Validation Studies of a Detailed Soot Chemistry for Gasoline and Diesel Engines 2021-01-0618

Accurately predicting the evolution of soot mass and soot particle numbers under engine conditions is critical to advanced engine design. A detailed soot-chemistry model that can capture soot under gasoline and diesel conditions without tuning is necessary for such predictions. Building confidence in the predictive usage of the chemistry in engine simulations requires validating the soot kinetics over a wide range of operating conditions and fuels, using data from different experimental techniques, and using sources from laboratory flames to engines. This validation study focuses on a soot-chemistry model that considers multiple nucleation, growth, and oxidation reaction pathways. It involves 14 gas-phase precursors and considers the effect of different soot-particle surface sites. The validation starts with well controlled one-dimensional flames for fuels relevant to automotive engines, including n-heptane, n-dodecane, methyl cyclohexane (MCH) and toluene in addition to gasoline and diesel fuels. The impact of temperature, residence time, and fuels on the evolution of soot particle size distribution is validated using Ansys Chemkin-Pro reactor models. We then consider pressure effects under shock-tube conditions. Next, we consider soot formed in gasoline and diesel engines over a range of load, speed, and EGR conditions using 3-D CFD simulations. The Chemkin-Pro cases use method of moments or sectional method as appropriate, and the CFD cases model soot with the method of moments. Finally, we considered validation with high-pressure lifted flames in a constant volume reactor. The model is able to capture the important trends across this wide range of combustion conditions, providing confidence in its usage for engine simulations.