Experimental Investigation on the Laminar Burning Velocities and Markstein Lengths of Methane and PRF95 Dual Fuels

Abstract

Natural gas is a promising alternative fuel. The main constituent of natural gas is methane. The slow burning velocity of methane poses significant challenges for its utilization in future energy efficient combustion applications. The effects of methane addition to PRF95 on the fundamental combustion parameters, laminar burning velocity (Su0) and Markstein length (Lb), were experimentally investigated in a cylindrical combustion vessel at equivalence ratios of 0.8, 1, and 1.2, initial pressures of 2.5, 5, and 10 bar, and a constant temperature of 373 K. Methane was added to PRF95 in three different energy ratios 25%, 50%, and 75%. Spherically expanding flames were used to derive the flow-corrected flame velocities, from which the corresponding Lb and Su0 were obtained. The flame velocities were corrected for the motion of burned gas induced by the cylindrical confinement. It has been found that at stoichiometric conditions there is a linear decrease in Lb and Su0 with the dual fuel (DF) ratio in all investigated pressures. At rich conditions, all DFs resulted in having lower Su0 as compared to methane and to a larger extent PRF95. The values of Lb for all DFs were lower than methane and comparable to those of PRF95. At lean conditions, the values of Lb for all DFs are biased toward those of methane whereas the values of Su0 are found to be higher than those of PRF95 at pressures of 2.5 and 5 bar. At 10 bar both Lb and Su0 reduce with DF ratio although Su0 of all DFs converge to that of PRF95. The findings of the current study indicate a distinct synergy in the utilization of dual fueling in future lean burn energy efficient combustion applications.