Matthew A. Ratcliff

Diesel particle filter and fuel effects on heavy-duty diesel engine emissions.

The impacts of biodiesel and a continuously regenerated (catalyzed) diesel particle filter (DPF) on the emissions of volatile unburned hydrocarbons, carbonyls, and particle associated polycyclic aromatic hydrocarbons (PAH) and nitro-PAH, were investigated. Experiments were conducted on a 5.9 L Cummins ISB, heavy-duty diesel engine using certification ultra-low-sulfur diesel (ULSD, S ≤ 15 ppm), soy biodiesel (B100), and a 20% blend thereof (B20). Against the ULSD baseline, B20 and B100 reduced engine-out emissions of measured unburned volatile hydrocarbons and PM associated PAH and nitro-PAH by significant percentages (40% or more for B20 and higher percentage for B100). However, emissions of benzene were unaffected by the presence of biodiesel and emissions of naphthalene actually increased for B100. This suggests that the unsaturated FAME in soy-biodiesel can react to form aromatic rings in the diesel combustion environment. Methyl acrylate and methyl 3-butanoate were observed as significant species in the exhaust for B20 and B100 and may serve as markers of the presence of biodiesel in the fuel. The DPF was highly effective at converting gaseous hydrocarbons and PM associated PAH and total nitro-PAH. However, conversion of 1-nitropyrene by the DPF was less than 50% for all fuels. Blending of biodiesel caused a slight reduction in engine-out emissions of acrolein, but otherwise had little effect on carbonyl emissions. The DPF was highly effective for conversion of carbonyls, with the exception of formaldehyde. Formaldehyde emissions were increased by the DPF for ULSD and B20.

Impact of Higher Alcohols Blended in Gasoline on Light-Duty Vehicle Exhaust Emissions

Certification gasoline was splash blended with alcohols to produce four blends: ethanol (16 vol%), n-butanol (17 vol%), i-butanol (21 vol%), and an i-butanol (12 vol%)/ethanol (7 vol%) mixture; these fuels were tested in a 2009 Honda Odyssey (a Tier 2 Bin 5 vehicle) over triplicate LA92 cycles. Emissions of oxides of nitrogen, carbon monoxide, non-methane organic gases (NMOG), unburned alcohols, carbonyls, and C1-C8 hydrocarbons (particularly 1,3-butadiene and benzene) were determined. Large, statistically significant fuel effects on regulated emissions were a 29% reduction in CO from E16 and a 60% increase in formaldehyde emissions from i-butanol, compared to certification gasoline. Ethanol produced the highest unburned alcohol emissions of 1.38 mg/mile ethanol, while butanols produced much lower unburned alcohol emissions (0.17 mg/mile n-butanol, and 0.30 mg/mile i-butanol); these reductions were offset by higher emissions of carbonyls. Formaldehyde, acetaldehyde, and butyraldehyde were the most significant carbonyls from the n-butanol blend, while formaldehyde, acetone, and 2-methylpropanal were the most significant from the i-butanol blend. The 12% i-butanol/7% ethanol blend was designed to produce no increase in gasoline vapor pressure. This fuels exhaust emissions contained the lowest total oxygenates among the alcohol blends and the lowest NMOG of all fuels tested.

Fuels for Advanced Combustion Engines Research Diesel Fuels: Analysis of Physical and Chemical Properties

The CRC Fuels for Advanced Combustion Engines working group has worked to identify a matrix of research diesel fuels for use in advanced combustion research applications. Nine fuels were specified and formulated to investigate the effects of cetane number aromatic content and 90% distillation fraction. Standard ASTM analyses were performed on the fuels as well as GC/MS and /u1H//u1/u3C NMR analyses and thermodynamic characterizations. Details of the actual results of the fuel formulations compared with the design values are presented, as well as results from standard analyses, such as heating value, viscosity and density. Cetane number characterizations were accomplished by using both the engine method and the Ignition Quality Tester (IQT/sT) apparatus.

The Impacts of Mid-Level Alcohol Content in Gasoline on SIDI Engine-Out and Tailpipe Emissions

The influences of ethanol and iso-butanol on gasoline engine performance, engine-out and tailpipe emissions were studied using a General Motors (GM) 2.0L turbocharged gasoline spark ignition direct injection (SIDI) engine. U.S. federal certification gasoline (E0), two ethanol-blended fuels (E10 and E20), and 11.7% iso-butanol blended fuels were tested. Fourier-Transform Infrared (FTIR) spectroscopy was used to measure non-regulated species including methane, ethylene, acetylene, formaldehyde, acetaldehyde, isobutylene, 1,3-butadiene, n-pentane, and iso-octane. A Fast Mobility Particle Sizer (FMPS) spectrometer was used to measure the particle number (PN) size distribution in the range from 5.6 to 560 nm. The regulated emissions total hydrocarbon (THC), carbon monoxide (CO), and oxides of nitrogen (NOx ) were also measured. Both engine-out and tailpipe emissions results are presented as functions of alcohol content. In general, the alcohols tested reduced total PN emissions, with iso-butanol demonstrating the greatest reduction. Increasing ethanol content and iso-butanol increased formaldehyde emissions, with iso-butanol exhibiting the highest increase. Iso-butanol increased iso-butylene emission; however, it reduced emissions of 1,3-butadiene. Within the context of this study, the alcohols did not significantly change the other regulated emissions.© 2010 ASME

Effects of Heat of Vaporization and Octane Sensitivity on Knock-Limited Spark Ignition Engine Performance

Knock-limited loads for a set of surrogate gasolines all having nominal 100 research octane number (RON), approximately 11 octane sensitivity (S), and a heat of vaporization (HOV) range of 390 to 595 kJ/kg at 25°C were investigated. A single-cylinder spark-ignition engine derived from a General Motors Ecotec direct injection (DI) engine was used to perform load sweeps at a fixed intake air temperature (IAT) of 50 °C, as well as knock-limited load measurements across a range of IATs up to 90 °C. Both DI and pre-vaporized fuel (supplied by a fuel injector mounted far upstream of the intake valves and heated intake runner walls) experiments were performed to separate the chemical and thermal effects of the fuels’ knock resistance. The DI load sweeps at 50°C intake air temperature showed no effect of HOV on the knocklimited performance. The data suggest that HOV acts as a thermal contributor to S under the conditions studied. Measurement of knock-limited loads from the IAT sweeps for DI at late combustion phasing showed that a 40 vol% ethanol (E40) blend provided additional knock resistance at the highest temperatures, compared to a 20 vol% ethanol blend and hydrocarbon fuel with similar RON and S. Using the prevaporized fuel system, all the high S fuels produced nearly identical knock-limited loads at each temperature across the range of IATs studied. For these fuels RON ranged from 99.2 to 101.1 and S ranged from 9.4 to 12.2, with E40 having the lowest RON and highest S. The higher knock-limited loads for E40 at the highest IATs examined were consistent with the slightly higher S for this fuel, and the lower engine operating condition K values arising from use of this fuel. The study highlights how fuel HOV can affect the temperature at intake valve closing, and consequently the pressure-temperature history of the end gas leading to more negative values of K, thereby enhancing the effect of S on knock resistance.

Measured and Predicted Vapor Liquid Equilibrium of Ethanol-Gasoline Fuels with Insight on the Influence of Azeotrope Interactions on Aromatic Species Enrichment and Particulate Matter Formation in Spark Ignition Engines

A relationship has been observed between increasing ethanol content in gasoline and increased particulate matter (PM) emissions from direct injection spark ignition (DISI) vehicles. The fundamental cause of this observation is not well understood. One potential explanation is that increased evaporative cooling as a result of ethanol’s high HOV may slow evaporation and prevent sufficient reactant mixing resulting in the combustion of localized fuel rich regions within the cylinder. In addition, it is well known that ethanol when blended in gasoline forms positive azeotropes which can alter the liquid/vapor composition during the vaporization process. In fact, it was shown recently through a numerical study that these interactions can retain the aromatic species within the liquid phase impeding the in-cylinder mixing of these compounds, which would accentuate PM formation upon combustion. To better understand the role of the azeotrope interactions on the vapor/liquid composition evolution of the fuel, distillations were performed using the Advanced Distillation Curve apparatus on carefully selected samples consisting of gasoline blended with ethanol and heavy aromatic and oxygenated compounds with varying vapor pressures, including cumene, p-cymene, 4-tertbutyl toluene, anisole, and 4-methyl anisole. Samples collected during the distillation indicate an enrichment of the heavy aromatic or oxygenated additive with an increase in initial ethanol concentration from E0 to E30. A recently developed distillation and droplet evaporation model is used to explore the influence of dilution effects versus azeotrope interactions on the aromatic species enrichment. The results suggest that HOV-cooling effects as well as aromatic species enrichment behaviors should be considered in future development of predictive indices to forecast the PM potential of fuels containing oxygenated compounds with comparatively high HOV.