The Effect Of Fuel Properties And Injection Strategies On Combustion And Emission Characteristics In Compression Ignition Engines

At present, many countries have developed strict emission regulations for internalcombustion engine, and standards are becoming stricter. The target is fromlow-emissions, ultra-low emissions to zero emissions. For the same time, as moreattention paid to the global energy conservation and low-carbon economy, improvingthe thermal efficiency of the internal combustion engine and reducing fuelconsumption and exhaust emissions have become much more important. As we allknow, the combustion and emissions of internal combustion engine are closely relatedto the physical and chemical properties of the fuel. Engine combustion processdepends primarily on physical process, such as fuel evaporation and mixing process,and chemical reactions of working substance in the cylinder, which is closely relatedto the physical and chemical characteristics of the fuel. So in order to organize thecombustion rationally and reduce the emissions, it is necessary to further study therelationship of physical and chemical characteristics of fuel and the combustion.In order to study the influence of the coordinated control strategy of fuelcharacteristics and combustion boundary conditions to combustion and emissions, thegasoline and diesel were blended according to certain proportion for ignitability,volatility and distillation range between present gasoline and diesel fuel for widedistillation range in this study. The study involved experiments conducted on gasolineand diesel blended fuel. The results have shown that the blended fuel has longerignition delay, higher proportion of premixed combustion, which effectively reducessmoke without affecting NOx emissions. However, it will lead to incompletecombustion products, low combustion efficiency and thermal efficiency with too highgasoline ratio. Through the researches on combustion phase position, EGR,injection pressure, pre-injection timing, pre-injection volume optimal control showthat combustion phase determines the combustion thermal efficiency in a certainextent. When CA50control in5°CA ATDC, the engine has maximum indicated thermal efficiency, the lower smoke, the lower CO emissions and HC emissions, but itcan result in the increase of NOx emission. EGR can significantly reduce the NOxemissions in the range of selected EGR rates. With the blend ratio of gasoline increasein the wide distillation range fuel, smoke intensity has less sensitivity on EGR rate,and the EGR rate has little effect on IMEP. In selected experiment conditions, theways of improving injection pressure and changing pilot injection timing have littleeffect on emissions and economy of wide distillation range fuel engine. With pilotinjection quantity increase, the NOx emissions of G0reduce, the smoke emissionsincrease and the IMEP decreases slightly. However, for the fuels of G30and G50,with pilot injection quantity increase, the NOx emissions reduce obviously while thesmoke emissions remain almost unchanged.In selected experiment load conditions, in order to give considerations of fueleconomy and emissions, the optimum control strategies of wide distillation range fuelengine are that the blend ratio of gasoline is30%-50%, the combustion phase iscontrolled at5°CA ATDC, the best EGR rate is30%and the proportion of pilotinjection is30%without more injection pressure and pilot injection timing.