperature profiles measured by Raman scattering.