Residual Gas Visualization with Laser Induced Fluorescence

The influence of residual gases on the cycle-to-cycle variations in engine combustion was investigated. Two-photon planar laser-induced fluorescence was used for 2D-visualization of residual gas water. In order to avoid influence from fuel fluorescence and inhomogeneities premixed natural gas was used as fuel. Measurements were conducted at different load conditions with varying inlet manifold pressure. To find out how the residual gas distribution influences the combustion process the pressure development during combustion was monitored. From the pressure information a measure of the combustion rate at different phases of the flame development was calculated. The correlation between residual gas distribution and combustion rate was evaluated on a cycle to cycle basis. The results show that with an inlet manifold pressure of 0.3 bar the correlation between residual gas fraction and rate of combustion were 0.5-0.6. At full load though, lower correlation was found.