| Particulate matter (PM) and nitrogen oxides (NOx) emissions from engines can beremarkably reduced by homogenous charge compression ignition (HCCI) combustiondue to the elimination of formation conditions of PM and NOx. HCCI combustion issimilar to isometric and increases engine heat efficiency, which is considered one ofthe most promising technologies that can substitute conventional engine combustionmode. So HCCI combustion research is a focus in the I.C. Engine industry at present.In the dissertation, the formation of gas mixture and process of compression ignitionwere investigated in by the experiment and simulation method in the differentconditions. Meanwhile, the characteristics of compression ignition in premixed gasformation and of its combustion were presented as well as the effects of differentparameters on premixed compression combustion process were analyzed. In addition,the conditions to realize premixed compression combustion process were developed atthe different conditions with calculation code.Many experiment results showed that the soot and NOx is very little at the lowand medium load in the diesel engine. It is found that, at a given condition, diesel fuelis completely vaporized before diesel is ignited, namely, diesel engines is conductingpremixed compression ignition combustion. As conventionally known, the lowemission of soot and NOx is favored of higher intake air volumetric efficiency at partload. It has initially suggested that the reduction of soot and NOx emissions is relatedto the premixed compression ignition combustion.In order to deeply investigate into the characteristics of fuel evaporation, mixturegas formation and ignition and combustion process with premixed compressionignition under different environment, the visualization equipment for diesel engine,including the advanced laser measurement technique and the high speed CCD systemwere applied to directly record mixture gas formation and ignition and combustionprocess for diesel fuel in the different gases such as air, CNG-air and CO2-air incylinder of normal engine. The experimental results showed that, in the different gases,the diesel fuel injected less than the certain amount, can realize premixed compressioncombustion. The ignition delay period of diesel fuel in CNG-air and CO2-air incylinder is longer and the ignition points distributed in chamber are more than thoseof in the air. Therefore, their combustion process is fairly similar to premixedhomogeneous charge compression ignition.In the dissertation, author initially compared premixed compression ignition ofdiesel fuel in the different environment with HCCI combustion process. Thecharacteristic of former combustion process is that it has many points when ignitionoccurs, however, HCCI combustion is free of boundary while the combustion happens,which is greatly different from that of the former one.In order to analyze the mechanism of mixture gas formation, ignition andcombustion and to find out the determinate conditions to realize diesel fuel premixedcompression ignition in the different environment, the modified KIVA code widelyemployed at the present time was applied to simulate combustion process of aconventional diesel engine and a premixed natural gas engine ignited by pilot diesel.The corrected Shell model used to dual fuel engine to predict the pilot fuel ignitionwas developed. Based on the Arrhenius arithmetic, taking effect of the turbulenceflow on the chemical kinetics under consideration, a new model with dual fueloperation was introduced. The simulation results revealed that, at low load undernormal diesel operation, the different injection advance angle is corresponding withthe maximum injection fuel amount that can be completely evaporated before fuel incylinder was ignited. Because diesel fuel ignition delay in CNG-air is greater than thatof the diesel fuel, it is revealed that the premixed natural gas ignited by pilot dieselfuel can realize premixed compression combustion with the relative much pilot dieselfuel amount.
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