Study On Combustion And Emission Characteristics Of A Spark-Ignition Engine With ABE/Gasoline Blends

As a new potential alternative biomass fuel for internal combustion engines,ABE exhibits numbers of advantages and potential application prospects over traditional bio-alternative fuels in terms of its low cost,renewable properties.Because of these advantages of ABE,it has received extensive attention from more and more researchers.However,at present,the research is still in its infancy,and whether ABE is suitable as an alternative fuel for the engine still needs to be evaluated from the aspects of the power,fuel economy,cycle-to-cycle variation characteristics and emission characteristics of the internal combustion engine fueled with ABE.In this study,ABE/gasoline blended fuels with different component ratios and different blending ratios were studied.The combustion characteristics,cyclic-to-cycle variation characteristics and emission characteristics of ABE/gasoline blended fuel engines were studied by experimental research and numerical simulation,as well as the chemical reaction mechanism of ABE/gasoline blended fuel.The research work is of great significance for the feasibility evaluation of ABE as an alternative fuel for engines and the improvement of ABE/gasoline blended fuel engine performance.According to the needs of the spark ignition engine fueled with ABE/gasoline experiments,the ABE/gasoline blend fuel engine test bench was set up;the gas chromatography method was selected as the analysis method for the unregulated emissions.The flame ionization detector and the mass spectrometer are selected as the detecting method for unregulated emission quantification and identification;the gas chromatograph has been calibrated,and the calibration curves have been obtained.ABE/gasoline blended fuel for testing and the test plan were determined.Through the experimental method,the effects of ABE component ratio and ABE/gasoline blending ratio on engine combustion characteristics,fuel economy,cycle-to-cycle variation characteristics,and regulated and unregulated emission characteristics were studied.Through the research,the combustion characteristics,fuel economy,cycle-to-cycle variation characteristics,regulated emission characteristics,aldehydes,olefins and aromatic hydrocarbon emissions are obtained fueled with different ABE blend ratios and component ratios at different engine load equivalence ratio conditions.A simplified chemical reaction mechanism of ABE/gasoline blended fuel containing 78 components and 312-step reactions was established using DRGEP-SA and CSP-QSSA methods.This simplified chemical reaction mechanism can accurately predict the ignition delay,laminar flame speed and concentration of acetone,butanol,ethanol,n-heptane,isooctane,toluene,gasoline alternative fuels.By using this simplified chemical reaction mechanism,the interaction between the components of ABE/gasoline blended fuel,as well as the reaction pathway of intermediate of ABE/gasoline blended fuel during oxidation process were analyzed.According to the properties of ABE fuel and its combustion characteristics in spark-ignition engine,the laminar flame velocity model and turbulent flame velocity model in the G equation combustion model are modified.The large eddy simulation mathematical model and numerical simulation model,which were used for calculating in-cylinder combustion and cycle-to-cycle variation of ABE/gasoline blended fuel have been established.Through the research,the fuel composition coefficient in the laminar flame velocity model is modified,and the original turbulent flame velocity model is modified by introducing the progress variable.According to the numerical simulation research requirements of the combustion process fueled with ABE/gasoline blended fuel,a numerical simulation model of large eddy simulation combustion model for in-cylinder combustion and cyclic-to-cycle variation fueled with ABE/gasoline blended fuel has been established and validated.Through the numerical simulation method,by using the numerical simulation model of the in-cylinder combustion process of the ABE/gasoline blended fuel,the combustion,emission,cycle-to-cycle variation characteristics of ABE/gasoline blended fuel,as well as their mechanism of influence were investigated.Through the research,the mechanisms of influence of the active free radicals which have the greatest influence on combustion,and the key reaction paths which have the greatest influence on emission of pure gasoline and ABE/gasoline blended fuel are obtained.Besides,the mechanisms of influence of the active free radicals with the greatest influence on the cyclic-to-cycle variation of pure gasoline and ABE/gasoline blended fuel are obtained as well.There are 118 figures,14 tables and 234 references in the dissertation.