Browsing by Author "Lee, Hsu Chew"

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    A Detailed Chemical Kinetics Mechanism for Biogas and Syngas Combustion
    (2016) Lee, Hsu Chew; Mohamad, Abdulmajeed; Jiang, Lei-Yong; Gollahalli, Subramanyam; Mahinpey, Nader; Johansen, Craig; Du, Ke
    The interests in alternative renewable fuels such as syngas and biogas have intensified the search for an accurate chemical kinetics model to describe the combustion of syngas and biogas fuels. Unfortunately, a generally accepted mechanism for the fuels of interest remains elusive. Therefore, this thesis is aimed at developing the most up-to-date chemistry model for syngas and biogas combustion. Based on comprehensive comparison between several notable mechanisms available in the literature, the NUIG2013 mechanism [1] was found to have the closest agreement with the experimental data for H2 –CO–CH4 –CO2 fuel mixtures diluted with N2 and H2O. However, the NUIG2013 mechanism failed to predict accurately the ignition delay time at several experimental conditions and the NUIG2013 consists of too many irrelevant species and reactions for syngas and biogas combustion purpose. Therefore, sensitivity analysis were conducted to identify the cause of discrepancies observed between the predicted results and experimental data, and Genetic Algorithm (GA) approach was proposed and validated to optimally extract relevant reactions for H2/CO/CH4/CO2 mixtures from the detailed NUIG2013 chemical kinetics mechanism. Two new rate constants for H+O2(+CO2) = HO2(+CO2) and CH4+OH = CH3+H2O reactions were proposed based on the sensitivity analysis, and it was found that the modified rate constants reconciled the observed discrepancies between the predicted and the measured results. The GA eliminated 1777 insensitive reactions in the NUIG2013 mechanism [1], where the final detailed chemical kinetics model presented in this thesis for biogas/syngas fuel mixtures comprised of 290 reactions and 72 species. The final detailed chemical kinetics model with the incorporation of the two modified rate constants was validated against a large set of experimental data, and excellent agreements were found between the predicted and experimental data. Consequently, the final mechanism presented in this thesis is currently the most up-to-date detailed chemical kinetics mechanism that is suitable for predicting the combustion properties of biogas/syngas accurately.