Browse Topic: Catalysts

Items (973)

Characteristics of Transient NOx Emissions of HEV under Real Road Driving

2020-01-03804/14/2020

To meet the request of China National 6b emission regulations which will be officially implemented in China, firstly including the RDE emission test limits, the transient emissions on real road condition are paid more attention. A non-plug-in hybrid light-duty gasoline vehicles (HEV) sold in the Chinese market was selected to study real road emissions employed fast response NOx analyzer from Cambustion Ltd. with a sampling frequency of 100Hz, which can measure the missing NO peaks by standard RDE gas analyzer now. Emissions from PEMS were also recorded and compared with the results from fast response NOx analyzer. The concentration of NOx emissions before and after the Three Way Catalyst (TWC) of the hybrid vehicle were also sampled and analyzed, and the working efficiency of the TWC in real road driving process was investigated. It is found that when the engine is at high-speed and heavy-load conditions, especially when fuel is injected after fuel cut, instantaneous spikes in tailpipe NO emissions could be observed, which means that traffic positions such as crosswalks, speed bumps, expressway entrances, traffic lights, would lead to higher NOx emissions, because the instantaneous fuel cut-off occurs during the acceleration shifting process, the TWC is in an oxygen-rich state. Obvious transient effects were revealed and the results could be used for further reducing NOx emissions from automotive RDE and engine calibration of RDE.

Zhang, Yonghao, Deng, Jun, Li, Qiang, Liu, Yintong, He, Bo, Hu, Zongjie, Bo, Shi, Li, Liguang

Deep Optimization of Catalyst Layer Composition via Data-Driven Machine Learning Approach

2020-01-08594/14/2020

Proton exchange membrane fuel cell (PEMFC) provides a promising future low carbon automotive powertrain solution. The catalyst layer (CL) is its core component which directly influences the output performance. PEMFC performance can be greatly improved by the effective optimization of CL composition. This work demonstrates a deep optimization of CL composition for improving the PEMFC performance, including the platinum (Pt) loading, Pt percentage of carbon-supported Pt and ionomer to carbon ratio of the anode and the cathode,. The simulation results by a PEMFC three-dimensional (3D) computation fluid dynamics (CFD) model coupled with the CL agglomerate model is used to train the artificial neural network (ANN) which can efficiently predict the current density under different CL composition. Squared correlation coefficient (R-square) and mean percentage error in the training set and validation set are 0.9867, 0.2635% and 0.9543, 1.1275%, respectively. It illustrates that the well-trained ANN has a comparable accuracy with the physical model. Then, the ANN is utilized as the fitness function in the genetic algorithm (GA) to search the optimal CL composition for maximizing the current density. For verification, the optimal solution of CL composition is returned to the physical model and the comparison between the ANN predicted current density and the physical model simulated current density is provided. The percentage error is only 2.418% which can illustrate the validity of this work.

Wang, Bowen, Xie, Biao, Xuan, Jin, Gu, Wen, Zhao, Dezong, Jiao, Kui

Relevance of Exhaust Aftertreatment System Degradation for EU7 Gasoline Engine Applications

2020-01-03824/14/2020

Exhaust aftertreatment systems must function sufficiently over the full useful life of a vehicle. In Europe this is currently defined as 160.000 km. With the introduction of Euro 7 it is expected that the required mileage will be extended to 240.000 km. This will then be consistent with the US legislation. In order to quantify the emission impact of exhaust system degradation, an Euro 7 exhaust aftertreatment system is aged by different accelerated approaches: application of the Standard Bench Cycle, the ZDAKW cycle, a novel ash loading method and borderline aging. The results depict the impact of oil ash on the oxygen storage capacity. For tailpipe emissions, the maximum peak temperatures are the dominant aging factor. The cold start performance is effected by both, thermal degradation and ash accumulation. An evaluation of this emission increase requires appropriate benchmarks. For this purpose, an analysis of the emission impacts of ambient temperatures, driving modes and particulate filter regenerations follows. The comparison shows the severe impact of very low ambient conditions. Considering the high statistical relevance of catalyst degradation however, full useful life optimization requires special attention for Euro 7 gasoline engine applications.

Sterlepper, Stefan, Claßen, Johannes, Pischinger, Stefan, Görgen, Michael, Cox, Jim, Nijs, Martin, Scharf, Johannes

Effects of Using an Electrically Heated Catalyst on the State of Charge of the Battery Pack for Series Hybrid Electric Vehicles at Cold Start

2020-01-04444/14/2020

Battery models are being developed as a component of the powertrain systems of hybrid electric vehicles (HEVs) to predict the state of charge (SOC) accurately. Electrically heated catalysts (EHCs) can be employed in the powertrains of HEVs to reach the catalyst light off temperature in advance. However, EHCs draw power from the battery pack and hence sufficient energy needs to be stored to power auxiliary components. In series HEVs, the engine is primarily used to charge the battery pack. Therefore, it is important to develop a control strategy that triggers engine start/stop conditions and reduces the frequency of engine operation to minimize the equivalent fuel consumption. In this study, a battery pack model was constructed in MATLAB-Simulink to investigate the SOC variation of a high-power lithium ion battery during extreme engine cold start conditions (-7°C) with/without application of an EHC. The EHC was simulated in MATLAB to determine the energy required to heat the catalyst during cold start conditions. The effect of the EHC in emissions purification at -7°C was studied using a three-way catalyst (TWC) model. The EHC was operated only during the initial few seconds before the engine start to increase the bed temperature of the catalyst. This was found to have a significant impact on exhaust gas emissions even under cold start conditions. However, powering the EHC lowered the SOC of the battery pack, triggering the engine to run and consume more fuel. Hence, an engine ON/OFF control strategy was proposed to control the engine operation conditions and effectively charge the battery pack. The SOC variation of the battery pack and the effects on emissions and fuel consumption were simulated and compared with/without the EHC. The battery model was validated with a control strategy proposed in simulations at 23°C and a parameter study was conducted at -7°C.

Sivakumar, Suchitra, Shingyouchi, Hajime, Yan, Xieyang, Okajima, Toshinori, Yamaguchi, Kyohei, Kusaka, Jin, Nagata, Makoto

Numerical Optimization of a SCR System Based on the Injection of Pure Gaseous Ammonia for the NOx Reduction in Light-Duty Diesel Engines

2020-01-03564/14/2020

Selective Catalytic Reduction (SCR) systems are nowadays widely applied for the reduction of NOx emitted from Diesel engines. The typical process is based on the injection of aqueous urea in the exhaust gases before the SCR catalyst, which determines the production of the ammonia needed for the catalytic reduction of NOx. However, this technology is affected by two main limitations: a) the evaporation of the urea water solution (UWS) requires a sufficiently high temperature of the exhaust gases and b) the formation of solid deposits during the UWS evaporation is a frequent phenomenon which compromise the correct operation of the system. In this context, to overcome these issues, a technology based on the injection of gaseous ammonia has been recently proposed: in this case, ammonia is stored at the solid state in a cartridge containing a Strontium Chloride salt and it is desorbed by means of electrical heating. In this work, an after-treatment system based on the injection of gaseous ammonia in the SCR system is considered. Numerical 1D and 3D CFD simulations are applied in order to optimize the NOx reduction process. In particular, CFD methodology is applied to study in details the process of injection of the gaseous ammonia in the main exhaust gas stream and the effectiveness of the mixing process. Different geometrical layouts are compared to evaluate their performances in terms of uniformity of the NH3 distribution across the inlet section of the catalyst and pressure drop introduced in the exhaust line. Moreover, a 1D simulation tool is applied to evaluate the performances of the entire exhaust after-treatment system. The 1D model is calibrated on the basis of the information coming from detailed CFD simulations, in particular for what concerns the modeling of the effects of the different mixer geometries in terms on NH3 distribution. In this case, a simplified 3D catalyst is simulated, to take into account the maldistribution of ammonia at the inlet cross section and to evaluate its impact on the global deNOx performance of the system for different dosing strategies and for different levels of the ammonia maldistribution.

Della Torre, Augusto, Montenegro, Gianluca, Onorati, Angelo, Cerri, Tarcisio, Tronconi, Enrico, Nova, Isabella

Effects of Sub-Chamber Configuration on Heat Release Rate in a Constant Volume Chamber simulating Lean-burn Natural Gas Engines

2019-32-05511/24/2020

Sub-chamber is a useful device with regard to sustaining stable operation of compressed natural gas (CNG) engines under lean burn conditions. In our previous studies, we applied a sub-chamber injection system to CNG engines, in which a single injector and a spark plug are mounted in a small sub-chamber. The aim of this study is to investigate the effect of the sub-chamber configuration on heat release in the main combustion chamber. 11 types of sub-chamber with different nozzle number, nozzle diameter, and sub-chamber volume were examined under a condition that pressure is 2.3 MPa, and global equivalence ratio is 0.6. When the sub-chamber with smaller nozzles are used, the penetration velocity of burned gas jet increases. In addition, the velocity also increases with an increasing sub-chamber volume. The high-speed penetration of burned gas jet shortens the period of initial flame development. This is because the high-temperature burned gas quickly reaches to side wall of main chamber, and immediately ignites lean mixtures existing in the main chamber. Consequently, combustion duration time until heat release reaches 90 % is also shortened. On the other hand, the velocity difference between the jets from sub-chambers with different nozzle numbers is small. To predict the penetration velocity, we proposed an empirical formula based on the volume, nozzle diameter and nozzle number of sub-chamber. The jet intensity evaluated from the formula shows correlations with duration times of combustion periods as well as penetration velocities of burned gas jets.

Nada, Yuzuru, Kidoguchi, Yoshiyuki, Yamashita, Yuto, Furukawa, Ryo, Kaya, Ryu, Nakano, Hideaki, Kobayashi, Shinichi

3D-Printed Liquid Lab-on-a-Chip

TBMG-3527910/1/2019

Researchers have 3D-printed an all-liquid device that, with the click of a button, can be repeatedly reconfigured on demand to serve a wide range of applications from making battery materials to screening drug candidates.

Graphene Lid Extends Photoemission Electron Microscopy to Liquids

TBMG-347537/1/2019

By capping liquids with graphene (an ultrathin sheet of pure carbon), researchers can easily image and analyze liquid interfaces and the surface of nanometer-scale objects immersed in liquids. In the imaging technique known as photoemission electron microscopy (PEEM), ultraviolet light or X-rays bombard a sample, stimulating the material to release electrons from a region at or just beneath its surface. Electric fields act as lenses, focusing the emitted electrons to create an image.

Event-Driven Simulation of Particle-Particle and Particle-Surface Collisions in Ice Crystal Icing

2019-01-20146/10/2019

This paper describes an event-driven simulation tool for predicting particle-particle and particle-surface interactions in ice crystal icing (ICI). A new accretion model which is much less empirical than existing models for predicting ICI accretion is also described. Unlike previous models, the new “gouge/bounce model” (GBM) differentiates between (erosion) losses resulting from particle bounce and those resulting from particle gouging. A bounce threshold based on the tangential Stokes number is used to calculate most of the bounce loss. The GBM also predicts ejecta velocities and directions, at least approximately, which is important because most of the mixed-phase mass flux impacting a surface actually bounces off or erodes existing material in ICI, thereby increasing the mass flux downstream. The event-driven simulation tool, denoted COLLIDE, has been applied to two test cases in which accretion growth appeared to be affected by TWC in a manner beyond that which would be expected from the accumulation parameters. An existing correlation-based accretion model (CBM), modified to predict erosion dependence on particle diameter, is also implemented and applied to the test cases. COLLIDE predicted the observed accretion dependence on TWC in a least a qualitative fashion for the majority of model/test case permutations, supporting the hypothesis that collisions between backscattered and incident particles reduces erosion and thereby increases sticking efficiency as observed in experiments with larger particles. The predictions suggest scattering of incident particles by impacts with ejecta is the dominant mechanism responsible for the flux interference effect, not particle size reduction due to particle-particle collisions.

Currie, Thomas Charles

Analysis and Automated Detection of Ice Crystal Icing Conditions Using Geostationary Satellite Datasets and In Situ Ice Water Content Measurements

2019-01-19536/10/2019

Recent studies have found that high mass concentrations of ice particles in regions of deep convective storms can adversely impact aircraft engine and air probe (e.g. pitot tube and air temperature) performance. Radar reflectivity in these regions suggests that they are safe for aircraft penetration, yet high ice water content (HIWC) is still encountered. The aviation weather community seeks additional remote sensing methods for delineating where ice particle (or crystal) icing conditions are likely to occur, including products derived from geostationary (GEO) satellite imagery that is now available in near-real time at increasingly high spatio-temporal detail from the global GEO satellite constellation. A recent study using a large sample of co-located GEO satellite and in-situ isokinetic evaporator probe (IKP-2) total water content (TWC) datasets found that optically thick clouds with tops near to or above the tropopause in close proximity (≤ 40 km) to convective updrafts were most likely to contain high TWC (TWC ≥ 1 g m-3). These parameters are detected using automated algorithms and combined to generate a HIWC probability (PHIWC) product at the NASA Langley Research Center (LaRC). Seven NASA DC-8 aircraft flights were conducted in August 2018 over the Gulf of Mexico and the tropical Pacific Ocean during the HIWC Radar II field campaign. The convection sampled during four flights was observed by GOES-16 at 1- or 5-minute intervals, providing the first opportunity to analyze product performance from this new satellite. This paper will (1) present initial comparisons between GOES-16 and IKP-2 datasets during HIWC Radar II, (2) demonstrate GOES-16 products for select periods when high TWC was encountered with an emphasis on three flights with 1-minute imagery, (3) compare GOES observations and derived products from the HIWC Radar I and II campaigns.

Bedka, Kristopher, Yost, Christopher, Nguyen, Louis, Strapp, J. Walter, Ratvasky, Thomas, Khlopenkov, Konstantin, Scarino, Benjamin, Bhatt, Rajendra, Spangenberg, Douglas, Palikonda, Rabindra

Scientists 3D Print All-Liquid ‘Lab on a Chip’

TBMG-345526/1/2019

Researchers at DOE's Lawrence Berkeley National Laboratory (Berkeley Lab) have 3D printed an all-liquid device that, with the click of a button, can be repeatedly reconfigured on demand to serve a wide range of applications — from making battery materials to screening drug candidates.

Fuel Reforming and Catalyst Deactivation Investigated in Real Exhaust Environment

2019-01-03154/2/2019

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 the WGS reaction but not the SR reaction. Similar to the WGS catalyst testing, the SR catalyst deactivated quickly due to coking. While neither of these approaches displayed acceptable long-term performance, the exhaust environment still poses a significant opportunity for the production of hydrogen rich reformate to deliver improvement in engine efficiency.

Bartley, Gordon, Gukelberger, Raphael, Henderson, Robert, Henry, Cary

Deposit Reduction in SCR Aftertreatment Systems by Addition of Ti-Based Coordination Complex to UWS

2019-01-03134/2/2019

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 between catalyst and substrate, thereby improving deposit reduction efficacy. This method of reducing deposits has been shown to reduce deposits by 89% at a 215 °C operating condition.

Hartley, Ryan, Henry, Cary, Eakle, Scott, Tonzetich, Zachary

Study on Improvement of NOx Reduction Performance at Low Temperature Using Urea Reforming Technology in Urea SCR System

2019-01-03174/2/2019

To reduce NOx and PM emissions in exhaust gas, after-treatment systems for low NOx emissions are being developed in combination with improvements of engine combustion. In recent years, the exhaust gas temperature has been dropping because of enhanced low-fuel consumption of the engine. Therefore, it is urgent to develop NOx reduction technologies that work at a low temperature under 200degC. Since NOx is reduced by reacting with ammonia supplied to the SCR catalyst, it is necessary to make the urea solution decompose into ammonia using the heat of the exhaust gas to supply sufficient ammonia to the SCR catalyst. However, both the decomposition reaction and hydrolysis reaction of the urea have insufficient exhaust heat, thus making it difficult for urea to decompose and hydrolyze to ammonia at a low temperature. To solve this problem, it focuses on forcibly decomposing the urea solution without depending on the exhaust gas temperature. We selected a urea reforming method in which the urea is directly heated using the glow plug as the heat source. In this study, we have considered further improvement of the NOx reduction performance at a low temperature with a view to improving the ammonia generation efficiency by urea reforming.

Okada, Yuichi, Hirabayashi, Hiroshi, Sato, Shinya, Inoue, Hiroshi

Numerical Modeling Study of Detailed Gas Diffusivity into Catalyst Washcoat for Lean NOx Catalyst

2019-01-09934/2/2019

To evaluate the relationship between the exhaust gas purification performance and the catalyst pore properties related to gas diffusion, an elementary reaction model was combined with gas diffusion into catalyst pores, referred to as the pseudo-2D gas diffusion/reaction model. It was constructed for Pt/Al2O3 + CeO2 catalyst as lean NOx catalyst. The gas diffusion was described as macro pore diffusion between the catalyst particles and meso pore diffusion within the particle. The kinetic model was composed of 26 reactions of NO/CO/O2 chemistry including 17 Pt/Al2O3 catalyst reactions and 9 CeO2 reactions. Arrhenius parameters were optimized using activity measurement results from various catalysts with various pore properties, meso pore volume and diameter, macro pore volume and diameter, particle size, and washcoat thickness. Good agreement was achieved between the measured and calculated values. Moreover, as compared to the performance of other catalysts which was not used for reaction model calibration, the simulated results were in good agreement with this experimental data. Using the calibrated reaction model combined with detailed gas diffusion model, a sensitivity analysis for NOx concentration was performed to identify key diffusion parameters of the lean NOx catalyst. In summary, parameters with the highest sensitivity were catalyst particle size, washcoat thickness, CeO2 meso pore volume, and diameter. Also, catalyst macro pore volume and diameter showed no dependence. Consequently, to increase the NOx purification performance, the meso pore parameters and washcoat thickness should be increased, particle size should be decreased. With these changes, the gaseous NOx will easily move to the catalyst surface and into the active site of meso pore, resulting in better performance.

Yamamoto, Osami, Matsuo, Yuichi, Tosa, Shinichi, Okayama, Tatsuya, Zhang, Zhiwei, Tolsma, John

Diagnostics of Field-Aged Three-Way Catalyst (TWC) on Stoichiometric Natural Gas Engines

2019-01-09984/2/2019

Three-way catalysts have been used in a variety of stoichiometric natural gas engines for emission control. During real-world operation, these catalysts have experienced a large number of temporary and permanent deactivations including thermal aging and chemical contamination. Thermal aging is typically induced either by high engine-out exhaust temperatures or the reaction exotherm generated on the catalysts. Chemical contamination originates from various inorganic species such as Phosphorous (P) and Sulfur (S) that contain in engine fluids, which can poison and/or mask the catalyst active components. Such deactivations are quite difficult to simulate under laboratory conditions, due to the fact that multiple deactivation modes may occur at the same time in the real-world operations. In this work, a set of field-aged TWCs has been analyzed through detailed laboratory research in order to identify and quantify the real-world aging mechanisms. Based on the measured NOx conversion efficiency, we identified that thermal aging was the major aging mechanism for all the field-aged TWCs investigated. Additionally, chemical contaminants such as Phosphorous (P) and Sulfur (S) containing species were also detected at the front portion of the catalyst location that is closer to the engine outlet, leading to decreased NOx and CH4 conversions at this location. However, the NOx and CH4 conversions at the rest of the catalyst locations were mildly impacted due to the sharp axial gradient of these chemical contaminants deposition.

Wang, Di, An, Hongmei, Gong, Jian, Li, Junhui, Kamasamudram, Krishna, Currier, Neal, Yezerets, Aleksey

Ash Transport and Deposition, Cake Formation and Segregation-A Modeling Study on the Impact of Ash on Particulate Filter Performance

2019-01-09884/2/2019

Non-combustible particles, commonly summarized as ash, influence the lifetime performance of wall flow filters. This study aims to investigate this influence by means of simulation. An existing transient 1D+1D wall flow filter model is extended by dedicated transport balances for soot and ash (1), by a discrete cake model describing changing soot and ash compositions over the cake height (2), by a phenomenological cake filtration model (3), by dedicated cake property models (4) and by a phenomenological model capturing the radial mobility of solids within the cake (5). Results of three different types of simulations are shown. First, the various sub-models are assessed in isolated simulation configurations. The combination of these shall serve as theoretical model validation. Second, isolated loading and passive regeneration simulations are performed. This aims to identify the impact of different filtration and cake migration constants on soot and ash segregation (i.e. ash accumulation) and on soot conversion performance. Third, the impact of ash during a combined loading and passive regeneration cycle is investigated. This aims to identify the impact of ash on the formation of a soot balance point.

Wurzenberger, Johann C., Kutschi, Susanne, Nikodem, Astrid

Modeling of Engine Aftertreatment System Cooling for Hybrid Vehicles

2019-01-09894/2/2019

Exhaust aftertreatment systems are essential components in modern powertrains, needed to reach the low legislated levels of NOx and soot emissions. A well designed diesel engine exhaust aftertreatment system can have NOx conversion rates above 95%. However, to achieve high conversion the aftertreatment system must be warm. Because of this, large parts of the total NOx emissions come from cold starts where the engine has been turned off long enough for the aftertreatment system to cool down and loose its capacity to reduce NOx. It is therefore important to understand how the aftertreatment cools down when the engine in turned off. Experimental data for a catalyst cool-down process is presented and analyzed. The analysis shows that it is important to capture the spatial distribution of temperatures both in axial and radial directions. The data and analysis are used to design a catalyst thermal model that can be used for model based catalyst temperature monitoring and control.

Holmer, Olov, Blomgren, Fredrik, Eriksson, Lars

High Load Expansion of Catalytic EGR-Loop Reforming under Stoichiometric Conditions for Increased Efficiency in Spark Ignition Engines

2019-01-02444/2/2019

The use of fuel reformate from catalytic processes is known to have beneficial effects on the spark-ignited (SI) combustion process through enhanced dilution tolerance and decreased combustion duration, but in many cases reformate generation can incur a significant fuel penalty. In a previous investigation, the researchers showed that, by controlling the boundary conditions of the reforming catalyst, it was possible to minimize the thermodynamic expense of the reforming process, and in some cases, realize thermochemical recuperation (TCR), a form of waste heat recovery where exhaust heat is converted to usable chemical energy. The previous work, however, focused on a relatively light-load engine operating condition of 2000 rpm, 4 bar brake mean effective pressure (BMEP). The present investigation demonstrates that this operating strategy is applicable to higher engine loads, including boosted operation up to 10 bar BMEP. By controlling the reforming catalyst boundary conditions, it is possible to achieve fuel reforming without experiencing high temperature exotherms that could be damaging to the catalyst. Additionally, the thermodynamic air handling consequences of operating a highly dilute strategy at high loads is quantified. The results confirm that this operating strategy provides an efficiency benefit at all conditions investigated, with relative efficiency increases of 3-6%, and is therefore applicable over wider regions of the engine operating map.

Szybist, James P., Pihl, Josh, Huff, Shean, Kaul, Brian

Review of Vehicle Engine Efficiency and Emissions

2019-01-03144/2/2019

This review paper covers major regulatory and technology developments in 2018 pertinent to tailpipe emissions of greenhouse gases and criteria pollutants. Europe has proposed ambitious reductions in CO2 limits for both light- and heavy-duty sectors. The challenge is compounded with changing measurement norms and a significant shift away from fuel efficient diesels in the light-duty (LD) space. Both incremental and step changes are being made to advance internal combustion. New studies show that in-use NOx emissions from diesels can be much lower than required by the Euro 6 regulation. Discussions have already started on Euro 7 regulations, and the leading regulatory concepts and proposed technical solutions are provided. In the heavy-duty (HD) sector, the progress is outlined in improving engine and vehicle fuel efficiency through the US Department of Energy’s (DOE’s) SuperTruck II program and other representative studies. Common approaches among the participants include hybridization, waste heat recovery, and both open- and closed cycle incremental improvements. Emissions control focus is on evaluating pathways to achieve California’s contemplated low-NOx standards, recently also supported by the US EPA through the Cleaner Trucks Initiative. The challenge is to reduce cold start and low load emissions, requiring innovative engine and after-treatment system solutions. Leading concepts include close-coupled SCR (selective catalytic reduction), use of passive NOx adsorbers, integration of SCR (selective catalytic reduction) on DPFs (diesel particulate filters), low temperature urea or ammonia injection, dual SCR, and active and passive thermal management to raise exhaust temperatures. Work is also underway on a new low load certification cycle. Continued advancement is made on after-treatment components. Aged three-way catalysts (TWCs) and diesel oxidation catalysts (DOCs) are nearing 90% conversion at 150 °C. SCR catalysts continue to improve both their low temperature conversion as well as high temperature durability. Particulate regulations in Europe, China and India are leading to widespread adoption of gasoline particulate filters (GPFs). Lean burn gasoline engines can offer significant fuel economy benefits. NOx control is a challenge, and passive SCR systems and new catalysts are proposed.

Joshi, Ameya

Optimized Driving Cycle Oriented Control for a Highly Turbocharged Gas Engine

2019-01-01934/2/2019

The article is focused on a 1-D drive dynamic simulation of a highly turbocharged gas engine. A mono fuel CNG engine has been developed as a downsized replacement of the diesel engine for a medium size van. The basic engine parameters optimization is provided in a steady state operation and a control adjustment is applied to a dynamic vehicle model for a transient response improvement in highly dynamic operation modes of the WLTC (world light duty test cycle), selected for investigation. Vehicle simulation model with optimized control system is used for driving cycle fuel consumption and CO2 emissions predictions compared with the basic engine settings.

Dolecek, Vit, Vavra, Jiri, Skarohlid, Marcel

Regeneration Strategies for Gasoline Particulate Filters

2019-01-09694/2/2019

Gasoline particulate filters (GPFs) are extremely effective at reducing tailpipe emissions of particulate mass and particulate number. Especially in the European and Chinese markets, where a particulate number standard is legislated, we see gasoline particulate filters being deployed in production on gasoline direct injected engines. Due to the high temperature in gasoline exhaust, most applications are expected to be passively regenerating without the help of an active regeneration strategy. However, for the few cases where a customer drive cycle has consistently low speed over a long time frame, an active regeneration strategy may be required. This involves increasing the exhaust temperature at the GPF up to around 600 degC so that soot can be combusted. We compare two different ways of achieving these temperatures, namely spark retard and air fuel ratio modulation. The former generates heat in the engine, the latter generates heat in one or more catalysts in the exhaust system. We list some benefits and drawbacks of both methods, and validate our work with experimental data.

Van Nieuwstadt, Michiel, Shah, Anil, Serban, Emil, Martin, Douglas

Towards Quantitative Prediction of Urea Thermo-Hydrolysis and Deposits Formation in Exhaust Selective Catalytic Reduction (SCR) Systems

2019-01-09924/2/2019

In order to assist in fast design cycle of Diesel engines selective catalytic reduction (SCR) exhaust systems, significant endeavor is currently being made to improve numerical simulation accuracy of urea thermo-hydrolysis. In this article, the achievements of a recently developed urea semi-detailed decomposition chemical scheme are assessed using three available databases from the literature. First, evaporation and thermo-hydrolysis of urea-water solution (UWS) single-droplets hanged on a thin thermocouple ring (127 μm) as well as on a thick quartz (275 μm), have been simulated at ambient temperature conditions ranging from 473K to 773K. It has been shown that the numerical results, in terms of evaporation rate and urea gasification, as well as droplet temperature history are very close to the experiments if the heat flux coming from the droplet support is properly accounted for. Indeed, an additional conduction flux has proved to be necessary in the evaporation model in order to account for the droplet heating coming from the support (i.e. thermocouple ring or quartz bead). This additional heat conduction flux has shown more critical for droplets suspended on a thick quartz. It is also argued that our detailed kinetic mechanism is able to ensure accurate thermal decompositions as long as the temperature inside the droplet is still nearly uniform. This assumption is shown to be true at low temperature and so, at low evaporation and thermo-hydrolysis rates. However, for high gas temperature, bubble nucleation near the support surface induces non-uniform temperature distribution.. This process makes accurate simulation of thermal decomposition extremely dependent on the local temperature inside such large suspended droplets. These results are also relevant and underline the modelling difficulties that we must tackle when it comes to studying the evaporation, boiling and thermolysis of liquid films and deposits on the exhaust walls. Next verification of the models has been carried out using UWS sprays injected in 6-m long pipe under typical Diesel engine exhaust manifold conditions. In this case, good agreement with experiments in terms of urea to ammonia (NH3) conversion efficiencies has been obtained under different temperatures and residence times. In addition, it proved that by-products (like solid biuret, Cyanuric acid and even ammelide) can be formed in the spray parcels upon water evaporation is completed during their travel to the exhaust catalyst inlet. These solid by-product particles may clog the catalyst inlet section.

Habchi, Chaouki, Quan, Shaoping, Drennan, Scott, Bohbot, Julien

Designing Self-Propelled, Chemically Active Sheets

TBMG-337092/1/2019

Researchers have created a two-dimensional, shape-changing sheet that moves autonomously in a reactant-filled fluid. The integrated system utilizes a chemical reaction to activate the fluid motion that simultaneously transports a flexible object and “sculpts” its shape, all occurring autonomously.

Model-Based Approaches in Developing an Advanced Aftertreatment System: An Overview

2019-01-00261/15/2019

Cummins has recently launched next-generation aftertreatment technology, the Single ModuleTM aftertreatment system, for medium-duty and heavy-duty engines used in on-highway and off-highway applications. Besides meeting EPA 2010+ and Euro VI regulations, the Single ModuleTM aftertreatment system offers 60% volume and 40% weight reductions compared to current aftertreatment systems. In this work, we present model-based approaches that were systematically adopted in the design and development of the Cummins Single ModuleTM aftertreatment system. Particularly, a variety of analytical and experimental component-level and system-level validation tools have been used to optimize DOC, DPF, SCR/ASC, as well as the DEF decomposition device. The highlights of this work can be summarized as follows: a). internal dosing is more efficient than external dosing to control HC slip; High CPSI DOCs show better HC oxidation performance at high SV due to enhanced mass transfer; b). the adopted advanced DPF technologies enable greater ash capacity for long maintenance intervals; c). SCR performance was optimized with the use of a hydrothermally robust Cu-Zeolite catalyst coated on high CPSI substrates.

Su, Changsheng, Brault, Joseph, Munnannur, Achuth, Liu, Z. Gerald, Milloy, Sean, Harinath, Arvind, Dunnuck, David, Federle, Ken

NOx-Conversion Comparison of a SCR-Catalyst Using a Novel Biomimetic Effervescent Injector on a Heavy-Duty Engine

2019-01-00471/15/2019

NOx pollution from diesel engines has been stated as causing over 10 000 pre-mature deaths annually and predictions are showing that this level will increase [1]. In order to decrease this growing global problem, exhaust after-treatment systems for diesel engines have to be improved, this is especially so for vehicles carrying freight as their use of diesel engines is expected to carry on into the future [2]. The most common way to reduce diesel engine NOx out emissions is to use SCR. SCR operates by injecting aqueous Urea solution, 32.5% by volume (AUS-32), that evaporates prior the catalytic surface of the SCR-catalyst. Due to a catalytic reaction within the catalyst, NOx is converted nominally into Nitrogen and Water. Currently, the evaporative process is enhanced by aggressive mixer plates and long flow paths. The mixer plates create extra exhaust back pressure and cool the exhaust gases, which decreases engine and catalyst efficiency, resulting in overall poor NOx conversion (<40%) and higher CO2 production under real life drive cycle conditions. To achieve future emission legislation targets, SCR efficiency has to be improved, especially under low catalyst temperature conditions. It should also be noted that Ammonia slip has to be avoided as it is now legislated against [3]. In this study a novel biomimetic effervescent aqueous urea injector, its design inspired by the natural spray phenomenon of the Bombardier Beetle, is used to compare against a market-leading aqueous urea doser in comparable exhaust conditions with and without aggressive mixer plates being installed. The novel biomimetic effervescent injector operates by increasing the temperature of the Urea solution inside a constant volume chamber to its saturated vapour pressure. At the required time of injection an electromagnetically controlled outlet valve opens exposing the now superheated fluid to lower pressure conditions, this results in a hot, effervescent spray being ejected which rapidly breaks up into very fine droplets (<20um) projected at high velocity (60m/s) into the exhaust stream targeted at the face of the SCR catalyst. The novel biomimetic effervescent injector shows great potential with a significant higher NOx conversion rate and lower ammonia slip compared to the market-leading doser on a heavy-duty engine.

Larsson, Peter, Ravenhill, Paul, Tunestal, Per

Investigation of an Advanced Combustion System for Stoichiometric Diesel to Reduce Soot Emissions

2019-01-00231/15/2019

Diesel engines are facing increased competition from gasoline engines in the light-duty and small non-road segments, primarily due to the high relative cost of emissions control systems for lean-burn diesel engines. Advancements in gasoline engine technology have decreased the operating cost advantage of diesels and the relatively high initial-cost disadvantage is now too large to sustain a strong business position. SwRI has focused several years of research efforts toward enabling diesel engine combustion systems to operate at stoichiometric conditions, which allows the application of a low-cost three-way catalyst emission control system which has been well developed for gasoline spark-ignited engines. One of the main barriers of this combustion concept is the result of high smoke emissions from poor fuel/air mixing. The current study focuses on improving the combustion system by investigating different fuel/air mixing strategies that enhance fuel spray - piston bowl interaction while simultaneously optimizing the fuel injection system. Computational Fluid Dynamics (CFD) simulations were carried out in conjunction with engine testing to evaluate different piston bowl designs as well as injector nozzle designs with reduced hole diameters to improve in-cylinder mixing and reduce spray over penetration. By using proposed combustion strategy, it was demonstrated that smoke emissions were reduced significantly from baseline under stoichiometric diesel operation.

Chase, Avery, Miwa, Jason, Abidin, Zainal, Cung, Khanh

Modeling of Aftertreatment Technologies to Meet a Future HD Low-NOx Standard

2019-01-00431/15/2019

The low-NOx standard for heavy duty trucks proposed by the California Air Resources Board represents a significant challenge to the engine and aftertreatment system. In this study, exhaust thermal management requirements were quantified using a combination of engine and aftertreatment modeling. First, a 1-D engine model was used to develop a control strategy capable of increasing the exhaust enthalpy and decreasing the engine-out NOx over the initial portion of the cold FTP cycle. The outputs from this model were then used as inputs to a 1-D model of a representative HD aftertreatment system. Several different passive exhaust thermal management technologies were evaluated with this aftertreatment system model, including insulating the downpipe, close-coupling the aftertreatment system, and reducing the thermal inertia of the DOC and DPF; the last option provides the most benefit to early NOx conversion. As an example of active exhaust thermal management, a model of a mini-burner was inserted into the system model; this device is able to raise the system temperature quickly, using less fuel than the engine control strategy. Lastly, early NH3 dosing and NH3 preloading on the SCR catalyst were examined; pre-loading would appear to be much more effective.

Harris, Thomas Miller, Gardner, Timothy

Piston Detergency and Anti-Wear Performance of Non-Phosphorus and Non-Ash Engine Oil

2019-01-00211/15/2019

The deposition of ash derived from engine oil on the surface of diesel particle filters (DPF) has recently been reported to degrade the performance of the DPF. It is generally known that phosphorus in engine oil is adsorbed on the surface of an automotive exhaust catalyst, reducing the performance of the catalyst. Thus, the amounts of ash and phosphorus in engine oil have been decreased. We have developed a non-phosphorus, non-ash engine oil (NPNA) that does not contain metal-based detergents or zinc dialkyldithiophosphate (ZnDTP). Various engine tests were performed, and we confirmed that under normal running conditions, the NPNA oil had a sufficiently high piston detergency and wear resistance-two important requirements for engine oil-to meet current American and Japanese standards. However, the piston detergency of NPNA required further improvement when engine running conditions were more severe. We performed a hot tube test to evaluate the piston detergency of NPNA at high temperatures and developed additives (ashless detergents) that did not contain ash (metallic elements). We then evaluated the piston detergency and valve train wear prevention of the improved NPNA. The tests were performed using two engines: one manufactured by Caterpillar Inc. and regulated by the guidelines of the American Society for Testing and Materials (ASTM) D6750, and one manufactured by Hino Motors, Ltd. and regulated by the Japanese Automotive Standards Organization (JASO) M354:2015. We confirmed that the improved NPNA possessed excellent piston detergency and provided outstanding valve train wear prevention.

Kasai, Moritsugu, Koshima, Hiroaki, Takashima, Yoriyuki

Optimization of Performance of Oxygen Storage Component (OSC) for NO Reduction in Three Way Catalysts to Achieve BS VI Emission Norms

2019-26-01331/9/2019

Current restrictions on environmental pollution worldwide has created the need for new methodologies and technology development which should not only ensure ultra-low emission level from different categories of engine but should also use less fuel resulting in lower carbon dioxide (CO2) emissions. The state-of-art technology to achieve ultra-low emissions placed after engine in exhaust line is a ‘catalytic converter’. Catalytic converter is an after treatment device which typically oxidizes or reduces the toxic pollutants emitted by any engine to carbon dioxide (CO2), nitrogen (N2) and water (H2O). Catalytic converters used in Gasoline / CNG operated vehicles contains oxygen storage component as a key component for supplying oxygen in rich mode of operation and the oxygen concentration release rate is function of gas concentration and air to fuel ratio (A/F) or lambda (λ). Conventionally, the vehicles (two wheelers) operated using mechanical method such as carburetor, a source for injection fuel in the engine and the lambda range produced from this method is of wide window (0.95-1.06). The catalyst located downstream the engine needs an optimum amount of oxygen storage component required to supply oxygen in rich mode of operation and excess oxygen concentration released during these period results in to a significant drop in oxygen storage capacity (OSC). The drop in OSC corresponds to drop in NOx conversion efficiency. Moving from BS IV to BS VI, the NOx conversion requirement is over 90% including deterioration factor limit and thus requires a tight control in terms of lambda as well as oxygen storage component optimization. The lambda control can be achieved by switching from mechanical method of injection to electronic method i.e. electronic fuel injection (EFI) and subsequently the need for oxygen storage component optimization is required. Illustrative case studies has been presented in this paper, to demonstrate the role of oxygen storage component in NOx conversion.

Kumar, Arvind, Rajan, Bosco, Harkonen, Matti, Trigunayat, Alok, Muthusamy, Vishnuvarthan, Mishra, Sushil

New Catalyst for Plastic Production Also Creates Hydrogen

TBMG-3339012/1/2018

Researchers have developed a new, low-cost catalyst for plastic production that turns a biorefinery product into a starting material for the synthesis of plastics, which could represent a sustainable alternative to widespread PET. At the same time, hydrogen can also be formed during the reaction.

Impact of Secondary Air Injection on Small Engine Motorcycle Intended for BS VI Applications

2018-32-006810/30/2018

On April 2020, India will move from Bharat Stage IV to Bharat Stage VI where the combined emission limit of Total Hydrocarbons (THC) and Nitrogen oxides (NOx) of 0.79g/km will independently reduce to 0.1g/km and 0.06g/km respectively. This reduction in emission limit however may prove to be challenging for small engines (below 200 cc) with the existing generation of engines predominantly in cold operating conditions. When the vehicle is started after soaking (engine turned off for few hours), considerable amount of THC emission is generated which can be attributed to poor fuel vaporization and incomplete combustion due to flame quenching in the combustion chamber. Also, the catalyst is inactive to chemical reactions until the accumulated heat energy from the hot exhaust mass flow elevates the catalyst temperature to facilitate efficient conversion of THC, CO and NOx to H2O, CO2 and N2. This temperature point is termed as catalyst light off temperature. Hence, most of the tail pipe emissions vented out to the atmosphere in cold phase is without after-treatment. In case of two wheelers on a typical drive cycle, around 60% (fig. 3) of the total tail pipe THC emitted is before the catalyst attains light off temperature. Thus, any form of exhaust gas treatment that can lead to reduction of pre-catalyst emissions and faster catalyst light off, will prove to be beneficial in overall emission reduction. In this context, Secondary Air injection (SAI) is explored as an effective exhaust treatment method in tackling cold phase emissions. In the present study, a series of tests were conducted on a single cylinder 200cc engine fitted with a Mechanical throttle body and electronic fuel injection system. From these tests, various aspects of cold phase emissions were characterized. This paper explores in detail the impact of SAI on pre-catalytic oxidation of THC, catalyst temperatures and catalytic reactions. Present study also gives an insight into the operation of SAI such that it does not compromise the functionality of the three way catalyst (TWC). It was also observed that it is beneficial to have different modes of SAI operation such as open loop mode without oxygen sensor feedback, closed loop mode with oxygen sensor feedback and engine load specific operation of SAI. Upon application of best optimal configuration of SAI a reduction of 25% in THC and 4% of NOx was observed.

Sabu, Abhijith, Reddemreddy, Pramod, Parmar, Manojkumar

Waste Frying Oil Conversion to Biodiesel in Presence of Advanced Alumina Heterogeneous Catalyst

2018-01-17509/10/2018

This paper reports experimental conversion of spent vegetable oil with bio-ethanol to long chain biodiesel fuel in presence of a new developed solid K3PO4 heterogeneous catalyst. Examined catalyst was synthesized following dipping impregnation of γ-Al2O3 solid support in an aqueous solution of potassium phosphate tri-basic K3PO4. K3PO4/γ-Al2O3 catalyst samples were distinguished based on their percentage loadings of K3PO4 (CK3PO4) and averaged particle size (dp). Produced catalyst samples were characterized in terms of their textural and surface properties using nitrogen adsorption-desorption isotherms and carbon dioxide & ammonia temperature programmed desorption techniques respectively. While the liquid phase of the product was analyzed using a GC-Mass spectroscopy technique. Ethanolysis runs were carried out following surface response methodology, central composite design (CCD). Parameters including catalyst percentage loading (CK3PO4), catalyst particle size (dp) as well as catalyst reactor weight (cat) were simulated the design factors. While percentage of ethyl ester yield (EEY%) was used as design response. Experimental results revealed an optimal measured EEY% of 92% achieved at 15:1 reactants molar ratio, 70 °C reaction temperature, 1000r.min−1 agitation speed, 25% percentage loading, 115 μm catalyst average particle size and 10 g/200 ml of catalyst weight in the reaction mixture. A high accuracy mathematical model was established for predicting the examined EEY% response results in terms of the above indicated operating parameters. Optimal EEY% of 95.43% was predicted under same operating conditions. The used catalyst was approved to be highly active, reliable and steady available solid heterogeneous catalyst that may promote the future of a more environmentally friendly biodiesel fuel.

Al-Zaini, Essam O., Abdullah, Ali A., Adesina, Adesoji

The Use of Ozone in Low Temperature Methane Control for Natural Gas Applications

2018-01-17029/10/2018

Lean operating natural gas heavy duty applications have advantages in terms of lower CO2 and PM compared to Diesel applications. This makes operating heavy duty applications on natural gas attractive and currently, they do not have to implement an exhaust particulate filter. However, the challenge is controlling methane emissions over a range of vehicle operating conditions. Methane is extremely stable and light off occurs at temperatures above 400 °C, with high efficiency occurring >500 °C and requires high precious metal loaded catalysts in the range of 150 - 200 g/ft3. Under stoichiometric conditions, 500 °C can be met in many engine operating points however, for lean operating applications, the exhaust temperature can be significantly lower than 500 °C posing a significant challenge for exhaust catalytic CH4 control. This paper will discuss synthetic gas reactor study results using ozone in the feed gas to perform low temperature methane control. A range of catalysts were characterised for the development of low temperature methane control and a non-precious metal catalyst was found to give high efficiency at low temperatures. The best catalyst screened did not contain PGM and was a current production catalyst that gave >60% CH4 control at 220 °C, in the presence of water. All other catalysts screened gave no significant methane control activity at low temperatures. The feed gas composition played a key role in the peak efficiency obtained. The data shows a significant improvement in ozone enhanced catalysis compared to more traditional precious metal based CH4 control routes.

Keenan, Matthew, Nicole, Jacques, Poojary, Damodara

Application of Genetic Algorithm for the Calibration of the Kinetic Scheme of a Diesel Oxidation Catalyst Model

2018-01-17629/10/2018

In this work, a methodology for building and calibrating the kinetic scheme for the 1D CFD model of a zone-coated automotive Diesel Oxidation Catalyst (DOC) by means of a Genetic Algorithm (GA) approach is presented. The methodology consists of a preliminary experimental activity followed by a modelling, optimization and validation process. The tested aftertreatment component presents zone coating, with the front brick side covered with Zeolites in order to ensure hydrocarbons trapping at low temperature, and Platinum Group Metal (PGM), while the rear brick side presents an alumina washcoat with a different PGM loading. Reactor scale samples representative of each coating zone were tested on a Synthetic Gas Bench (SGB), to fully characterize the component’s behavior in terms of Light-off and hydrocarbons (HC) storage for a wide range of inlet feed compositions and temperatures, representative of engine-out conditions. On the modeling side, a 1D-CFD model of the component was built in GT-SUITE environment and a global kinetic scheme was defined, based on the available literature, expressed in the Arrhenius form. A Genetic Algorithm optimization tool was then used to calibrate reaction rate parameters and active sites densities, by means of a sequential calibration strategy, categorizing the reaction model into several steps according to the experimental test protocol. In each step of the calibration, the number of independent variables was reduced as much as possible and the reactions could be isolated using primary single species tests, moving then to more complex gas mixtures to calibrate the mutual interaction of different species. The model was finally validated over experimental data, showing satisfactory predictive capabilities in terms of both light-off temperatures and oxidation rates, capturing the differences between different coating types as well. The presented methodology has revealed promising advancement in the modelling and calibration of aftertreatment components, showing that GA can be used for complex problems, such as the calibration of a global kinetic scheme, with an acceptable computational effort.

Millo, Federico, Rafigh, Mahsa, Sapio, Francesco, Barrientos, Eduardo J., Ferreri, Paolo

Polycyclic Aromatic Hydrocarbons in Diesel Engine Exhaust Both with and without Aftertreatment

2018-01-18129/10/2018

Since the conception of the internal combustion engine, smoky and ill-smelling exhaust was prevalent. Over the last century, significant improvements have been made in improving combustion and in treating the exhaust to reduce these effects. One group of compounds typically found in exhaust, polycyclic aromatic hydrocarbons (PAH), usually occurs at very low concentrations in diesel engine exhaust. Some of these compounds are considered carcinogenic, and most are considered hazardous air pollutants (HAP). Many methods have been developed for sampling, handling, and analyzing PAH. For this study, an improved method for dilute exhaust sampling was selected for sampling the PAH in diesel engine exhaust. This sampling method was used during transient engine operation both with and without aftertreatment to show the effect of aftertreatment. A total of 23 different PAH were measured using a 2012 medium-duty diesel engine equipped with a diesel oxidation catalyst (DOC), a diesel particulate filter (DPF), and a selective catalytic reduction (SCR) catalyst in series. The PAH were then analyzed by gas chromatography/mass (GC/MS) spectrometry to determine the individual concentrations for engine-out (without aftertreatment) and aftertreatment-out emissions. Concentrations for the engine-out PAH were significantly higher than when the aftertreatment was present. PAH in the exhaust were then compared to the PAH in the fuel.

Fanick, E. Robert, Kroll, Svitlana

Kinetic Measurements of HNCO Hydrolysis over SCR Catalyst

2018-01-17649/10/2018

To meet the strict emission regulations for diesel engines, an advanced processing device such as a Urea-SCR (selective catalytic reduction) system is used to reduce NOx emissions. The Real Driving Emissions (RDE) test, which is implemented in the European Union, will expand the range of conditions under which the engine has to operate [1], which will lead to the construction of a Urea-SCR system capable of reducing NOx emissions at lower and higher temperature conditions, and at higher space velocity conditions than existing systems. Simulations are useful in improving the performance of the urea-SCR system. However, it is necessary to construct a reliable NOx reduction model to use for system design, which covers the expanded engine operation conditions. In the urea-SCR system, the mechanism of ammonia (NH3) formation from injected aqueous urea solution is not clear. Thus, it is important to clarify this mechanism to improve the NOx reduction model. In particular, the investigation of the hydrolysis of isocyanic acid (HNCO), which is formed as an intermediate product in the process of NH3 formation from urea-water solution, is required. Although previous studies have reported the rate constant of HNCO hydrolysis, these were obtained from indirect rather than direct measurements of HNCO. In this study, the reaction rate of HNCO hydrolysis over Cu-ZSM5 catalyst was measured by generating high-purity HNCO and conducting high-precision HNCO measurements. The reaction rate of HNCO hydrolysis is used in the simulation of the urea-SCR system in order to construct a reliable NOx reduction model for system design.

Matsuoka, Masahiro, Kitamura, Takaaki, Obuchi, Akira, Tsuchida, Jun, Tanaka, Kotaro, Konno, Mitsuru

Effects of Clamping Force on the Operating Behavior of PEM Fuel Cell

2018-01-17189/10/2018

Proton exchange membrane (PEM) fuel cell is widely recognized as an outstanding portable power plant and expected to be possibly commercialization in the near future. As is well known, mechanical stresses implemented on the bipolar plates during the assembly procedure should have prominent influences on mass and heat transfer behavior inside the cell, as well as the resultant performance. In this study, an analytical model is proposed to comprehensively investigate the influence of clamping force on the mass transport, electrochemical properties and overall cell output capability of a PEM fuel cell. The results indicate that proper clamping force not only benefits the gas leakage prevention but also increases the contact area between the neighboring components to decrease the contact ohmic resistance. However, deformation always takes place simultaneously, changing the local physical structures of the cell components, which possibly leads to the decrement of porosity and permeability of the gas diffusion layer (GDL) and catalyst layer (CL), hinders the gas species and liquid water transport in GDL, and also decreases the cross-sectional flow area in the channel. The combined effect of the aforementioned factors finally contributes to the cell performance fluctuation. Moreover, although the contact resistance decreases with increasing stresses, more significant mass transfer losses, e.g. lower membrane water content and larger gradient in liquid saturation, results in more serious concentration voltage losses and weaker proton conductivity in the membrane, further impairing the cell voltage output. Therefore, cell performance should be optimized by the balancing among the transport properties and the contact resistance involved in the fuel cell. By using this analytical model, optimal cell design parameters and clamping pressure exerted on the fuel cell can be quickly predicted accordingly. Proper discussions are carried out and suggestions are proposed.

Chen, Rouxian, Qin, Yanzhou, Du, Qing, Peng, Jun

Effects of Soot Deposition on NOx Purification Reaction and Mass Transfer in a SCR/DPF Catalyst

2018-01-17079/10/2018

Experimental studies were carried out to investigate the effect of soot deposition on NOx purification phenomena in an ammonia selective catalytic reduction coated diesel particulate filter (SCR/DPF) catalyst. To study soot deposition effects on the chemical reactions and mass transfer, two types of testing device were used. A synthetic gas bench enabling tests to be conducted with temperature and flow rate ranges relevant to real driving conditions was used to investigate the soot influence on reduction of NOx to N2 (DeNOx). A micro-reactor that removed the effect of soot deposition on mass transfer in the catalyst layer was used to analyze chemical reactions on a soot surface and their interaction with the SCR catalyst. A filter test brick of a Cu-zeolite SCR/DPF catalyst and a powder catalyst were used for the synthetic gas bench and micro-reactor tests, respectively. Engine soot was sampled in all the tests. The synthetic gas bench results showed that soot deposition had a negative impact on NOx conversion performance. The micro-reactor results showed that NOx purification reactions took place simultaneously with side reactions, e.g., NH3 oxidation and NO2 related reactions, even when no SCR catalyst was present. Reactions on the soot surface decreased the NOx purification performance of the SCR catalyst. The influence of soot deposition on the reactivity of side reactions in the filter test brick showed the opposite effect to the powder catalyst: the former effect was intensified as the flow rate was increased. It was concluded that both the effect of reaction on the soot surface and the influence on mass transfer of soot deposition must be considered to describe the internal phenomena of NOx purification in a SCR/DPF catalyst.

Tsukamoto, Yoshihisa, Utaki, Shun, Zhang, Wencong, Fukuma, Takao, Kusaka, Jin

Recycling of the platinum of vehicle catalysts at end of life

2018-36-01069/3/2018

Due to the large number of end of life vehicles in our country, our work is aimed at recycling a very important material present in all cars, which is the platinum found in automotive catalysts. Platinum is a rare metal and high value-added, recovery from secondary sources is crucial to ensure its supply for various applications in the market, especially in regions with scarce resources. For this reason, the recycling of platinum, particularly of automotive catalysts becomes very important for the market. The methodology to be applied along the development of the work approaches from the characterization of the catalyst (by technical analysis of microscopy), recycling of platinum (by hydro-metallurgical processes), finally the tests and analysis of the recycled platinum, through physical tests, chemicals. Through the platinum recycling process, it is expected that an economically feasible form has been determined as well as the process method for platinum recycling, in addition to achieving a sample of recycled platinum with physical and chemical characteristics that provide for its reuse. However, the process of recycling platinum comes as an ecological alternative for the extraction, and through this research they propose a recycling method to return it to the market, suppressing its scarcity.

da Silva, Lucas Gonçalves, de Almeida, Rodolpho Faria Dias, Silva Faustino, Vinícius Marinho, Júnior, Pedro Américo Almeida Magalhãe

Passive Metal Hydride Module Concept for Enhanced Low-Temperature Catalyst Performance

2018-01-50015/4/2018

A technology concept applicable to stoichiometric and lean burn engine operation-a metal hydride (MHx) module for the generation of H2 via reaction with gaseous H2O-was evaluated for the introduction of low levels of H2 (ca. 500 ppmv) into internal combustion engine exhaust for the enhancement of catalyst performance at low temperatures, such as during cold-start. Projected MHx module packaging volume, replacement frequency, and costs over the lifetime of a light duty vehicle are excessive, and considered prohibitive to technology viability.

Bradford, Michael C.

The Development of Low Temperature Three-Way Catalysts for High Efficiency Gasoline Engines of the Future: Part II

2018-01-09394/3/2018

It is anticipated that future gasoline engines will have improved mechanical efficiency and consequently lower exhaust temperatures at low load conditions, although the exhaust temperatures at high load conditions are expected to remain the same or even increase due to the increasing use of downsized turbocharged engines. In 2014, a collaborative project was initiated at Ford Motor Company, Oak Ridge National Lab, and the University of Michigan to develop three-way catalysts with improved performance at low temperatures while maintaining the durability of current TWCs. This project is funded by the U.S. Department of Energy and is intended to show progress toward the USDRIVE target of 90% conversion of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx) at 150 °C after high mileage aging. The testing protocols specified by the USDRIVE ACEC team for stoichiometric S-GDI engines were utilized during the evaluation of experimental catalysts at all three facilities. This paper summarizes work performed at Ford on the development of a catalyst formulation with significantly lower lightoff temperatures than a current production TWC after aging on a high temperature 4-mode durability cycle. The new catalyst consists of rhodium post-impregnated onto an overlayer of titanium deposited onto a silica-stabilized Al2O3 support. A rhodium loading study revealed that the lowest T90 s after 4-mode aging were obtained with 0.5% Rh. A titanium loading study showed that that the best performance after 4-mode aging was obtained with 8% titanium, which corresponded to the monolayer coverage of titanium. TEM analysis confirmed that the titanium monolayer remained well dispersed after the high temperature aging. A fresh sample of the optimized catalyst was evaluated after sulfur poisoning and after a stoichiometric desulfation.

Theis, Joseph R., Getsoian, Andrew (Bean), Lambert, Christine K.

Solid Particle Number and Ash Emissions from Heavy-Duty Natural Gas and Diesel w/SCRF Engines

2018-01-03624/3/2018

Solid and metallic ash particle number (PN) and particulate matter (PM) mass emission measurements were performed on a heavy-duty (HD) on-highway diesel engine and a compressed natural gas (CNG) engine. Measurements were conducted under transient engine operation that included the FTP, WHTC and RMC. Both engines were calibrated to meet CARB ultra low NOX emission target of 0.02 g/hp-hr, a 90% reduction from current emissions limit. The HD diesel engine final exhaust configuration included a number of aftertreatement sub-systems in addition to a selective catalytic reduction filter (SCRF). The stoichiometric CNG engine final configuration included a closed coupled Three Way Catalyst (ccTWC) and an under floor TWC (ufTWC). The aftertreatment systems for both engines were aged for a full useful life (FUL) of 435,000 miles, prior to emissions testing. PM mass emissions from both engines were comparable and well below the US EPA emissions standard. However, the CNG engine emitted a substantially higher number of solid particles, larger and smaller than 25 nm in diameter, compared to the number of particles emitted from the HD diesel engine for each of the three transient cycles tested. The CNG engine metallic ash particle number emission was also much higher than that of the diesel. The stringent solid particle number regulation in the EU and China will address the CNG particle number emission problem. However, in the USA there is no such regulation to specifically address particle number emissions, which is a short coming. Ultrafine PN emissions from engines is a health concern. Reducing solid particle number emissions from old and new CNG engines to a level comparable to that of a diesel with DPF is an important task that needs to be addressed by policy makers around the globe.

Khalek, Imad A., Badshah, Huzeifa, Premnath, Vinay, Brezny, Rasto

Water Recovery from Gasoline Engine Exhaust for Water Injection

2018-01-03694/3/2018

Water injection (WI) can improve gasoline engine performance and efficiency, and on-board water recovery technology could eliminate the need for customers to refill an on-board water reservoir. In this regard, the technical feasibility of exhaust water recovery (EWR) is described in this paper. Water injection testing was conducted at a full load condition (5000 rpm/18.1 bar BMEP) and a high load condition (3000 rpm/14.0 bar BMEP) on a turbocharged gasoline direction injection (GTDI) engine. Water recovery testing was conducted both after the exhaust gas recirculation (EGR) cooler and after the charge air cooler (CAC) at a high load (3000 rpm/14.0 bar BMEP), as well as a part load (2080 rpm/6.8 bar BMEP) condition, at temperatures ca. 10-15 °C below the dew point of the flow stream. Three types of water separation designs were tested: a passive cyclone separator (CS), a passive membrane separator (MEM), and an active separator (AS). Water injection and recovery amount was also simulated on three different drive cycles: FTP, WLTP and US06. The results showed that using water injection at full load reduced fuel enrichment requirements and reduced knock, yielding a 13% fuel economy improvement. Engine testing at high load condition showed that WI had a negligible effect on three-way catalyst (TWC) conversion efficiency under stoichiometric conditions. EWR was shown to be effective both post EGR cooler and post CAC. The CS and AS showed better performance than the MEM separator for water recovery. With the CS, up to ~100% condensate separation efficiency was achieved with very low pressure drop (~1 kPa). All the condensate samples collected with low sulfur fuel showed near neutral pH levels (6.5-8.5). From the appearance of the condensate samples, MEM-collected water had better quality than the CS and AS collected water. Water collected after the CAC showed better quality and lower pH than that collected downstream of the EGR cooler. Water recovered from post-TWC EGR showed better quality and higher pH than that collected from pre-TWC EGR. Water injection and collection simulations on three different drive cycles using GT-Drive showed that more water could be collected than was required for injection on FTP and WLTP drive cycles, while 40~70% of required water for injection could be collected on the US06 cycle.

Sun, Yong, Fischer, Michael, Bradford, Michael, Kotrba, Adam, Randolph, Eric

Experimental and Kinetic Modeling of Degreened and Aged Three-way Catalysts: Aging Impact on Oxygen Storage Capacity and Catalyst Performance

2018-01-09504/3/2018

The aging impact on oxygen storage capacity (OSC) and catalyst performance was investigated on one degreened and one aged (hydrothermally aged at 955 °C for 50 h) commercial three-way catalyst (TWC) by experiments and modeling. The difference of OSC between the degreened and aged TWCs was dependent on catalyst temperature. The largest difference was found at 600 °C, at which the amount of OSC decreased by 45.5%. Catalyst performance was evaluated through lightoff tests at two simulated engine exhaust conditions (lean and rich) on a micro-reactor. The aging impact on the catalyst performance was different under lean and rich environments and investigated separately. At the lean condition, oxidation of CO and C3H6 was significantly suppressed while oxidation of C3H8 was relatively less degraded. At the rich condition, the inhibition effect was more pronounced on the aged TWC and inhibiting hydrocarbon species from C3H6 partial oxidation can survive at temperatures up to 450 °C. However, NO reduction activity declined less compared to CO and C3H6 oxidation. More NH3 formed at low temperature and N2O formation was suppressed on the aged TWC. A generic TWC model including a dual-site oxygen storage sub-model and PGM kinetics was developed to predict the aging impact on dynamic OSC and catalyst performance. The PGM kinetics include oxidation of H2, CO, and hydrocarbons as well as water-gas shift (WGS) and hydrocarbon steam reforming. NO reduction kinetics including N2O and NH3 formation and decomposition were also considered. The TWC models were calibrated on the degreened and aged TWCs separately based on experimental data. With the dual-site OSC model and calibrated kinetics, the dynamic OSC and lightoff performance on the fresh and aged TWCs were successfully predicted. The resulting changes of the OSC as well as lightoff performance due to aging were quantified and discussed with the help of the TWC models.

Gong, Jian, Wang, Di, Li, Junhui, Kamasamudram, Krishna, Currier, Neal, Yezerets, Aleksey

CFD Investigation of the Impact of Electrical Heating on the Light-off of a Diesel Oxidation Catalyst

2018-01-09614/3/2018

In the last years, as a response to the more and more restrictive emission legislation, new devices (SRC, DOC, NOx-trap, DPF) have been progressively introduced as standard components of modern after-treatment system for Diesel engines. In addition, the adoption of electrical heating is nowadays regarded with interest as an effective solution to promote the light-off of the catalyst at low temperature, especially at the start-up of the engine and during the low load operation of the engine typical of the urban drive. In this work, a state-of-the-art 48 V electrical heated catalyst is considered, in order to investigate its effect in increasing the abatement efficiency of a standard DOC. The electrical heating device considered is based on a metallic support, arranged in a spiral layout, and it is heated by the Joule effect due to the passage of the electrical current. As a result of the spiral arrangement, the distribution of the heat source on the heating section is not uniform, determining a certain spatial distribution of the temperature of the gas entering the DOC section. This has also an influence on the pollutant conversion, both in term of light-off time and overall conversion. In order to simulate the after-treatment system, a suitable CFD framework has been implemented on the basis of the open-source OpenFOAM code. In particular, it is based on a multi-region approach, where overlapping meshes, describing fluid and solid regions, are employed in order to model the presence of porous substrates. Specific models are implemented in order to couple fluid and solid regions in terms of heat-transfer and mass-transfer. Catalytic reaction model is introduced in order to describe the chemical surface reactions occurring on the washcoat of the porous substrate. The model is firstly validated resorting to experimental data. Then, it is applied for the investigation of the effects of the electrical heating on the pollutant abatement, with particular focus on the effects of the non-uniform temperature distribution related to different layouts of the heating spirals. The study points out the benefits related to the adoption of the electrical heating in terms of reduction of the overall pollutant emissions over the RDE cycle. Moreover, the effects of the non-uniform heating is investigated, showing a certain role in promoting the light-off of the reactions as a consequence of the formation of hot spots in the catalyst.

Della Torre, Augusto, Montenegro, Gianluca, Onorati, Angelo, Cerri, Tarcisio

Development of Three-Way Catalysts Enhanced NOx Purifying Activity

2018-01-09424/3/2018

Growing concerns about the depletion of raw materials as vehicle ownership continues to increase is prompting automakers to look for ways of decreasing the use of platinum-group metals (PGMs) in the exhaust systems. This research has developed a new catalyst with strong robustness against fluctuations in the exhaust gas and excellent nitrogen oxide (NOx) conversion performance. One of the key technologies is a new OSC material that has low surface area (SA) and high OSC performance. We enhanced the pyrochlore- ceria/zirconia (CZ) which has a very small SA. In order to enhance the heat resistance and promote the OSC reaction, we selected and optimized the additive element. This material showed high OSC performance especially in the temperature range of 400 degrees or less. Another key technology is washcoat structure that has high gas diffusivity by making connected pore in the washcoat (New pore forming technology). The connected pore means that some pores are connected each other unlike conventional structure which has isolated pores. Compared with the conventional washcoat structure, the new technology has high gas diffusivity. As a result, the developed catalyst showed high NOx purifying activity which enabled nearly 30% reduction of precious metal usage.

Chinzei, Isao, Saito, Yoshinori, Morikawa, Akira, Kato, Satoru, Ohashi, Tatsuya, Hirao, Tetsuhiro

Modelling of a Coupled Catalyst and Particulate Filter for Gasoline Direct Injection Engines

2018-01-09864/3/2018

There has been extensive research in the development of Gasoline Direct Injection ‘GDI’ engine exhaust systems with the aim of reducing engine-out emissions and meeting legislation requirements. Depending on the room available for packaging the exhaust system, the engine may be equipped with a single catalyst or two catalysts one close to the engine and another one located further downstream. With the strict particulate matter emission regulations of GDI engine, the engine has to be equipped with a Gasoline Particulate Filter ‘GPF’ in addition to the Closed Coupled Catalyst ‘CCC’. The common practice is to have the GPF further downstream the catalyst. In this paper, an assessment method is carried for a new design of a hot end exhaust system. The new design brings the GPF closer to ‘CCC’ to be packed in the same enclosure. The gas flow velocity and pressure distributions inside the exhaust system are identified using CFD for a uniform exhaust gas flow inlet conditions. The system also has been investigated considering a typical inlet exhaust gas flow conditions from a GDI engine turbocharger. Results showed that the new design offers better flow uniformity in both the catalyst and GPF. Moreover, lower pressure drop across the whole system is observed relative to the baseline design with the GPF separated from the catalyst through an intermediate exhaust pipe. The GPF enclosure end shape is found to have influence on the flow uniformity and pressure drop.

Cirstea, Remus, Abo-Serie, Essam F., Bastien, Christophe, Guo, Hua

Modelling the Variation in Precious Metal Dispersion in a Three Way Catalytic Converter after Aging

2018-01-09594/3/2018

With emission legislations becoming ever more stringent, there is an increased pressure on after-treatment systems and more specifically three-way catalysts. With recent developments in emission legislations, there is a requirement for more complex after-treatment systems and understanding of the aging process. Whilst the body of understanding on catalyst deactivation and, in particular, catalyst aging is growing, there are still significant gaps in understanding, particularly how real world variations in temperature, flow rate and gas concentrations affect catalyst behavior. Under normal driving conditions, the catalyst can experience varying oxygen concentrations, such as under heavy acceleration or cruising down a hill will show a variation in oxygen from the engine emissions. The effect that varying oxygen concentrations has on the rate of aging is not fully understood and hence the total deactivation and conversion efficiencies are not known throughout the catalyst lifetime. Traditionally, catalyst specification has relied heavily on catalyst testing over a wide range of mileage, with catalyst aging being conducted via vehicle/bench testing, focusing on 3 main parameters; flow (space velocity), temperature (inlet/bed) and lambda (oxygen concentration). The main drawback of this approach, particularly in the early stages of powertrain development, is the cost and resource required to conduct the testing. It is in this area of development that a kinetic model to predict the catalyst performance taking into account aging time, temperature, flow rate and exposure to oxygen concentration would be of great benefit. This paper presents a continuation of previous work into the investigation of the effect of varying oxygen concentration on the rate of catalyst aging. A number of commercially available palladium three-way catalysts were aged over a precise temperature cycle at varying oxygen concentrations for different aging times related back to a mileage. The results were analyzed in detail and fed into a catalyst model in which a built in optimizer calculated the initial pre-exponential and activation energy for characterization tests. Once optimized, the model then calculated the variation in dispersion for the catalysts aged under varying levels of oxygen at a range of set mileage. The variation in dispersion over aging is presented and compared with predictions based on the standard aging algorithm and with others proposed in literature.

Irwin, Kurtis, Douglas, Roy, Stewart, Jonathan David, Pedlow, Andrew, Woods, Andrew

Effects of NO _X Storage Component on Ammonia Formation in TWC for Passive SCR NO _X Control in Lean Gasoline Engines

2018-01-09464/3/2018

A prototype three-way catalyst (TWC) with NOX storage component was evaluated for ammonia (NH3) generation on a 2.0-liter BMW lean burn gasoline direct injection engine as a component in a passive ammonia selective catalytic reduction (SCR) system. The passive NH3 SCR system is a potential approach for controlling nitrogen oxides (NOX) emissions from lean burn gasoline engines. In this system, NH3 is generated over a close-coupled TWC during periodic slightly-rich engine operation and subsequently stored on an underfloor SCR catalyst. Upon switching to lean, NOX passes through the TWC and is reduced by the stored NH3 on the SCR catalyst. Adding a NOX storage component to a TWC provides two benefits in the context of a passive SCR system: (1) enabling longer lean operation by storing NOX upstream and preserving NH3 inventory on the downstream SCR catalyst; and (2) increasing the quantity and rate of NH3 production during rich operation. Since the fuel penalty associated with passive SCR NOX control depends on the fraction of time that the engine is running rich rather than lean, both benefits (longer lean times and shorter rich times achieved via improved NH3 production) will decrease the passive SCR fuel penalty. However, these benefits are primarily realized at low to moderate temperatures (300-500 °C), where the NOX storage component is able to store NOX, with little to no benefit at higher temperatures (>500 °C), where NOX storage is no longer effective. This study discusses engine parameters and control strategies affecting the NH3 generation over a TWC with NOX storage component.1

Prikhodko, Vitaly, Pihl, Josh, Toops, Todd, Parks, James

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