Analysis of Alternative Fuel Combustion in a Perfectly Stirred Reactor

The combustion of methane, isooctane, and ethanol with air has been simulated in a perfectly stirred reactor. The CHEMKIN computer code was used to facilitate the solution of the chemical kinetic mechanisms obtained from literature. The models used for methane, isooctane, and ethanol were developed by Miller and Bowman, Maurice et al., and Marinov, respectively. The reaction mechanisms of methane and isooctane include comprehensive submechanisms describing NOx chemistry, whereas that for ethanol describes only C/H/O interaction. The objective of this work is to examine the effects of reactor pressure and charge residence time on adiabatic flame temperatures and emissions over a wide range of equivalence ratios. For methane and isooctane, the production of pollutants carbon monoxide (CO) and nitric oxide (NO) is investigated, while for ethanol only CO formation is considered. A comparison of fuels is also conducted to assess their relative merit. Here, the emissions of CO2 and H2O have also been included because of their contribution to greenhouse gases. Flame temperatures have been discovered to increase with reactor pressure and residence time, and it was revealed that isooctane generates the highest temperatures regardless of inlet mixture strength. With an increase in pressure, CO formation decreases for each fuel, while the amount of NO produced increases only for methane. The effect of pressure on NO formation for isooctane combustion depends on the fuel-air stoichiometry. As residence time is increased, lower CO and higher NO are produced by each fuel. The strong dependence on temperature for NO formation is also demonstrated. It is discovered that the production of NO is reduced when residence times are sufficiently short due to the relatively slow reaction rates of the mechanism primarily responsible for high temperature formation. The fuel emissions comparison reveals that, in general, CO and CO2 production is largest for isooctane and ethanol, which yield similar values. It is also observed that NO formation is substantially higher for isooctane than methane, while isooctane combustion generates less H2O than the comparable levels for methane and ethanol