Chemical kinetic insights and numerical analysis of gasoline combustion with ozone as an additive

This work deals with a comprehensive 1-D numerical analysis to assess ozone-assisted combustion of Toluene Reference Fuel/air flames. Ozone, O3, represents a promising oxidizer that enhances the laminar flame speed of alkanes through its decomposition into atomic oxygen. Simulations have been carried out by using two different chemical kinetic mechanisms with the addition of an ozone sub-mechanism. Results show that ozone increases the laminar flame speed across all thermodynamic conditions for ozone concentrations ranging from 0 to 7000 ppm. At a reactants temperature of 358 K and ambient pressure, the highest enhancement occurred under lean conditions with a lower enhancement near stoichiometric conditions. Above 500 K, a cool flame occurred under both lean and stoichiometric conditions, as fast ozone decomposition favors both OH production and a sharp increase in temperature. Moreover, with an increase of the reactants pressure, the hydrogen diffusivity becomes less important leading to an enhancement of the laminar flame speed under stoichiometric mixture condition. Sensitivity analysis has shown that at high pressure and in the presence of ozone, the reaction pathway is drastically modified. This suggests that reactions involving OH radicals prevail and lead to the formation of cool flames.