Research On Microemulsion Methanol-diesel Physicochemical Properties And Combustion Characteristics

Methanol is considered as one of the most potential alternative fuels for diesel engine as its rich source and clean combustion. The most simple and convenient method to use methanol in diesel engine is emulsification. However, methanol and diesel can’t be dissolved each other. It should be added emulsifier and stirred with high speed or applying ultrasonic oscillating. Emulsion is non-transparent or semitranslucent, easily stratified, and shorter storage.A formula on methanol-diesel is optimized based on microemulsion theory in this dissertation. The physical and chemical properties of methanol-diesel are studied as the formula. The chemical and dynamic model is set up to analyze combustion characteristic of methanol-diesel. The characteristic of methanol-diesel applying in diesel engine is also studied based on experimental bench and numerical simulation of three-dimension. The dissertation mainly includes the following several aspects:(1) It optimizes a formula and a process on methanol-diesel. The emulsification efficiency of different microemulsifier is experimentally studied under different conditions on methanol-diesel based on microemulsion theory. A methanol-diesel formula is determined by the uniform design method. It is uses oleic acid as primary emulsifier, isobutyl alcohol as auxiliary emulsifier, and mixed with ethyl acetate and soybean oil. The process is simple, it does not need any external support.(2) It puts forward microstructure characteristics of methanol-diesel by small angle X-ray scattering technique (SASX). Methanol-diesel particle is spherical. Besides scattering particles, it exists uneven microelectronic density area. There is interface layer in methanol-diesel. Methanol-diesel particle characterized with quality fractal. And its microstructure is similar with that of diesel.(3) It achieves the liquidity and stability of methanol-diesel on the formula are achieved. The influence of each component and water content on temperature stability and time stability, the influence of each component on viscosity, solidifying point and cold filtration point, and the influence of temperature on viscosity are achieved. Its solidifying point, viscosity and cold filtration point are lower than that of diesel.(4) It structures the chemical kinetics model of methanol-diesel. The the model of the simplified chemical kinetics mechanism of N-heptane(40/192), methanol(18/45), the coupling of N-heptane and methanol(35/77) are built. The40/192mechanism model can simulate ignition delay period, the laminar flame speed and mass flow rate of N-heptane in wide range; the18/45mechanism model can simulate ignition delay period, the laminar flame speed and mass flow rate of methanol in wide range; the35/77mechanism model can simulate the combustion characteristic of HCCI engine fueled n-heptane and methanol.(5) The experimental study and numerical simulation of three-dimension are conducted on4B26turbocharged direct injection diesel engine fueled with methanol-diesel. The macroscopic parameters are achieved by the experimental study and micro information is achieved by the numerical simulation. The experiment shows the cylinder pressure curve flued methanol-diesel is similar with that of diesel. is similar with that of diesel the peak cylinder pressure is slightly lower than fueled MO. The rate of and rise acceleration of the pressure rise are higher than fueled MO. Difference of combustion noise between methanol-diesel and diesel is very small at low frequency band, the former is much higher at intermediate frequency band, and slightly higher at high frequency band.The load characteristic fueled methanol-diesel cylinder pressure sound lever A is almost the same as that of diesel. Study on the heat release rate shows that the heat release rate fueled methanol-diesel was similar with fueled diesel under heavy load and high speed. Under low load or low speed full load, ignition delay period become longer, the duration of heat release become significantly shorter, but heat release rate increase with increase of methanol content. The performance and emissions is studied fueled methanol-diesel by three-dimensional numerical simulation. It achieves the flow field, temperature field, oil concentration, NO concentration field and Soot concentration field which is difficult to achieve by experiment.