A Reduced Chemical Kinetic Mechanism of Toluene Reference Fuel (toluene/n-heptane) for Diesel Engine Combustion Simulations 2015-01-0387

In the present study, we developed a reduced chemical reaction mechanism consisted of n-heptane and toluene as surrogate fuel species for diesel engine combustion simulation. The LLNL detailed chemical kinetic mechanism for n-heptane was chosen as the base mechanism. A multi-technique reduction methodology was applied, which included directed relation graph with error propagation and sensitivity analysis (DRGEPSA), non-essential reaction elimination, reaction pathway analysis, sensitivity analysis, and reaction rate adjustment. In a similar fashion, a reduced toluene mechanism was also developed. The reduced n-heptane and toluene mechanisms were then combined to form a diesel surrogate mechanism, which consisted of 158 species and 468 reactions. Extensive validations were conducted for the present mechanism with experimental ignition delay in shock tubes and laminar flame speeds under various pressures, temperatures and equivalence ratios related to engine conditions. The results showed the capability of the present mechanism to accurately predict the ignition delay and laminar flame speeds for n-heptane, toluene and diesel fuel under a wide range of experimental conditions. We also implemented the new mechanism in a multi-dimensional engine combustion simulation to predict the combustion characteristics of diesel engines. Good agreements in ignition timings, cylinder pressures and heat release rates were achieved between experimental and calculated results under the various engine operating conditions. In summary, the present mechanism represents the elementary reaction pathways of the detailed chemical kinetic mechanism well, and it is suitable to be used for diesel engine combustion simulations.