| The paper is granted and supported by China westem transportation construction projects.Physical and chemical characteristics, spraying,combustion and emission performance ofbiodiesel,diesel and biodiesel-diesel mixture are compared. Combustion and emissiondisciplines of fuels are determined. According to high NO_X emission caused by biodiesel,water is joined in biodiesel to form micro-emulsion fuel for the NO_X condition. Advantages ofmicro-emulsion are discussed compared with emulsion, and then precondition ofmicro-emulsion is confirmed. Biodiesel-water micro-emulsion fuel preparation and itsformation mechanism are studied and analyzed. Quantitative relationship between maximalwater capacity and polar flux ethanol and different emulsifiers for biodiesel micro-emulsionfuel is found. Two formula biodiesel micro-emulsion fuels are chosed, combustion andemission performances of the fuels are compared with biodiesel and relative rules areascertained. Results solute the NO_X emission problem effectively. Accordingly, the paperprovides academic and experimental base for new environmental and economical altemativefuels.Major contents and innovation points(marked with ~*) are reflected and listed in thefollowing:(1) Physical and chemical characteristics and spraying quality are compared. Results indicate:viscosity of biodiesel is high and liquidity is poor. At the injection pressure of 24.8MPa, thespraying angle of biodiesel is lower than that of diesel; when the diameter is smaller than 42micron, amount proportion of biodiesel is lower than that of diesel; at the same accumulativevolume proportion, diameter of biodiesel is larger than that of diesel; all character diametersof biodiesel are larger than those of diesel correspondingly. High viscosity results in the poorspraying condition of biodiesel.(2) At different speeds and loads, engine performances and emissions using biodiesel,dieseland their mixture are compared. Results indicate: power output of biodiesel and itsdifferent-ratio mixtures with diesel are lower than that of diesel. Specific fuel consumption ofbiodiesel and its different-ratio mixtures with diesel is higher than that of diesel both at fullload condition and at 1500r/min condition, it increases with the addment of biodiesel ratio and the differences between the fuels and diesel decrease with the increasement of load. Specificenergy consumption of biodiesel and its different-ratio mixtures with diesel has no relationwith biodiesel ratio at full load: when the speed is low, the energy consumption of the fuels ishigher than that of diesel. With the increasement of speed, the differences of energyconsumption between the fuels and diesel decrease. When the speed reaches 2000r/min,energy consumption of the fuels is lower than that of diesel. At 1500r/min, energyconsumption of the fuels is higher than that of diesel, it increases with the addment ofbiodiesel ratio, and the differences between the fuels and diesel decrease with theincreasement of load. Compared with diesel, HC emission of biodiesel and its different-ratiomixtures with diesel decreases at full load having no relation with biodiesel ratio and at1500r/min it decreases with the increasement of biodiesel ratio; CO emission of biodiesel andits different-ratio mixtures with diesel decreases at full load having no relation with biodieselratio, at small load of 1500r/min it varies little and at big load of 1500r/min it decreasesobviously having no relation with biodiesel ratio; NO_X emission of biodiesel and itsdifferent-ratio mixtures with diesel is higher than that of diesel, and it increases with theincreasement of biodiesel ratio; smoke emission of biodiesel and its different-ratio mixtureswith diesel is lower than that of diesel at full load and it decreases with the increasement ofbiodiesel ratio, at small load of 1500r/min smoke emission of biodiesel and its different-ratiomixtures with diesel maintains invariable, at big load of 1500r/min smoke emission decreasesand it decreases with the increasement of biodiesel ratio.(3) At different speeds and loads, combustion performances of biodiesel,diesel and theirmixture are compared. Results indicate: ignition delay period of biodiesel and itsdifferent-ratio mixtures with diesel is shorter than that of diesel; peak pressure of biodieseland its different-ratio mixtures with diesel represents different rules; peak pressure increaseratio is higher than that of diesel at small and middle loads and is lower at big loads; peak heatrelease ratio of biodiesel and its different-ratio mixtures with diesel is higher than that ofdiesel at small and middle loads and is lower at big loads; increasement of biodiesel ratioconduces to the improvement of cycle constant volume degree.*(4) Preparation and mechanism of biodiesel and water micro-emulsion fuel are firstlystudied, and relationship between ethanol ratio,different addments for different emulsifiers and maximal water volume for biodiesel-water micro-emulsion fuel is studied quantitatively.With the increasement of ethanol proportion, maximal water volume increases; usingemulsifier can also increases the maximal water volume; with the increasement of emulsifierquality, the maximal water volume increases; the maximal water volume of G is the largestamong S,G and L; effection of complex emulsifier is worse than single emulsifier. Twoconcepts are determined: maximal water volume for micro-emulsion fuel and micro-emulsionefficiency. Formation mechanism of micro-emulsion fuels is studied systematically. It isconsidered that necessary condition for biodiesel-ethanol-water micro-emulsion is thathydrogen bond effection of hydrophilic groups in biodiesel and emulsifier and hydroxyl ofethanol on water is no less than corresponding Laplace pressure gradient.*(5) Performances and combustion characteristics of biodiesel and water micro-emulsionfuels are studied firstly on diesel engine. Power and torque of micro-emulsion fuels are lowerthan those of biodiesel. Specific fuel consumption of micro-emulsion fuel increases andspecific energy consumption decreases, accordingly fuel economy improves. Micro-emulsionfuel can decrease both the smoke and NO_X emission, the two micro-emulsion fuels accordwith the trade-off relationship. Ignition delay period prolongs and the end time advances,accordingly cycle constant volume degree of micro-emulsion fuel increases at middle and bigloads. At small loads, peak pressure and peak heat release ratio of micro-emulsion fuels arelower than those of biodiesel, with the increasement of loads, they increase fastly and they arehigher than those of biodiesel.*(6) NO_X emission control of biodiesel is firstly studied and a formula of micro-emulsionfuel is given for NO_X control. At the precondition that power reduces not that much, R20W0.5can decrease effective energy consumption and decrease NO_X and smoke emission,accordingly it is considered as the best formula for R20 base fuel.
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