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Use of Nitric Acid to Control the NO2:NOX Ratio Within the Exhaust Composition Transient Operation Laboratory Exhaust Stream

Southwest Research Institute-Robert Henderson, Ryan Hartley, Cary Henry
  • Technical Paper
  • 2020-01-0371
To be published on 2020-04-14 by SAE International in United States
The Exhaust Composition Transient Operation Laboratory (ECTO-Lab) is a burner system developed at Southwest Research Institute (SwRI) for simulation of IC engine exhaust. The current system design requires metering and combustion of nitromethane in conjunction with the primary fuel source as the means of NOX generation. While this method affords highly tunable NOX concentrations even over transient cycles, no method is currently in place for dictating the speciation of nitric oxide (NO) and nitrogen dioxide (NO2) that constitute the NOX mixture. NOX generated through combustion of nitromethane is dominated by NO, and generally results in a NO2:NOX ratio of <5 %. Generation of any appreciable quantities of NO2 is therefore dependent on an oxidation catalyst to oxidize a fraction of the NO to NO2. Presented within this manuscript is a method for precise control of the NO2:NOX ratio within the ECTO-Lab exhaust stream by using nitric acid as the NOX precursor molecule in lieu of nitromethane. While decomposition of nitromethane generates NO as the dominate component of the NOX mixture, nitric acid decomposition produces primarily…
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Investigation into Low-Temperature Urea-Water Solution Decomposition by Addition of Titanium-Based Isocyanic Acid Hydrolysis Catalyst and Surfactant

Southwest Research Institute-Ryan Hartley, Nolan Wright, Cary Henry
University of Texas-Zachary Tonzetich
  • Technical Paper
  • 2020-01-1316
To be published on 2020-04-14 by SAE International in United States
Mitigation of urea deposit formation and improved ammonia production at low exhaust temperatures continues to be one of the most significant challenges for current generation selective catalytic reduction (SCR) aftertreatment systems. Various technologies have been devised to alleviate these issues including: use of alternative reductant sources, and thermal treatment of the urea-water solution (UWS) pre-injection. The objective of this work was to expand the knowledge base of a potential third option, which entails chemical modification of UWS by addition of a titanium-based urea/isocyanic acid (HNCO) decomposition catalysts and/or surfactant to the fluid. Physical solid mixtures of urea with varying concentrations of ammonium titanyl oxalate (ATO), oxalic acid, and titanium dioxide (TiO2) were generated, and the differences in NH3 and CO2 produced upon thermal decomposition were quantified. It was found that addition of 2.0 mol % ATO to urea increased CO2 production by821 % and NH3 production by 96 % at temperatures ≤ 215 °C, indicating significantly enhanced hydrolysis of HNCO. Conversely, it was demonstrated that addition of oxalic acid or TiO2 to urea exhibited little…
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Deposit Reduction in SCR Aftertreatment Systems by Addition of Ti-Based Coordination Complex to UWS

Southwest Research Institute-Cary Henry, Scott Eakle
University of Texas-San Antonio-Ryan Hartley, Zachary Tonzetich
Published 2019-04-02 by SAE International in United States
Formation of urea-derived deposits in selective catalytic reduction (SCR) aftertreatment systems continues to be problematic at temperatures at and below 215 °C. Several consequences of deposit formation include: NOx and NH3 slip, exhaust flow maldistribution, increased engine backpressure, and corrosion of aftertreatment components. Numerous methods have been developed to reduce deposit formation, but to date, there has been no solution for continuous low-temperature dosing of Urea-Water Solution (UWS). This manuscript presents a novel methodology for reducing low-temperature deposit formation in SCR aftertreatment systems. The methodology described herein involves incorporation and dissolution of an HNCO hydrolysis catalyst directly into the UWS. HNCO is a transient species formed by the thermolysis of urea upon injection of UWS into the aftertreatment system. Ideally HNCO undergoes hydrolysis to form NH3 and CO2, but under certain conditions HNCO may polymerize or react with other constituents in the exhaust. Reaction of HNCO with species other than water generally results in the formation of deposits in the aftertreatment system. Addition of an HNCO hydrolysis catalyst directly into the UWS provides maximum contact…
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Fuel Reforming and Catalyst Deactivation Investigated in Real Exhaust Environment

Raphael Gukelberger
Bartley Consulting LLC-Gordon Bartley
Published 2019-04-02 by SAE International in United States
Increased in-cylinder hydrogen levels have been shown to improve burn durations, combustion stability, HC emissions and knock resistance which can directly translate into enhanced engine efficiency. External fuel reformation can also be used to increase the hydrogen yield. During the High-Efficiency, Dilute Gasoline Engine (HEDGE) consortium at Southwest Research Institute (SwRI), the potential of increased hydrogen production in a dedicated-exhaust gas recirculation (D-EGR) engine was evaluated exploiting the water gas shift (WGS) and steam reformation (SR) reactions. It was found that neither approach could produce sustained hydrogen enrichment in a real exhaust environment, even while utilizing a lean-rich switching regeneration strategy. Platinum group metal (PGM) and Ni WGS catalysts were tested with a focus on hydrogen production and catalyst durability. Although 4% additional hydrogen was initially produced in the EGR stream, leading to improvements in the coefficient of variation (CoV) and brake specific fuel consumption (BSFC), catalyst activity decreased within a few hours regardless of the regeneration strategy employed. With an SR catalyst, a small amount of hydrogen was produced in the EGR stream via…
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Comparison of Accelerated Ash Loading Methods for Gasoline Particulate Filters

Southwest Research Institute-Scott Eakle, Stephen Avery, Phillip Weber, Cary Henry
Published 2018-09-10 by SAE International in United States
Recent legislation enacted for the European Union (EU) and the United States calls for a substantial reduction in particulate mass (and number in the EU) emissions from gasoline spark-ignited vehicles. The most prominent technology being evaluated to reduce particulate emissions from a gasoline vehicle is a wall flow filter known as a gasoline particulate filter (GPF). Similar in nature to a diesel particulate filter (DPF), the GPF will trap and store particulate emissions from the engine, and oxidize said particulate with frequent regeneration events. The GPF will also collect ash particles in the wall flow substrate, which are metallic components that cannot be oxidized into gaseous components. Due to high temperature operation and frequent regeneration of the GPF, the impact of ash on the GPF has the potential to be substantially different from the impact of ash on the DPF. Therefore, traditional accelerated ash loading methods used for DPFs may not be applicable to the GPF technology. This paper summarizes three accelerated ash loading strategies that were evaluated and compared to a field generated component…
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Achieving Ultra Low NOX Emissions Levels with a 2017 Heavy-Duty On-Highway TC Diesel Engine and an Advanced Technology Emissions System - Thermal Management Strategies

SAE International Journal of Engines

ARB-Michael Carter, Seungju Yoon
Low Emission Technology Solutions-Cynthia C. Webb
  • Journal Article
  • 2017-01-0954
Published 2017-03-28 by SAE International in United States
The most recent 2010 emissions standards for heavy-duty engines have established a tailpipe limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, it is projected that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (CARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions. This paper details the thermal management strategies employed by the engine and supplemental exhaust heat addition device as was needed to achieve Ultra-Low NOX levels on a heavy-duty diesel engine with an advanced technology aftertreatment solution Further development is necessary for optimizing vocational test cycle emissions, but the results presented here demonstrate a potential pathway to achieving ultra-low NOX emissions on future heavy duty vehicles.
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Achieving Ultra Low NOX Emissions Levels with a 2017 Heavy-Duty On-Highway TC Diesel Engine - Comparison of Advanced Technology Approaches

SAE International Journal of Engines

ARB-Seungju Yoon, Michael Carter
Low Emission Technology Solutions-Cynthia C. Webb
  • Journal Article
  • 2017-01-0956
Published 2017-03-28 by SAE International in United States
The 2010 emissions standards for heavy-duty engines have established a limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, the California Air Resource Board (ARB) projects that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter (PM) and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (CARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions. This paper details the work performed on a heavy-duty diesel engine to explore the feasibility of various configurations of Traditional Technology (diesel oxidation catalyst-diesel particulate filter-selective catalytic reduction (SCR)) and Advanced Technology (passive NOX adsorber or diesel oxidation catalyst - SCR on Filter - SCR) to demonstrate ultra-low NOX emissions. Active and passive performance modifiers were also evaluated to demonstrate low NOX emissions, including heated dosing, gaseous dosing, and supplemental heat addition devices. The proposed Ultra Low NOX emission levels of 0.02 g/hp-hr…
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Achieving Ultra Low NOX Emissions Levels with a 2017 Heavy-Duty On-Highway TC Diesel Engine and an Advanced Technology Emissions System - NOX Management Strategies

SAE International Journal of Engines

ARB-Seungju Yoon
Low Emission Technology Solutions-Cynthia C. Webb
  • Journal Article
  • 2017-01-0958
Published 2017-03-28 by SAE International in United States
Recent 2010 emissions standards for heavy-duty engines have established a limit of oxides of nitrogen (NOX) emissions of 0.20 g/bhp-hr. However, CARB has projected that even when the entire on-road fleet of heavy-duty vehicles operating in California is compliant with 2010 emission standards, the National Ambient Air Quality Standards (NAAQS) requirement for ambient particulate matter and Ozone will not be achieved without further reduction in NOX emissions. The California Air Resources Board (ARB) funded a research program to explore the feasibility of achieving 0.02 g/bhp-hr NOX emissions. This paper details engine and aftertreatment NOX management requirements and model based control considerations for achieving Ultra-Low NOX (ULN) levels with a heavy-duty diesel engine. Data are presented for several Advanced Technology aftertreatment solutions and the integration of these solutions with the engine calibration. Further development is necessary for optimizing vocational test cycle emissions, but the results presented here demonstrate a potential pathway to achieving ultra-low NOX emissions on future heavy duty vehicles.
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Investigation of Urea Derived Deposits Composition in SCR Systems

Southwest Research Institute-Scott Eakle, Svitlana Kroll, Cary Henry
Published 2016-10-17 by SAE International in United States
Ideally, complete decomposition of urea should produce only two products in active Selective Catalytic Reduction (SCR) systems: ammonia and carbon dioxide. In reality, urea decomposition reaction is a two-step process that includes the formation of ammonia and isocyanic acid as intermediate products via thermolysis. Being highly reactive, isocyanic acid can initiate the formation of larger molecular weight compounds such as cyanuric acid (CYN), biuret (BIU), melamine (MEL), ammeline (AML), ammelide (AMD), and dicyandimide (DICY). These compounds can be responsible for the formation of deposits on the walls of the decomposition reactor in urea SCR systems. Composition of these deposits varies with temperature exposure, and under certain conditions can create oligomers that are difficult to remove from exhaust pipes. Deposits can affect efficiency of the urea decomposition, and if large enough, can inhibit the exhaust flow and negatively impact ammonia distribution on the SCR catalyst. This paper presents results of investigation of the deposits collected at various gas temperatures for quantification of urea and by-products of urea thermal decomposition and for their trace elements. Urea related…
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Detailed Characterization of Criteria Pollutant Emissions from D-EGR® Light Duty Vehicle

Southwest Research Institute-Cary Henry, Svitlana Kroll, Vinay Premnath, Ian Smith, Peter Morgan, Imad Khalek
Published 2016-04-05 by SAE International in United States
In this study, the criteria pollutant emissions from a light duty vehicle equipped with Dedicated EGR® technology were compared with emissions from an identical production GDI vehicle without externally cooled EGR. In addition to the comparison of criteria pollutant mass emissions, an analysis of the gaseous and particulate chemistry was conducted to understand how the change in combustion system affects the optimal aftertreatment control system. Hydrocarbon emissions from the vehicle were analyzed usin g a variety of methods to quantify over 200 compounds ranging in HC chain length from C1 to C12. The particulate emissions were also characterized to quantify particulate mass and number. Gaseous and particulate emissions were sampled and analyzed from both vehicles operating on the FTP-75, HWFET, US06, and WLTP drive cycles at the engine outlet location. HC emissions were observed to increase with the LTC D-EGR strategy, and a shift in species was observed, with those less reactive fuel components dominating the emission spectrum. Changes in particulate emissions were more complex, with an observed increase in soot mass and number for…
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