Application of Toluene Fuel Tracer LIF to Examine the Mixture Formation Process in a Light-Duty Diesel Engine

Quantitative in-cylinder spatial distributions of equivalence ratio are measured in a light-duty diesel engine using a tracer-based planar laser-induced fluorescence (PLIF) technique. The first portion of the talk describes the diagnostic technique and its application, including corrections to allow for the temperature dependency of the absorption cross-section and the fluorescence quantum yield.  In the second portion of the talk, the results obtained by applying the technique to examine the mixture formation process under low-temperature combustion conditions characterized by a prolonged ignition delay period are presented. These results are coupled to the predictions of homogeneous reactor simulations to better understand the influence of the mixture distributions on emissions of HC and CO. The impact of injection pressure, swirl ratio, and injection timing on the equivalence ratio distributions is discussed and the expected HC and CO emissions based on the mixture distribution at the time of ignition are compared with engine-out emissions measurements.