A Reduced Mechanism Development Of Biodiesel Fuels Blend Surrogate And Reaction Path Analysis

With the intensification of global energy crisis and the improvement of people environmental protection consciousness, a new type of clean and renewable biomass has been excavated. Biodiesel, as a kind of biomass energy, has the stable source and mature production technology. It has high oxygen content and its combustion emissions has greatly reduced compared with fossil fuel, which makes biodiesel became one of the most promising alternative fuel internal combustion engine now.The article selected methyl decenoate, methyl-9-decenoate and n-heptane as biodiesel fuels blend surrogate and established a detailed chemical kinetic mechanisms. A reduced chemical kinetic mechanisms including 116 species and 379 reactions was established by using three mechanism reduction methodology: DRGEP, isomer lumping and sensitivity analysis option in DRGEP. The reduce mechanism has a good ability to predicate the ignition delay time and can reproduce the negative temperature coefficient and the production of early CO2 at biodiesel combustion phase though the verification of experimental data.CHEMKIN- PRO software was applied to the reduced mechanism reaction path analysis,the results showed that methyl decenoate and methyl-9-decanoate mainly through dehydrogenation reaction to produce hydrocarbon ester in the low temperature combustion phase with OH,HO2 and O radicals.The hydrocarbon ester generate the peroxide hydrocarbon ester after isomerization reactions though the first addition of O2,the unsaturated hydrocarbon ester easily generate alkene C4H6 though the decomposition reactions caused that C=C double bond make the C-H bond energies be weak, the peroxide hydrocarbon ester finally become ketone substance and aldehyde. In the high temperature combustion phase, the substance of ketone and aldehyde generate the small molecule aldehyde substance CH₂ O, CH₂ CHO, C2H3 CHO the small molecule ketone substance CH₂ CO, C2H3 CO the oxygen function CH3 O, CH3 CO and alkene C2H4, this small molecule function finally a consumed to CO2.By changing the way of component molar ratio to research the influence of the C=C double bond for ignition delay time, it is showed that ignition delay time could decrease along with the increase of C=C double bond. The study of mechanism for how C=C double bond reduce the ignition delay time at the combustion of biodiesel showed that: the existence of C=C double bond can make fuel molecule generate small molecule propenyl C3H5-a and propylene C3H6 though the decomposition of C-C bond near by C=C double bond, then the propylene was consumed to generate formaldehyde CH₂ O and aldehyde radical CH₂ CHO that can promote the homogeneous charge compression ignition, reducing the ignition delay time.