Measurements of laminar flame speeds and flame instability analysis of E30-air premixed flames at elevated temperatures and pressures

Ethanol is regarded as one of the most promising alternative renewable fuels and as well as an oxygenate blending component in gasoline fuels, with widespread usage in many countries around the world. Laminar flame speeds can have strong influence on the stability and operability of Spark-Ignition combustion in certain operating regimes, and so the effects of different initial conditions on laminar combustion characteristics of E30 (gasoline blended with ethanol of 30% liquid volume) were analyzed in a constant-volume combustion vessel using the high-speed Schlieren method. This work presents results for equivalence ratios of 0.7-1.4, dilution ratios of 0%, 5%, 10%, and at different initial temperatures (408, 453 and 498 K) and initial pressures (1, 2 and 3 bar). It can be concluded that the laminar burning velocity has a positive correlation with initial temperature, but negative correlation with initial pressure and dilution ratio. The laminar burning velocity always reaches its maximum value at an equivalence ratio of 1.1 and does not change with varying initial conditions' the adiabatic flame temperature displays a similar variation with the initial conditions. The flame instability of E30-air mixture is enhanced as the initial pressure increases. Flame stability at lean and rich mixtures are exactly opposite at different initial temperature and dilution ratio. The laminar burning velocity was significantly promoted relative to gasoline and E10 by the addition of higher volume fractions of ethanol, highlighting one of the benefits of ethanol's use as a blending component in gasoline fuels.