| As an alternative fuel of automobile, butanol has great practical significance in the realization of "energy saving and emission reduction" of automobile, it can effectively alleviate the crisis of increasing depletion of fossil energy, while reducing the pollution of automobile emissions on the atmospheric environment, in line with the current national energy development strategy; At the same time, it can reduce the dependence of domestic crude oil, and help to alleviate the country’s energy security problems. This paper targets at butanol as the basic object of study, summarizes the application progress of butanol as a vehicle fuel, analyzes the combustion chemical kinetic mechanism of butanol,the influence of different combustion boundary conditions on the combustion characteristics of butanol is studied by using the constant volume combustion bomb, and the difference between the combustion characteristics of 93 gasoline and butanol is compared, analyzes the influence of butanol/gasoline blended fuels on the performance of the engine through the engine bench test,makes low temperature cold start test with butanol/gasoline blended fuels in low temperature chamber, analyzes the emission characteristics and formation mechanism of conventional and unconventional emissions, evaluates butanol from energy balance and greenhouse gas emissions two aspects applying the life cycle theory.Chemkin software is utilized for constructing butanol chemical reaction kinetics model based on C1-C4 chemical material oxidation mechanism proposed by Dagaut, etc.The thermodynamic databases from Goos, Burcat and Ruscic, etc. is combined, and jet stirring reactor module of Chemkin software is combined for simulating butanol oxidation under premixed non-flame environment and calculating the concentration of homogeneous combustion products on the basis of constructing butanol chemical reaction kinetics model; Hedge flow diffusion flame module is applied for simulating butanol combustion under non-premixed flame environment and calculating the concentration of combustion product. Reaction path analysis and sensitivity analysis are respectively implemented on butanol oxidation and combustion in order to achieve more in-depth analysis on the simulation results. The research results show that butanol is mainly consumed mainly through H atom extraction reaction under the given conditions. Fuel radicals are generated, which are then broken down into smaller hydrocarbons and oxygen composition. Hydroxyl portion in butanol molecules contribute directly generates butyl aldehyde, formaldehyde, acetaldehyde and other compounds containing oxygen.The heat release law during actual combustion of engine is combined for constructing quasi-dimensional two-zone combustion model, according to constant volume fire bomb bench operation mechanism adopted in the experiment. Three boundary conditions of butanol mixture gas concentration, constant volume fire bomb initial pressure and initial temperature are obtained. The difference in combustion characteristics between butanol and gasoline is compared aiming at laws affecting combustion characteristics such as butanol combustion duration, combustion delay time, combustion pressure, combustion temperature, combustion heat release, etc. Chemical reaction mechanism of butanol and gasoline combustion is utilized for analyzing the test results of combustion characteristics from the theoretical level. The research results show that butanol combustion characteristics are very similar to the gasoline combustion characteristics, but the combustion duration and ignition delay time of butanol have been extended.Five test fuels, namely gasoline, butanol/gasoline blended fuels, etc. in different volume ratios, are selected for engine full load characteristic test and partial load characteristic tests with rotation speed of 2000 r/min and 2500 r/min. Influence law of five test fuels on engine dynamic property, economy and emission performance is obtained. The research results show that the dynamic property of combusting butanol/gasoline blended fuel on the engine is equivalent compared with gasoline. The economy is not prominently reduced. NOx emission is firstly increased and reduced subsequently but allways higher than gasoline, and emission of HC and CO is reduced under the full-load working condition with the increase of rotation speed. The volume ratio of butanol in blended fuel is larger, NOx emission is higher, and emission of HC and CO is lower under the condition of partial load.Low temperature tank is utilized for engine bench test. Exhaust gas analyzer is adopted for measuring and analyzing HC and CO in engine exhaust. The method of combining gas chromatography and liquid chromatography is adopted for measuring and analyzing CH2O, CH3CHO and other unconventional emissions. Conventional and unconventional emission characteristics of butanol/gasoline blended fuel at-7℃ within the initial 120s of cold start and idle machine warm-up are obtained. Butanol combustion mechanism is combined for analyzing formation mechanism of emission. The research results show that HC emission and CO emission are gradually reduced with increase of butanol volume ratio in the fuel within the initial 120s of cold start. HC and CO emission of each fuel is increased firstly and reduced subsequently. Butanol volume fraction in the fuel is increased from 10% to 30%, ethylene emission volume fraction is increased by 37%, formaldehyde emission is increased by 67.6%, acetaldehyde emission is increased by 69.9%, benzene emission is reduced by 40.5%, volume fraction of methane emission is decreased by 16%, and acetylene discharge volume fraction is decreased by 12.5%.Using butanol insteaded of conventional vehicle fuel is regarded as the research object. The life cycle system model of butanol is constructed.The energy consumption and environmental emissions from the production to vehicle use of gasoline in life cycle is regared as evaluation criteria. The energy consumption and greenhouse gas emission of butanol fuel are quantitatively analyzed, and the environmental impact of butanol as an alternative fuel is evaluated systematically from the point of view of life cycle. The research results show that corn is used as raw material to produce butanol for entirely replacing gasoline fuel. Energy consumption and greenhouse gas emissions can be effectively reduced from the perspective of life cycle. Net energy surplus is 9.65 MJ/kg, and the energy ratio is 1.18; By-products are based on different allocation plans. Corn butanol life cycle greenhouse gas emission can be reduced by 26% to 49.5% compared with gasoline at the same calorific value.The research results in the paper can lay theory analysis and experimental study foundation for applying butanol as vehicle alternative fuel, and beneficial reference can be provided for studying butanol combustion mechanism. It has certain reference value for using butanol as alternative fuel in cold area. |
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