The Influence Mechanism Of Fuel Chemical Structure On Mixed Combustion Of C5 Esters/Alcohols

With the shortage of fossil energy and the aggravation of environmental pollution, biodiesel has gradually become a hot research topic of biomass energy in many countries. Biodiesel is mainly composed of some saturated and unsaturated fatty acid methyl esters and ethyl esters, with complex structure, domestic and foreign scholars usually use some alternatives or alternative mixtures which can reproduce the main characteristics of combustion oxidation for biodiesel, with relatively simple structures, to explore the specific combustion process and mechanism of the biodiesel. In this paper, the combustion characteristics of biodiesel isomeric substitute fuels methyl butanoate and ethyl propionate, and the effects of exhaust gas recirculation and alcohols on the combustion characteristics of the two fuels were analyzed and discussed, mainly completed the following work:Firstly, in order to explore the influences of exhaust gas recirculation on combustion characteristics of methyl butanoate and ethyl propionate, from lean-burn to rich-burn, the comparative studies on premixed combustion of the two fuels adding CO2 and HiO were investigated. The isomerization effects of biodiesel alternative fuels on main products and intermediates were analyzed with particular emphasis on the chemical effects of CO2 and H2O addition on two fuels combustion. The results show that, the effects of CO2 addition on the combustion characteristics of the two fuels are significantly higher than the effects of H2O. The addition of CO2 can obviously reduce the flame temperature of the two fuels, and has significant inhibitory effects for the generation of soot precursor, aldehydes and ketones pollutants in the two flames. And the chemical effects of CO2 obviously inhibite the formation of acetaldehyde in the two fuels, and is more apparent in the ethyl propionate flame. Under lean-burn conditions, the consumption path analysis of the two fuels with CO2 addition was carried out. The results find that impacts of adding CO2 on the consumption path of methyl butanoate is obviously higher than the impacts on ethyl propionate.Secondly, for the research about impacts of alcohols on the two isomeric fuels combustion, at different equivalence ratios, the chemical kinetic analysis about adding different proportions of ethanol to methyl butanoate and ethyl propionate premixed flame was carried out. The influences of ethanol on the main products, important intermediates and free radicals; of the two isomeric fuels combustion were mainly discussed. And the chemical effects of ethanol in the two flames were identified. The results show that the addition of ethanol promote the formation of H, O and OH three radicals, and result in a significant increase in the concentrations of ketone and acetaldehyde in methyl butanoate flame. In the premixed combustion of ethyl propionate, the addition of ethanol promotes the formation of propargyl. Here, the chemical effects of ethanol are the main cause of the increase of free radical and important intermediate products.Finally, in order to make further research about the impacts of alcohols on the combustion characteristics of methyl butanoate and ethyl propionate, the experiments on the opposed flow diffusion flame platform were carried out. The fuels in the erperiments are methyl butyrate and propionate blended into 20% 1-butanol respectively. The effects of 1-butanol on main combustion products and stable intermediate products, and the generation path of potential contaminants in the two flames were explored. Known from the reaults, the addition of 1-butanol can delay the consumption of the two fuels, which result in a significant increase in the concentration of the major products, and the peak value of the product mole fractions moving to the air side. The main reason is that, through a series of reactions, the dehydrogenation products of 1-butanol can generate some substances. They are the main ways to produce acetylene, propargyl, acetaldehyde and other products. Moreover,1-butanol is the main source of three butene isomers in two mixed fuels.