Study On Effect Of Injection And Fuel Composition On Diesel Engine Combustion

Energy and environmental issues are important factors of socialdevelopment and economic progress. Relevant laws and regulations forenergy and power technology have become increasingly stringent. Theengine field particularly is put forward higher requirements for itscombustion performance. In this thesis, direct-injection turbochargedfour-cylinder diesel engine is selected to study the effect of injection andblends of DDCL (DDCL, Diesel from Direct Coal Liquefaction) andpetrochemical diesel on diesel engine combustion.Experimental apparatus is setup to study the engine combustion,emissions and performance. The apparatus includes a superchargedfour-cylinder direct-injection four-stroke electronically controlled commonrail diesel engine, eddy current dynamometer, combustion analyzer, NOxexhaust gas analyzer, the engine control system, test bench fuelconsumption meter, engine cooling thermostat.The effect of the fuel injection on diesel engine combustion andperformance has been studied in the experiment, which includespilot-injection timing and quantity and post-injection timing and quantity.The results show that the advanced pilot-injection increases in-cylinderpressure and the maximum combustion temperature. The lowest fuelconsumption is corresponds with the optimal pilot-injection timing. Theincreasd pilot-injection quantity advances ignition timing, prolongescombustion duration and increases fuel consumption. The retardedpost-injection delays the ignition timing of post-combustion significantlyand increases fuel consumption. The increased post-injection quantity increases the combustion cylinder pressure, the peak of heat release rate,in-cylinder temperature, and combustion duration and fuel consumption.The effect of the blends between DDCL and petrochemical diesel ondiesel engine combustion and performance and emissions has been studiedin the experiment. The results show that the increased DDCL compositionin the blends delays the combustion phase and advances the inflectionpoint of combustion duration. At the same time, the increased DDCLproportion also reduces soot emissions, and increases fuel consumption.NOx emissions of DDCL50are always the lowest compared with otherfuel.The effect of injection timing and EGR ratio on combustion,performance and emissions of DDCL-diesel blends has been studied in theexperiment. The results show retarded injection and increased EGR ratiodelay the combustion phase, extend the combustion duration, and increasefuel consumption. For different fuel, the appropriate injection timing andEGR ratio can reduce NOx and soot emissions simultaneously, then thecombustion optimization is obtained.