Influence of Ethanol and Exhaust Gas Recirculation on Laminar Burning Behaviors of Fuels for Advanced Combustion Engines (FACE‑C) Gasoline and Its Surrogate

Laminar burning velocities
of fuels for advanced combustion engines
(FACE-C) gasoline and a surrogate comprising toluene primary reference
fuels (TPRFs) were investigated under the effects of exhaust gas recirculation
(EGR) dilution and ethanol blending. Measurements were conducted in
a spherical constant volume combustion chamber for a range of equivalence
ratios from 0.8 to 1.6 at initial temperatures and pressures up to
383 K and 0.6 MPa, respectively. These measurements highlighted the
effects of real combustion residuals (using combustion products directly)
at mole fractions up to 0.3 and various volumetric percentages of
ethanol blending. For both studied fuels, significant reductions in
stretched and unstretched flame speeds were observed for mixtures
laden with real combustion residuals. Blends with less than 50% ethanol
showed barely a minimal enhancement in the flame speed. By combining
both EGR and ethanol blending, the flame speed reduction by EGR can
be compensated for with ethanol addition. For example, up to 10% of
EGR requires 60% ethanol blending to maintain the same flame speed.
Flame stability enhancement by EGR addition was also quantified through
the determination of the Markstein length.