Experimental Study of Premixed Laminar Combustion Characteristics of Gasoline/Air Mixtures in Constant Volume Vessel

This work measures the laminar combustion characteristics of gasoline-air mixtures at different equivalence ratios (ϕ = 0.8, 0.9, 1.0, 1.1 and 1.2) using the pressure rise method combined with a constant volume combustion chamber. The pressure rise method requires a more complex analysis but has the advantage that a single experiment generates data at engine-like conditions. The laminar combustion is characterized by laminar burning velocity (SL), heat release rate (HRR), flame developing time (FDT), and flame rising time (FRT). SL value was then obtained by a least-square fit of the observed pressure–time p(t). SL was calculated at 10% to 90% of HRR to avoid the effect of ignition energy and flame-wall interaction, where HRR was directly taking the time differentiation on p(t). FDT was determined as a time duration from the start ignition command to 10% of HRR, while FRT is the time duration from 10 to 90% of HRR. The results revealed that the value of SL reaches its maximum value of 42-cm/s at ϕ ≈ 1.0 ÷ 1.05; beyond this range, SL decreases. The SL values are quite close to the previous data obtained by different techniques, showing the reliability of the pressure rise method in this study. HRR is proportional to SL, while FDT and FRT are inversely proportional to SL when varying ϕ from 0.8 to 1.2. The results of the lean gasoline-air mixture (ϕ < 1.0) also suggest the necessity of enhancing flame propagation when applying the lean burn technology to improve engine thermal efficiency and NOx emission.