Joseph McDonald

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.

Progress in the Development of Tier 2 Light-Duty Diesel Vehicles

The U.S. Environmental Protection Agency (U.S. EPA) has been conducting a test program to evaluate efforts to bring light-duty diesel vehicles into compliance with U.S. Federal Tier 2 Light-duty Emission Standards. Between April 2002 and October 2003, five advanced prototype light-duty diesel vehicles equipped with NOx adsorption catalysts, PM-traps, and diesel oxidation catalysts were tested at the U.S. EPA’s National Vehicle and Fuel Emission Laboratory (NVFEL). The vehicle testing was conducted using low sulfur (<15 ppm) diesel fuel. All of the tested vehicles demonstrated the considerable progress recently made by vehicle manufacturers and systems integrators in applying advanced NOx and PM emission control technology to light duty diesel vehicles in anticipation of the U.S. Lightduty Tier 2 emission standards. PM emissions for all of the vehicles were well below the Tier 2 Bin-5 emission levels. The most recently tested vehicle demonstrated intermediate-useful life (50,000 miles) PM, NOx, and NMHC emissions at or below the Tier 2 Bin-5 levels. This paper represents an early survey of emissions from the first generation of prototype clean diesel vehicles.

Biodiesel: Effects on Exhaust Constituents

Fatty-acid mono-ester fuels, commonly referred to as “Biodiesel” fuels, are currently under evaluation for use as an alternative diesel fuel in the United States. Blends of Biodiesel fuels with petroleum diesel fuel have been tested in a large number of urban bus transit demonstrations, and they are currently under consideration for commercial use in confined environments such as underground mines in the United States and Canada. The use of Biodiesel fuels, such as soy-and rapeseed-oil methyl esters, has been shown to significantly reduce emissions of the carbon-soot constituents of diesel particulate matter (PM), while increasing the emissions of soluble or volatile organic particulate matter. The use of Biodiesel fuels has also been shown to reduce the emissions of some PAH and nitro-PAH compounds. When used in conjunction with an appropriately selected diesel oxidation catalyst, significant reductions in total PM emissions from diesel engines have been realized. This paper will present a summary of recent work conducted in the United States to characterize the exhaust emissions of diesel engines using a soy-methyl-ester Biodiesel fuel, including the effects of the Biodiesel fuel on exhaust gas composition, PM composition, and particle-size distribution.

Testing of the Toyota Avensis DPNR at U.S. EPA-NVFEL

An advanced prototype of the Toyota Avensis light-duty diesel vehicle equipped with a version of Toyota’s DPNR exhaust emission control system was tested at the U.S. EPA – NVFEL facility. The vehicle is under development by Toyota Motor Corporation for introduction in Europe. While this particular model is not anticipated to be offered for sale in the U.S., EPA evaluated the vehicle to gauge the current state of light-duty diesel vehicle technology. The vehicle was tested using a low sulfur (6 ppm) diesel fuel with a cetane number that was improved to near typical European levels (~50 cetane). Emission levels over the FTP75 consistent with U.S. Federal Light-Duty Tier 2 emission standards were achieved at levels of fuel economy that are competitive with current light-duty diesel passenger vehicles offered for sale in the U.S. The vehicle was tested with relatively low accumulated mileage. Further testing at 50,000-120,000 accumulated miles will be necessary to determine the long-term durability of the emission control system.

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

CMS - An Evolution of the CVS - A Full Flow, Constant Mass Flow, Sampling System

The CMS system commissioned by EPA and built by AVL, is a “start from a clean sheet of paper” approach to a full flow sampling system for aerosol matter from engine exhaust. The challenge of measuring 2007 level post DPF type particulate matter and polyaromatic hydrocarbons led to this re-thinking of sampler design. Previously used CVS designs had evolved to include elements that were not ideally suited for scaling up to large flow rates, and had mixing tunnels that were less than ideal for the sampling of complicated aerosols. The solution presented in this paper used ultrasonic time-offlight flowmeters in place of the usual Venturi flow tubes, reducing the size and cost of air handling components. Acoustically designed dampeners were used to reduce pulsation disturbances to the flow measurement. In addition, the aerosol mixing tunnel was designed with the aid of CFD simulations to provide a portion of the dilution through the walls of its mixing zone to reduce sample loss from thermophoretic and diffusion deposition. This paper will explain the engineering design considerations and calculations, as well as the results of flow calibrations and in-use measurements that confirm them. The ultrasonic flowmeter calibrations are verified with a subsonic orifice flowmeter traceable to a standard at the National Institute of Standards and Technology. Pulsation measurements are presented for verification of the dampener performance. Data from the usual propane stratification checks verify the static performance of mixing. The viability of the use of alternative flowmeters and modified mixing schemes to lower the cost and improve the performance of a large full flow emissions sampling system is confirmed. INTRODUCTION An exhaust emissions sampling system is described below which offers both innovative and unique solutions for using full flow dilution to measure gaseous and particulate exhaust emissions from heavy duty diesel (HDD) engines. While recent research and improvements in full flow dilution sampling technology or the CVS (Constant Volume Sampling) method have resulted in significant improvements in low emissions measurement, most of this effort has been focused on spark ignited, or SI engines. The measurement of exhaust emissions from HDD engines differs substantially from that of their SI engine counterparts. In heavy duty diesel testing, the measurement focus is on particulate matter and NOx. The PM measurement has historically used the full flow dilution tunnel, and the gaseous emissions are measured hot and recorded continuously [1]. The heavy duty test cycles are also different in that they generate high engine loads and consequently high heat loads on the emissions sampling system. Upcoming reductions in regulated emissions from heavy duty engines have put renewed interest in developing accurate methods to measure low levels of PM and NOx. There is also interest in studying nonregulated organic compounds in diesel exhaust, such as toxic compounds. In the interest of trying to address and study the issues specific to heavy duty diesel emissions measurement, the Environmental Protection Agency issued a contract to AVL NA to build a novel and new exhaust emissions sampling system. This system, called the Constant Mass Sampling, or CMS system, started with the idea of the traditional CVS approach and developed new solutions for the unique needs of heavy duty diesel testing. The new solutions generally addressed two areas: reduce or eliminate the loss of particulate matter and organic compounds in the dilution tunnel, and design the system for high flow and high temperature capacity with the ability to operate at constant mass flow rate. The dilution tunnel was designed to allow a small portion of the dilution air to be introduced into the tunnel through the tunnel wall. This flow of air or “wall flow,” is intended to prevent particulate matter or organic material from attaching to the tunnel wall through any mechanism of particle deposition. The velocity of air traveling through the tunnel wall is sufficient to counteract the forces driving the particles to the wall. This velocity, as it turns out, does not have to be large. The tunnel wall flow actually delays mixing because dilution air is being added later in the tunnel reducing the amount of time available to mix before the sample zone. Special mixing orifice plates were installed to develop turbulent flow profiles before the mixing tee. A CFD study was conducted during the design phase to optimize the tunnel wall flow and mixing orifice designs. Stratification tests were conducted on the finished system which confirmed adequate mixing. In order to achieve high flow rates, a low pressure loss system was designed. This included the use of a new type of flow meter in this application; ultrasonic flow meters. The ultrasonic flow meters allow virtually open pipe flow, so the pressure losses are negligible. In addition to the flow benefits, this flow metering technology has improved greatly in recent years and offers good response rates and accuracy. Two flow meters were used, one to measure dilution air and one to measure total flow or dilute exhaust. The ultrasonic flow meters are sensitive to pressure pulsations, so care is needed to reduce or minimize pulsations generated by the engine. Pulsations dampers were used in this design before and after the dilution tunnel to isolate the pressure pulsations and reduce their level before reaching the flow meters. Measurement of exhaust pressure pulsations in the final system confirmed the pulsation dampers provide the designed attenuation level of 98% reduction. Operating the system at constant mass flow simplifies the collection of samples from the tunnel. A constant flow sample is all that is needed to take a proportional sample from the tunnel. A control strategy was developed to operate the system at a constant mass flow rate. This was done by using a variable speed main blower and control software. A dilution air blower, also variable speed, controls tailpipe pressure. The main benefit of designing the system for low pressure loss is that high flow rates can be achieved without placing a high demand on blower performance. The CMS system is designed for operation from 100 to 270 kg/min and temperatures up to 191 deg C. The main blower is an industrial exhauster capable of operating at high temperatures and requiring only a 30 kW motor. The features described above are illustrated schematically in Figure 1 below. The CMS system was installed at EPA’s National Vehicle and Fuel Emissions Laboratory, in Ann Arbor, Michigan during 2004. Diagnostic and evaluation testing has begun, however additional testing is still being planned. The results are encouraging so far using pre2007 engines. Further investigation is planned to study the low level measurement capability. We expect this work to be presented at a later time.

Locomotive Exhaust Temperatures During High Altitude Tunnel Operation in Donner Pass

Locomotives in heavy-haul service at high altitude and within unventilated tunnels operate under some of the most extreme conditions encountered in the U.S. with regard to high ambient temperatures and high locomotive exhaust temperatures. Consideration of such conditions is crucial to the design of future catalytic emission control systems for locomotives. Field testing was conducted on two locomotives certified to U.S. Federal Tier 2 locomotive emissions standards operating as part of a four-locomotive consist pulling a heavy-freight train west-bound through the Donner Pass Region in late August 2007. The highest post-turbine exhaust temperatures observed over the entire test route occurred within Union Pacific Tunnel 41 — an approximately two-mile-long, unventilated tunnel located near Norden, California. Engine protection measures within the electronic locomotive and engine management systems of both locomotives limited the peak exhaust temperatures encountered during the tests to less than 560°C.Copyright

Modeling and Controls Development of 48 V Mild Hybrid Electric Vehicles

The Advanced Light-Duty Powertrain and Hybrid Analysis tool (ALPHA) was created by EPA to evaluate the Greenhouse Gas (GHG) emissions of Light-Duty (LD) vehicles. ALPHA is a physics-based, forward-looking, full vehicle computer simulator capable of analyzing various vehicle types combined with diferent powertrain technologies. Te ALPHA desktop application was developed using MATLAB/Simulink. Te ALPHA tool was used to evaluate technology efectiveness and of-cycle technologies such as air-conditioning, electrical load reduction technology and road load reduction technologies of conventional, non-hybrid vehicles for the Midterm Evaluation of the 2017-2025 LD GHG rule by the U.S. Environmental Protection Agency (EPA) Ofce of Transportation and Air Quality (OTAQ). Tis paper presents controls development, modeling results, and model validation for simulations of a vehicle with a 48 V Belt Integrated Starter Generator (BISG) mild hybrid electric vehicle and an initial model design for a 48 V inline on-axis P2-confguration mild hybrid electric vehicle. Both confgurations were modeled with a MATLAB/Simulink/Statefow tool, which has been integrated into EPA’s ALPHA vehicle model and was also used to model components within Gamma Technology GT-DRIVE simulations. Te mild hybrid electric vehicle model was validated using vehicle data obtained from Argonne National Laboratory (ANL) chassis dynamometer tests of a 2013 Chevrolet Malibu Eco 115 V 15 kW BISG mild hybrid electric vehicle. Te simulated fuel economy, engine torque/speed, motor torque/speed, engine on-of controls, battery voltage, current, and State of Charge (SOC) were all in good agreement with the vehicle test data on a number of drive schedules. Te developed 48 V mild hybrid electric vehicle model can be used to estimate the GHG emissions and fuel economy of 48 V mild hybrid electric vehicles over the EPA regulatory drive cycles and to estimate of-cycle GHG emissions. Te 48 V mild hybrid electric vehicle model will be further validated with additional 48 V mild hybrid electric vehicle test data in the future as more vehicle models become available. EPA has included 48 V BISG mild hybrid electric vehicle technology in its assessment of CO2-reducing technologies available for compliance with U.S. GHG standards.