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

Abstract

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, n-propanol, i-propanol, acetone, and toluene) were blended in binary mixtures with n-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 n-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.

An overview of the effects of fuel molecular structure on the combustion and emissions characteristics of compression ignition engines

“…Eveleigh et al 112 carried out a similar isotope-labelling experiment and blended a number of alcohols (ethanol, n- propanol and isopropanol) and a ketone (acetone) into binary mixtures with n -heptane to a level of 10% (molar concentration), which were combusted in a diesel engine and a flow reactor. Similar results were obtained in both systems, where in the case of the alcohols, the carbon atoms bonded to the hydroxyl groups contributed to soot formation in all cases, but to a reduced extent compared with the average carbon atom.…”

Isotopic Tracers for Combustion Research

“…Using the same 13 C technique, tracer studies were also carried out using both the tube reactor and a direct injection compression ignition engine (Eveleigh et al, 2015(Eveleigh et al, , 2016. In the first study, the engine was fueled with labeled single-component oxygenated fuels, a free fatty acid (oleic acid), and a fatty acid methyl ester (methyl oleate; Eveleigh et al, 2015).…”

“…The double bonded carbon atoms in oleic acid did contribute to PM formation, but at a similar rate as the average alkyl chain carbon atom; suggesting no extra contribution of the double bonded carbon atoms to particulate formation. In the second study, a range of molecules (ethanol, n-and i-propanol, acetone, and toluene) were blended in binary mixtures with n-heptane (to 10 mol%) and the contribution of individual carbon atoms to PM was assessed (Eveleigh et al, 2016). One of the interesting results from this study was that in the engine, the aromatic toluene component of the binary mixture contributed disproportionately to the formation of PM, which was consistent with the result of Sorek and Anderson (1985) obtained in a diffusion flame (discussed above).…”

“…Mayer et al (1980), Hilden and Mayer (1984) Diesel engine 14 C Unspecified PM (bulk) Burley and Rosebrock (1979) Diesel engine 14 C AMS PM (bulk, and non-volatile organic fraction) Buchholz et al (2003), Jones et al (2005) Diesel engine D GC/MS PM (volatile organics/PAH) Buttini and Manni (2001), Lombaert et al (2006), Zielinska et al (2008) Diesel engine Lieb and Roblee Jr. (1970), Homan and Robbins (1986), Sorek et al (1984), Anderson (1985,1986), Schmieder (1985) Premixed flames 13 C Spectroscopic intensity C 2 radical species Ferguson (1955) Combustion bomb 13 C MS Soot, and various gaseous species (CO, CO 2 , CH 4 , etc.) Ferguson (1957), Ferguson and Yokley (1958) Tube reactor and diesel engine Buchholz et al (2004), Eveleigh et al (2016), Buchholz et al (2002) Diesel engine 14 C AMS CO 2 Mack et al (2005aMack et al ( , 2005b Tube reactor Petch et al (1990), Rhead ...…”

Kerosene-Like Fuel Production from Coconut Oil and Cashew-Nut Oil - Effects of Fatty Acid Degree of Saturation and Chain Length

“…Unlike FAME, they do not have any oxygen in their molecular structures. The presence of oxygen in a fuel has two main advantages; there is a reduction of carbon content in the fuel, thus, soot formation (emission) of the fuel is significantly reduced, 28,29 and secondly, aircraft's engine particulate matter emissions fall by almost 40 % when jet fuel was blended with oxygenated fuels. 30 A lot more effort in research is still needed in this field.…”