| Energy controls the power and fate of the development of national economy.85% of it is provided by the combustion of fossil fuels worldwide, while in China, the portion reaches around 90%. Nowadays, exploiting the fossil fuels on a large scale has led to intolerable stress on energy security and global environment. Bioalcohol, which is used as additives or replacement for gasoline can relieve the pressures on energy demand and environmental crisis. Methanol is the simplest alcohol, and can be used as octane booster or as a biofuel component to improve SI engine performance and efficiency. As the model fuel of alcohols, the combustion kinetic studies on methanol is of significantly importance. On the other hand,2-methyl-1-butanol, which contains five carbon atoms, has several advantages over smaller alcohols. For example, it has higher energy density and much lower vapor pressure. Besides, it is also low hydroscopic and mixes well with hydrocarbons. Therefore, it is becoming one of the "hot fuels" served as additive for gasoline in the near future.In this work, focused on methanol and 2-methyl-1-butanol, we attempted to investigate the basic combustion regulation of alcohol fuels. On the one hand, we optimized methanol model as the base model of alcohol fuel, on the other hand, we choose 2-methyl-1-butanol as a respesentative to explore the decomposition kinetics of large alcohols. Both experimental and modeling investigations are included in this work. For the experimental aspect, we conducted the laminar flame speed measurements and premixed flame structure measurement for methanol, obtaining both macroscopic parameters and detailed concentration information. Using the platform of our spherical combustion vessel, the laminar burning velocities for methanol-air mixture at an unburned temperature of 423 K and a pressure range of 1-10 atm were determined. And the laminar premixed flame of stoichiometric CH3OH-O2-Ar at 30 Torr was conducted using synchrotron VUV photoionization mass spectrometry (SVUV-PIMS). Based on the same experimental method, the pyrolysis of 2-methyl-l-butanol from 750 to 1400 K was investigated in a flow reactor at the pressures of 30 and 760 Torr to study the initial decomposition of fuel. For the modeling aspect, we firstly collected previous experimental and theoretical reports on the two fuels and constructed their kinetic models, respectively. And then we simulated the present and previous experimental data using CHEMKIN-PRO software. A detailed kinetic model for methanol was developed and optimized, which can achieve good performance under a wide range of experimental conditions. Based on the present pyrolysis data, we also proposed a pyrolysis model for 2-methyl-1-butanol. We investigated the effect of methyl branch on the decomposition characteristics of alcohol family through the comparison between 2-methyl-l-butanol and butanol isomers. Specific contributions are as follows:Firstly, we measured the laminar burning velocities of methanol-air flame in a spherical combustion vessel. In particular, we expanded the range of equivalence ratios up to 2.1 at 1-10 atm. Based on the kinetic analysis, HO2 radical is dominant at ultra-rich conditions, and the reactions related to HO2 radical present high sensivivity under these conditions. The updation of HO2 reactions involved in H2 mechanism, CH2O, and CH3OH sub-mechanism has large influence on the predictions of the radical pool, and significantly improves the predictions of the present model under high pressure and ultra-rich conditions.Secondly, based on the SVUV-PIMS method, we distinguished the fuel-specific radicals of methanol, i.e. hydroxymethyl radical (CH2OH) and methoxy radical (CH3O), and quantified the hydroxymethyl radical (CH2OH) for the first time in methanol flame. The measured mole fractions of CH2OH, as well as other C1 intermidiates, suggested that the contribution of pathway from CH2OH to CH2O was over-estimated by most previous models due to the over-estimated rate constant of CH2OH+O2= CH2O+HO2 in high temperature region. Besides, based on the present measurements, we found that the methyl radical recombination reactions were far from enough to predict the formation of C2 species, so we discussed and guessed CH2OH recombination pathways leading to the formation of C2 species, which could improve the performance of C2 species greatly.In the end, based on the SVUV-PIMS method, we measured the mole fraction profiles of fuel, intermediates and final products during the pyrolysis of 2-methyl-l-butanol, providing stringent constraint for model development. At the same time, we proposed a pyrolysis model for 2-methyl-1-butanol and tested it against the present experimental data. Compared with butanol isomers, the contributions of unimolecular reactions in 2-methyl-1-butanol are much lower than H abstraction reactions, which shows a similar decomposition rule to i-butanol rather than I-butanol. |
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