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Sensitivity Study on Thermal and Soot Oxidation Dynamics of Gasoline Particulate Filters

Stanford University-Aki Takahashi, Slava Korneev, Simona Onori
Published 2019-04-02 by SAE International in United States
Gasoline particulate filters (GPFs) are devices used to filter soot emitted by gasoline direct injection (GDI) engines.A numerical model for a ceria-coated GPF presented in a previous paper by H. Arunachalam et al. in 2017 was developed to predict internal temperature and soot amount combusted during regeneration events. Being that both the internal temperature and the accumulated soot cannot be directly measured during real-time operation and owing to their critical importance for GPF health monitoring as well as regeneration scheduling, the above model turns out to be a valuable tool for OBD applications. In this paper, we first conduct a stochastic analysis to understand the relation between the model parameters and the initial value of the ceria (IV) oxide volume fraction, as a deterministic value for such a state is not known. A particle swarm optimization (PSO) algorithm was employed to define what type of relationship the model parameters were with respect to the initial state of the ceria (IV) oxide volume fraction. A sensitivity study is then conducted over the model parameters to study…
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Realizing Stoichiometric, Natural Gas-Fueled Combustion in Diesel Engines

Stanford University-Nathaniel Oliver, Chris Edwards
Published 2018-04-03 by SAE International in United States
For high-load applications, natural gas represents a clean burning, readily available, and relatively inexpensive alternative to number 2 Diesel fuel. However, the fuel’s poor ignitability has previously limited implementation to spark ignited and dual-fueled engines. These approaches suffer from reduced peak load and high engine-out particulate emissions, respectively, requiring lean operation and expensive aftertreatment to meet regulatory standards. A high-temperature combustion strategy can overcome the difficult ignitibility, allowing for true Diesel-style combustion of pure methane-the least ignitable and least sooting component of natural gas. In order to achieve this result, a compression system was designed to supply fuel at pressures suitably high to achieve good mixing and short injection durations, and a solenoid-actuated Diesel fuel injector was modified to function at these pressures with a gaseous fuel. This fuel supply system was paired with a single-cylinder research engine equipped with an insulated piston face. An intake preheat temperature of 250 °C was shown to provide the best combination of ignition delay and engine performance. A sweep of equivalence ratio then demonstrated soot emissions close to or…
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Improving Fuel Economy of Thermostatic Control for a Series Plugin-Hybrid Electric Vehicle Using Driver Prediction

Stanford University-Michael Ryan Mallory
University of Washington-Brian Magnuson, Brian Fabien, Ajay Gowda
Published 2016-04-05 by SAE International in United States
This study investigates using driver prediction to anticipate energy usage over a 160-meter look-ahead distance for a series, plug-in, hybrid-electric vehicle to improve conventional thermostatic powertrain control. Driver prediction algorithms utilize a hidden Markov model to predict route and a regression tree to predict speed over the route. Anticipated energy consumption is calculated by integrating force vectors over the look-ahead distance using the predicted incline slope and vehicle speed. Thermostatic powertrain control is improved by supplementing energy produced by the series generator with regenerative braking during events where anticipated energy consumption is negative, typically associated with declines or decelerations. Matlab and Simulink (Colgren, 2007) are used both to run the prediction and optimization algorithms as well as simulate a rear-wheel drive, series plug-in, hybrid-electric vehicle, a city road-network, and multiple simulated vehicle drivers each with different driving characteristics. Initial results show an improvement of 8.4% in petroleum energy consumption over a non-predictive thermostatic propulsion controller.
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From Trolley to Autonomous Vehicle: Perceptions of Responsibility and Moral Norms in Traffic Accidents with Self-Driving Cars

Stanford University-Jamy Li, Mu-Jung Cho, Wendy Ju
Brown University-Xuan Zhao, Bertram F. Malle
Published 2016-04-05 by SAE International in United States
Autonomous vehicles represent a new class of transportation that may be qualitatively different from existing cars. Two online experiments assessed lay perceptions of moral norms and responsibility for traffic accidents involving autonomous vehicles. In Experiment 1, 120 US adults read a narrative describing a traffic incident between a pedestrian and a motorist. In different experimental conditions, the pedestrian, the motorist, or both parties were at fault. Participants assigned less responsibility to a self-driving car that was at fault than to a human driver who was at fault. Participants confronted with a self-driving car at fault allocated greater responsibility to the manufacturer and the government than participants who were confronted with a human driver at fault did. In Experiment 2, 120 US adults read a narrative describing a moral dilemma in which a human driver or a self-driving car must decide between either allowing five pedestrians to die or taking action to hit a single pedestrian in order to save the five. The “utilitarian” decision to hit the single pedestrian was considered the moral norm for…
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Exploring Transitional Automation with New and Old Drivers

Stanford University-David Miller, Mishel Johns, Hillary Page Ive, Nikhil Gowda, David Sirkin, Srinath Sibi, Brian Mok, Wendy Ju
Ford Motor Company-Sudipto Aich
Published 2016-04-05 by SAE International in United States
Age and experience influence driver ability to cope with transitions between automated and manual driving, especially when drivers are engaged in media use. This study evaluated three age cohorts (young/new drivers, adults, and seniors) on their performance in transitions from automated driving to manual vehicle control in a laboratory driving simulator. Drivers were given three tasks to perform during the automated driving segments: to watch a movie on a tablet, to read a story on a tablet, or to supervise the car's driving. We did not find significant differences in people's driving performance following the different tasks. We also did not find significant differences in driving performance between the people in each age group who successfully completed the study; however, the rejection rate of the senior age group was over 30% because many of the people in this age group had difficulty hearing instructions, understanding tasks, or remembering what to do. We also observed pronounced differences in typical driving behaviors between groups which designers of automated systems need to take into account.
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Exploring the Pathway to High Efficiency IC Engines through Exergy Analysis of Heat Transfer Reduction

SAE International Journal of Engines

Stanford University-Bernard Johnson, Chris Edwards
  • Journal Article
  • 2013-01-0278
Published 2013-04-08 by SAE International in United States
Heat transfer is one of the largest causes of exergy destruction in modern engines. In this paper, exergy distribution modeling was used to determine the potential of reduced engine heat transfer to provide significant gains in engine efficiency. As known from prior work, of itself, reducing heat transfer creates only a small increase in efficiency-most of the exergy is redirected into the exhaust stream-requiring both mechanical and thermal recovery of the exhaust exergy. Mechanical regeneration, through turbocharging and over-expansion, can lead to efficiencies exceeding 50%. Adding thermal regeneration, through high enthalpy steam injection or a bottoming cycle, can increase the efficiency potential to approximately 60%. With implementation of both mechanical and thermal regeneration, the only remaining cause of substantial exergy destruction is the combustion process. Thus, efficiency gains significantly beyond 60% are only possible by reducing the entropy generated in the fuel conversion process.
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Multi-Dimensional Flamelet Modeling of Multiple Injection Diesel Engines

Stanford University-Eric M. Doran, Heinz Pitsch
Robert Bosch LLC-David J. Cook
Published 2012-04-16 by SAE International in United States
To enable the modeling of modern diesel engines, this work furthers the development of multi-dimensional flamelet models for application to designs that employ multiple injection strategies. First, the flamelet equations are extended to two dimensions following the work of Hasse and Peters [1] and Doran et al. [2] and a method of coupling the resulting equations interactively to a turbulent flow simulation for use in unsteady calculations is described. The external parameters required to solve the flamelet equations are the scalar dissipation rates. In previous studies, the dissipation rates of each mixture fraction have been scaled according to their realizable bounds and the cross-dissipation rate between mixture fractions has been neglected. In this work, new models for the scalar dissipation rate of each mixture fraction in a two-dimensional space are introduced along with a method for obtaining the cross-dissipation rate, the role of which in obtaining a general representation of three stream mixing is further discussed. The model framework is then applied to a split-injection diesel engine over a range of operating conditions and exhaust…
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Crank-angle-resolved Measurements of Air-fuel Ratio, Temperature, and Liquid Fuel Droplet Scattering in a Direct-injection Gasoline Engine

Stanford University-Jay B. Jeffries, Jason M. Porter, Sung Hyun Pyun, Ronald K. Hanson
Nissan Motor Co., Ltd.-Kevin R. Sholes, Kiyotaka Shouji, Tomohiro Chaya
Published 2010-10-25 by SAE International in United States
Simultaneous crank-angle-resolved measurements of gasoline vapor concentration, gas temperature, and liquid fuel droplet scattering were made with three-color infrared absorption in a direct-injection spark-ignition engine with premium gasoline. The infrared light was coupled into and out of the cylinder using fiber optics incorporated into a modified spark plug, allowing measurement at a location adjacent to the spark plug electrode. Two mid-infrared (mid-IR) laser wavelengths were simultaneously produced by difference-frequency-generation in periodically poled lithium niobate (PPLN) using one signal and two pump lasers operating in the near-infrared (near-IR). A portion of the near-IR signal laser residual provided a simultaneous third, non-resonant, wavelength for liquid droplet detection. This non-resonant signal was used to subtract the influence of droplet scattering from the resonant mid-IR signals to obtain vapor absorption signals in the presence of droplet extinction.The sensor was applied to a direct-injection engine in both early-injection homogeneous charge and late-injection stratified charge operation. For the early-injection cases, liquid droplets were detected only during a brief period of the intake stroke just after start of injection. Late in the…
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Quantifying the Fuel Consumption Penalties for an Operational Contrail Avoidance System

Stanford University-Emily Schwartz
Boeing Commercial Airplanes-Steven L. Baughcum, David L. Daggett
Published 2009-11-10 by SAE International in United States
Recent work has shown that when an aircraft encounters ambient ice-supersaturated conditions (where contrails may form and persist), it may be possible to avoid contrail formation by shifting cruise altitude up or down 2000 feet. If an aircraft's cruise altitude is shifted from the optimal profile during a portion of the mission, fuel consumption increases. Because on average approximately 20% of distance flown by commercial airliners is through ice-supersaturated regions, this study quantifies the fuel burn penalties for the notional scenario of flying the same fraction of cruise at altitude displacements of +2000, -2000, and -4000 ft. Present aircraft performance data was used to generate accurate fuel burn penalty estimates.This study finds that the net penalties for existing aircraft to fly contrail avoidance shifts vary between 0.2% and 0.7% increase in block fuel consumption. The magnitude of the fuel penalty can be reduced by approximately 0.25% by slowing down during the shifted segment. Further reductions are attainable for future aircraft with application of engine and aerodynamic technology intended to improve off-design performance. This suggests that…
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A Multi-dimensional Flamelet Model Framework Applied to Split-injection DI Diesel Engines

Stanford University-Eric Doran, Heinz Pitsch
Robert Bosch LLC-David J. Cook
Published 2009-06-15 by SAE International in United States
A general model framework for investigating various injection strategies in compression ignition engines with both mixture and thermal inhomogeneities is presented using an extended representative interactive flamelet model. The equations describing evolution of chemistry are written for a scalar phase space of either one or two dimensions and an approach for modeling multiple injections is given. The combustion model is solved interactively with the turbulent flow field by coupling with a Reynolds-Averaged Navier-Stokes (RANS) solver. The model is applied in the simulation of a split-injection diesel engine and results are compared to experimental data obtained from a single cylinder research engine.
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