Detailed chemical kinetic reaction mechanism for biodiesel components methyl stearate and methyl oleate

Abstract

International audienceNew chemical kinetic reaction mechanisms are developed for two of the five major components of biodiesel fuel, methyl stearate and methyl oleate. The mechanisms are produced using existing reaction classes and rules for reaction rates, with additional reaction classes to describe other reactions unique to methyl ester species. Mechanism capabilities were examined by computing fuel/air autoignition delay times and comparing the results with more conventional hydrocarbon fuels for which experimental results are available. Additional comparisons were carried out with measured results taken from jet-stirred reactor experiments for rapeseed oil methyl ester fuels. In both sets of computational tests, methyl oleate was found to be slightly less reactive than methyl stearate, and an explanation of this observation is made showing that the double bond in methyl oleate inhibits certain low temperature chain branching reaction pathways important in methyl stearate. The resulting detailed chemical kinetic reaction mechanism includes more approximately 3500 chemical species and more than 17,000 chemical reactions

Detailed chemical kinetic reaction mechanisms for soy and rapeseed biodiesel fuels

“…The two distinct reaction regimes are shown very strongly in both the experimental and computational results, and the agreement between the experimental and computational results is excellent. The slightly greater amount of low temperature conversion of methyl palmitate than that of n-decane can be attributed primarily to the weakly bound H atoms at the '2' site adjacent to the methyl ester group in methyl palmitate [28][29][30]36,37], so the total rate of methyl palmitate consumption is slightly greater than that of n-decane. It is interesting to note that the 1-olefin concentrations are significantly higher than their corresponding 1-olefin methyl esters.…”

“…These studies have examined ignition and combustion of alkyl esters from methyl and ethyl hexanoate and methyl and ethyl heptanoate to methyl decanoate [24][25][26][27][28][29][30][31][32][33], followed closely by extensions to methyl stearate and rapeseed methyl ester [34][35][36][37].…”

“…In these studies, ignition of n-heptane, n-decane, and iso-octane [43,66,67] was studied, showing very clearly a region of negative temperature coefficient (NTC) of reaction, with the amount of NTC behavior depending on the molecular structure of the fuel, as well as on equivalence ratio and pressure. Subsequently, the same test conditions have been used to test reaction mechanisms for many other fuels [37,[39][40][41]55,57,58], and further 34 experiments have been carried out to compare the intermediate temperature ignition of other fuels [54]. Part of the value of such experiments and kinetic modeling is the fact that n-heptane and iso-octane are primary reference fuels (PRF) for octane ratings of automotive fuels, and it has been interesting to use these shock tube experiments and simulations to relate other fuels to the PRF references.…”

Numerical Simulations of Nitric Oxide (NO) Formation in Methane, Methanol and Methyl Formate in different Flow Configurations

“…However, several kinetics models for both small-chain and long-chain methyl esters have been developed. These include: detailed chemical kinetic mechanism for methyl formate [9]- [11], methyl butanoate [10], methyl hexanoate and methyl heptanoate [12], methyl-5-decenoate and methyl-9-decenoate [13], methyl stearate and methyl oleate [14]. Recently, Westbrook et al [15] developed a mechanism for the five major components of soy biodiesel and rapeseed biodiesel fuel.…”

“…Recently, Westbrook et al [15] developed a mechanism for the five major components of soy biodiesel and rapeseed biodiesel fuel. These mechanisms usually have numerous chemical species taking part in enormous reactions, for instance, Naik et al [14] chemical reaction mechanism has 3500 species taking part in 17,000 chemical reactions. These detailed mechanisms can only be used to model fuels in zero dimensional homogenous transient system.…”