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In an effort of providing better understanding of regeneration mechanisms of diesel particulate matter (PM), this experimental investigation focused on evaluating the amount of heat release generated during the thermal reaction of diesel PM and the concentrations of soluble organic compounds (SOCs) dissolved in PM emissions. Differences in oxidation behaviors were observed for two different diesel PM samples: a SOC-containing PM sample and a dry soot sample with no SOCs. Both samples were collected from a cordierite particulate filter membrane in a thermal reactor connected to the exhaust pipe of a light-duty diesel engine. A differential scanning calorimeter (DSC) and a thermogravimetric analyzer (TGA) were used to measure the amount of heat release during oxidation, along with subsequent oxidation rates and the concentrations of SOCs dissolved in particulate samples, respectively.

Detailed characteristics of morphology, nanostructures, and sizes were analyzed for particulate matter (PM) emissions from low-temperature combustion (LTC) modes of a single-cylinder, light-duty diesel engine. The LTC engines have been widely studied in an effort to achieve high combustion efficiency and low exhaust emissions. Recent reports indicate that the number of nucleation mode particles increased in a broad engine operating range, which implies a negative impact on future PM emissions regulations in terms of the nanoparticle number. However, the size measurement of solid carbon particles by commercial instruments is indeed controversial due to the contribution of volatile organics to small nanoparticles. In this work, an LTC engine was operated with various biofuel blends, such as blends (B20) of soy bean oil (soy methyl ester, SME20) and palm oil (palm methyl ester, PME20), as well as an ultra-low-sulfur diesel fuel.

A thermophoretic particulate sampling device was used to investigate the detailed morphology and microstructure of diesel particulates at various engine-operating conditions. A 75 HP Caterpillar single-cylinder direct-injection diesel engine was operated to sample particulate matter from the high-temperature exhaust stream. The morphology and microstructure of the collected diesel particulates were analyzed using a high-resolution transmission electron microscope and subsequent image processing/data acquisition system. The analysis revealed that spherical primary particles were agglomerated together to form large aggregate clusters for most of engine speed and load conditions. Measured primary particle sizes ranged from 34.4 to 28.5 nm at various engine-operating conditions. The smaller primary particles observed at high engine-operating conditions were believed to be caused by particle oxidation at the high combustion temperature.

Detailed properties of particulate matter (PM) emissions from a gasoline direct injection (GDI) engine were analyzed in terms of size, morphology, and nanostructures, as gasoline and its ethanol blend E20 were used as a fuel. PM emissions were sampled from a 0.55L single-cylinder GDI engine by means of a scanning mobility particle sizer (SMPS) for size measurements and a self-designed thermophoretic sampling device for the subsequent analyses of size, morphology and nanostructures using a transmission electron microscope (TEM). The particle sizes were evaluated with variations of air-fuel equivalence ratio and fuel injection timing. The most important result from the SMPS measurements was that the number of nucleation-mode nanoparticles (particularly those smaller than 10 - 15 nm) increased significantly as the fuel injection timing was advanced to the end-of-injection angle of 310° bTDC.

A three-dimensional (3-D) computational fluid dynamics (CFD) code has been developed to predict flow dynamics and pressure drop characteristics in geometry-modified filters in which the normalized distance of the outlet channel plugs from the inlet has been varied at 0.25, 0.50, and 0.75. In clean filter simulations, the pressure drop in geometry-modified filters showed higher values than for conventional filters because of the significant change in the pressure field formed inside the channel that determines the amount of flow entering the modified channel. This flow through the modified channel depends on plug position initially but has a maximum limit when pressure difference and geometrical change are compromised. For soot loading simulations, a Lagrangian multiphase flow model was used to interpret the hydrodynamics of particle-laden flow with realistic inputs.

Diesel injections with various nozzle geometries were tested to investigate the spray characteristics by optical imaging techniques. Sac-nozzle and VCO nozzle with single guided needle coupled with rotary-type mechanical pump were compared in terms of macroscopic spray development and microscopic behavior. These nozzles incorporated with common-rail system were tested to see the effect of high pressure injection. Detailed investigation into spray characteristics from the holes of VCO nozzles, mostly with double guided needle, was performed. A variety of injection hole geometries were tested and compared to give tips on better injector design. Different hole sizes and taper ratio, represented as K factor, were studied through comprehensive spray imaging techniques. Global characteristics of a diesel spray, such as spray penetration, spray angle and its pattern, were observed from macroscopic images.

Particulate and nitrogen oxide emissions from a 1.9-liter Volkswagen diesel engine were measured for three different fuels: neat diesel fuel, a blend of diesel fuel with 10% ethanol, and a blend of diesel fuel with 15% ethanol. Engine-out emissions were measured on an engine dynamometer for five different speeds and five different torques using the standard engine-control unit. Results show that particulate emissions can be significantly reduced over approximately two-thirds of the engine map by using a diesel-ethanol blend. Nitrogen oxide emissions can also be significantly reduced over a smaller portion of the engine map by using a diesel-ethanol blend. Moreover, there is an overlap between the regions where particulate emissions can be reduced by up to 75% and nitrogen oxide emissions are reduced by up to 84% compared with neat diesel fuel.

The detailed morphological properties of diesel particulate matter were analyzed along the exhaust system at various engine operating conditions (in a range of 1000 - 2500 rpm and 10 - 75 % loads of maximum torques). A 1.7-L turbocharged light-duty diesel engine was powered with California low-sulfur diesel fuel injected by a common-rail injection system, of which particulate emissions were controlled by an exhaust gas recirculation (EGR) system and two oxidation catalysts. A unique thermophoretic sampling system first developed for internal combustion engine research, a high-resolution transmission electron microscope (TEM), and a customized image processing/data acquisition system were key instruments that were used for the collection of particulate matter, subsequent imaging of particle morphology, and detailed analysis of particle dimensions and fractal geometry, respectively.

The physical and morphological properties of the particulate matter emitted from a 1.7-liter light-duty diesel engine were characterized by observing its evolution in size and fractal geometry along the exhaust system. A common-rail direct-injection diesel engine, the exhaust system of which was equipped with a turbocharger, EGR, and two oxidation catalysts, was powered with a California low-sulfur diesel fuel at various engine-operating conditions. A unique thermophoretic sampling system, a high-resolution transmission electron microscope (TEM), and customized image processing/data acquisition systems were key instruments that were used for the collection of particulate matter, subsequent imaging of particle morphology, and detailed analysis of particle dimensions and fractal geometry, respectively. The measurements were carried out at four different positions along the exhaust pipe.

Their high fuel economy is making light-duty vehicles with spark-ignition direct-injection (SIDI) engines attractive. However, the implications for exhaust emissions and the effects of fuel quality on emissions are not clear for this type of engine. A Mitsubishi Legnum with a 1.8-L GDI™ engine was tested on federal test procedure (FTP) and highway fuel economy cycles. The results were compared with those for a production Dodge Neon vehicle with a 2.0-L port fuel-injection (PFI) engine. The Mitsubishi was tested with Indolene, Amoco Premium Ultimate, and a low-sulfur gasoline. The Neon was tested only with Indolene. Both engine-out and tailpipe emissions were measured. Second-by-second emissions and hydrocarbon speciation were also evaluated. The SIDI engine provided up to 24% better fuel economy than the PFI engine on the highway cycle. Tailpipe emissions of oxides of nitrogen (NOx) from the SIDI vehicle using low-sulfur fuel were 40% less than those when using Indolene.

Detailed diesel particulates morphology, nanostructures, fractal geometry, and nitrogen oxides (NOx) emissions were analyzed for five different test fuels in a 1.7-L, common-rail direct-injection diesel engine. The accurately formulated fuels permit the effects of sulfur, paraffins, aromatics, and naphthene concentrations to be determined. A novel thermophoretic sampling technique was used to collect particulates immediately after the exhaust valves. The morphology and nanostructures of particulate samples were examined, imaged with a high-resolution transmission electron microscope (HRTEM), and quantitatively analyzed with customized digital image processing/data acquisition systems. The results show that the particle sizes and the total mass of particulate matter (PM) emissions correlate most strongly with the fuels' aromatics and sulfur content.

Lean operation of natural gas fired reciprocating engines has been the preferred mode of operation as it allows low NOx emissions and simultaneous high overall efficiencies. In such engines, the operation point is often close to where the ignition boundary and the knock limiting boundary cross-over. While knocking is, to a large extent, limited by engine design, ignition of lean-mixtures is limited by the mode of ignition. Since significant benefits can be achieved by extending the lean-ignition limits, many groups have been researching alternate ways to achieve ignition reliably. One of the methods, laser ignition, appears promising as it achieves ignition at high pressures and under lean conditions relatively easily. However, most of the current knowledge about laser ignition is based on measurements performed at room temperature. In this paper, ignition studies on methane-air mixtures under in-cylinder conditions are presented.

This paper describes the initial experiments and computational simulations aimed to measure and quantify the level of nano-sized particulate production from combustion in low temperature combustion (LTC). This work measures nano-sized particles in a laminar ethylene flame both by the use of small-angle x-ray scattering at the Advanced Photon Source and through a technique called thermophoretic sampling. Future experiments will perform similar measurements in a Rapid Compression Machine under conditions typical for HCCI engines. The simulation work involves the use of coupled Computational Fluid Dynamics (CFD) and Chemistry Kinetics codes to predict the fuel/air mixture composition and temperature distribution in the combustion region and directly complements the experimental work. The results show that nano-particles are created under rich, premixed conditions, even with low temperature reactions (T<2000K).

The effects of nitrogen-enriched air, supplied by an air separation membrane, on NOx emissions from a 1.9-L turbocharged direct-injection diesel engine were investigated. To enrich combustion air with more nitrogen, prototype air separation membranes were installed between the after-cooler and intake manifold without any additional controls. The effects of nitrogen-enriched combustion air on NOx emissions were compared with and without exhaust gas recirculation (EGR). At sufficient boost pressures (>50 kPag), nitrogen-enriched air from the membrane provided intake oxygen levels that were similar to those of EGR. Compared with EGR, nitrogen-enriched air provided 10-15% NOx reductions during medium to high engine loads and speeds. At part loads, when turbocharger boost pressure was low, the air separation membrane was not effective in enriching air with nitrogen. As a result, NOx reduction was lower, but it was 15-25% better than when EGR was not used.

This experimental work focuses on defining the detailed morphology of secondary emission products derived from the combustion of cerium (Ce) fuel-borne catalyst (FBC) doped with diesel fuel. Cerium is often used to promote the oxidation of diesel particulates collected in diesel aftertreatment systems, such as diesel particulate filters (DPFs). However, it is suspected that the secondary products could be emitted from the vehicle tailpipe without being effectively filtered by the aftertreatment systems. In this work, these secondary emissions were identified by means of a high-resolution transmission electron microscope (TEM), and their properties were examined in terms of morphology and chemistry. In preparation for fuel doping, a cerium-based aliphatic organic compound solution was mixed with a low-sulfur (110 ppm) diesel fuel at 50 ppm in terms of weight concentration.

The limited spatial area in conventional diesel particulate filter (DPF) systems requires frequent regenerations to remove collected particulate matter (PM) emissions, consequently resulting in higher energy consumption and potential material failure. Due to the complex geometry and difficulty in access to the internal structure of diesel particulate filters, in addition, many important characteristics in filtration processes remain unknown. In this work, therefore, the geometry of DPF membrane channels was modified basically to increase the filtration areas, and their filtration characteristics were evaluated in terms of pressure drop across the DPF membranes, effects of soot loading on pressure drop, and qualitative soot mass distribution in the membrane channels. In this evaluation, an analytical model was developed for pressure drop, which allowed a parametric study with those modified membranes.

This paper reports our efforts to develop an instrument, TG-1, to measure particulate emissions from diesel engines in real-time. TG-1 while based on laser-induced incandescence allows measurements at 10 Hz on typical engine exhausts. Using such an instrument, measurements were performed in the exhaust of a 1.7L Mercedes Benz engine coupled to a low-inertia dynamometer. Comparative measurements performed under engine steady state conditions showed the instrument to agree within ±12% of measurements performed with an SMPS. Moreover, the instrument had far better time response and time resolution than a TEOM® 1105. Also, TG-1 appears to surpass the shortcomings of the TEOM instrument, i.e., of yielding negative values under certain engine conditions and, being sensitive to external vibration.

Air can be enriched with oxygen and/or nitrogen by selective permeation through a nonporous polymer membrane; this concept offers numerous potential benefits for piston engines. The use of oxygen-enriched intake air can significantly reduce exhaust emissions (except NOx), improve power density, lessen ignition delay, and allow the use of lower-grade fuels. The use of nitrogen-enriched air as a diluent can lessen NOx emissions and may be considered an alternative to exhaust gas recirculation (EGR). Nitrogen-enriched air can also be used to generate a monatomic-nitrogen stream, with nonthermal plasma, to treat exhaust NOx. With such synergistic use of variable air composition from an on-board polymer membrane, many emissions problems can be solved effectively. This paper presents an overview of different applications of air separation membranes for diesel and spark-ignition engines. Membrane characteristics and operating requirements are examined for use in automotive engines.