Daniel K. Carder

Influence of Real-World Engine Load Conditions on Nanoparticle Emissions from a DPF and SCR Equipped Heavy-Duty Diesel Engine

The experiments aimed at investigating the effect of real-world engine load conditions on nanoparticle emissions from a Diesel Particulate Filter and Selective Catalytic Reduction after-treatment system (DPF-SCR) equipped heavy-duty diesel engine. The results showed the emission of nucleation mode particles in the size range of 6-15 nm at conditions with high exhaust temperatures. A direct result of higher exhaust temperatures (over 380 °C) contributing to higher concentration of nucleation mode nanoparticles is presented in this study. The action of an SCR catalyst with urea injection was found to increase the particle number count by over an order of magnitude in comparison to DPF out particle concentrations. Engine operations resulting in exhaust temperatures below 380 °C did not contribute to significant nucleation mode nanoparticle concentrations. The study further suggests the fact that SCR-equipped engines operating within the Not-To-Exceed (NTE) zone over a critical exhaust temperature and under favorable ambient dilution conditions could contribute to high nanoparticle concentrations to the environment. Also, some of the high temperature modes resulted in DPF out accumulation mode (between 50 and 200 nm) particle concentrations an order of magnitude greater than typical background PM concentrations. This leads to the conclusion that sustained NTE operation could trigger high temperature passive regeneration which in turn would result in lower filtration efficiencies of the DPF that further contributes to the increased solid fraction of the PM number count.

Characterization of Particulate Matter Emissions from a Current Technology Natural Gas Engine

Experiments were conducted to characterize the particulate matter (PM)-size distribution, number concentration, and chemical composition emitted from transit buses powered by a USEPA 2010 compliant, stoichiometric heavy-duty natural gas engine equipped with a three-way catalyst (TWC). Results of the particle-size distribution showed a predominant nucleation mode centered close to 10 nm. PM mass in the size range of 6.04 to 25.5 nm correlated strongly with mass of lubrication-oil-derived elemental species detected in the gravimetric PM sample. Results from oil analysis indicated an elemental composition that was similar to that detected in the PM samples. The source of elemental species in the oil sample can be attributed to additives and engine wear. Chemical speciation of particulate matter (PM) showed that lubrication-oil-based additives and wear metals were a major fraction of the PM mass emitted from the buses. The results of the study indicate the possible existence of nanoparticles below 25 nm formed as a result of lubrication oil passage through the combustion chamber. Furthermore, the results of oxidative stress (OS) analysis on the PM samples indicated strong correlations with both the PM mass calculated in the nanoparticle-size bin and the mass of elemental species that can be linked to lubrication oil as the source.

Emission Rates of Regulated Pollutants from Current Technology Heavy-Duty Diesel and Natural Gas Goods Movement Vehicles

Chassis dynamometer emissions testing of 11 heavy-duty goods movement vehicles, including diesel, natural gas, and dual-fuel technology, compliant with US-EPA 2010 emissions standard were conducted. Results of the study show that three-way catalyst (TWC) equipped stoichiometric natural gas vehicles emit 96% lower NOx emissions as compared to selective catalytic reduction (SCR) equipped diesel vehicles. Characteristics of drayage truck vocation, represented by the near-dock and local drayage driving cycles, were linked to high NOx emissions from diesel vehicles equipped with a SCR. Exhaust gas temperatures below 250 °C, for more than 95% duration of the local and near-dock driving cycles, resulted in minimal SCR activity. The low percentage of activity SCR over the local and near-dock cycles contributed to a brake-specific NOx emissions that were 5-7 times higher than in-use certification limit. The study also illustrated the differences between emissions rate measured from chassis dynamometer testing and prediction from the EMFAC model. The results of the study emphasize the need for model inputs relative to SCR performance as a function of driving cycle and engine operation characteristics.

A CFR1065-Compliant Transportable/On-Road Low Emissions Measurement Laboratory With Dual Primary Full-Flow Dilution Tunnels

In 2007, certification standards for heavy duty diesel particulate matter (PM) emissions were reduced from 0.1g/bhp-hr to 0.01g/bhp-hr, representing an order of magnitude reduction in pollutant level. Coincident with these standards revisions are refinements to test procedures that target reductions in measurement uncertainties. The 2007 U.S. Environmental Protection Agency (US EPA) specifications, as defined in 40 CFR parts 86, and US EPA 2010 specifications, as defined in CFR 1065, require significant updates to established laboratory measurement systems and test procedures. Moreover, additional regulatory standards pertaining to in-use compliance of heavy duty diesel engines will significantly impact the future of heavy duty diesel emissions measurement. As a result of the reduced emission production levels, demand for ‘real-world’ emissions measurements, and subsequent development and evaluation of on-board emissions measurement systems, West Virginia University’s Center for Alternative Fuels, Engines, and Emissions (CAFEE) has designed and constructed, with support from the U.S. Department of Energy (DOE), the ‘next level’ transportable dual primary full-flow dilution tunnel emissions measurement laboratory. The objective of this project was to build a mobile emissions measurement laboratory, of engine test cell quality, that is capable of measuring regulated and non-regulated emissions, and meets US EPA 2007 and 2010 specifications. A thirty-foot long cargo container was constructed to house a portable emissions measurement facility, comprised of a High Efficiency Particulate Air (HEPA) primary dilution unit, two primary full-flow dilution tunnels, a subsonic venturi, a secondary particulate matter sampling system, a gaseous emissions analytical bench instrumentation system, a computer based data acquisition (DAQ) and control system, full air conditioning and ventilation system, and chassis dynamometer control systems. Dual tunnels, of 18 inches ID and 20 feet long provide dedicated measurement capability for both lower PM vehicles, as well as legacy diesel fueled vehicles. This provision reduces tunnel history effects between test programs which address differing exhaust composition and PM loading. The laboratory grade analytical system can be transported to virtually any location with a demand for emissions testing, either with or without WVU’s transportable medium or heavy duty chassis dynamometers. Alternatively, the system can be loaded onto a flatbed trailer in order to test emissions while a vehicle is operated over the road. This paper describes each sub-system of this transportable laboratory in the aspect of specifications and design considerations, and presents results of qualification tests on the laboratory.Copyright

Unregulated, Greenhouse Gas and Ammonia Emissions from Current Technology Heavy-Duty Vehicles.

ABSTRACT The study presents the measurement of carbonyl, BTEX (benzene, toluene, ethyl benzene, and xylene), ammonia, elemental/organic carbon (EC/OC), and greenhouse gas emissions from modern heavy-duty diesel and natural gas vehicles. Vehicles from different vocations that included goods movement, refuse trucks, and transit buses were tested on driving cycles representative of their duty cycle. The natural gas vehicle technologies included the stoichiometric engine platform equipped with a three-way catalyst and a diesel-like dual-fuel high-pressure direct-injection technology equipped with a diesel particulate filter (DPF) and a selective catalytic reduction (SCR). The diesel vehicles were equipped with a DPF and SCR. Results of the study show that the BTEX emissions were below detection limits for both diesel and natural gas vehicles, while carbonyl emissions were observed during cold start and low-temperature operations of the natural gas vehicles. Ammonia emissions of about 1 g/mile were observed from the stoichiometric natural gas vehicles equipped with TWC over all the driving cycles. The tailpipe GWP of the stoichiometric natural gas goods movement application was 7% lower than DPF and SCR equipped diesel. In the case of a refuse truck application the stoichiometric natural gas engine exhibited 22% lower GWP than a diesel vehicle. Tailpipe methane emissions contribute to less than 6% of the total GHG emissions. Implications: Modern heavy-duty diesel and natural gas engines are equipped with multiple after-treatment systems and complex control strategies aimed at meeting both the performance standards for the end user and meeting stringent U.S. Environmental Protection Agency (EPA) emissions regulation. Compared to older technology diesel and natural gas engines, modern engines and after-treatment technology have reduced unregulated emissions to levels close to detection limits. However, brief periods of inefficiencies related to low exhaust thermal energy have been shown to increase both carbonyl and nitrous oxide emissions.

Comparison of Regulated and Unregulated Exhaust Emissions From a Fleet of Multi-Fuel Solid Resource Collection Vehicles

The refuse truck segment of the heavy duty diesel vehicle population has been identified as the most fuel inefficient sector. This is predominantly due to the stop and go driving pattern associated with these trucks. Constantly evolving emissions norms are forcing large truck fleet operators to explore the economic viability of alternative fueled vehicles to combat the increasing operating costs in terms of retrofit requirements of heavy-duty diesel vehicles. The objective of this study was to determine the emissions benefits and the economic viability of introducing liquefied natural gas (LNG), and LNG-Ultra-low sulfur diesel (ULSD) dual-fueled vehicles into the solid resource collection vehicle fleet (SRCV) in the city of Los Angeles. The 12 vehicles tested in this study were part of a multi-fuel refuse truck fleet. It should be noted that these vehicles are not representative of the state-of-the-art advanced technology engines that power the present day fleets. Vehicles were exercised over the AQMD refuse truck cycle and a newly developed compaction cycle on a heavy-duty chassis dynamometer. Regulated emissions together with a whole spectrum of unregulated speciation including the analysis of 1,3 butadiene with an on-site gas chromatograph was performed. Results showed that PM distance-specific mass emissions from LNG-fueled vehicles were on an average 82% lower than diesel trucks equipped with a DPF. Chemical speciation of exhaust from different fueled trucks indicated a characteristic emissions profile specific to the fuel used in these vehicles. While emissions from LNG vehicles were characterized by carbonyls, and other lower chain hydrocarbon compounds, emissions from diesel vehicles were dominated by polyaromatic hydrocarbons (PAH) and higher chain hydrocarbons.Copyright

Atmospheric Emissions from a Passenger Ferry with Selective Catalytic Reduction

Abstract The two main propulsion engines on Staten Island Ferry Alice Austen (Caterpillar 3516A, 1550 hp each) were fitted with selective catalytic reduction (SCR) aftertreatment technology to reduce emissions of oxides of nitrogen (NOx). After the installation of the SCR system, emissions from the ferry were characterized both pre- and post-aftertreatment. Prior research has shown that the ferry operates in four modes, namely idle, acceleration, cruise, and maneuvering modes. Emissions were measured for both engines (designated NY and SI) and for travel in both directions between Manhattan and Staten Island. The emissions characterization used an analyzer system, a data logger, and a filter-based particulate matter (PM) measurement system. The measurement of NOx, carbon monoxide (CO), and carbon dioxide (CO2) were based on federal reference methods. With the existing control strategy for the SCR urea injection, the SCR provided approximately 64% reduction of NOx for engine NY and 36% reduction for engine SI for a complete round trip with less than 6.5 parts per million by volume (ppmv) of ammonia slip during urea injection. Average reductions during the cruise mode were 75% for engine NY and 47% for engine SI, which was operating differently than engine NY. Reductions for the cruise mode during urea injection typically exceeded 94% from both engines, but urea was injected only when the catalyst temperature reached a 300 °C threshold pre- and postcatalyst. Data analysis showed a total NOx mass emission split with 80% produced during cruise, and the remaining 20% spread across idle, acceleration, and maneuvering. Examination of continuous NOx data showed that higher reductions of NOx could be achieved on both engines by initiating the urea injection at an earlier point (lower exhaust temperature) in the acceleration and cruise modes of operation. The oxidation catalyst reduced the CO production 94% for engine NY and 82% for engine SI, although the high CO levels during acceleration did cause analyzers to over-range. No clear, quantitative conclusions could be made regarding the effects of the SCR on PM

Particulate matter emissions and smoke opacity from in-use heavy-duty vehicles

Abstract Numerous pollution control agencies around the world are attempting to implement smoke opacity tests in efforts to lower ambient fine particulate matter levels. However, this approach is valid only if lower smoke opacity levels do result in lower mass emissions rates and lower number count of particulate matter emissions. This paper is limited to measurements of mass emission rates of particulate matter and smoke opacity. Particle size distributions and concentrations are not discussed. In this study in‐use emissions were measured from eighteen transit buses powered by electronic controlled six‐cylinder, turbo‐charged, after‐cooled engines. Eleven of these were fueled with diesel no. 1 while the remaining were running on bio‐diesel. Vehicle exhaust smoke opacity measurements were made using the Snap‐Acceleration Test procedure using a partial flow smoke meter, Bosch RTT 100 Diesel Smoke Opacimeter. Raw smoke opacity data was analyzed using the running half‐second average and the second order Bessel filter. In most cases the half‐second average gave a higher peak value than the Bessel filter. The smoke opacity data was compared with the mass emission rates of total particulate matter that were obtained during transient testing of these vehicles on the West Virginia University Transportable Heavy‐duty Vehicle Testing Laboratory. The vehicles were operated over the Central Business District cycle on the chassis‐dynamometer based laboratory. While smoke opacity and mass emission rates of particulate matter from heavy‐duty vehicles do exhibit a trend, there is no correlation between these two measurements.

Integrated Physical and Chemical Measurements of PM Emissions of Dispersing Plume Heavy-Duty Diesel Truck: Wind Tunnel Studies: Part I — Design and Commissioning

Over the past few decades there has been considerable progress made in understanding the processes leading to formation and evolution of particulate matter (PM) emissions from heavy duty diesel engines (HDDE). This progress has been primarily made under controlled laboratory conditions with the use of constant volume sampling (CVS) systems and to a limited extend through on-road chase studies. West Virginia University (WVU) is attempting to close the present knowledge gap by conducting detailed experiments in a custom designed and constructed environmental wind tunnel. The understanding and knowledge has recently been further extended to new emission reduction technologies, such as the diesel particulate filter (DPF) which has dramatically changed the size distribution and chemical composition of PM. Additionally, the selective catalytic reduction (SCR) technology has shown to further enhance the formation of nucleation mode particles as well as alter their morphology. Even with advances in technology there remains a considerable gap in the current level of understanding of PM formation and evolution, since the combustion generated PM from diesel engines is not discernible from the atmospheric background PM measured beyond 300m from highways. After being emitted from the vehicle exhaust system, the process of dilution in the atmosphere leads to a multitude of PM transformation phenomena, such as volatilization, coagulation, and condensation. The work presented herein has been divided into two parts which are published separately from each another.The first part describes the design and commissioning process of the wind tunnel focusing on both, aerodynamic and structural constraints, which ultimately led to the definition of the main characteristics of the facility. The resulting design is a subsonic, non-recirculating, suction type tunnel, with a 16ft high and 16ft wide test section capable of housing a full-size heavy-duty tractor cab. A 2,200hp suction fan is employed to provide up to 80 mph wind speeds. The 115ft test cell length guarantees for a 2 second residence time for the exhaust plume evolution (at 35 mph) and complies with turbulence intensity (less than 1%) and quality flow requirement as identified for this type of application. In addition, the West Virginia University (WVU) wind tunnel has been equipped with a custom made sampling system able to move in all three dimensions in order to measure spatially resolved plume characteristics.The second part will describe the actual test procedures and the experimental results and will be published in a separate paper.Copyright

Development of an Ammonia Reduction Aftertreatment Systems for Stoichiometric Natural Gas Engines

Development of an Ammonia Reduction After-treatment Systems for Stoichiometric Natural Gas Engines