Study On Spray Characteristics And Combustion Process On Compression Ignition Engines Based On Fuel Design Concept

Nowadays, the problems of the environmental pollution, the consumption of fossil fuels and the greenhouse effect was increasingly more serious. The researchers pay more attentions on searching the diversified, clean alternative fuel for the engine of car. From the aspect of fuel modified, the use of oxygen-contain fuel can reduce the adverse effect of thermal efficiency and Soot emission which cause by the raise of attitude. When the attitude raise, the atmospheric pressure and oxygen volume fraction in the atmosphere decreased. This paper has carries out the fuel design base on different attitude conditions. Study the influence and function mechanism on common-rail engine combustion process and emissions generated. It has the important theory significance and engineering application value for realize the combustion of efficient and clean, so it can satisfy the ultra low emission regulations in the future.This paper has carries out the fuel design base on plateau conditions using the common-rail diesel engine as test engine. The Study put forward the group of fossil fuel blend with oxygen-contain fuel (bio-diesel and n-butanol). The CFD calculation model of Constant volume chamber was established in the first time. The calculation investigated the spray characteristics of the different physical and chemical characteristics fuel. Results show that, the atomization effect of bio-diesel(B100) was worse than diesel(BO). but when blend n-butanol in the bio-diesel, it can improve the atomization effect of the fuel. By the increase of the environment pressure or use the smaller nozzle diameter, the atomization effect of B100 and B70N30(70% biodiesel and 30% n-butanol blends) was closer with B0.The test was held in the plateau of 2,000 meters attitude and test of models for the D19 high pressure common rail diesel engine. Investigated the performance and emission characteristics of different types of B100(jatropha, rubber and waste-oil) Results show that, When compared to B0, the power output and actual fuel consumption are comparable and the effective thermal efficiency is higher for B100 at low speed and full load conditions. As engine speed increases, the power output for B100 reduces, and actual fuel consumption increases as compared to B0, meanwhile, the effective thermal efficiency of B100 is closed to that of BO gradually. The differences lies in physical and chemical characteristics have little effects on engine performance, and they have similar combustion characteristics and NOx emissions at the same torque conditions. However, waste cooking oil has the highest level of smoke, and then followed by rubber seed and jatropha.The CFD calculation model of diesel engine was established based on the bench test. The Simulation investigated the combustion mechanism of the three types of fuel (B0,B100 and B7ON3O) in different attitude (0-4,000 meters). Research shows that:with the decrease of oxygen volume fraction in the atmosphere, diesel engine fueled with oxy fuel or non-oxygenated fuel, emissions of Soot and CO was increasing. Compared with BO and B100, B70N30 cylinder equivalence ratio decreased, active free radicals (OH, O) increased, Soot emissions peak decreases, Soot and CO emissions increase with elevation (oxygen concentration) final value increasingly lower than B100. For the B70N30, with the increase of EGR rate, NOx is greatly reduced, CO was significantly increased, Soot emissions increase than without EGR, but smaller changes. With the increase of nozzle diameter, the fuel consumption rate of B100 is lower than that of B0. When using the same nozzle diameter, NO emission rises with the increase of biodiesel blending ratio, soot and CO emissions of B100 lower than those of B0. However, the soot of B10 is little higher than that of B0 with increasing nozzle diameter. When blend n-butanol in the bio-diesel, the Soot emissions reduce more obvious with the nozzle diameter increase.