| China is a country lacking petroleum resources,and the fuel consumption from petroleum is very huge at present.Therefore,the search for alternatives to traditional fossil fuels has always been the focus of scientific researchers.At the same time,China's coal resources are relatively abundant.In addition to direct use of coal for combustion,coal-liquefied diesel with high-efficiency clean coal technology has received attention.In order to directly apply diesel of coal liquefaction to the existing diesel engine,it is necessary to understand its compatibility with the commonly used metal materials and seals on diesel engines,and their injection and spray characteristics.In this paper,the compatibility,injection and spray of coal-liquefied diesel were studied and compared with that of national ? diesel.The surface tension,density and viscosity of coal-liquefied diesel were measured,and the material compatibility of coal-liquefied diesel was studied.The metal immersion test showed that the corrosion rate of iron,aluminum,brass and red copper in coal-liquefied diesel and national ? diesel did not exceed ±0.31‰/year,and did not exceed ±0.46‰/year when immersed at 70?.Nitrile butadiene rubber,fluorine rubber and polytetrafluoroethylene had better compatibility with coal-liquefied diesel,while EPDM,chloroprene rubber and silicone rubber were worse.When the fuel temperature and time changed,there were some differences in the effects of different fuels on different rubbers,but in general,the rubber properties after immersion would deteriorate.Tests on the high-pressure common rail injection test bench showed that there were some differences in fuel injection characteristics between coalliquefied diesel and ordinary diesel due to different density and viscosity.During the injection process,the pressure fluctuation amplitude and frequency of coal-liquefied diesel,the maximum volume injection rate and injection quantity of volume were larger than ordinary diesel,but the injection delay was small.Different injection pulse widths affected the time interval of fluctuation,but had no significant effect on injection delay and initial injection rate.Injection quantity of volume increased with the increase of pulse width.With the increase of rail pressure,the injection duration,maximum volume injection rate and injection quantity of volume,the amplitude and frequency of pressure fluctuation increased,but the effect of large pulse width on the amplitude of pressure fluctuation would be weakened.On the constant volume bomb,the spray characteristics of coal-liquefied diesel were studied by high-speed photography including spray penetration,spray front speed,spray area and spray angle.The results showed that the spray penetration of coal-liquefied diesel was smaller than that of common diesel.The spray speed of common diesel was larger,but the spray area and spray angle were smaller than those of coal-liquefied diesel;Under the same experimental conditions,the spray size of coal liquefied diesel was smaller than that of diesel,and the atomization effect was better.The difference in spray characteristics between fuels was primarily affected by density,viscosity and surface tension.Changing the fuel injection pulse width had little effect on the spray angle of the same fuel,and had no obvious effect on the spray penetration and the spray front velocity at the early stage of injection.However,the spray penetration,the front velocity and the spray angle increased with the increase of pulse width in the late injection stage,and the effect of pulse width on different fuels was basically the same.The increase in injection pressure also increased the four element values of the spray,and it was also found that the maximum spray front velocity of coalliquefied diesel was earlier than normal diesel.The increase of ambient pressure leaded to an increase in motion resistance,resulting in reduced spray penetration and area.For both diesels,the ambient pressure had little effect on the spray angle defined in this paper. |
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