Samuel A. Lewis

Low Temperature Urea Decomposition and SCR Performance

Urea-SCR systems are potentially a highly-effective means of NO x reduction for light-duty diesel vehicles. However, use of urea-SCR technologies at low temperatures presents unique technical challenges. This study was undertaken to provide more knowledge about low temperature urea decomposition and the resulting effects on SCR performance. Data are presented for experiments using two SCR catalysts of differing size with a light-duty diesel engine. Analyses of the NO x reduction efficiency, NH 3 storage phenomena, and unregulated emissions are shown. Over production of NO 2 by the oxidation catalyst is demonstrated to be problematic at 25,000 hr-1 space velocity for a range of temperatures. This leads to production of N 2 O by both SCR catalysts that is higher when urea is injected than when NH 3 is injected.

Processes Involved in the Development of Latent Fingerprints Using the Cyanoacrylate Fuming Method

Chemical processes involved in the development of latent fingerprints using the cyanoacrylate fuming method have been studied. Two major types of latent prints have been investigated-clean and oily prints. Scanning electron microscopy (SEM) has been used as a tool for determining the morphology of the polymer developed separately on clean and oily prints after cyanoacrylate fuming. A correlation between the chemical composition of an aged latent fingerprint, prior to development, and the quality of a developed fingerprint has been observed in the morphology. The moisture in the print prior to fuming has been found to be more important than the moisture in the air during fuming for the development of a useful latent print. In addition, the amount of time required to develop a high quality latent print has been found to be within 2 min. The cyanoacrylate polymerization process is extremely rapid. When heat is used to accelerate the fuming process, typically a period of 2 min is required to develop the print. The optimum development time depends upon the concentration of cyanoacrylate vapors within the enclosure.

Fuel Economy and Emissions of the Ethanol-Optimized Saab 9-5 Biopower

Saab Automobile recently released the BioPower engines, advertised to use increased turbocharger boost and spark advance on ethanol fuel to enhance performance. Specifications for the 2.0 liter turbocharged engine in the Saab 9-5 Biopower 2.0t report 150 hp (112 kW) on gasoline and a 20% increase to 180 hp (134 kW) on E85 (nominally 85% ethanol, 15% gasoline). While FFVs sold in the U.S. must be emissions certified on Federal Certification Gasoline as well as on E85, the European regulations only require certification on gasoline. Owing to renewed and growing interest in increased ethanol utilization in the U.S., a European-specification 2007 Saab 9-5 Biopower 2.0t was acquired by the Department of Energy and Oak Ridge National Laboratory (ORNL) for benchmark evaluations. Results show that the vehicle’s gasoline equivalent fuel economy on the Federal Test Procedure (FTP) and the Highway Fuel Economy Test (HFET) are on par with similar U.S.-legal flex-fuel vehicles. Regulated and unregulated emissions measurements on the FTP and the US06 aggressive driving test (part of the supplemental FTP) show that despite the lack of any certification testing requirement in Europe on E85 or on the U.S. cycles, the vehicle is within Tier 2, Bin 5 emissions levels (note that full useful life emissions have not been measured) on the FTP, and also within the 4000 mile (6400 km) US06 emissions limits. Emissions of hydrocarbon-based hazardous air pollutants are higher on Federal Certification Gasoline while ethanol and aldehyde emissions are higher on ethanol fuel. The advertised power increase on E85 was confirmed through acceleration tests on the chassis dynamometer as well as on-road.

Time-Resolved Measurements of Emission Transients By Mass Spectrometry

Transient emissions occur throughout normal engine operation and can significantly contribute to overall system emissions. Such transient emissions may originate from various sources including cold start, varying load and exhaust-gas recirculation (EGR) rates; all of which are dynamic processes in the majority of engine operation applications (1). Alternatively, there are systems which are inherently dynamic even at steady-state engine-operation conditions. Such systems include catalytic exhaust-emissions treatment devices with self-initiated and sustained oscillations (2) and NOX adsorber systems (3,4,5). High-speed diagnostics, capable of temporally resolving such emissions transients, are required to characterize the process, verify calculated system inputs, and optimize the system.

Novel Characterization of GDI Engine Exhaust for Gasoline and Mid- Level Gasoline-Alcohol Blends

Gasoline direct injection (GDI) engines can offer improved fuel economy and higher performance over their port fuelinjected (PFI) counterparts, and are now appearing in increasingly more U.S. and European vehicles. Small displacement, turbocharged GDI engines are replacing large displacement engines, particularly in light-duty trucks and sport utility vehicles, in order for manufacturers to meet more stringent fuel economy standards. GDI engines typically emit the most particulate matter (PM) during periods of rich operation such as start-up and acceleration, and emissions of air toxics are also more likely during this condition. A 2.0 L GDI engine was operated at lambda of 0.91 at typical loads for acceleration (2600 rpm, 8 bar BMEP) on three different fuels; an 87 anti-knock index (AKI) gasoline (E0), 30% ethanol blended with the 87 AKI fuel (E30), and 48% isobutanol blended with the 87 AKI fuel. E30 was chosen to maximize octane enhancement while minimizing ethanol-blend level and iBu48 was chosen to match the same fuel oxygen level as E30. Particle size and number, organic carbon and elemental carbon (OC/EC), soot HC speciation, and aldehydes and ketones were all analyzed during the experiment. A new method for soot HC speciation is introduced using a direct, thermal desorption/pyrolysis inlet for the gas chromatograph (GC). Results showed high levels of aromatic compounds were present in the PM, including downstream of the catalyst, and the aldehydes were dominated by the alcohol blending.

Implications of Particulate and Precursor Compounds Formed During High-Efficiency Clean Combustion in a Diesel Engine

Advanced diesel combustion modes offer the promise of reduced engine-out particulate and nitrogen oxide emissions, thereby reducing the demand on post-combustion emission control devices. In this activity, a light-duty diesel engine was operated in conventional and advanced combustion modes. The advanced combustion modes investigated correspond to both clean (i.e., low PM and low NO x ) and clean efficient combustion. The low-NOx, low-PM mode is considered an intermediate condition and the low-NO x , low-PM efficient mode is referred to as high efficiency clean combustion (HECC). Particulate and gaseous emissions were analyzed during all of these experiments. The detailed exhaust chemistry analysis provided significant new information to improving our understanding of these modes as well as identifying potentially important unregulated emissions.

Fuel chemistry and cetane effects on diesel homogeneous charge compression ignition performance, combustion, and emissions

Abstract The effects of cetane number (CN) on homogeneous charge compression ignition (HCCI) performance and emissions were investigated in a single-cylinder engine with port fuel injection, using intake air temperature for control. Commercial fuels and blends of the diesel secondary reference fuels were evaluated, covering a CN range from 19 to 76. Sweeps of intake air temperature showed that low-CN fuels needed higher intake temperatures than high-CN fuels to achieve ignition. As a function of intake air temperature, each fuel passed through a point of maximum indicated mean effective pressure (i.m.e.p.). High-CN fuels required a combustion phasing approximately 10 crank angle degrees (CAD) earlier than the lowest CN fuels in order to prevent misfire. The high-CN fuels exhibited a strong low-temperature heat release (LTHR) event, while no LTHR was detected for fuels with CN ≤ 34. All of the fuels yielded comparable NOx emissions (< 6 ppm at 3.5 bar i.m.e.p.) at their respective maximum i.m.e.p. timeing. Low-CN fuels were prone to excessive pressure rise rates and NOx emissions at advanced phasing, while high-CN fuels were prone to excessive CO emissions at retarded phasing. These results suggest that the products of LTHR, which are high in CO, are more sensitive to the quenching effects of cylinder expansion. Engine speed was found to suppress LTHR since higher engine speed reduces the time allowed for the LTHR reactions. In addition to measurements of standard gaseous emissions, additional sampling and analysis techniques were used to identify and measure the individual exhaust HC species including an array of oxygenated compounds. In addition to high concentrations of formaldehyde and other low molecular weight carbonyls, results showed an abundance of organic acids, ranging from formic to nonanoic acid. Concentrations of high molecular weight partially oxidized species were highest for the high-CN fuels at retarded phasing, and are believed to be a direct product of LTHR.

Particulate Matter and Aldehyde Emissions from Idling Heavy-Duty Diesel Trucks

As part of a multi-agency study concerning emissions and fuel consumption from heavy-duty diesel truck idling, Oak Ridge National Laboratory personnel measured CO, HC, NOx, CO2, O2, particulate matter (PM), aldehyde and ketone emissions from truck idle exhaust. Two methods of quantifying PM were employed: conventional filters and a Tapered Element Oscillating Microbalance (TEOM). A partial flow micro-dilution tunnel was used to dilute the sampled exhaust to make the PM and aldehyde measurements. The work was performed at the U.S. Armys Aberdeen Test Centers (ATC) climate controlled chamber. ATC performed 37 tests on five class-8 trucks (model years ranging from 1992 to 2001). One was equipped with an 11 hp diesel auxiliary power unit (APU), and another with a diesel direct-fired heater (DFH). The APU powers electrical accessories, heating, and air conditioning, whereas a DFH heats the cab in cold weather. Both devices offer an alternative to extended truck-engine idling. Exhaust emission measurements were also made for the APU and DFH. Trucks were idled at a high and low engine speed in the following environments: 32 °C (90 °F) with cabin air conditioning on, −18 °C (0 °F) with the cabin heater on, and 18 °C (65 °F) with no accessories on. ATC test technicians adjusted the air conditioning or heater to maintain a target cabin temperature of 21 °C (70 °F). Each test was run for approximately three hours. Comparison of the results from the APU to those from the idling trucks implies that use of an APU to replace truck idling gives fuel savings (and CO2 reduction) on the order of 60-85%, 50-97% reductions in NOx, CO and HC, and PM reductions of -20% to 95%. PM emissions from the APU were higher than the “best” idling truck engine cases. The diesel-fired heater had significantly lower emissions and fuel consumption than the APU. The potential for fuel savings and environmental benefits are readily apparent. Results for PM emissions showed a wide range of emissions rates from <1 g/hr to over 20 g/hr, with the newest trucks in the 1-5 g/hr range. PM emissions generally decreased with an increase in ambient temperature and increased disproportionately with an increase in engine speed. Aldehyde mass emissions rate increased with both decreasing temperature and increasing engine speed. The mass emissions rate of regulated gaseous species generally increased with increasing engine speed. A comparison of PM measurements with the TEOM and the filter-based methods is presented.

Fuel Property Effects on Emissions from High Efficiency Clean Combustion in a Diesel Engine

High-efficiency clean combustion (HECC) modes provide simultaneous reductions in diesel particulate matter and nitrogen-oxides emissions while retaining efficiencies characteristic of normal diesel engines. Fuel parameters may have significant impacts on the ability to operate in HECC modes and on the emissions produced in HECC modes. In this study, 3 diesel-range fuels and 2 oxygenated blends are burned in both normal and HECC modes at 3 different engine conditions. The results show that fuel effects play an important role in the emissions of hydrocarbons, particulate matter, and carbon monoxide but do not significantly impact NOX emissions in HECC modes. HECC modes are achievable with 5% biodiesel blends in addition to petroleum-based and oil-sands derived fuels. Soot precursor and oxygenated compound concentrations in the exhaust were observed to generally increase with the sooting tendency of the fuel in HECC modes.

Exhaust Chemistry of Low-NOX, Low-PM Diesel Combustion

The exhaust chemistry of combustion regimes characterized by simultaneous low-NOx and low-PM emissions were investigated on a Mercedes 1.7-L diesel engine. Two approaches for entering low-NOx low-PM regimes were explored using a California specification low aromatic certification diesel fuel. Detailed characterizations of gas-phase hydrocarbons, particulate soluble organics, and aldehydes are presented for both approaches. Results indicate significant formation of partially oxygenated hydrocarbons and fuel reformation products during periods of low-NOx, low-PM combustion.