Developing Planar Laser-Induced Fluorescence for the Investigation of the Mixture Formation Process in Hydrogen Engines

Planar laser-induced fluorescence (PLIF) has been successfully used for the investigation of the mixture formation process in hydrogen engines. Detailed information has been obtained about the process development (qualitative measurements) and on the fuel/air-ratio (quantitative measurements) in the combustion chamber. These results can be used for further optimization of the mixture formation and the combustion process concerning emissions and fuel consumption. The measurement technique used here is not limited to hydrogen and can also be applied to other fuel gases like natural gas. The main topic of this paper is the experimental verification of the PLIF data by simultaneous Raman scattering measurements. By Raman scattering the fuel/air-ratio can directly be determined from the direct concentration measurements of the different gas species. The fuel/air-ratios determined by PLIF and Raman measurements are in good agreement indicating that a quantitative fuel/air-ratio measurement during the mixture formation process of hydrogen engines is possible by PLIF. This is also confirmed by other measurements (e.g. the global fuel/air-ratio calculated from the measured intake air and fuel gas flows).