Analysis of Reduced Order Chemical Mechanisms for Oxygen-Enriched Combustion of Methane and N-Decane

Micro-combustors operating with oxygen-enriched combustion of hydrocarbon fuels promise exceptionally high energy densities. However, to effectively design and analyze novel micro-combustor concepts using computational fluid dynamics (CFD) models, the CFD tools must employ accurate and efficient chemical mechanisms to represent the combustion process, especially with oxygen-enrichment. Accurate modeling of the laminar flame speed is a critical aspect to micro-combustor performance and must be accurately predicted using reduced order chemical mechanisms. The flame speeds of premixed oxygen-enriched combustion of methane and n-decane fuels were analyzed using new reduced order mechanisms in CHEMKIN which are suitable for use in numerical models of micro-combustor performance. Methane has been taken as a preliminary test case. Numerical simulations were run in CHEMKIN to predict flame properties of methane. The numerical and experimental data were in good agreement. In addition to the rate of production analysis and identification of rate-limiting reaction techniques, this study also considers flame speed sensitive reactions to determine the accuracy of the reduced model based upon the flame speed. Simulations are run to perform analysis of three reduced order methane and n-decane mechanisms at = 0.8, 1.0 and 1.2 and at oxygen concentrations of 21%, 25% and 30%. These simulations showed the percent error or deviation in flame speeds from the actual mechanism.