Influence Of Mixture Reactivity Distribution On Diesel/n-butanol Compound Combustion

Due to the limitation of petroleum resources and the impact of emission regulations,the renewable alternative fuels and in-cylinder emission reduction technology have become the main research directions of internal combustion engines.As a new alternative fuel,n-butanol has received extensive attention due to its excellent physical and chemical properties.Experiment completed n-butanol/diesel compound combustion under operation condition of 2000 r/min speed,0.13 MPa intake pressure,75 ℃ intake temperature and 85 ℃ coolant temperature.The start of injection(SOI)of diesel fuel was set to be-8、-4、0、4、8 deg ATDC(after top dead center)and n-butanol injection quantity and diesel injection quantity were changed respectively at a constant SOI,thus to study the effects of coupling action of diesel injection timing and mixture reactivity on the mixture state before ignition,the formation of combustion process and the emission performance in compound combustion.The research results shown that: when Mb=15 mg and SOI was retarded from-8 deg ATDC to 0 deg ATDC,increasing Md expanded the effects of increasing diesel mixture mixing degree before ignition and decreasing the mixture concentration,changed the combustion process variation from increasing ignited n-butanol mixture into showing a few n-butanol low temperature heat release and increasing ignited n-butanol when decreasing diesel diffusion combustion,deceased the growth of NOx emission but increased the growth of soot emission,and enlarged the differences of THC and CO emission.When Mb=15 mg and SOI was retarded from 0 deg ATDC to 8 deg ATDC,increasing Md amplified the effects of decreasing diesel mixture mixing degree and concentration before ignition,transformed the combustion process variation from showing a few n-butanol low temperature heat release and increasing ignited n-butanol when decreasing diesel diffusion combustion into increasing self-ignited n-butanol mixture,deceased the growth of NOx emission slightly but increased the growth of soot emission,and strongly expanded the differences of THC and CO emission.When Md=6 mg and SOI was retarded from-8 deg ATDC to 0 deg ATDC,increasing Mb weaked the promotion of diesel mixture mixing degree and concentration before ignition,decreased the growth of ignited n-butanol mixture in combustion process,deceased the growth of NOx emission the difference of soot emission,and also reduced the increasing rages of THC and CO emission.When Mb=6 mg and SOI was retarded from 0 deg ATDC to 8 deg ATDC,increasing Mb converted the increase of diesel mixture mixing degree and concentration before ignition into decrease,transformed the combustion process variation from increasing ignited n-butanol and decreasing diesel diffusion combustion into substantially increasing self-ignited n-butanol mixture,slightly deceased the growth of NOx emission but increased the defference of soot emission,and brought down the growth of THC emission but raised the growth of CO emission.