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

This work measures the laminar combustion characteristics of gasolineair mixtures at different equivalence ratios (phi = 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 (S-L), heat release rate (HRR), flame developing time (FDT), and flame rising time (FRT). S-L value was then obtained by a least-square fit of the observed pressure-time p(t). S-L 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 phi approximate to 1.0 o 1.05; beyond this range, S-L decreases. The S-L 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 S-L, while FDT and FRT are inversely proportional to S-L when varying phi from 0.8 to 1.2. The results of the lean gasoline-air mixture (phi < 1.0) also suggest the necessity of enhancing flame propagation when applying the lean burn technology to improve engine thermal efficiency and NOx emission.