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Viewing 1 to 30 of 242
Technical Paper
2014-04-01
Michael D. Kass, Mark W. Noakes, Brian Kaul, Dean Edwards, Timothy Theiss, Lonnie Love, Ryan Dehoff, John Thomas
Abstract The performance of a 4cc two-stroke single cylinder glow plug engine was assessed at wide open throttle for speeds ranging from 2000 to 7000RPM. The engine performance was mapped for the stock aluminum head and one composed of titanium, which was printed using additive manufacturing. The engine was mounted to a motoring dynamometer and the maximum torque was determined by adjusting the fuel flow. Maximum torque occurred around 3000 to 3500RPM and tended to be higher when using the aluminum head. At slower speeds, the titanium head produced slightly higher torque. For each test condition, maximum torque occurred at leaner conditions for the titanium head compared to the stock aluminum one. Higher efficiencies were observed with the aluminum head for speeds greater than 3000RPM, but the titanium heads provided better efficiency at the lower speed points. The titanium head was equipped with an in-cylinder pressure sensor and the combustion performance was assessed at maximum torque for speeds of 4000, 6000, and 7000RPM.
Technical Paper
2014-04-01
Forrest Jehlik, Tim Laclair
Response surface methodology (RSM) techniques were applied to develop a predictive model of electric vehicle (EV) energy consumption over the Environmental Protection Agency's (EPA) standardized drive cycles. The model is based on measurements from a synthetic composite drive cycle. The synthetic drive cycle is a minimized statistical composite of the standardized urban (UDDS), highway (HWFET), and US06 cycles. The composite synthetic drive cycle is 20 minutes in length thereby reducing testing time of the three standard EPA cycles by over 55%. Vehicle speed and acceleration were used as model inputs for a third order least squared regression model predicting vehicle battery power output as a function of the drive cycle. The approach reduced three cycles and 46 minutes of drive time to a single test of 20 minutes. Application of response surface modeling to the synthetic drive cycle is shown to predict energy consumption of the three EPA cycles within 2.6% of the actual measured values.
Technical Paper
2014-04-01
Jan-Mou Li, David Smith
Abstract Driver is a key component in vehicle simulation. An ideal driver model simulates driving patterns a human driver may perform to negotiate road profiles. There are simulation packages having the capability to simulate driver behavior. However, it is rarely documented how they work with road profiles. This paper proposes a new truck driver model for vehicle simulation to imitate actual driving behavior in negotiating road grade and curvature. The proposed model is developed based upon Gipps' car-following model. Road grade and curvature were not considered in the original Gipps' model although it is based directly on driver behavior and expectancy for vehicles in a stream of traffic. New parameters are introduced to capture drivers' choice of desired speeds that they intend to use in order to negotiating road grade and curvature simultaneously. With the new parameters, the proposed model can emulate behaviors like uphill preparation for different truck drivers. Speed variation while cruising can be explained by the empirical model and therefore facilitating a better estimation of performance in vehicle simulation.
Technical Paper
2014-04-01
Jing Dong, Zhenhong Lin, Changzheng Liu, Yanghe Liu
Abstract This paper utilizes GPS tracked multiday travel activities to estimate the temporal distribution of electricity loads and assess battery electric vehicle (BEV) grid impacts at a significant market penetration level. The BEV load and non-PEV load vary by time of the day and day of the week. We consider two charging preferences: home priority assumes BEV drivers prefer charging at home and would not charge at public charging stations unless the state of charge (SOC) of the battery is not sufficient to cover the way back to home; and charging priority does not require drivers to defer charging to home and assumes drivers will utilize the first available charging opportunity. Both home and charging priority scenarios show an evening peak demand. Charging priority scenario also shows a morning peak on weekdays, possibly due to workplace charging. Assuming a significant percentage of the vehicle population in Seattle is displaced by BEVs, the BEV electricity demand is added to the non-PEV load.
Technical Paper
2014-04-01
Vitaly Y. Prikhodko, James E. Parks, Josh A. Pihl, Todd J. Toops
A commercial three-way catalyst (TWC) 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 low cost 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. NH3 generation was evaluated at different air-fuel equivalence ratios at multiple engine speed and load conditions. Near complete conversion of NOX to NH3 was achieved at λ=0.96 for nearly all conditions studied. At the λ=0.96 condition, HC emissions were relatively minimal, but CO emissions were significant. Operation at AFRs richer than λ=0.96 did not provide more NH3 yield and led to higher HC and CO emissions.
Technical Paper
2014-04-01
Adam Dempsey, Scott Curran, John Storey, Mary Eibl, Josh Pihl, Vitaly Prikhodko, Robert Wagner, James Parks
Abstract Low temperature combustion (LTC) has been shown to yield higher brake thermal efficiencies with lower NOx and soot emissions, relative to conventional diesel combustion (CDC). However, while demonstrating low soot carbon emissions it has been shown that LTC operation does produce particulate matter whose composition appears to be much different than CDC. The particulate matter emissions from dual-fuel reactivity controlled compression ignition (RCCI) using gasoline and diesel fuel were investigated in this study. A four cylinder General Motors 1.9L ZDTH engine was modified with a port-fuel injection system while maintaining the stock direct injection fuel system. The pistons were modified for highly premixed operation and feature an open shallow bowl design. RCCI operation was carried out using a certification grade 97 research octane gasoline and a certification grade diesel fuel. To study the particulate matter emissions from RCCI operation, particle size distributions were measured with a Scanning Mobility Particle Sizer (SMPS) and total particulate concentration in the exhaust was determined using membrane filters.
Technical Paper
2014-04-01
John Thomas, Shean Huff, Brian West
To quantify the fuel economy (FE) effect of some common vehicle accessories or alterations, a compact passenger sedan and a sport utility vehicle (SUV) were subjected to SAE J2263 coastdown procedures. Coastdowns were conducted with low tire pressure, all windows open, with a roof top or hitch-mounted cargo carrier, and with the SUV pulling an enclosed cargo trailer. From these coastdowns, vehicle dynamometer coefficients were developed which enabled the execution of vehicle dynamometer experiments to determine the effect of these changes on vehicle FE and emissions over standard drive cycles and at steady highway speeds. In addition, two minivans were subjected to coastdowns to examine the similarity in derived coefficients for two duplicate vehicles of the same model. The FE penalty associated with the rooftop cargo box mounted on the compact sedan was as high as 25-27% at higher speeds, where the aerodynamic drag is most pronounced. For both vehicles, use of a hitch mounted cargo tray carrying a similar load resulted in very small FE penalties, unlike the rooftop cargo box.
Technical Paper
2014-04-01
Zhenhong Lin, Jan-Mou Li, Jing Dong
Abstract This study attempts to establish a quantitative linkage between deployment of dynamic wireless power transfer (DWPT) and the market adoption of plug-in electric vehicles (PEV). This linkage can be useful for analyzing the societal benefits of DWPT and justifying investments in its research, development, demonstration and deployment. Spatial relationships between charging opportunity and DWPT availability are estimated for four metropolitan areas. The consumer value of DWPT is formulated as a function of key DWPT deployment parameters and then integrated into an existing validated consumer choice model, where sales of PEVs are endogenous. Results indicate significant impacts on PEV sales of DWPT deployment, even only at 0.5% of road length by 2050. Significant impact heterogeneity is observed. Larger impacts appear to be on battery electric vehicles (BEV) as opposed to plug-in hybrid electric vehicles (PHEV), on short-range BEVs as opposed to long-range ones, and on consumers with charging challenges, such as consumers without adequate home or workplace charging and consumers with high driving intensity.
Technical Paper
2014-04-01
John M. Storey, Sam Lewis, James Szybist, John Thomas, Teresa Barone, Mary Eibl, Eric Nafziger, Brian Kaul
Gasoline direct injection (GDI) engines can offer improved fuel economy and higher performance over their port fuel-injected (PFI) counterparts, and are now appearing in increasingly more U.S. and European vehicles. Small displacement, turbocharged GDI engines are replacing large displacement engines, particularly in light-duty trucks and sport utility vehicles, in order for manufacturers to meet more stringent fuel economy standards. GDI engines typically emit the most particulate matter (PM) during periods of rich operation such as start-up and acceleration, and emissions of air toxics are also more likely during this condition. A 2.0 L GDI engine was operated at lambda of 0.91 at typical loads for acceleration (2600 rpm, 8 bar BMEP) on three different fuels; an 87 anti-knock index (AKI) gasoline (E0), 30% ethanol blended with the 87 AKI fuel (E30), and 48% isobutanol blended with the 87 AKI fuel. E30 was chosen to maximize octane enhancement while minimizing ethanol-blend level and iBu48 was chosen to match the same fuel oxygen level as E30.
Technical Paper
2014-04-01
Michael D. Kass, Timothy Theiss, Steve Pawel, James Baustian, Les Wolf, Wolf Koch, Chris Janke
The compatibility of elastomeric materials used in fuel storage and dispensing applications was determined for test fuels representing neat gasoline and gasoline blends containing 10 and 17 vol.% ethanol, and 16 and 24 vol.% isobutanol. The actual test fuel chemistries were based on the aggressive formulations described in SAE J1681 for oxygenated gasoline. Elastomer specimens of fluorocarbon, fluorosilicone, acrylonitrile rubber (NBR), polyurethane, neoprene, styrene butadiene rubber (SBR) and silicone were exposed to the test fuels for 4 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 20 hours at 60°C and then remeasured for volume and hardness. Dynamic mechanical analysis (DMA) was also performed to determine the glass transition temperature (Tg). Comparison to the original values showed that all elastomer materials experienced volume expansion and softening when wetted by the test fuels. The fluorocarbons underwent the least amount of swelling (<25 %) while the SBR and silicone samples exhibited the highest level of expansion (>100%).
Technical Paper
2014-04-01
Michael D. Kass, Chris Janke, Timothy Theiss, Steve Pawel, James Baustian, Les Wolf, Wolf Koch
The compatibility of plastic materials used in gasoline storage and dispensing applications was determined for test fuels representing neat gasoline (Fuel C), and blends containing 25% ethanol (CE25a), 16% isobutanol (CiBu16a), and 24% isobutanol (CiBu24a). A solubility analysis was also performed and compared to the volume swell results obtained from the test fuel exposures. The plastic specimens were exposed to each test fuel for16 weeks at 60°C. After measuring the wetted volume and hardness, the specimens were dried for 65 hours at 60°C and then remeasured for volume and hardness. Dynamic mechanical analysis (DMA), which measures the storage modulus as a function of temperature, was also performed on the dried specimens to determine the temperature associated with the onset of the glass-to-rubber transition (Tg). For many of the plastic materials, the solubility analysis was able to predict the relative volume swell for each test fuel. Those plastic materials commonly used as permeation barriers exhibited the least amount of volume and hardness change (<5%) when exposed to the test fuels.
Technical Paper
2014-04-01
Krishna Kamasamudram, Ashok Kumar, Jinyong Luo, Neal Currier, Aleksey Yezerets, Thomas Watkins, Larry Allard
Abstract An operational challenge associated with SCR catalysts is the NH3 slip control, particularly for commercial small pore Cu-zeolite formulations as a consequence of their significant ammonia storage capacity. The desorption of NH3 during increasing temperature transients is one example of this challenge. Ammonia slipping from SCR catalyst typically passes through a platinum based ammonia oxidation catalyst (AMOx), leading to the formation of the undesired byproducts NOx and N2O. We have discovered a distinctive characteristic, an overlapping NH3 desorption and oxidation, in a state-of-the-art Cu-zeolite SCR catalyst that can minimize NH3 slip during temperature transients encountered in real-world operation of a vehicle. In this work we show new insights, gained from NH3 temperature programmed desorption and oxidation experiments, into the Cu-zeolite catalyst functions responsible for the overlap of NH3 desorption and oxidation characteristics and the impact of hydrothermal treatment on these functions.
Technical Paper
2014-04-01
Aaron Williams, Robert McCormick, Michael Lance, Chao Xie, Todd Toops, Rasto Brezny
Small impurities in the fuel can have a significant impact on the emissions control system performance over the lifetime of the vehicle. Of particular interest in recent studies has been the impact of sodium, potassium, and calcium that can be introduced either through fuel constituents, such as biodiesel, or as lubricant additives. In a collaboration between the National Renewable Energy Laboratory and the Oak Ridge National Laboratory, a series of accelerated aging studies have been performed to understand the potential impact of these metals on the emissions control system. This paper explores the effect of the rate of accelerated aging on the capture of fuel-borne metal impurities in the emission control devices and the subsequent impact on performance. Aging was accelerated by doping the fuel with high levels of the metals of interest. Three separate evaluations were performed, each with a different rate of accelerated aging. The aged emissions control systems were evaluated through vehicle testing and then dissected for a more complete analysis of the devices.
Technical Paper
2014-04-01
C. Scott Sluder, Brian H. West, Aron D. Butler, Arvon L. Mitcham, William J. Ruona
During the 1980s, the U.S. Environmental Protection Agency (EPA) incorporated the R factor into fuel economy calculations in order to address concerns about the impacts of test fuel property variations on corporate average fuel economy (CAFE) compliance, which is determined using the Federal Test Procedure (FTP) and Highway Fuel Economy Test (HFET) cycles. The R factor is defined as the ratio of the percent change in fuel economy to the percent change in volumetric heating value for tests conducted using two differing fuels. At the time the R-factor was devised, tests using representative vehicles initially indicated that an appropriate value for the R factor was 0.6. Reassessing the R factor has recently come under renewed interest after EPA's March 2013 proposal to adjust the properties of certification gasoline to contain significant amounts of ethanol. This proposed change will likely result in a significant deviation from the CAFE baseline test fuel heating value, and thus increased importance of the R factor.
Technical Paper
2014-04-01
Sujit Das
Advanced lightweight materials are increasingly being incorporated into new vehicle designs by automakers to enhance performance and assist in complying with increasing requirements of corporate average fuel economy standards. To assess the primary energy and carbon dioxide equivalent (CO2e) implications of vehicle designs utilizing these materials, this study examines the potential life cycle impacts of two lightweight material alternative vehicle designs, i.e., steel and aluminum of a typical passenger vehicle operated today in North America. LCA for three common alternative lightweight vehicle designs are evaluated: current production (“Baseline”), an advanced high strength steel and aluminum design (“LWSV”), and an aluminum-intensive design (AIV). This study focuses on body-in-white and closures since these are the largest automotive systems by weight accounting for approximately 40% of total curb weight of a typical passenger vehicle. Secondary mass savings resulting from body lightweighting are considered for the vehicles' engine, driveline and suspension.
Technical Paper
2014-04-01
Zhiming Gao, Tim J. LaClair, C. Stuart Daw, David E. Smith, Oscar Franzese
We present simulated fuel economy and emissions of city transit buses powered by conventional diesel engines and diesel-hybrid electric powertrains of varying size. Six representative city drive cycles were included in the study. In addition, we included previously published aftertreatment device models for control of CO, HC, NOx, and particulate matter (PM) emissions. Our results reveal that bus hybridization can significantly enhance fuel economy by reducing engine idling time, reducing demands for accessory loads, exploiting regenerative braking, and shifting engine operation to speeds and loads with higher fuel efficiency. Increased hybridization also tends to monotonically reduce engine-out emissions, but tailpipe (post-aftertreatment) emissions are affected by complex interactions between engine load and the transient catalyst temperatures, and the emissions results were found to depend significantly on motor size and details of each drive cycle.
Technical Paper
2014-01-15
Matthew Langholtz, Mark Downing, Robin Graham, Fred Baker, Alicia Compere, William Griffith, Raymond Boeman, Martin Keller
Lignin by-products from biorefineries has the potential to provide a low-cost alternative to petroleum-based precursors to manufacture carbon fiber, which can be combined with a binding matrix to produce a structural material with much greater specific strength and specific stiffness than conventional materials such as steel and aluminum. The market for carbon fiber is universally projected to grow exponentially to fill the needs of clean energy technologies such as wind turbines and to improve the fuel economies in vehicles through lightweighting. In addition to cellulosic biofuel production, lignin-based carbon fiber production coupled with biorefineries may provide $2,400 to $3,600 added value dry Mg−1 of biomass for vehicle applications. Compared to producing ethanol alone, the addition of lignin-derived carbon fiber could increase biorefinery gross revenue by 30% to 300%. Using lignin-derived carbon fiber in 15 million vehicles per year in the US could reduce fossil fuel consumption by 2-5 billion liters year−1, reduce CO2 emissions by about 6.7 million Mg year−1, and realize fuel savings through vehicle lightweighting of $700 to $1,600 per Mg biomass processed.
Article
2013-08-29
Scientists at the U.S. Department of Energy's Oak Ridge National Laboratory have developed a new oxygen "sponge" that can easily absorb or shed oxygen atoms at low temperatures. Materials with these novel characteristics would be useful in devices such as rechargeable batteries, sensors, gas converters, and fuel cells.
Article
2013-06-10
Oak Ridge National Laboratory (ORNL) is preparing to open a Vehicle Systems Integration Laboratory in July, with a focus on powertrain. Manufacturers will be able to test different designs under real-world conditions, which helps save time and cost. 
Article
2013-04-17
The lab runs fuel-economy tests with A/C on maximum vs. A/C "comfort level," A/C-off and with windows open and closed. Some results are surprising, including an unexpected "crossover" point in testing on a Toyota Corolla.
Technical Paper
2013-04-08
Zhiming Gao, C. Stuart Daw, David E. Smith
We summarize results from comparative simulations of hybrid electric vehicles with either stoichiometric gasoline or diesel engines. Our simulations utilize previously published models of transient engine-out emissions and models of aftertreatment devices for both stoichiometric and lean exhaust. Fuel consumption and emissions were estimated for comparable gasoline and diesel light-duty hybrid electric vehicles operating over single and multiple urban drive cycles. Comparisons between the gasoline and diesel vehicle fuel consumptions and emissions were used to identify potential advantages and technical barriers for diesel hybrids.
Technical Paper
2013-04-08
Brian West, C. Scott Sluder
Automobile manufacturers strive to minimize oil consumption from their engines due to the need to maintain emissions compliance over the vehicle life. Engine oil can contribute directly to organic gas and particle emissions as well as accelerate emissions degradation due to catalyst poisoning. During the Department of Energy Intermediate Ethanol Blends Catalyst Durability program, vehicles were aged using the Standard Road Cycle (SRC). In this program, matched sets of three or four vehicles were acquired; each vehicle of a set was aged on ethanol-free retail gasoline, or the same base gasoline blended with 10, 15, or 20% ethanol (E0, E10, E15, E20). The primary purpose of the program was to assess any changes in tailpipe emissions due to the use of increased levels of ethanol. Oil consumption was tracked during the program so that any measured emissions degradation could be appropriately attributed to fuel use or to excessive oil consumption. In addition, excessive oil consumption was used to help diagnose potential engine maintenance problems.
Technical Paper
2013-04-08
C. Stuart Daw, Zhiming Gao, David E. Smith, Tim J. Laclair, Josh A. Pihl, K. Dean Edwards
We compare the simulated fuel economy and emissions for both conventional and hybrid class 8 heavy-duty diesel trucks operating over multiple urban and highway driving cycles. Both light and heavy freight loads were considered, and all simulations included full aftertreatment for NOx and particulate emissions controls. The aftertreatment components included a diesel oxidation catalyst (DOC), urea-selective catalytic NOx reduction (SCR), and a catalyzed diesel particulate filter (DPF). Our simulated hybrid powertrain was configured with a pre-transmission parallel drive, with a single electric motor between the clutch and gearbox. A conventional heavy duty (HD) truck with equivalent diesel engine and aftertreatment was also simulated for comparison. Our results indicate that hybridization can significantly increase HD fuel economy and improve emissions control in city driving. However, there is less potential benefit for HD hybrid vehicles during highway driving. A major factor behind the reduced hybridization benefit for highway driving is that there are fewer opportunities to utilize regenerative braking.
Technical Paper
2013-04-08
James P. Szybist, Brian H. West
Ethanol is a very attractive fuel from an end-use perspective because it has a high chemical octane number and a high latent heat of vaporization. When an engine is optimized to take advantage of these fuel properties, both efficiency and power can be increased through higher compression ratio, direct fuel injection, higher levels of boost, and a reduced need for enrichment to mitigate knock or protect the engine and aftertreatment system from overheating. The ASTM D5798 specification for high level ethanol blends, commonly called “E85,” underwent a major revision in 2011. The minimum ethanol content was revised downward from 68 vol% to 51 vol%, which combined with the use of low octane blending streams such as natural gasoline introduces the possibility of a lower octane “E85” fuel. While this fuel is suitable for current “ethanol tolerant” flex fuel vehicles, this study experimentally examines whether engines can still be aggressively optimized for the resultant fuel from the revised ASTM D5798 specification.
Technical Paper
2013-04-08
Paul Chambon, Dean Deter, David Irick, David Smith
Plug-in hybrid electric vehicles (PHEV) operate predominantly as electric vehicles (EV) with intermittent assist from the engine. As a consequence, the engine can be subjected to multiple cold start events. These cold start events have a significant impact on tailpipe emissions due to degraded catalyst performance and starting the engine under less than ideal conditions. On current conventional vehicles, the first cold start of the engine dictates whether or not the vehicle will pass federal emissions tests. PHEV operation compounds this problem due to infrequent, multiple engine cold starts. ORNL, in collaboration with the University of Tennessee, developed an Engine-In-the-Loop (EIL) test platform to investigate cold start emissions on a 2.0l Gasoline Turbocharged Direct Injection (GTDI) Ecotec engine coupled to a virtual series hybrid electric vehicle. The end-goal of this project is to demonstrate the benefits of coordinating engine and powertrain supervisory control strategies to minimize cold start emissions.
Technical Paper
2013-04-08
Tsung-Yu Pan, Zhili Feng, Michael Santella, Jian Chen
Development of reliable magnesium (Mg) to steel joining methods is one of the critical issues in broader applications of Mg in automotive body construction. Ultrasonic spot welding (USW) has been demonstrated successfully to join Mg to steel and to achieve strong joints. In this study, corrosion test of ultrasonic spot welds between 1.6 mm thick Mg AZ31B-H24 and 0.8 mm thick galvanized mild steel, without and with adhesive, was conducted. Adhesive used was a one-component, heat-cured epoxy material, and was applied between overlapped sheets before USW. Corrosion test was conducted with an automotive cyclic corrosion test, which includes cyclic exposures of dipping in the 0.5% sodium chloride (NaCl) bath, a constant humidity environment, and a drying period. Lap shear strength of the joints decreased with the cycles of corrosion exposure. Good joint strengths were retained at the end of 30-cycle test. Failure mode of joints without adhesive was Mg nugget pull-out, but was interfacial failure of samples with adhesive.
Technical Paper
2013-04-08
Wei-Jen Lai, Jwo Pan, Zhili Feng, Michael Santella, Tsung-Yu Pan
Failure modes and fatigue behaviors of ultrasonic spot welds in lap-shear specimens of magnesium AZ31B-H24 and hot-dipped-galvanized mild steel sheets with and without adhesive are investigated. Ultrasonic spot welded, adhesive-bonded, and weld-bonded lap-shear specimens were made. These lap-shear specimens were tested under quasi-static and cyclic loading conditions. The ultrasonic spot weld appears not to provide extra strength to the weld-bonded lap-shear specimen under quasi-static and cyclic loading conditions. The quasi-static and fatigue strengths of adhesive-bonded and weld-bonded lap-shear specimens appear to be the same. For the ultrasonic spot welded lap-shear specimens, the optical micrographs indicate that failure mode changes from the partial nugget pullout mode under quasi-static and low-cycle loading conditions to the kinked crack growth mode under high-cycle loading conditions. For the adhesive-bonded lap-shear specimens, the optical micrographs indicate that failure mode changes from the cohesive failure mode near the interfaces under quasi-static and low-cycle loading conditions to the kinked crack growth mode under high-cycle loading conditions.
Technical Paper
2013-04-08
Seung Hoon Hong, Katherine Avery, Jwo Pan, Michael Santella, Zhili Feng, Tsung-Yu Pan
Failure mode and fatigue behavior of friction stir spot welds made with convex and concave tools in lap-shear specimens of dissimilar high strength dual phase steel (DP780GA) and hot stamped boron steel (HSBS) sheets are investigated based on experiments and a kinked fatigue crack growth model. Lap-shear specimens with the welds were tested under both quasistatic and cyclic loading conditions. Optical micrographs indicate that under both quasi-static and cyclic loading conditions, the welds mainly fail from cracks growing through the upper DP780GA sheets where the tools were plunged in during the welding processes. Based on the observed failure mode, a kinked fatigue crack growth model is adopted to estimate fatigue lives of the welds. In the kinked crack fatigue crack growth model, the stress intensity factor solutions for fatigue life estimations are based on the closed-form solutions for idealized spot welds in lap-shear specimens. The fatigue life estimations are reasonably in agreement with the experimental results under low-cycle loading conditions but lower than the experimental results under high-cycle loading conditions.
Technical Paper
2013-04-08
Jan-Mou Li, Zhiming Gao
It is rare for an attempt towards optimization at the fleet-level when consideration is given to the sheer number of seemingly unpredictable interactions among vehicles and infrastructure in congested urban areas. To close the gap, we introduce a simulation based framework to explore the impact of speed synchronization on fuel economy improvement for fleets in traffic. The framework consists of traffic and vehicle modules. The traffic module is used to simulate driver behavior in urban traffic; and the vehicle module is employed to estimate fuel economy. Driving schedule is the linkage between these two modules. To explore the impact, a connected vehicle technology sharing vehicle speed information is used for better fuel economy of a fleet including six vehicles. In all scenarios analyzed, the leading vehicle operates under the EPA Urban Dynamometer Driving Schedule (UDDS), while the other five vehicles follow the leader consecutively. Every follower in the fleet was governed by a driver behavior model and their desired speeds may be adjusted according to received speed information of the leading vehicle.
Technical Paper
2013-04-08
Brian Kaul, Robert Wagner, Johney Green
Operation of spark-ignition (SI) engines with high levels of charge dilution through exhaust gas recirculation (EGR) achieves significant engine efficiency gains while maintaining stoichiometric operation for compatibility with three-way catalysts. Dilution levels, however, are limited by cyclic variability - including significant numbers of misfires - that becomes more pronounced with increasing dilution. This variability has been shown to have both stochastic and deterministic components. Stochastic effects include turbulence, mixing variations, and the like, while the deterministic effect is primarily due to the nonlinear dependence of flame propagation rates and ignition characteristics on the charge composition, which is influenced by the composition of residual gases from prior cycles. The presence of determinism implies that an increased understanding of the dynamics of such systems could lead to effective control approaches that allow operation near the edge of stability, effectively extending the dilution limit.
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