Research On Construction Of A Compact Skeletal Mechanism For Diesel-IBE Using A Decoupling Methodology And Its Application

In recent years,biofuels have attracted widespread attention under the pressure of resource shortage as well as environmental pollution.Studies have shown that proper addition of Iso-propanol-Butanol-Ethanol（IBE）to diesel can help improve the combustion and emission characteristics of internal combustion engines.However,the study of the kinetic mechanism of diesel-IBE blends for engine numerical simulation is not yet mature.In this paper,we construct a diesel-IBE blend chemical reaction kinetic reduction mechanism including soot and NOx prediction models,and apply the constructed mechanism to engine numerical simulation to study the combustion and emission characteristics of diesel-IBE fuel blends for engines with different EGR rates and blending ratios.The main contents of this paper are as follows:Firstly,the shortcomings of the existing studies related to the kinetic mechanism of diesel-IBE fuel combustion chemistry were analyzed,and the idea of constructing the reduction mechanism based on the decoupling method and its advantages compared with the traditional methods were introduced.Then,n-dodecane,iso-cetane,iso-octane,decalin and toluene were used to characterize the diesel fuel,and the H₂/CO/C₁ bottom sub-mechanism,C₂-C₃ transition sub-mechanism,diesel single-component top mechanism and iso-propanol,n-butanol and ethanol top mechanism as well as NOx and soot emission models were coupled based on the decoupling method,which finally formed a diesel-IBE reduction mechanism containing 157 components and 603 reactions.The constructed mechanism was verified for n-dodecane,iso-cetane,iso-octane,decalin and toluene with iso-propanol,n-butanol,ethanol single-component and diesel multi-component in terms of ignition delay,laminar flame speed and premixed flame concentration.The diesel-IBE reduced mechanism was coupled with the open source program KIVA3V2 to perform 3D combustion simulation to verify the cylinder pressure and heat release rate in comparison.The combustion and emission under different EGR rate and IBE blending ratio were investigated,and it can be seen that the addition of IBE accelerates the in-cylinder combustion process and reduces soot emission,but at the same time brings an increase in NOx emission.EGR can reduce NOx emissions and the soot emissions of IBE15 are still smaller than the soot emissions of pure diesel combustion at the same EGR rate.The above results show that a certain IBE blending ratio combined with EGR can reduce both NOx and soot emissions of diesel engines.