Fundamental spray and combustion measurements of soy methyl-ester biodiesel

Abstract

Nerva, J.; Genzale, CL.; Kook, S.; García Oliver, JM.; Pickett, LM. (2013) soy methyl-ester biodiesel is injected into a constant-volume combustion facility. A range of optical diagnostics is performed, comparing biodiesel to a conventional #2 diesel at the same injection and ambient conditions. Schlieren imaging shows virtually the same vapor-phase penetration for the two fuels, while simultaneous Mie-scatter imaging shows that the maximum liquid-phase penetration of biodiesel is higher than diesel due to their different boiling-point temperatures. But the different liquid-phase penetration does not affect overall mixing rate and downstream vapor-phase penetration because each fuel spray has similar momentum and spreading angle. The ignition delay and lift-off length are only slightly less for biodiesel compared to diesel, consistent with the CN. Because of the similarity in lift-off length, the differences in equivalence ratio distribution at the lift-off length are mainly affected by the fuels oxygen content. For biodiesel, the equivalence ratio is reduced, which, along with the fuel molecular structure and oxygen content, significantly affects soot formation downstream. Spatially-resolved soot volume fraction measurements obtained by combining laser extinction measurements with planar laser-induced incandescence imaging show that the soot concentration can be reduced by an order of magnitude for biodiesel. These integrated measurements of spray mixing, combustion, and quantitative soot concentration provide new validation data for the development of CFD spray, combustion, and soot formation models suitable for the latest biofuels. AbstractThough biodiesel has begun to penetrate the fuel market, its effect on injection processes, combustion, and emissions formation under diesel engine conditions remains somewhat unclear. Typical tailpipe measurements from engines running biodiesel indicate that PM, CO and UHC are decreased, whereas NO X emissions tend to be increased. However, these observations are the result of complex interactions between physical and chemical processes occurring in the combustion chamber, for which understanding is still needed.To characterize and decouple the physical and chemical influences of biodiesel on spray mixing, ignition, combustion and soot formation, a soy methyl-ester biodiesel is injected into a constant-volume combustion facility under diesel-like operating conditions. A range of optical diagnostics is performed, comparing biodiesel to a conventional #2 diesel at the same injection and ambient conditions.Schlieren high-speed imaging shows virtually the same vapor-phase penetration for the two fuels, while simultaneous Mie-scatter imaging shows that the maximum liquid-phase penetration of biodiesel is higher than diesel. Differences in the liquid-phase penetration are expected because of the different boiling-point temperatures of the two fuels. But the different liquid-phase penetration does not affect overall mixing rate and downstream vapor-phase penetration because each...

A reduced mechanism for biodiesel surrogates for compression ignition engine applications

“…10. Measured [58] and predicted liquid spray penetration and vapor penetration vs. time for biodiesel fuel at an ambient temperature of 900 K. Fig. 11.…”

“…25% MD, 25% MD9D and 50% nheptane in mole fraction, is used in the simulations. The experimental dataset was obtained by the Sandia National Laboratories [58], where a constant-volume, quiescent, pre-burn-type combustion vessel was used to generate high-temperature and high-pressure gases. A premixed combustible mixture was spark-ignited and the combustion products cool over a long time.…”

Influence of fuel properties on fundamental spray characteristics and soot emissions using different tailor-made fuels from biomass

“…Moreover, the model indicated the presence of an "entrainment wave" that travels along the jet from upstream, promoting fuel air mixing after EOI. This model has been also used to explain results obtained by means of combustion vessels [14] and optical single-cylinder research engine [29] [30].…”

A Review on Atomization and Sprays of Biofuels for IC Engine Applications

“…are observed to have a significant effect on lift-off length and ignition delay [2]. Vapour and liquid penetration of soy biodiesel and diesel along with spray combustion characteristics are studied by Nerva et al [63] which showed that, in spite of having a higher liquid penetration for biodiesel, both biodiesel and diesel have similar vapour penetration. Higher peak heat release rate and shorter combustion duration were observed for biodiesels as compared to diesel indicating faster combustion [64,65].…”

“…Significant reduction in soot production is observed in biodiesel spray combustion. It is believed that the presence of oxygen in biodiesel is mainly responsible for the soot reduction [63,66]. In the quasi-steady diffusion combustion phase, physical processes such as evaporation and mixing are observed to have a major effect on ignition and combustion processes.…”