Study On Injection And Combustion Of Coal-biomassbased Blended Fuel

Diesel from Direct Coal Liquefaction(DDCL) and biodiesel are two kinds of alternative fuels which have promising future of development and application in our country.The common rail injection quantifier system and the fuel spray characteristic test system are set up. An engine test bench is set up, including a diesel engine, an eddy current dynamometer, a combustion analyzer, an exhaust gas analyzer and an engine control system.The injection processes of coal-biomass-based blended fuels are compared. The result shows the blended fuel injection process is influenced by energizing pulse width and common rail pressure. Injection duration, mass injection rate and injector inlet pressure fluctuation increase with the increase of energizing pulse width while the injection delay changes little. The increase of common rail pressure lifts mass injection rate and injector inlet pressure fluctuation. Injector inlet pressure of D80 fluctuates in a similar way to but with a bigger amplitude than that of D60.Such factors as rail pressure, ambient pressure, energizing pulse width, fuel blending ratio, influencing spray characteristics of coal-based & biomass-based blended fuels, are experimentally studied. And also based on the same cyclic heat value, the effect of fuel blending ratio is exmined. The result shows that the increase of rail pressure increases spray penetration, spray angle and spray area. Spray penetration and spray area are reduced with the increase of ambient pressure, while the spray angle increases at the same time. The increase of energizing pulse width raises spray penetration while influences spray angle little. Besides, the increased ratio of DDCL in blended fuels raises spray penetration, spray angle and spray area. When injecting different fuels with the same cyclic heat value, the existence of DDCL improves the atomization.The combustion and emissions characteristics of coal-biomass-based blended fuel at various main injection timings, post-injection quantities and post-injection intervals are studied. The main injection delay leads to the delay of combustion center, and reduced in-cylinder pressure and heat release rate. Also it reduces CO and NOx emissions and increases the fuel consumption. The increased post-injection quantity influences main combustion little while raises in-cylinder pressure and heat release rate during the post combustion process.Also it reduces the emission of NOx and consumes more fuel.Proper post-injection quantity gets soot emission down. The in-cylinder pressure and heat release rate do not change much as the post-injection quantity interval increases, but more fuel is consumed.