This study presents the sooting tendencies exhibited by binary mixtures of synthetic fuels i.e. n-heptane/toluene and isooctane/toluene, in terms of Yield Sooting Indices (YSIs) measured in nitrogen diluted diffusion flames of methane and seeded with the vapors of the aforementioned blends, probed using light extinction method using a Santoro's burner. These values are then extrapolated to reveal the soot production tendencies of tri-component surrogate gasoline fuels through an interpolation technique. Soot volume fraction maps in these flames are then inferred from line-of-sight attenuation measurements and are converted into apparatus-independent YSIs which affords the possibility to compare the relative influence of fuel formulation on soot production. The trends in soot production capacity as a function of toluene mole fraction (X_(tol).) are first analyzed by curve fitting YSI data and a nonlinear evolution of the sooting tendency as a function of X_(tol). in the binary mixtures reveals especially for isooctane/toluene blends at lower X_(tol).. Two Quadratic equations adequately model the evolution of YSI as a function of toluene mole fraction in n-heptane/toluene and isooctane/toluene blends. A synergistic effect is only visible when certain types of hydrocarbons are present in the fuel mixture (branched-chain alkanes and alkyl-benzenes in our case). These non-linear trends are adequately translated into predicted sooting tendencies of tri-component blends and can be very helpful while formulating fuel mixing strategies in view of the future engine and environmental exigencies.
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