Biodiesel is a renewable transportation fuel consisting of fatty acid methyl esters (FAME), generally produced by transesterification of vegetable oils and animal fats. In this review, the fatty acid (FA) profiles of 12 common biodiesel feedstocks were summarized. Considerable compositional variability exists across the range of feedstocks. For example, coconut, palm and tallow contain high amounts of saturated FA; while corn, rapeseed, safflower, soy, and sunflower are dominated by unsaturated FA. Much less information is available regarding the FA profiles of algal lipids that could serve as biodiesel feedstocks. However, some algal species contain considerably higher levels of poly-unsaturated FA than is typically found in vegetable oils. Differences in chemical and physical properties among biodiesel fuels can be explained largely by the fuels’ FA profiles. Two features that are especially influential are the size distribution and the degree of unsaturation within the FA structures. For the 12 biodiesel types reviewed here, it was shown that several fuel properties – including viscosity, specific gravity, cetane number, iodine value, and low temperature performance metrics – are highly correlated with the average unsaturation of the FAME profiles. Due to opposing effects of certain FAME structural features, it is not possible to define a single composition that is optimum with respect to all important fuel properties. However, to ensure satisfactory in-use performance with respect to low temperature operability and oxidative stability, biodiesel should contain relatively low concentrations of both long-chain saturated FAME and poly-unsaturated FAME.

Review of biodiesel composition, properties, and specifications

Soot processes in compression ignition engines

Review of the effects of biodiesel on NOx emissions

Conceptual models for partially premixed low-temperature diesel combustion

Computational fluid dynamic (CFD) simulations that include realistic combustion/emissions chemistry hold the promise of significantly shortening the development time for advanced high-efficiency, low-emission engines. However, significant challenges must be overcome to realize this potential. This paper discusses these challenges in the context of diesel combustion and outlines a technical program based on the use of surrogate fuels that sufficiently emulate the chemical complexity inherent in conventional diesel fuel. The essential components of such a program are discussed and include: (a) surrogate component selection; (b) the acquisition or estimation of requisite elementary chemical kinetic, thermochemical, and physical property data; (c) the development of accurate predictive chemical kinetic models, together with the measurement of the necessary fundamental laboratory data to validate these mechanisms; and (d) mechanism reduction tools to render the coupled chemistry/flow calculations feasible. In parallel to these efforts, the need exists to develop similarly robust models for fuel injection and spray processes involving multicomponent mixtures of wide distillation character, as well as methodologies to include all of these high fidelity submodels in computationally efficient CFD tools. Near- and longerterm research plans are proposed based on an application target of premixed diesel combustion. In the near term, the recommended surrogate components include n-decane, iso-octane, methylcyclohexane, and toluene. For the longer term, n-hexadecane, heptamethylnonane, n-decylbenzene, and 1-methylnaphthalene are proposed.

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Development of an Experimental Database and Kinetic Models for Surrogate Diesel Fuels

Application of Biodiesel Fuel to Modern Diesel Engine

Achievement of Medium Engine Speed and Load Premixed Diesel Combustion with Variable Valve Timing

Miller-PCCI Combustion in an HSDI Diesel Engine with VVT

Modeling Atomization and Vaporization Processes of Flash-Boiling Spray

Flash-boiling occurs when a fuel is injected into a combustion chamber where the ambient pressure is lower than the saturation pressure of the fuel It has been known that flashing is a favorable mechanism for atomizing liquid fuels On the other hand, alternative fuels, such as gaseous fuels and oxygenated fuels, are used to achieve low exhaust emissions in recent years In general, most of these alternative fuels have high volatility and flash-boiling takes place easily in the fuel spray when injected into the combustion chamber of an internal combustion engine under high pressure In addition the multicomponent mixture of high- and low-volatility fuels has been proposed in the previous study in order to control the spray and combustion processes in an internal combustion engine It was found that the multicomponent fuel produces flash-boiling with an increase in the initial fuel temperature Therefore, it is important to investigate these flash-boiling processes in fuel spray

In the present study, the submodels of a flash-boiling spray are constructed These submodels consider the bubble nucleation, growth, and disruption in the nozzle orifice and injected fuel droplets The model is implemented in KIVA3V and the spray characteristics of multicomponent fuel with and without flashing are numerically investigated In addition, these numerical results are compared with experimental data obtained in the previous study using a constant volume vessel The flashing spray characteristics from numerical simulation qualitatively show good agreement with the experimental results In particular, it is confirmed from both the numerical and experimental data that flash-boiling effectively accelerates the atomization and vaporization of fuel droplets This means that a lean homogeneous mixture can be quickly formed using flash-boiling in the combustion chamber © 2006 Wiley Periodicals, Inc Heat Trans Asian Res, 35(5): 369–385, 2006; Published online in Wiley InterScience (wwwintersciencewileycom) DOI 101002/htj20117

Daisuke Kawano

Papers

Application of Biodiesel Fuel to Modern Diesel Engine

Achievement of Medium Engine Speed and Load Premixed Diesel Combustion with Variable Valve Timing

Miller-PCCI Combustion in an HSDI Diesel Engine with VVT

Modeling Atomization and Vaporization Processes of Flash-Boiling Spray

Numerical study on flash-boiling spray of multicomponent fuel