Characterization of the impact of ethanol on the formation of soot particles in gasoline turbulent diffusion flames
Résumé
The objective of this study was to characterize the impact of ethanol as a fuel additive on soot formation in turbulent diffusion flames for different gasoline mixtures of varying alcohol concentrations. These jet spray flames were stabilized at atmospheric pressure. A TRF mixture (Toluene Reference Fuel) defined as a surrogate representative of the composition of standard gasolines of type SP95 was used as reference flame. To characterize the impact of ethanol on soot formation, 11 flames of TRF mixed with various ethanol mole fraction from 0 to 100% were studied by keeping either the lower heating value (LHV) or the mass flow rate (MFR) constant. Soot volume fraction (fv) were measured by laser induced incandescence (LII). Absolute fv values were obtained by an autocalibrated method requiring a radiation source of known luminance to calibrate the detection system. The experimental results highlight a quasi-linear reduction of the soot formation with the added mole fraction of ethanol, until their complete disappearance for a pure ethanol flame. These results also highlight a stronger effect of ethanol on the soot reduction for ethanol addition with constant MFR characterized by a gradual decrease of the flame height. Experiments with commercial gasoline SP95-E10 and E85 were also carried out. The measured fv profiles show strong similarities with the fv profiles determined for their corresponding surrogates. These results illustrate that the TRF is an appropriate gasoline surrogate for studies aimed at characterizing soot formation. A modeling work, currently in progress, will be investigated to explain the inhibiting effect of ethanol on soot formation kinetics.
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