Investigations Into The Combustion Kinetics Of Several Novel Oxygenated Fuels

To search for novel clean fuels,and to control the combustion processes through the fuel design and the optimization of combustion parameters are essential contents of the exploration into the combustion science.To achieve the above goals,it's meaningful to figure out the schemes for fuel consumption and pollutant formation during the combustion,and to develop combustion kinetic models which can be applied under wide ranges of operating conditions.In this work,attention was paid to several novel oxygenated fuels—carbonates,polyethers and ketones.Combustion kinetic investigations were performed for typical representative compounds,including dimethyl carbonate,diethyl carbonate,cyclopentanone,3-pentanone,1,2-dimethoxyethane and dimethoxymethane.For experiments,suitable diagnostic techniques were used to measure the detailed speciation information of the target fuels under different conditions.For kinetic modeling,rate coefficients for crucial elementary reactions were obtained through high-level theoretical calculations.Based on that,validated kinetic models with good predictive performances were developed.On the basis of experimental measurements and model interpretations,this work highlighted two important combustion characteristics regarding the practical use:the pollutant formation and the ignition performance.Besides,the correlation between oxygen-containing functional groups and the aforementioned combustion characteristics was revealed.By performing kinetic investigations of dimethyl carbonate and diethyl carbonate under pyrolysis and flame conditions,it was found that due to the presence of the carbonate functional group,fuels of this category have special unimolecular decomposition channels,and CO₂ is easily released from their combustion processes.Therefore,one carbon atom in the fuel need to combine with two oxygen atoms to be prevented from participating in the formation of soot precursors.In this way,the oxygen atoms are not efficiently used.The flame chemistry of cyclopentanone and 3-pentanone was also investigated in this work.The carbon-carbon double bond in the ketone fuels are tightly bounded,so carbonyl functionalities tend to be released in CO,fragmenting the carbon chains in fuel molecules,and inhibiting the direct formation of larger hydrocarbon species from the fuel consumption.Meanwhile,oxygen atoms in carbonyl moieties are not able to participate in the formations of small aldehyde and ketone pollutants.Low-temperature oxidation chemistry of two polyethers,1,2-dimethoxyethane and dimethoxymethane,was explored in this work.It was found that 1,2-dimethoxyethane has remarkable low-temperature oxidation reactivity,which is due to chain branching processes subsequent to the second oxygen addition reactions.While dimethoxymethane has negligible low-temperature oxidation reactivity,because the dominant fuel radical decomposes rapidly under low temperature conditions,impeding the occurrences of the oxygen addition reactions.It can be seen that under low-temperature oxidation conditions,the influence of the ether functional group on the fuel reactivity is quite complicated,which can be affected by the fuel-specific molecular features and the complex reaction network.To reveal the potential interactions between the reaction networks of oxygenated additives and the hydrocarbon base fuels during combustion.Two typical systems,ethane blending dimethyl carbonate?or dimethoxymethane?and benzene blending ethanol?or dimethyl ether?,were selected.By changing the initial fuel composition under laminar premixed flame conditions,the addition effects of the oxygenates on the fuel consumption and pollutant formation behaviors were explored.It was found that complicated chemical interactions do not exist in the reaction networks under the investigated conditions.