| Methanol is rich in sources,the oxygen content up to 50% and can be burned clean.It is one of the most potential diesel alternative fuels.The polarity of methanol is very strong and it is difficult to be miscible with diesel.There are two main applications of methanol in diesel engines at this stage: the first is the use of a dual-fuel system,and the second is the use of an emulsion method.The dual fuel supply system has a complex structure and the cost of manufacturing and maintenance is increased.Compared to dual fuel systems,emulsion fuels can be used directly on diesel engines.However,the stability of the emulsion fuel itself is poor,and it is prone to stratification.Compared with emulsified fuels,micro-emulsified fuels are more stable,uniform,and difficult to be stratified.In this paper,the three phrase intersolubility of diesel oil,n-pentanol and methanol was tested at different temperatures.It was found that at room temperature,when the volume ratio of diesel oil was 70%,the maximum amount of methanol could be added to 15% volume ratio,thus the maximum oxygen content of micro-emulsified fuel was obtained,recorded as D70P15M15,and D80P20 and D70P20M10 micro-emulsified fuels were prepared to study the effects of different alcohols and methanol content on the combustion and emission characteristics of micro-emulsified fuel.Research shows that:(1)With the increase of methanol content,in order to avoid the separation of methanol-diesel phase,the required n-pentanol also increased;the three phrase intersolubility of diesel-N-pentanol-methanol is affected by temperature,the higher the temperature,the lower the amount of N-pentanol required for dissolving the same methanol;and with the increase of methanol,the viscosity,the condensation point,the calorific value and the cetane number of the micro-emulsified fuel decreased.(2)Under each load condition,with the increase of methanol content,the combustion start point of the engine is delayed,and the ignition delay period is prolonged;the combustion end point is advanced,and the combustion duration is shorter;the peak heat release rate is increased;the maximum combustion temperature increases.With the increase of methanol content,the peak pressure of the engine will increase under small and medium load conditions;and under the low load conditions,the peak pressure will decrease.(3)With the increase of methanol,the effective fuel consumption rate of the micro-emulsified fuel is increased;the micro-emulsified fuel with the addition of methanol,under the mean effective pressure of 0.16 Mpa,the effective thermal efficiency is lower than the D100 fuel,in the rest of the load condition,the effective thermal efficiency of fuel are higher than the D100,and the economical efficiency of micro-emulsified fuel is better than that of D100 fuel.(4)With the increase of methanol,the emission of carbon smoke of the engine decreases;when the fuel injection time is changed at the same load,the average effective pressure is 0.48 MPa and the injection advance angle is 8°CA BTDC,the engine has the smallest carbon emission;when the average effective pressure is 1.29 MPa and the injection advance angle is 16°CA BTDC,the engine has the smallest carbon emission.(5)With the increase of methanol content,the NOx emission of the engine increases;when the injection time is changed at the same load,with the delay of the injection time,the emission of the engine’s NOx is also increased.(6)With the increase of methanol,the total volume concentration and total number concentration of ultrafine particles formed by the micro-emulsified fuel of diesel engines decreased;between the same fuel,as the load increases,the total volume concentration and total concentration of ultrafine particles first decreases and then increases. |
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