Inhibition of autoignition and combustion rate for <i>n</i>-heptane homogeneous charge compression ignition combustion by methanol additive

Lü, Xingcai; Yu-chun, Hou; Zu, Linlin; Huang, Zhen

doi:10.1243/09544070jauto252

Cited by 7 publications

(2 citation statements)

References 14 publications

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“…), we expect hydrocarbon radicals to abstract the weak α hydrogen atom from ethanol, limiting their chain-branching oxidation via the above R • + 2O 2 mechanism (this chain branching process is even more significant in longer chain alkanes such as n -heptane, due to reduced ring strain in transition states for intramolecular hydrogen abstraction). This helps explain why ethanol delays the onset of autoignition and the NTC regime when blended with hydrocarbon fuels …”

Section: Resultsmentioning

confidence: 96%

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O₂ Reaction

et al. 2009

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Bioethanol is currently a significant gasoline additive and the major blend component of flex-fuel formulations. Ethanol is a high-octane fuel component, and vehicles designed to take advantage of higher octane fuel blends could operate at higher compression ratios than traditional gasoline engines, leading to improved performance and tank-to-wheel efficiency. There are significant uncertainties, however, regarding the mechanism for ethanol autoignition, especially at lower temperatures such as in the negative temperature coefficient (NTC) regime. We have studied an important chemical process in the autoignition and oxidation of ethanol, reaction of the alpha-hydroxyethyl radical with O2(3P), using first principles computational chemistry, variational transition state theory, and Rice-Ramsperger-Kassel-Marcus (RRKM)/master equation simulations. The alpha-hydroxyethyl + O2 association reaction is found to produce an activated alpha-hydroxy-ethylperoxy adduct with ca. 37 kcal mol(-1) of excess vibrational energy. This activated adduct predominantly proceeds to acetaldehyde + HO(2), with smaller quantities of the enol vinyl alcohol (ethenol), particularly at higher temperatures. The reaction to acetaldehyde + HO2 proceeds with such a low barrier that collision stabilization of C2O3H5 isomers is unimportant, even for high-pressure/low-temperature conditions. The short lifetimes of these radicals precludes the chain-branching addition of a second O2 molecule, responsible for NTC behavior in alkane autoignition. This result helps to explain why ignition delays for ethanol are longer than those for ethane, despite ethanol having a weaker C-C bond energy. Given its relative instability, it is also unlikely that the alpha-hydroxy-ethylperoxy radical acts as a major acetaldehyde sink in the atmosphere, as has been suggested.

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Section: Resultsmentioning

confidence: 96%

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O₂ Reaction

et al. 2009

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“…Of all the oxygenated fuels, methanol contains the highest ratio of oxygen and mainly produced by coal with relative rich reserves, so it can be acted as alternative fuel for the traditional engine fossil oil that be about to dried up [12]. The methanol has been used as additive on HCCI engine fuelled with n-heptane [13]. And some researchers have investigated the cyclic variations of methanol HCCI combustion by statistical method at a constant engine speed [11].…”

Section: Introductionmentioning

confidence: 99%

Research on Combustion Characteristics and Performances of an HCCI Engine Fuelled with Methanol

Wu¹,

Zhang²,

Pan³

et al. 2013

Proceedings of the 2012 International Conference on Automobile and Traffic Science, Materials, Metallurgy Engineering

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The impacts of engine operating parameters, including intake charge temperature, fuel-air equivalence ratio and engine speed, on methanol HCCI combustion and performances were investigated on a modified diesel engine. The results show that the intake charge temperature is the most sensitive parameter of methanol HCCI combustion. The engine speed scopes are changed with boundary conditions, and the optimum speed increases gradually with equivalence ratio. But, the equivalence ratio just has a little influence on thermal efficiency. Moreover, CA50 is more sensitive to the boundary conditions than CA10, and the appropriate combustion phase for methanol HCCI engine may be within 8°CA for CA50 and within 11°CA for combustion duration.

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Autoignition of methanol: Experiments and computations

Kumar

Sung

2011

Int J of Chemical Kinetics

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An experimental and computational investigation into the autoignition of methanol under high-pressure and low-to-intermediate temperature conditions is conducted. The ignition delay results have been obtained using a heated rapid compression machine, over a pressure range of 7-30 bar, a temperature range of 850-1100 K, and an equivalence ratio range of 0.25-2.0. Using kinetic schemes recently reported in the literature for the combustion of methanol, the experimental results are compared to computationally obtained values. The kinetic schemes studied are found to significantly underpredict ignition delays for the conditions investigated. A sensitivity analysis of the computed results to reaction rate constants is also conducted. It is shown that the reaction of methanol with HO 2 radical is critical to the predicted values of ignition delays under the current experimental conditions. C

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Inhibition of autoignition and combustion rate for n-heptane homogeneous charge compression ignition combustion by methanol additive

Cited by 7 publications

References 14 publications

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O₂ Reaction

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O₂ Reaction

Research on Combustion Characteristics and Performances of an HCCI Engine Fuelled with Methanol

Autoignition of methanol: Experiments and computations

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Inhibition of autoignition and combustion rate for n-heptane homogeneous charge compression ignition combustion by methanol additive

Cited by 7 publications

References 14 publications

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O2 Reaction

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O2 Reaction

Research on Combustion Characteristics and Performances of an HCCI Engine Fuelled with Methanol

Autoignition of methanol: Experiments and computations

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Product

Resources

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Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O₂ Reaction

Ethanol Oxidation: Kinetics of the α-Hydroxyethyl Radical + O₂ Reaction