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The use of urea-based selective catalytic reduction (SCR) is a promising method for achieving U.S. Tier 2 diesel emission standards for NOx. To meet the Tier 2 standards for Particulate Matter (PM), a catalyzed diesel particulate filter (CDPF) will likely be present and any ammonia (NH3) that is not consumed over an SCR catalyst would pass over the CDPF to make nitrous oxide (N2O) emissions and/or oxides of nitrogen (NOx), or exit the exhaust system as NH3. N2O is undesirable due to its high greenhouse gas potential, while NOx production from the slipped NH3 would reduce overall system NOx conversion efficiency. This paper reviews certain conditions where NH3 slip past an SCR system may be a concern, looks at what would happen to this slipped NH3 over a CDPF, and evaluates the performance of various supplier NH3 slip catalysts under varied space velocities, temperatures and concentrations of NH3 and NOx.

A 1-D 2-layer model developed previously at MTU was used in this research to predict the pressure drop, filtration characteristics and various properties of the particulate filter and the particulate deposit layer. The model was calibrated and validated for this CPF with data obtained from steady state experiments conducted using a 1995 Cummins M11-330E heavy-duty diesel engine with manual EGR and using ULSF. The CPF used is a NGK filter having a cordierite substrate with NEX catalyst type formulation (54% porosity, 15.0 μm mean pore diameter and 50 gms/ft3 Pt). The filter was catalyzed using a wash coat process. The model was used to predict the pressure drop, particulate mass retained inside the CPF, particulate mass filtration efficiency and concentration downstream of the CPF with agreement between the experimental and simulated data.

A 1-D 2-layer model developed previously at MTU was used in this research to predict the pressure drop, filtration characteristics and various properties of the particulate filter and the particulate deposit layer. The model was used along with dilute emission data to characterize two catalyzed particulate filters (CPFs) having different catalyst loading and catalyst application processes. The model was calibrated and validated with data obtained from steady state experiments conducted using a 1995 Cummins M11-330E heavy-duty diesel engine with manual EGR with different fuels for the two different CPFs. The two different catalyzed particulate filters were CPF III (5 gms/ft3 Pt) and CPF V (50 gms/ft3 Pt). Both the CPFs had cordierite substrates with CPF III and CPF V had MEX and NEX catalyst type formulation respectively. The CPF III filter was catalyzed using a solution-impregnated process while the CPF V filter was catalyzed using a wash coat process.

The effects of fuel sulfur concentration on heavy-duty diesel emissions have been studied at two EPA steady-state operating conditions, mode 9 (1900 RPM, 75% Load) and mode 11(1900 RPM, 25% Load). Data were obtained using one fuel at two sulfur levels (Low Sulfur, LS = 0.01 wt% S and Doped Low Sulfur DS = 0.29 wt% S). All tests were conducted using a Cummins LTA10-300 heavy-duty diesel engine. No significant changes were found for the nitrogen oxides (NOx), soluble organic fractions (SOF) and XAD-2 (a copolymer of styrene and divinylbenzene) organic component (XOC) due to the fuel sulfur level increase at either engine mode. The hydrocarbon (HC) levels were not significantly affected by sulfur at mode 9; however, at mode 11 the HC levels were reduced by 16%. The total particulate matter (TPM) levels increased by 17% at mode 11 and by 24% at mode 9 (both significantly different).

The objective of this research was to study the effects of a CCRT®, henceforth called Diesel Oxidation Catalyst - Catalyzed Particulate Filter (DOC-CPF) system on particulate and gaseous emissions from a heavy-duty diesel engine (HDDE) operated at Modes 11 and 9 of the old Environmental Protection Agency (EPA) 13-mode test cycle Emissions characterized included: total particulate matter (TPM) and components of carbonaceous solids (SOL), soluble organic fraction (SOF) and sulfates (SO4); vapor phase organics (XOC); gaseous emissions of total hydrocarbons (HC), carbon monoxide (CO), oxides of nitrogen (NOx), nitric oxide (NO) and nitrogen dioxide (NO2), oxygen (O2) and carbon dioxide (CO2); and particle size distributions at normal dilution ratio (NDR) and higher dilution ratio (HDR). Significant reductions were observed for TPM and SOL (>90%), SOF (>80%) and XOC (>70%) across the DOC-CPF at both modes.

Selective catalytic reduction (SCR) is a promising technology for diesel aftertreatment to meet NOx emissions targets in several countries. In established markets such as the US and Europe, zeolite SCR systems are expected to be used due to their ability to survive the exhaust gas temperatures seen in an active diesel particulate filter regeneration. In emerging markets where the fuel sulfur level may be as high as 2000 parts per million, zeolite SCR catalysts may have durability issues. In these markets, low sulfur fuel is needed overall to meet emissions standards and to avoid high sulfate emissions, but the aftertreatment system must be durable to high sulfur levels because there is a risk of exposure to high sulfur fuel. Also, emissions standards may be met without a DPF in some applications, so that the exhaust system would not see temperatures of 600°C or higher.

The effects of an oxidation catalytic converter (OCC), an emulsified fuel, and their combined effects on particle number and volume concentrations compared to those obtained when using a basefuel were studied. Particle size and particulate emission measurements were conducted at three operating conditions; idle (850 rpm, 35 Nm), Mode 11 (1900 rpm, 277 Nm) and Mode 9 (1900 rpm, 831 Nm) of the EPA 13 mode cycle. The individual effects of the emulsified fuel and the OCC as well as their combined effects on particle number and volume concentrations were studied at two different particle size ranges; the nuclei (less than or equal to 50 nm) and accumulation (greater than 50 nm) modes. An OCC loaded with 10 g/ft3 platinum metal (OCC1) and a 20% emulsified fuel were used for this study and a notable influence on the particle size with respect to number and volume distributions was observed.

A study was conducted to assess the effects of a water-diesel fuel emulsion with and without an oxidation catalytic converter (OCC) on steady-state heavy-duty diesel engine emissions. Two OCCs with different metal loading levels were used in this study. A 1988 Cummins L10-300 heavy-duty diesel engine was operated at the rated speed of 1900 rpm and at 75% and 25% load conditions (EPA modes 9 and 11 respectively) of the 13 mode steady-state test as well as at idle. Raw exhaust emissions' measurements included total hydrocarbons (HC), oxides of nitrogen (NOx) and nitric oxide (NO). Diluted exhaust measurements included total particulate matter (TPM) and its primary constituents, the soluble organic (SOF), sulfate (SO42-) and the carbonaceous solids (SOL) fractions. Vapor phase organic compounds (XOC) were also analyzed. The SOF and XOC samples were analyzed for selected polynuclear aromatic hydrocarbons (PAHs).

Recently, outboard engine technology has advanced significantly. With these new technologies comes a substantial improvement in emissions compared to traditional carbureted two-stroke engines. Some two-stroke gasoline direct injection (GDI) marine outboard engines are now capable of meeting California Air Resources Board 2008 Ultra-Low emissions standards. With improvement of gaseous emissions, studies are now being conducted to assess particulate matter (PM) emissions from all new technology marine outboard engines which include both four-stroke and two-stroke designs. Methods are currently being developed to determine the best way to measure PM from outboard engines. This study assesses gaseous and PM emissions, mutagenic activity of PM and oil consumption of two different technologies over the useful life of the engines.

In 2007 emissions regulations for on-road light to heavy duty Diesel trucks will require the use of Diesel Particulate Filters (DPFs). The uniform distribution of soot on the DPF is critical for adequate long term performance of these DPFs. This is especially true when cordierite is used instead of silicon carbide for the DPF substrate, due to the reduced thermal conductivity and reduced peak temperature capability of cordierite. In addition to flow uniformity, an inverted flow pattern where more of the flow is forced radially outward on the substrate face could be beneficial to counteract thermal losses in the converter. This paper describes a dispersion device that can improve flow geometry with a low backpressure penalty. Computational fluid dynamics (CFD) results and experimental data are presented for this device. Additionally, cone design options are explored, and CFD analysis results of the cone design are presented.

Steady-state particulate loading experiments were conducted on an advanced production catalyzed particulate filter (CPF), both with and without a diesel oxidation catalyst (DOC). A heavy-duty diesel engine was used for this study with the experiments conducted at 20, 40, 60 and 75 % of full load (1120 Nm) at rated speed (2100 rpm). The data obtained from these experiments were used and are necessary for calibrating the MTU 1-D 2-Layer CPF model. These experimental and modeling results were compared to previous research conducted at MTU that used the same engine but an earlier development version of the combination of DOC and CPF. The motivation for the comparison of the two systems was to determine whether the reformulated production catalysts performed as good or better than the early development catalysts. The results were compared to understand the filtration and oxidation differences between the two DOC+CPF and the CPF-only aftertreatment systems.

This research quantifies the effects of a copper fuel additive on the regulated [oxides of nitrogen (NOx), hydrocarbons (HC) and total particulate matter (TPM)] and unregulated emissions [soluble organic fraction (SOF), vapor phase organics (XOC), polynuclear aromatic hydrocarbons (PAH), nitro-PAH, particle size distributions and mutagenic activity] from a 1988 Cummins LTA10 diesel engine using a low sulfur fuel. The engine was operated at two steady state modes (EPA modes 9 and 11, which are 75 and 25% load at rated speed, respectively) and five additive levels (0, 15, 30, 60 and 100 ppm Cu by mass) with and without a ceramic trap. Measurements of PAH and mutagenic activity were limited to the 0, 30 and 60 ppm Cu levels. Data were also collected to assess the effect of the additive on regeneration temperature and duration. Copper species collected within the trap were identified and exhaust copper concentrations quantified.

A wide range of emissions were characterized from a heavy-duty diesel engine operated on conventional low sulfur (∼375 ppm) fuel, equipped with manually controlled EGR and a catalyzed particulate filter (CPF). The effect of the CPF and engine load was studied, along with a comparison of results between the gravimetric and thermal optical methods (TOM) for determining diesel particulate levels. Data were obtained from four of the EPA old 13 mode test cycle steady-state operating conditions, i.e., Modes 11, 10, 9, and 8 using a 1995 Cummins M11-330E engine with a Corning EX-80 cordierite particulate filter, coated with a platinum catalyst (5 g/ft3).

Urea selective catalytic reduction (SCR) catalysts have the capability to deliver the high NOx conversion efficiencies required for future emission standards. However, the potential for the occasional over-temperature can lead to the irreversible deactivation of the SCR catalyst. On-board diagnostics (OBD) compliance requires monitoring of the SCR function to make sure it is operating properly. Initially, SCR catalyst performance metrics such as NOx conversion, NH3 oxidation, NH3 storage capacity, and BET surface area are within normal limits. However, these features degrade with high temperature aging. In this work, a laboratory flow reactor was utilized to determine the impact on these performance metrics as a function of aging condition. Upon the completion of a full time-at-temperature durability study, four performance criteria were established to help determine a likely SCR failure.

This paper discusses the poisoning of a selective catalytic reduction (SCR) catalyst by trace levels of platinum originating from an upstream diesel oxidation catalyst (DOC). A diesel aftertreatment system consisting of a DOC, urea based SCR Catalyst and a DPF was aged and evaluated on a 6.4 liter diesel engine dynamometer. The SCR catalyst system consisted of an Fe-zeolite catalyst followed by a Cu-zeolite catalyst. After approximately 400 hours of engine operation at varied exhaust flow rates and temperatures, deactivation of the SCR catalyst was observed. A subsequent detailed investigation revealed that the Cu catalyst was not deactivated and the front half of the Fe-based catalyst showed severe deactivation. The deactivated portion of the catalyst showed high activity of NH3 conversion to NOx and N2O formation. The cause of the deactivation was identified to be the presence of trace Pt contamination.

This research work has focused on measuring the effect of fuel/air mixing on performance and emissions for a homogeneous charge compression ignition engine running on propane. A laser instrument with a high-velocity extractive probe was used to obtain time-resolved measurements of the fuel concentration both at the intake manifold and from the cylinder for different levels of fuel-air mixing. Cylinder pressure and emissions measurements have been performed at these mixing levels. From the cylinder pressure measurements, the IMEP and peak cylinder pressure were found. The fuel-air mixing level was changed by adding the fuel into the intake system at different distances from the intake valve (40 cm and 120 cm away). It was found that at the intake manifold, the fuel and air were better mixed for the 120 cm fuel addition location than for the 40 cm location.

Modeling of diesel exhaust after-treatment devices is a valuable tool in the development and performance evaluation of these devices in a cost effective manner. Results from steady state loading experiments on a catalyzed particulate filter (CPF) in a Johnson Matthey CCRT®, performed with and without the upstream diesel oxidation catalyst (DOC) are described in this paper. The experiments were performed at 20, 40, 60 and 75% of full load (1120 Nm) at rated speed (2100 rpm) on a Cummins ISM 2002 heavy duty diesel engine. The data obtained were used to calibrate one dimensional (1-D) DOC and CPF models developed at Michigan Technological University (MTU). The 1-D 2-layer single channel CPF model helped evaluate the filtration and passive oxidation performance of the CPF. DOC modeling results of the pressure drop and gaseous emission oxidation performance using a previously developed model are also presented.

Passive regeneration (oxidation of particulate matter without using an external energy source) of particulate filters in combination with active regeneration is necessary for low load engine operating conditions. For low load conditions, the exhaust gas temperatures are less than 250°C and the PM oxidation rate due to passive regeneration is less than the PM accumulation rate. The objective of this research was to experimentally investigate active regeneration of a catalyzed particulate filter (CPF) using diesel fuel injection in the exhaust gas after the turbocharger and before a diesel oxidation catalyst (DOC) and to collect data for extending the MTU 1-D 2-layer model to include the simulation of active regeneration. The engine used in this study was a 2002 Cummins ISM turbo charged 10.8 L heavy duty diesel engine with cooled EGR. The exhaust after-treatment system consisted of a Johnson Matthey DOC and CPF (a CCRT®).

To meet future NO, heavy-duty diesel emissions standards, exhaust gas recirculation (EGR) technology is likely to be used. To improve fuel economy and further lower emissions, the recirculated exhaust gas needs to be cooled, with the possibility that cooling of the exhaust gas may form sulfuric acid condensate in the EGR cooler. This corrosive condensate can cause EGR cooler failure and consequentially result in severe damage to the engine. Both a literature review and a preliminary experimental study were conducted. In this study, a manually controlled EGR system was installed on a 1995 Cummins Ml l-330E engine which was operated at EPA mode 9* (1800 rpm and 75% load). The Goksoyr-Ross method (1)** was used to measure the particle-phase sulfate and vapor-phase H2SO4 and SO2 at the inlet and outlet locations of the EGR cooler, obtaining H2SO4 and SO2 concentrations. About 0.5% of fuel sulfur in the EGR cooler was in the particle-phase.

The effects of exhaust gas recirculation (EGR) on heavy-duty diesel emissions were studied at two EPA steady-state operating conditions, old EPA mode 9* (1800 RPM, 75% Load) and old EPA mode 11 (1800 RPM, 25% Load). Data were collected at the baseline, 10% and 16% EGR rates for both EPA modes. The study was conducted using a 1995 Cummins M11-330E heavy-duty diesel engine and compared to the baseline emissions from the Cummins 1988 and 1991 L10 engines. The baseline gas-, vapor- and particle-phase emissions were measured together with the particle size distributions at all modes of operation. The total particulate matter (TPM) and vapor phase (XOC) samples were analyzed for physical, chemical and biological properties. The results showed that newer engines with electronic engine controls and higher injector pressures produce TPM decreases from the 1988 to 1991 to 1995 engines with the solids decreasing more than the soluble organic fraction (SOF) of TPM.