Charles Schenk

High-Efficiency NOx and PM Exhaust Emission Control for Heavy-Duty On-Highway Diesel Engines

A diesel exhaust emission control system consisting of catalyzed diesel particulate filters and NOx adsorber catalysts arranged in a dual-path configuration was developed and evaluated using a 1999-specification 5.9 liter medium-heavy-duty diesel engine. NOx adsorber regeneration was accomplished via a secondary exhaust fuel injection system. An alternating restriction of the exhaust flow between the two flow paths allowed injection and adsorber regeneration to occur under very low space velocity conditions. NOx and PM reductions in excess of 90% were observed over a broad range of steady-state operating conditions and over the hot-start HDDE-FTP transient cycle.

Emissions of PCDD/Fs, PCBs, and PAHs from a Modern Diesel Engine Equipped with Catalyzed Emission Control Systems

Exhaust emissions of 17 2,3,7,8-substituted chlorinated dibenzo-p-dioxin/furan (CDD/F) congeners, tetra-octa CDD/F homologues, 12 2005 WHO chlorinated biphenyls (CB) congeners, mono-nona CB homologues, and 19 polycyclic aromatic hydrocarbons (PAHs) from a model year 2008 Cummins ISB engine were investigated. Testing included configurations composed of different combinations of aftertreatment including a diesel oxidation catalyst (DOC), catalyzed diesel particulate filter (CDPF), copper zeolite urea selective catalytic reduction (SCR), iron zeolite SCR, and ammonia slip catalyst. Results were compared to a baseline engine out configuration. Testing included the use of fuel that contained the maximum expected chlorine (Cl) concentration of U.S. highway diesel fuel and a Cl level 1.5 orders of magnitude above. Results indicate there is no risk for an increase in polychlorinated dibenzo-p-dioxin/furan and polychlorinated biphenyl emissions from modern diesel engines with catalyzed aftertreatment when compared to engine out emissions for configurations tested in this program. These results, along with PAH results, compare well with similar results from modern diesel engines in the literature. The results further indicate that polychlorinated dibenzo-p-dioxin/furan emissions from modern diesel engines both with and without aftertreatment are below historical values reported in the literature as well as the current inventory value.

Benchmarking and Hardware-in-the-Loop Operation of a 2014 MAZDA SkyActiv 2.0L 13:1 Compression Ratio Engine

As part of its technology assessment for the upcoming midterm evaluation (MTE) of the 2022-2025 Light-Duty Vehicle Greenhouse Gas (LD GHG) emissions standards, EPA has been benchmarking engines and transmissions to generate inputs for use in its Advanced Light-Duty Powertrain and Hybrid Analysis (ALPHA) model, a physics-based, forward-looking, full vehicle computer simulation tool. One of the most efficient engines today, a 2.0L Mazda SkyActiv engine, is of particular interest due to its high geometric compression ratio and use of an Atkinson cycle. EPA benchmarked the 2.0L SkyActiv at its National Vehicle and Fuel Emissions laboratory. EPA then incorporated ALPHA into an engine dynamometer control system so that vehicle chassis testing could be simulated with a hardware-in-the-loop (HIL) approach. In order to model the behavior of current and future vehicles, an algorithm was developed to dynamically generate transmission shift logic from a set of user-defined parameters, a cost function (e.g., engine fuel consumption) and vehicle performance during simulation. This paper first presents the results of EPA’s benchmarking of a Mazda 2.0L 13:1 CR SkyActiv engine. It then details the implementation of the SkyActiv 2.0L engine in an HIL test bed to represent chassis testing of an advanced vehicle configuration, which includes assumptions for a future high-efficiency transmission and reduced vehicle road loads. The engine was operated over simulated EPA city and highway test cycles to assess the greenhouse gas (GHG) emissions performance in the context of EPA’s LD GHG standards through year 2025.

Four-Flow Path High-Efficiency NOx and PM Exhaust Emission Control System for Heavy-Duty On-Highway Diesel Engines

A 5.9 liter medium-heavy-duty diesel engine, meeting the emissions performance of a MY 2000 US heavy-duty on-highway engine, was tested with and without a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and NO x adsorber catalysts arranged in a four-flow path configuration. This four-flow path system represents a significant reduction in catalyst volume when compared to previous systems tested by EPA. The goal of this project was to achieve high NO x reduction over the Heavy-Duty Diesel Engine Federal Test Procedure (HDDE-FTP) and Supplemental Emission Test (SET), consistent with the 2007 U.S. heavy-duty engine emissions standards, using this reduced volume system. Supply of hydrocarbon reductant for NO x adsorber regeneration was accomplished via a secondary exhaust fuel injection system. Alternating the restriction of the exhaust flow between the four-flow paths allowed reductant injection and adsorber regeneration to occur under very low space velocity conditions. Initial system tests showed impressive reductions of regulated pollutants. Emissions of NO x were reduced by 78% over the HDDE-FTP and 89% over the SET; and particulate matter (PM) emissions were reduced by 86% over the HDDE-FTP and SET. System improvements were identified during this testing which should allow the system to meet the 2007 emission targets. These improvements will be validated in future testing.

NOx Adsorber Desulfation Techniques for Heavy-Duty On-Highway Diesel Engines

A 5.9 liter medium-heavy-duty diesel engine, equipped with a diesel exhaust emission control system consisting of catalyzed diesel particulate filters (CDPF) and NOx adsorber catalysts arranged in a dual-path configuration, was evaluated with the goal of developing desulfation strategies for in-use NOx adsorber desulfation. NOx adsorber desulfation was accomplished by providing reductant via a secondary exhaust fuel injection system and exhaust flow via an exhaust bypass valve. An alternating restriction of the exhaust flow between the two flow paths allowed reductant injection and adsorber desulfation to occur under very low space velocity conditions. An exhaust bypass valve connecting the dual path configuration upstream of the catalyzed diesel particulate filters allowed controlled addition of exhaust into the desulfating pathway for desulfation method development. Exotherms from the oxidation of reductant on the CDPF, and subsequent convective heat transfer from the CDPF to the NOx adsorbers generated adsorber catalyst temperatures in excess of 750°C. The control of space velocity through the desulfating pathway minimized cooling, allowing the temperature to be held in the target desulfation temperature range for prolonged periods of time. Sulfur release in the form of hydrogen sulfide and sulfur dioxide was measured using a chemical ionization mass spectrometer.

Air Flow Optimization and Calibration in High-Compression-Ratio Naturally Aspirated SI Engines with Cooled-EGR

As part of the U.S. Environmental Protection Agency (U.S. EPA) “Midterm Evaluation of Light-duty Vehicle Standards for Model Years 2022-2025 [1]”, the U.S. EPA is evaluating engines and assessing the effectiveness of future engine technologies for reducing CO2 emissions. Such assessments often require significant development time and resources in order to optimize intake and exhaust cam variable valve timing (VVT), exhaust gas recirculation (EGR) flow rates, and compression ratio (CR) changes. Mazda