Jim Parks

Ammonia Production and Utilization in a Hybrid LNT+SCR System

A hybrid LNT+SCR system is used to control NOx from a light-duty diesel engine with in-cylinder regeneration controls. A diesel oxidation catalyst and diesel particulate filter are upstream of the LNT and SCR catalysts. Ultraviolet (UV) adsorption spectroscopy performed directly in the exhaust path downstream of the LNT and SCR catalysts is used to characterize NH3 production and utilization in the system. Extractive exhaust samples are analyzed with FTIR and magnetic sector mass spectrometry (H2) as well. Furthermore, standard gas analyzers are used to complete the characterization of exhaust chemistry. NH3 formation increases strongly with extended regeneration (or over regeneration ) of the LNT, but the amount of NOx reduction occurring over the SCR catalyst is limited by the amount of NH3 produced as well as the amount of NOx available downstream of the LNT. Control of lean-rich cycling parameters enables control of the ratio of NOx reduction between the LNT and SCR catalysts. During lean-rich cycling, fuel penalties are similar for either LNT dominant or LNT with supplemental SCR NOx reduction. However, stored NH3 after multiple lean-rich cycles can enable continued NOx reduction by the SCR after lean-rich cycling stops; thus, requirements for active regeneration of the LNT+SCR systemmorexa0» can be modified during transient operation.«xa0less

Characterization of Lean NOx Trap Catalysts with In-Cylinder Regeneration Strategies

Lean NOx trap (LNT) catalysts with different formulations have been characterized on a light-duty diesel engine platform. Two in-cylinder regeneration strategies were used during the study. The reductant chemistry differed for both strategies with one strategy having high levels of CO and H2 and the other strategy having a higher hydrocarbon component. The matrix of LNT catalysts that were characterized included LNTs with various sorbate loads and varying ceria content; the sorbate was Ba. Intra-catalyst measurements of exhaust gas composition were obtained at one quarter, one half, and three quarters of the length of the catalysts to better understand the affect of formulation on performance. Exhaust analysis with FTIR allowed measurement of NH3 and thereby, a measurement of N2 selectivity for the catalysts. Although overall NOx conversion increased with increasing sorbate load, the formation of NH3 increased as well. Interestingly, the presence of ceria in the LNT allowed NH3 to be oxidized to N2 in the downstream half of the LNT, thereby greatly reducing the tailpipe NH3 level. Despite different capacities for NOx sorption, a similar pattern for NOx adsorption as a function of the length of the catalyst was observed for catalysts with 8% and 20% Ba load. Results morexa0» from these engine based experiments will be discussed relative to the body of literature concerning fundamental and model LNT studies. «xa0less

Nitrogen Selectivity in Lean NOx Trap Catalysis with Diesel Engine In-Cylinder Regeneration

NOx emissions have traditionally been difficult to control from diesel engines; however, lean NOx trap catalysts have been shown to reduce NOx emissions from diesel engines by greater than 90% under some conditions. It is imperative that lean NOx traps be highly selective to N 2 to achieve the designed NOx emissions reduction. If selectivity for NOx reduction to NH 3 or N 2 O is significant then, ultimately, higher levels of pollution or greenhouse emissions will result. Here studies of the N 2 selectivity of lean NOx trap regeneration with in-cylinder techniques are presented. Engine dynamometer studies with a light-duty engine were performed, and a lean NOx trap in the exhaust system was regenerated by controlling in-cylinder fuel injection timing and amounts to achieve rich exhaust conditions. NH 3 and N 2 O emissions were analyzed with FTIR spectroscopy. Both engine and bench experiments show that excess reductant delivery during regeneration leads to high NH 3 emissions and poor N 2 selectivity. Specific design of in-cylinder regeneration techniques that minimize excess reductant or allow O 2 purge can optimize N 2 selectivity of the lean NOx trap catalyst.

In Situ Measurement of Fuel in the Cylinder Wall Oil Film of a Combustion Engine by LIF Spectroscopy

Hydrocarbon emissions remain an important concern for the automotive industry due to increasingly strict regulations. In an investigation of possible emission sources within the engine, the concentration of fuel absorbed in the oil film on the cylinder wall of a small internal combustion engine has been measured with laser-induced fluorescence (LIF) spectroscopy. A laser pulse from a nitrogen laser (337.1 nm) provided the excitation, and the fluorescence was monitored with an intensifled-charge-coupled device (ICCD) array mounted to a spectrometer. The excitation laser pulse was launched through a window in the engine head onto a fiber-optic probe mounted flush with the cylinder wall. The laser-excited oil film on the fiber-optic probe produced an LIF signal that was collected by the fiber-optic probe and analyzed for fuel content. The timing of the laser pulse and ICCD gate were controlled in order to synchronize the collection of data with a particular point in the engine cycle. Measurements made in situ, while the engine was running, yield information on the amount of unburned fuel stored in the oil film for various engine conditions. Fuel-in-oil concentrations were determined for various engine temperatures during cold starts, for different fuel enrichment levels, and as a function of the crank angle of the engine cycle. Fuel concentrations as high as 50% were detected during cold starts, and fuel concentrations reached levels greater than 25% for warm engine operation. Changes in the fuel content were also found to be related to enrichment and crank angle.

Detailed characterization of particulate matter emitted by lean-burn gasoline direct injection engine

This study presents detailed characterization of the chemical and physical properties of particulate matter emitted by a 2.0-L BMW lean-burn turbocharged gasoline direct injection engine operated under a number of combustion strategies that include lean homogeneous, lean stratified, stoichiometric, and fuel-rich conditions. We characterized particulate matter number concentrations, size distributions, and the size, mass, compositions, and effective density of fractal and compact individual exhaust particles. For the fractal particles, these measurements yielded fractal dimension, average diameter of primary spherules, and number of spherules, void fraction, and dynamic shape factors as function of particle size. Overall, the particulate matter properties were shown to vary significantly with engine operation condition. Lean stratified operation yielded the most diesel-like size distribution and the largest particulate matter number and mass concentrations, with nearly all particles being fractal agglomerates composed of elemental carbon with small amounts of ash and organics. In contrast, stoichiometric operation yielded a larger fraction of ash particles, especially at low speed and low load. Three distinct forms of ash particles were observed, with their fractions strongly dependent on engine operating conditions: sub-50u2009nm ash particles, abundant at low speed and low load, ash-containing fractal particles, and large compact ash particles that significantly contribute to particulate matter mass loadings.

Photon scanning-tunneling microscopy of unstained Mammalian cells and chromosomes.

The photon scanning-tunneling microscope (PSTM) yields opticalntopographical images of samples that are thin or that are transparentnat the wavelength used. A range of sample sizes can be imagednextending to well below the diffraction limit for sufficiently flatnsamples. But samples of the order of several to many micrometers innsize can be analyzed with less-refined resolution if total internalnreflection can be made to occur in the sample. We used the PSTM tonexamine the optical topography of mouse and human cells and ofnchromosomes that are unstained. Our objectives were to demonstratenthe images as an alternative to conventional microscopy and to providena sample-preparation methodology that will later permit localized,nsimultaneous fluorescence or absorption spectroscopy with the signalsncollected by the probe tip. Furthermore, the PSTM’s ability tonproduce optical profiles in air and in water was tested to establishnthe basis for future investigation of possible abnormalities in thenchromosomes. That is, we considered both physical and biologicalnobjectives. To this end we utilized the 442-nm line of a He–Cdnlaser as well as the 633-nm line from a He–Ne laser, the resultingnimage quality being tested partly to ascertain the increased effects ofnscattering at the smaller wavelength. It is shown that adequatenresolution and signal-to-noise ratio can be obtained with the shorternwavelength even in the presence of intensity fluctuations from thenlaser, thus showing that fluorescence and absorption studies can benexpected to be practicable.

An Optical Backscatter Sensor for Particulate Matter Measurement

Diesel engines are prone to emit particulate matter (PM) emissions under certain operation conditions. In-cylinder production of PM from diesel combustion control can occur under a wide variety of operating conditions, and in some cases, operation of a multi-cylinder engine can further complicate PM emissions due to variations in air or fuel charge due to manifold mixing effects. In this study, a probe for detecting PM in diesel exhaust was evaluated on a light-duty diesel engine. The probe is based on an optical backscattering effect. Due to the optical nature of the probe, PM sensing can occur at high rates. The feasibility of the probe for examining PM emissions in the exhaust manifold will be discussed.

Photon scanning tunneling microscopy of unstained mammalian cells and chromosomes

The photon scanning tunneling microscope (PSTM) yields topographical images of samples which are thin or which are transparent at the wavelength used. A wide range of samples sizes may be imaged extending to well below the diffraction limit, but samples on the order of several to many micrometers in size can be analyzed if total internal reflection occur in the sample. We have used the PSTM to examine the topography of mouse and human cells and of mouse chromosomes that are unstained. Our objectives were to compare the images as an improved resolution alternative to phase contrast microscopy, and to provide a sample preparation methodology that will permit localized simultaneous fluorescence or absorption spectroscopy with the signal collected by the probe tip of the PSTM. Further, the PSTMs ability to produce topographical profiles was tested in order to establish the basis for future investigation of possible structural abnormalities in the chromosomes. That is, we had both physical and biological objectives to consider. To this end we utilized the 442 nm line of a HeCd laser, the resulting image quality being tested partly on order to ascertain the increase effects of Rayleigh scattering relative to results at longer wavelengths. It is shown that adequate resolution and signal-to-noise ration can be obtained with the shorter wavelength even in the presence of intensity fluctuations from the laser, thus showing that fluorescence and absorption can be expected to be practicable.