Demonstrating Clean Burning Future Fuels at a Public Engagement Event

Sustainable future fuels are likely to be produced by a wide range of processes, and there exists the opportunity to engineer these fuels so that they burn more efficiently and produce fewer harmful emissions. Such potential is especially important within the context of reducing the emissions of both greenhouse gases (GHG) and toxic pollutants that adversely impact air quality and human health. To illustrate how fuel design on a molecular level may be exploited to reduce these emissions, the combustion and emission properties of three potential future fuels, geraniol, diethyl carbonate, and a biodiesel (soy methyl ester), were evaluated along with a fossil diesel. The fuels were assessed using “smoke point” tests and a Stirling engine. The purpose of the demonstration was to highlight to a general audience several burning characteristics of some possible future fuels, and thus the potential for the development of clean burning “designer” fuels. During the 15 min demonstration, significant differences in the combustion properties of the different fuels were shown. For example, the conventional fossil diesel fuel produced a significant amount of soot in flame tests, whereas diethyl carbonate, which is a potential second-generation biofuel, produced visibly lower amounts of soot

Quantification of the Fraction of Particulate Matter Derived from a Range of ¹³C‑Labeled Fuels Blended into Heptane, Studied in a Diesel Engine and Tube Reactor

This paper presents the results of an experimental study that was carried out to determine the conversion rates to particulate matter (PM) of several liquid fuel hydrocarbon molecules and specific carbon atoms within those molecules. The fuels investigated (ethanol, <i>n</i>-propanol, <i>i</i>-propanol, acetone, and toluene) were blended in binary mixtures with <i>n</i>-heptane to a level of 10 mol percent. The contribution of the additive molecules to PM was quantified using a carbon-13 (¹³C) labeling experiment, in which the fuel of interest was enriched with ¹³C to serve as an atomic tracer. Measurement of the ¹³C/¹²C in the fuel and in the resulting PM was carried out using isotope ratio mass spectrometry. The fuel binary mixtures were tested under pyrolysis conditions in a tube reactor and also combusted in a direct injection compression ignition engine. In the tube reactor, samples were generated under oxygen-free pyrolysis conditions and at a temperature of 1300 °C, while the engine experiments were carried out at an intermediate load. Both in the tube reactor and in the engine it was found that, dependent on the fuel molecular structure, there were significant differences in the overall conversion rates to PM of the fuel molecules and of the “submolecular” carbon atoms. A separate experiment was also carried out in the compression ignition engine, with <i>n</i>-heptane as fuel, in order to determine the contribution of the engine lubrication oil to exhaust PM; the results showed that a significant portion (∼60%) of the total particulate was derived from the lubrication oil