A computational study of a fast sampling valve designed to sample soot precursors inside a forming diesel spray plume

Accurate chemical reaction mechanisms are critically needed to fully optimize combustion strategies for modern internal-combustion engines. These mechanisms are needed to predict emission formation and the chemical heat release characteristics for traditional direct-injection diesel as well as recently-developed and proposed variant combustion strategies. Experimental data acquired under conditions representative of such combustion strategies are required to validate these reaction mechanisms. This paper explores the feasibility of developing a fast sampling valve which extracts reactants at known locations in the spray reaction structure to provide these data. CHEMKIN software is used to establish the reaction timescales which dictate the required fast sampling capabilities. The sampling process is analyzed using separate FLUENT and CHEMKIN calculations. The non-reacting FLUENT CFD calculations give a quantitative estimate of the sample quantity as well as the fluid mixing and thermal history. A CHEMKIN reactor network has been created that reflects these mixing and thermal time scales and allows a theoretical evaluation of the quenching process.