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Fuel Consumption and Emission Reduction for Hybrid Electric Vehicles with electrically heated Catalyst

TU Dresden-Frank Atzler
TU Muenchen-Georg Wachtmeister
  • Technical Paper
  • 2020-37-0017
To be published on 2020-06-23 by SAE International in United States
Hybridization is a promising way to further reduce the CO2 emissions of passenger vehicles. However, high engine efficiencies and the reduction of engine load, due to torque assist by an electric motor, cause a decrease of exhaust gas temperature levels. This leads to an increased time to light-off of the catalysts resulting in an overall lower efficiency of the exhaust aftertreatment system. Especially in low load driving conditions, at cold ambient temperatures and on short distance drives, the tailpipe pollutant emissions are severely impacted by these low efficiency levels. To ensure lowest emissions at all driving conditions, catalyst heating methods must be used. In conventional vehicles internal combustion engine measures, e.g. late combustion can be applied. A hybrid system with an electrically heated catalyst enables further methods such as the increase of engine load, the so-called load point shifting by the electric motor or using the energy from the battery for electric catalyst heating. Since these methods result either directly or indirectly in additional fuel consumption there is a conflict of objectives between a fast…
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Impact of Thermal Management of the Three-Way Catalyst on the Energy Efficiency of a P2 Gasoline FHEV

Università del Salento-Marco Benegiamo, Andrea Valletta, Antonio Carlucci
Università di Roma Tor Vergata-Vincenzo Mulone
  • Technical Paper
  • 2020-37-0019
To be published on 2020-06-23 by SAE International in United States
Gasoline Full Hybrid Electric Vehicles (FHEVs) are recognized as a cost-effective solution to comply with upcoming emissions legislation. However, several studies have highlighted that frequent start-and-stops worsen the HC tail-pipe emissions, especially when the light-off temperature of the three-way catalyst (TWC) has not been reached. In fact, strategies only addressing the minimization of fuel consumption tend to delay engine activation and hence TWC warming, especially during urban driving. Goal of the present research is therefore to develop an on-line powertrain management strategy accounting also for TWC temperature, in order to reduce the time needed to reach TWC light-off temperature. A catalyst model is incorporated into the model of the powertrain where torque-split is performed by an adaptive equivalent consumption minimization strategy (A-ECMS). The developed A-ECMS operates on a domain of power-split combinations between electric machine and internal combustion engine, which, aside from satisfying the torque demand, also ensure a controlled ICE torque derivative as well as a controlled ICE start-and-stop frequency. Hence, the algorithm which is extended for TWC thermal management, incorporates a penalty on…
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Ammonia Measurement Investigation Using Quantum Cascade Laser and Two Different Fourier Transform Infrared Spectroscopy Methods

Caterpillar UK Ltd-Richard Barrett, Jim Baxter
Loughborough university-Nilton Li, Ashraf El-Hamalawi
  • Technical Paper
  • 2020-01-0365
To be published on 2020-04-14 by SAE International in United States
Most diesel engine exhausts have been fitted with SCR (Selective Catalyst Reduction) in order to reduce NOX (Oxides of Nitrogen) by using NH3 (ammonia). However, both NOX and NH3 have been classified as compounds hazardous for the environment and human health. If the reaction between NOX and NH3 is unbalanced during treatment, it can lead to either NOX or NH3 being released into the environment. Accurate measurement is thus necessary. QCL (Quantum Cascade Laser) and FTIR (Fourier Transform InfraRed) are two methods that have been used to measure NH3 and NOX directly in diesel engine exhausts. However, only a few studies have compared those two methods of NH3 measurement, mainly from diesel engine exhausts. The aim of this paper is to compare the QCL and 2 different FTIR specifications for NH3 measurement directly from diesel engine exhausts under well-controlled laboratory conditions. Researchers have found that as NH3 is reactive, it is absorbed inside the exhaust pipe if the probe location is some distance away from the SCR. The results reported here contradict this and show…
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Vehicle Emission Solutions for China 6b and Euro 7

Umicore AutoCat (China) Co., Ltd.-Gu Weiwei
Umicore Autocat (China) Co., Ltd.-Xiangwei Meng
  • Technical Paper
  • 2020-01-0654
To be published on 2020-04-14 by SAE International in United States
Combinations of CC1 TWC and CC2 coated gasoline particulate filters (cGPF) were aged by 4-mode and fuel cut aging to simulate 200K kilometers of in-use aging in China and Europe, respectively. Separate combinations of catalysts were then evaluated on two low emission engines using the WLTC driving cycle. Catalyst volume and PGM mass were varied in the CC1. OSC/washcoat amounts were varied at constant PGM loading in the GPF. For the Chinese application, after the four-mode aging, it was found that the CC1 TWC catalyst volume should be greater than 1.0 L. High levels of OSC were needed in the GPF to meet CO and NOx emission targets. For the European application, after fuel cut aging, Euro 6d emissions were met with any combination of TWC and GPF catalysts. If the gaseous regulations for Euro 7 are similar to China 6b, the CC1 TWC catalyst should also be great than 1.0 L in order to meet CO and NOx emissions. Over all, results imply that CC1 TWC design is most critical for gaseous emissions. More…
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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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Effect of Geometry Variation in a Polymer Electrolyte Membrane Fuel Cell

Siemens Digital Industries Software-Carlo Locci, Chris Lueth, Huong Nguyen, Karin Frojd
  • Technical Paper
  • 2020-01-1174
To be published on 2020-04-14 by SAE International in United States
Water transport at high current densities is of main concern for polymer electrolyte membrane (PEM) fuel cells. The water content of the membrane must be high enough to provide maximum electrical conductivity and thus optimal stack performance. Dry-out may also lead to membrane degradation. However, a too high level of humidity leads to cell flooding, blocking the air and fuel flows to the catalyst sites and thus the reactions, resulting in a drop-in efficiency. Fuel cells water transport physics requires further investigation due to its complexity [1,2] and numerical modelling can improve the fundamental understanding of the phenomena. In this work, a 3D comprehensive model for fuel cells is presented. The PEM fuel cell is modelled in Siemens Simcenter STAR-CCM+ [3]. Anode and cathode GDL are modelled as porous media, with electrochemical reactions calculated in an infinitely thin catalyst layer. The membrane is modelled as a solid block including proton and water transport with electro-osmotic drag as well as ohmic heating. A two-phase approach is used to model the gas mixture and liquid water transport…
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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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Ammonium Nitrate Formation and Decomposition on an Extruded Vanadium-Based SCR Catalyst

Cummins Emission Solutions-Nathan Ottinger, Yuanzhou Xi, Christopher Keturakis, Z. Gerald Liu
  • Technical Paper
  • 2020-01-1320
To be published on 2020-04-14 by SAE International in United States
In this study, the formation and decomposition of ammonium nitrate (AN) on a state-of-the-art extruded vanadium-based SCR catalyst (V-SCR) under simulated exhaust conditions has been evaluated. Results show that AN readily forms and accumulates at temperatures below 200°C when exposed to NH3 and NO2. The rate of AN accumulation increases with decreasing temperature. A new low temperature NH3 release peak (not present following NH3 storage conditions with NH3 only) becomes apparent after AN accumulation at 100 and 125°C. This new NH3 release, with a peak release temperature of approximately 180°C, is evaluated in detail to better determine its origin. BET surface area, and thermal gravimetric analysis/differential scanning calorimetry (TGA/DSC), and reactor-based experiments are all used to characterize AN formed on the V-SCR catalyst in comparison to pure AN. Experiments on pure AN crystals reveal that the new low temperature NH3 peak is attributable to the release of NH3 from AN that is not related to AN volatilization, since this does not occur until above T > 200°C.This study expands the present understanding of AN formation…
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Model Predictive Control of an Air Path System for Multi-Mode Operation in a Diesel Engine

Garrett Advancing Motion-Paul Dickinson, Jaroslav Pekar, MinSeok Ko
Hyundai Motor Group-Buomsik Shin, Yohan Chi, Minsu Kim
  • Technical Paper
  • 2020-01-0269
To be published on 2020-04-14 by SAE International in United States
A supervisory model predictive control system is developed for the air system of diesel engine. The diesel air system is complicated, composing of many components and actuators, with significant nonlinear behavior. Furthermore, the engine usually often operates in various modes, for example to activate catalyst regeneration like LNT or DPF. Model predictive control (MPC) is based on a dynamical model of the controlled system and it features predicted actuator path optimization. MPC has been previously successfully applied to the diesel air path control problem, however, most of these applications were developed for a single operating mode (often called normal operating mode) which has only one set of high-level set point values. In reality, each engine operating mode requires a different set of set point maps in order to meet the various system requirements such as, HP-EGR modes for cold start purposes, heat-up modes for after-treatment conditioning, rich operation for catalyst purging and normal modes. Air mass and its composition requirement are heavily depending on each specific mode. This large array of mode specific set points…
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Large-Scale Simulation of PEM Fuel Cell Using a “3D+1D” Model

Imperial College London-Yang Jiang
Tianjin University-Biao Xie, Guobin Zhang, Yan Yin, Qing Du, Kui Jiao
  • Technical Paper
  • 2020-01-0860
To be published on 2020-04-14 by SAE International in United States
Nowadays, proton exchange membrane (PEM) fuel cell is widely seen as a promising energy conversion device especially for transportation application scenario because of its high efficiency, low operation temperature and nearly-zero road emission. Extensive modeling work have been done based on different dimensions during the past decades, including one-dimensional (1D), two-dimensional (2D), three-dimensional (3D) and intermediate combinations in between (e.g. “1+1D”). 1D model benefits from a rationally-chosen set of assumptions to obtain excellent calculation efficiency, yet at the cost of accuracy to some extent. In contrast, 3D model has great advantage over 1D model on acquiring more comprehensive information inside the fuel cell. For macro-scale modeling work, one compromise aiming to realize both acceptable computation speed and reasonable reflection of cell operation state is to simplify the membrane electrode assembly (MEA). Therefore in this study, a “3D+1D” model is developed in which the 3D domain contains flow field and gas diffusion layer (GDL) of cathode side. The remaining part of MEA and the anode side are treated as 1D domain. The model considers two-phase flow…