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The California Air Resources Board (CARB) adopted the Low Emission Vehicle (LEV) III regulations in January 2012, which lowered the particulate matter (PM) emissions standards for light-duty vehicles (LDVs) from 10 milligrams per mile (10 mg/mile) to 3 mg/mile beginning with model year (MY) 2017 and 1 mg/mile beginning with MY 2025. To confirm the ability to measure PM emissions below 1 mg/mile, a total of 23 LDVs (MY pre-2004 to 2009) were tested at CARB's Haagen-Smit Laboratory (HSL) (10 LDVs) and the United States Environmental Protection Agency's (US EPA) National Vehicle and Fuel Emissions Laboratory (NVEFL) (13 LDVs) using the federal test procedure (FTP) drive schedule. One LDV with PM emissions ranging from 0.6 - 0.8 mg/mile was tested at three CARB HSL test cells to investigate intra-lab and inter-lab variability. Reference, trip, and tunnel filter blanks were collected as part of routine quality control (QC) procedures.

Exhaust emissions of seventeen 2,3,7,8-substituted chlorinated dibenzo-p-dioxin/furan (CDD/F) congeners, tetra-octa CDD/F homologues, twelve WHO 2005 chlorinated biphenyls (CB) congeners, mono-nona CB homologues, and nineteen polycyclic aromatic hydrocarbons (PAHs) from a model year 2008 Cummins ISB engine equipped with aftertreatment including a diesel oxidation catalyst (DOC) and wall flow copper or iron urea selective catalytic reduction filter (SCRF) were investigated. These systems differ from a traditional flow through urea selective catalytic reduction (SCR) catalyst because they place copper or iron catalyst sites in close proximity to filter-trapped particulate matter. These conditions could favor de novo synthesis of dioxins and furans. The results were compared to previously published results of modern diesel engines equipped with a DOC, catalyzed diesel particulate filter (CDPF) and flow through urea SCR catalyst.

This paper summarizes the Heavy-Duty In-Use Testing (HDUIT) measurement allowance program for Particulate Matter Portable Emissions Measurement Systems (PM-PEMS). The measurement allowance program was designed to determine the incremental error between PM measurements using the laboratory constant volume sampler (CVS) filter method and in-use testing with a PEMS. Two independent PM-PEMS that included the Sensors Portable Particulate Measuring Device (PPMD) and the Horiba Transient Particulate Matter (TRPM) were used in this program. An additional instrument that included the AVL Micro Soot Sensor (MSS) was used in conjunction with the Sensors PPMD to be considered a PM-PEMS. A series of steady state and transient tests were performed in a 40 CFR Part 1065 compliant engine dynamometer test cell using a 2007 on-highway heavy-duty diesel engine to quantify the accuracy and precision of the PEMS in comparison with the CVS filter-based method.

Thermal management of the exhaust has become important as exhaust catalyst systems are being added to heavy duty (HD) diesel engines. The HD certification cycle consists of a cold-start transient cycle followed by a twenty minute soak with the engine off and then another ‘hot’ transient cycle. The first half of the HD transient cycle represents urban driving and consequently the engine duty cycle is very low. The low duty cycle results in low exhaust temperatures that can challenge the performance of catalysts. The cycle then transitions to a highway simulation at high loads. The high loads require high catalyst efficiency. If the catalysts are below optimum temperature prior to this transition, they need to warm up very quickly to prevent excessive emissions slip. The twenty minute soak also provides opportunity for catalysts to experience a significant temperature drop prior to the ‘hot’ cycle.

A 5.9 liter medium-heavy-duty diesel engine, equipped with a diesel exhaust aftertreatment system consisting of catalyzed diesel particulate filters and NOx adsorber catalysts arranged in a dual-path configuration was evaluated with the goal of studying the thermal aging characteristics of a number of NOx adsorber formulations and documenting adsorber formulation improvements over time. The performance of 2005 vintage NOx adsorber formulations was compared with the performance of older formulations. The testing was performed in three steps. The first was to run with zero sulfur fuel at a high temperature engine operating mode to characterize performance losses due to exposure to the highest temperatures experienced under normal operation. This was followed by aging without sulfur but with desulfation events to characterize the impact of the higher desulfation temperatures on catalyst deactivation.

Beginning June 1, 2006, 80% of the highway diesel fuel produced in the United States had to contain 15 ppm sulfur or less. To account for sulfur test method variability, the United States Environmental Protection Agency (US EPA) allowed a 2 ppm compliance margin, meaning that in an EPA enforcement action fuel measuring 17 ppm or less would still be deemed compliant since the true sulfur level could still be 15 ppm. Concern was voiced over the appropriateness of the 2 ppm compliance margin, citing recent American Society for Testing and Materials (ASTM) round-robin and crosscheck test program results that showed sulfur test lab-to-lab variability (reproducibility) on the order of 4 to 5 ppm depending on test method.

With input from industry, the United States Environmental Protection Agency (US EPA) has developed ramped modal versions of its steady-state certification duty cycles for land-based nonroad diesel engines. The Ramped Modal Cycle (RMC) calls for gathering gaseous and particulate emissions continuously over the cycle, while the steady-state test specifies that samples be taken for only a portion of the time at each mode. The RMC test was developed in part to capture discrete regeneration events associated with advanced catalyst systems like NOx adsorbers that are anticipated to meet future nonroad emission standards.1 To compare the emission levels between these two tests, a 5.9 liter medium-heavy-duty on-highway diesel engine rated for 260 hp @ 2500 rpm, was run at EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL), derated to 180 hp @ 2500 rpm, to simulate the configuration of a typical nonroad engine.

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 adsorber catalysts NOx 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 NOx 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 NOx adsorber regeneration was accomplished via a secondary exhaust fuel injection system.

A 5.9-liter medium-heavy-duty diesel engine, equipped with a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and NOx adsorber catalysts arranged in a dual flow path configuration was evaluated with the goal of studying the thermal aging characteristics of a number of NOx adsorber formulations. These adsorbers were tested with near zero sulfur fuel and low sulfur engine oil to minimize the impact of sulfur poisoning on the test results. Testing was performed at a high temperature engine operating mode to provide accelerated but not abusive aging. The test duration ranged from 100 to 250 hours depending on the severity of the aging at the 100 hour mark. The initial “zero” sulfur testing screened the NOx adsorber formulations for future testing and established a thermal aging baseline.

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.

A 5.9 liter medium-heavy-duty diesel engine was modified to approximate the emissions performance of a MY 2004 US heavy-duty on-highway engine. The engine was tested with and without a diesel exhaust emission control system consisting of catalyzed diesel particulate filters and NOx adsorber catalysts arranged in a dual-path configuration. The goal of this project was to achieve hot-start HDDE-FTP emissions consistent with the recently announced 2007 U.S. heavy-duty engine emissions standards. Supply of hydrocarbon reductant for 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 emissions over the hot-start portion of the HDDE-FTP transient cycle were 0.13 g/bhp-hr and less than 0.002 g/bhp-hr, respectively.