Kinetic Mechanism Study On Diesel Low Temperature Combustion

Diesel low temperature combustion(LTC) can reduce NOx and soot emissions and achieve high thermal efficiency. It has become a hot research topic in engine combustion theory and drawn great attention from domestic and foreign researchers in recent years. Chemical kinetics play a key role in LTC and is the basis for revealing the mechanism of it.The component of diesel is complex and some research suggests that to use the mechanism of n-heptane to represent diesel has a big error in high ERG LTC conditions. This paper studies the diesel surrogates based on previous work of our research group. In this study, n-heptane, toluene, and cyclohexane were chosen as the surrogates for diesel based on the real components of it. The mechanisms for n-heptane and cyclohexane were based on previous study, and some correction was made to it. The mechanism of cyclohexane was reduced firstly by DRG, and then reduced by using sensitivity analysis and rate of production analysis based on the boundary conditions of engines to make the final reduced mechanism for cyclohexane. The final reduced mechanism of n-heptane, toluene and cyclohexane contains 103 species and 200 reactions. The ignition delay and concentration of important species were verified by comparing with experimental results of shock tube and JSR. The results were good in wide boundary conditions. This study shows the H abstraction of cyclohexane is another important way to form benzene beside the routine of C2+C4 and C3+C3. The surrogate of 80% n-heptane, 10% toluene and 10% cyclohexane by mass can represent the chemical kinetics of diesel well.On the other hand, butanol is of the next generation of biomass oxygenated fuels, and has four isomers. Some research suggests that the blends of diesel and butanol can significantly improve the performance of LTC. In order to study the influence of diesel-butanol blends and the four isomers of butanol in the future, this paper also studies the kinetic mechanism of the four butanol isomers. A unified reduced mechanism of 85 species and 222 reactions for four isomers of butanol was built. Ignition delay was verified for the isomers and the results agreed well with the detailed mechanism and experiments. The four isomers all have two basic reaction routes. Under low temperature condition, H-abstraction is the main route and often happens where the bond energy of C-H is weakest. OH results in different reaction routes and species compared to straight-chain paraffin. Except n-heptane, the other three isomers do not have negative temperature region. Under high temperature, cracking reaction is the main routine for the four isomers, and results in C1, C2 and C3 species. Different positon of OH results in different species and reaction routines.