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

The rapid growth of eco-friendly biomass derived fuels in transportation requires a fundamental understanding of the uniqueness of their oxidation and combustion characteristics. This paper focuses on one specific class of biofuels, namely Fatty Acids Ethyl Esters (FAEE). A counterflow configuration was employed to measure the extinction limits of the diffusion flames of four ethyl esters (ethyl-butanoate, pentanoate, heptanoate, and nonanoate). The results were compared to that of methyl esters (Dievart et al., 2012, Proceedings of the Combustion Institute, 34). It was observed that both methyl esters and ethyl esters exhibit similar high temperature reactivity against extinction. The use of the transport-weighted enthalpy metric has revealed that all esters share similar chemical kinetics in the near extinction conditions of the present study. A previous detailed kinetic model has been extended to include the oxidation chemistry of ethyl esters, and used to interpret the experimental observations. Good agreement between the computed and experimental extinction limits was observed. The rates of consumption pathway analysis have shown that ethyl esters exclusively decomposed into ethylene and a carboxylic acid through an endothermic six-centered unimolecular decomposition reaction, while methyl esters oxidation preferentially progresses through H abstraction reactions. However, the growth of the radical pool was observed to be driven indifferently between ethyl and methyl esters, therefore resulting in similar global flame reactivity.Copyright © 2013 by ASME

A comparative study of the kinetics of ethyl and methyl esters in diffusion flame extinction

Publisher Summary This chapter analyzes an experimental study on the performance of a small-scale oxygen concentrator by pressure swing adsorption (PSA). A small-scale adjustable rich oxygen concentrator by PSA is designed and manufactured to study influences of nozzle size, purge quantity on characteristics of the production oxygen, such as its pressure, purity and volume flux. The purity of oxygen produced by this device could reach above 90% and up to 96% in volume. The flux of rich oxygen product could be adjusted intelligently in the range of 0.51/min–3.51/min. It is found that the small-scale concentrator could operate in optimum performance, with the purity of oxygen being above 90%. The relationship between the HPAP and the Q e is a typical curve of Langmuir. The optimal operating pressure of the experiment device is 0.18Mpa to 0.2MPa. The ratio of the purge quantity Q p to the flow of the product oxygen Q o is maintained above 2.5. The smaller the nozzle diameter, the higher the HPAP. The optimal nozzle diameter is from 0.8mm to 1.2mm while the adsorption time is 10 seconds. The highest purity of the production oxygen is about 96% in volume by using this small-scale concentrator while the flow of the production oxygen is of 2.0l/min. The small-scale concentrator is quite suitable for hospital, domestic usage, and oxygen bar. The device is quite usable in hospital, domestic application, oxygen bar and other places in shortage of oxygen. It would have great economic benefit in the future.

Jing Gong

Papers

A comparative study of the kinetics of ethyl and methyl esters in diffusion flame extinction

The experimental study on the performance of a small-scale oxygen concentrator by psa