Hierarchical and comparative kinetic modeling of laminar flame speeds of hydrocarbon and oxygenated fuels

Plasma assisted combustion: Dynamics and chemistry

Alcohol combustion chemistry

Furfural and 5-hydroxymethylfurfural stand out as bridges connecting biomass raw materials to the biorefinery industry. Their reductive transformations by hydroconversion are key routes toward a wide variety of chemicals and biofuels, and heterogeneous catalysis plays a central role in these reactions. The catalyst efficiency highly depends on the nature of metals, supports, and additives, on the catalyst preparation procedure, and obviously on reaction conditions to which catalyst and reactants are exposed: solvent, pressure, and temperature. The present review focuses on the roles played by the catalyst at the molecular level in the hydroconversion of furfural and 5-hydroxymethylfurfural in the gas or liquid phases, including catalytic hydrogen transfer routes and electro/photoreduction, into oxygenates or hydrocarbons (e.g., furfuryl alcohol, 2,5-bis(hydroxymethyl)furan, cyclopentanone, 1,5-pentanediol, 2-methylfuran, 2,5-dimethylfuran, furan, furfuryl ethers, etc.). The mechanism of adsorption of the ...

How Catalysts and Experimental Conditions Determine the Selective Hydroconversion of Furfural and 5-Hydroxymethylfurfural.

Biofuels have grabbed the attention of engine researchers ever since the oil-crisis and escalating costs of petro-chemicals cropped up in the ׳70s. Ethanol and methanol were the most widely researched alcohols in IC engines. However, the last decade has witnessed significant amount of research in higher alcohols due to the development of modern fermentation processes using engineered micro-organisms that improved yield. Higher alcohols are attractive second/third generation biofuels that can be produced from sugary, starchy and ligno-cellulosic biomass feedstocks using sustainable pathways. The present work reviews the current literature concerning the effects of using higher alcohols ranging from 3-carbon propanol to 20-carbon phytol on combustion, performance and emission characteristics of a wide range of diesel engines under various test conditions. The literature is abound with evidence that higher alcohols reduce carcinogenic particulate emissions that are prevalent in diesel engines. NOx emissions either increased or decreased based on the domination of either cetane number or heat of evaporation. Brake specific fuel consumption (BSFC) of the engine usually suffered due to low energy content of alcohols. A notable feature is that the combination of higher alcohols (like butanol or pentanol), high exhaust gas recirculation (EGR) rates and late injection timing enabled low temperature combustion (LTC) in diesel engines that can simultaneously reduce smoke and NOx emissions with improved engine efficiency. It can be concluded that higher alcohols reduce smoke emissions with their fuel-borne oxygen; enhance air/fuel mixing by offering long ignition delay and eventually replace fossil diesel (partially or wholly) to enable a clean and efficient combustion in compression-ignition engines. The chief thrust areas include developing mutant strains with higher yield, higher tolerance to toxic inhibition and low-cost substrates for fermentation. Further work is required in stipulating optimum blend-fuel characteristics and ensuring the long-term durability of the engines using these fuels.

Use of higher alcohol biofuels in diesel engines: A review

Emission characteristics of a spark-ignition engine fuelled with gasoline-n-butanol blends in combination with EGR

An experimental and numerical study on laminar flame characteristics of methane oxy-fuel mixtures highly diluted with CO2 was conducted using a constant volume chamber and CHEMKIN package. The effects of high CO2 dilution on combustion chemical reaction, flame instability, and flame radiation of CH4/CO2/O2 mixtures were studied. The laminar burning velocities of CH4/CO2/O2 mixtures decrease with the increase of the CO2 fraction. CO2 directly participates in the chemical reaction through the elementary reaction OH + CO = H + CO2 and inhibits the combustion process by the competition of the H radical between the reverse reaction of OH + CO = H + CO2 and the reaction H + O2 = O + OH. This effect is more obvious for highly diluted CO2 in the case of CH4/CO2/O2 mixtures. CO2 suppresses the flame instability by the combined effect of hydrodynamic and thermal-diffusive instabilities. The radiation of CH4 oxy-fuel combustion is much stronger than that of CH4/air combustion mainly because of the existence of a lar...

Experimental and Numerical Study on Laminar Flame Characteristics of Methane Oxy-fuel Mixtures Highly Diluted with CO2

Furan derivatives (DMF (2,5-dimethylfuran), MF (2-methylfuran), and furan) are the attractive oxygenated fuels to reduce the consumption of fossil fuel and engine emissions due to their comparable combustion properties to those of commercial gasoline and the productivities from lignocellulosic raw materials. Many experimental studies have been focused on these promising fuel characteristics including laminar burning velocities, laminar flame structures, ignition delay times, and pyrolysis species. Various kinetic mechanisms have been developed in detail as well based on up to date experimental data in accordance with the quantum chemical calculations. In the present study, the vast amount of experimental data have been collected, consolidated, and reviewed along with the kinetic model validations in order to envision a future fuel research on furan derivatives for minimizing the experimental uncertainties, improving the data fidelity, and developing accurate kinetic models.

Review on the production methods and fundamental combustion characteristics of furan derivatives

The diffusive extinction limits of a series of methyl ester flames, from methyl formate to methyl decanoate, have been measured in the counterflow configuration. Kinetic and transport effects are decoupled by use of the transport-weighted enthalpy term and reveal that the smaller methyl esters (C2 to C4) exhibit unique behavior while methyl esters inclusive and larger than methyl butanoate exhibit similar global reactivity to that of the n-alkanes. In order to interpret the experimental observations, a previous kinetic model for methyl butanoate and methyl decanoate has been extended to encompass the oxidation of the smaller methyl esters. Model rate of production analyses highlight the chemical kinetic specificities of methyl formate, methyl ethanoate, and methyl propanoate, through distinctive fuel reaction channels in methanol elimination, methyl radical production, and H atom production respectively. The similarity of global reactivity among the larger methyl esters and n-alkanes is elucidated based on the formation of formaldehyde and ethylene, which drive indifferently the growth of the radical pool at high temperature, thus the flame oxidation rate is similar at the global level.

A comparative study of the chemical kinetic characteristics of small methyl esters in diffusion flame extinction

The laminar flame speeds of C 3 oxygenated fuels ( n -propanol, propanal and acetone) and hydrocarbon (propane) were measured in a combustion bomb to compare combustion characteristics of C 3 alcohol, aldehyde, ketone, and alkane Propanal shows the highest flame speeds while acetone gives the lowest one The experimental observations are further interpreted with chemical kinetic models The effects of distinctive molecular structures on the fuel consumption pathways are clarified Propanal generates a large H atom pool that enhances the oxidation, leading to the highest flame speeds However, acetone forms methyl radical (CH 3 ) and has lower flame speeds as a consequence The calculated maximum concentrations of H, OH, and CH 3 confirm this analysis It is found that propanal yields the highest H and OH concentrations while acetone produces the lowest H and OH concentrations among all tested fuels Moreover, acetone presents higher CH 3 concentration, especially for fuel rich condition n -Propanol and propane show comparable flame speeds and similar radical concentrations, especially H and OH The different kinetics among hydrocarbon species with the same carbon numbers can provide a horizontal view in the hierarchical hydrocarbon chemistry

Jing Gong

Papers

Emission characteristics of a spark-ignition engine fuelled with gasoline-n-butanol blends in combination with EGR

Experimental and Numerical Study on Laminar Flame Characteristics of Methane Oxy-fuel Mixtures Highly Diluted with CO2

Review on the production methods and fundamental combustion characteristics of furan derivatives

A comparative study of the chemical kinetic characteristics of small methyl esters in diffusion flame extinction

A comparative study of n-propanol, propanal, acetone, and propane combustion in laminar flames