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Technical Paper

Piston Bowl Geometry Effects on Combustion Development in a High-Speed Light-Duty Diesel Engine

2019-09-09
2019-24-0167
In this work we studied the effects of piston bowl design on combustion in a small-bore direct-injection diesel engine. Two bowl designs were compared: a conventional, omega-shaped bowl and a stepped-lip piston bowl. Experiments were carried out in the Sandia single-cylinder optical engine facility, with a medium-load, mild-boosted operating condition featuring a pilot+main injection strategy. CFD simulations were carried out with the FRESCO platform featuring full-geometric body-fitted mesh modeling of the engine and were validated against measured in-cylinder performance as well as soot natural luminosity images. Differences in combustion development were studied using the simulation results, and sensitivities to in-cylinder flow field (swirl ratio) and injection rate parameters were also analyzed.
Technical Paper

Developing a Real-World, Second-by-Second Driving Cycle Database through Public Vehicle Trip Surveys

2019-07-08
2019-01-5074
Real-world second-by-second vehicle driving cycle data is very important for vehicle research and development. A project solely dedicated to generating such information would be tremendously costly and time consuming. Alternatively, we developed such a database by utilizing two publicly available passenger vehicle travel surveys: 2004-2006 Puget Sound Regional Council (PSRC) Travel Survey and 2011 Atlanta Regional Commission (ARC) Travel Survey. The surveys complement each other - the former is in low time resolution but covers driver operation for over one year whereas the latter is in high time resolution but represents only one-week-long driving operation. After analyzing the PSRC survey, we chose 382 vehicles, each of which continuously operated for one year, and matched their trips to all the ARC trips. The matching is carried out based on trip distance first, then on average speed, and finally on duration.
Technical Paper

An Assessment of the Impact of Exhaust Turbine Redesign, for Narrow VGT Operating Range, on the Performance of Diesel Engines with Assisted Turbocharger

2019-04-02
2019-01-0326
Electrically assisted turbochargers are a promising technology for improving boost response of turbocharged engines. These systems include a turbocharger shaft mounted electric motor/generator. In the assist mode, electrical energy is applied to the turbocharger shaft via the motor function, while in the regenerative mode energy can be extracted from the shaft via the generator function, hence these systems are also referred to as regenerative electrically assisted turbochargers (REAT). REAT allows simultaneous improvement of boost response and fuel economy of boosted engines. This is achieved by optimally scheduling the electrical assist and regeneration actions. REAT also allows the exhaust turbine to operate within a narrow range of optimal vane positions relative to the unassisted variable geometry turbocharger (VGT). The ability to operate within a narrow range of VGT vane positions allows an opportunity for a more optimal turbine design for a REAT system.
Technical Paper

Regeneration Strategies for Gasoline Particulate Filters

2019-04-02
2019-01-0969
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.
Technical Paper

Using Artificial Ash to Improve GPF Performance at Zero Mileage

2019-04-02
2019-01-0974
Gasoline particulate filters (GPF) with high filtration efficiency (>80%) at zero mileage are in growing demand to meet increasingly tight vehicle emission standards for particulate matter being implemented in US, EU, China and elsewhere. Current efforts to achieve high filter performance mainly focus on fine-tuning the filter structure, such as the pore size distribution and porosity of the bare substrate, or the washcoat loading and location of catalyzed substrates. However, high filtration efficiency may have a cost in high backpressure that negatively affects engine power. On the other hand, it has been recognized in a few reports that very low amounts of ash deposits (from non-combustible residue in the exhaust) can significantly increase filtration efficiency with only a mild backpressure increase.
Technical Paper

Duct Shape Optimization Using Multi-Objective and Geometrically Constrained Adjoint Solver

2019-04-02
2019-01-0823
In the recent years, adjoint optimization has gained popularity in the automotive industry with its growing applications. Since its inclusion in the mainstream commercial CFD solvers and its continuously added capabilities over the years, its productive usage became readily available to many engineers who were previously limited to interfacing the customized adjoint source code with CFD solvers. The purpose of this work is to demonstrate using an adjoint solver a method to optimize duct shape that meets multiple design objectives simultaneously. To overcome one of the biggest challenges in the duct design, i.e. the severe packaging constraints, the method here uses geometrically constrained adjoint to ensure that the optimum shape always fits into the user-defined packaging space. In this work, adjoint solver and surface sensitivity calculations are used to develop the optimization method.
Technical Paper

EMI Coupling Mechanisms and Mitigations in a DC-DC Converter

2019-04-02
2019-01-0609
The EMI coupling mechanisms of a DC-DC converter in electrified vehicles are investigated for both conducted and radiated EMI. The noise sources and propagation paths are identified and quantified. The results show that the magnetic coupling between noise sources to some sensitive locations, including HV/LV terminals and CAN connector, can cause excessive emissions. The coupling between different components of the EMI filters may also lead to the degradation of the filter performances. Strategies are proposed to reduce the coupling, improve the filter performance and mitigate the emissions. The performances are verified in experiment.
Journal Article

Improved Analytically Derived CO2 Prediction of Medium Duty Chassis-Certified Vehicles

2019-04-02
2019-01-0311
Medium duty vehicles come in many design variations, which makes testing them all for CO2 impractical. As a result there are multiple ways of reporting CO2 emissions. Actual tests may be performed, data substitution may be used, or CO2 values may be estimated using an analytical correction. The correction accounts for variations in road load force coefficients (f0, f1, f2), weight, and axle ratio. The EPA Analytically Derived CO2 equation (EPA ADC) was defined using a limited set of historical data. The prediction error is shown to be ±130 g/mile and the sensitivities to design variables are found to be incorrect. Since the absolute CO2 is between 500 and 1,000 g/mi, the equation has limited usefulness. Previous work on light duty vehicles has demonstrated a linear relationship between vehicle fuel consumption, powertrain properties and total vehicle work. This relationship improves the accuracy and avoids co-linearity and non-orthogonality of the input variables.
Technical Paper

Impacts of WLTP Test Procedure on Fuel Consumption Estimation of Common Electrified Powertrains

2019-04-02
2019-01-0306
The new European test procedure, called the worldwide harmonized light vehicle test procedure (WLTP), deviates in some details from the current NEDC-based test which will have an impact on the determination of the official EU fuel consumption values for the new vehicles. The adaptation to the WLTP faces automakers with new challenges for meeting the stringent EU fuel consumption and CO2 emissions standards. This paper investigates the main changes that the new test implies to a mid-size sedan electrified vehicle design and quantifies their impact on the vehicles fuel economy. Three common electrified powertrain architectures including series, parallel P2, and powersplit are studied. A Pontryagin’s Minimum Principle (PMP) optimization-based energy management control strategy is developed to evaluate the energy consumption of the electrified vehicles in both charge-depleting (CD) and charge-sustaining (CS) modes.
Journal Article

Smart DPF Regenerations - A Case Study of a Connected Powertrain Function

2019-04-02
2019-01-0316
The availability of connectivity and autonomy enabled resources, within the automotive sector, has primarily been considered for driver assist technologies and for extending the levels of vehicle autonomy. It is not a stretch to imagine that the additional information, available from connectivity and autonomy, may also be useful in further improving powertrain functions. Critical powertrain subsystems that must operate with limited or uncertain knowledge of their environment stand to benefit from such new information sources. Unfortunately, the adoption of this new information resource has been slow within the powertrain community and has typically been limited to the obvious problem choices such as battery charge management for electric vehicles and efforts related to fuel economy benefits from adaptive/coordinated cruise control. In this paper we discuss the application of connectivity resources in the management of an aftertreatment sub-system, the Diesel Particulate Filter (DPF).
Technical Paper

Copper Effect on the Ultrasonic Fatigue Life of A356 Aluminum Alloy Under Variable Humidity Levels

2018-04-03
2018-01-1411
Ultrasonic fatigue tests (testing frequency around 20kHz) have been conducted on A356 aluminum alloys with different copper contents and AS7GU aluminum alloy. Tests were performed in dry air and submerged in water conditions. The effect of copper content was investigated and it was concluded that copper content plays an important role influencing the humidity effect on A356 aluminum alloy ultrasonic fatigue lives. Also, for the same copper content, copper in solute solution or in precipitate have different humidity sensitivities.
Technical Paper

Ion Current Measurement of Diluted Combustion Using a Multi-Electrode Spark Plug

2018-04-03
2018-01-1134
Close-loop feedback combustion control is essential for improving the internal combustion engines to meet the rigorous fuel efficiency demands and emission legislations. A vital part is the combustion sensing technology that diagnoses in-cylinder combustion information promptly, such as using cylinder pressure sensor and ion current measurement. The promptness and fidelity of the diagnostic are particularly important to the potential success of using intra-cycle control for abnormal cycles such as super knocking and misfiring. Many research studies have demonstrated the use of ion-current sensing as feedback signal to control the spark ignition gasoline engines, with the spark gap shared for both ignition and ion-current detection. During the spark glow phase, the sparking current may affect the combustion ion current signal. Moreover, the electrode gap size is optimized for sparking rather than measurement of ion current.
Technical Paper

Gasoline Particulate Filter Efficiency and Backpressure at Very Low Mileage

2018-04-03
2018-01-1259
The need for gasoline particulate filter (GPF) technology is expected to grow with increasingly tight particle emissions standards being implemented in US, EU, China and elsewhere. Derived from the successful experience with diesel particulate filters (DPF), GPFs adopted the characteristic alternately plugged honeycomb structure that provides a large area of porous cordierite wall for filtering particles with minimal additional backpressure. However, unlike DPFs, continuous soot regeneration in GPFs makes it difficult to grow and sustain the soot cake on the filter wall that gives DPFs their high filtration efficiency. Therefore, filtration performance of low mileage GPFs relies heavily on the porous structure of filter media, which depends on both the substrate and the applied washcoat. In this work, a blank, two fresh washcoated filters and two washcoated filters with 3000 km mileage accumulation were characterized to compare their filtration performance.
Technical Paper

Development of Wireless Message for Vehicle-to-Infrastructure Safety Applications

2018-04-03
2018-01-0027
This paper summarizes the development of a wireless message from infrastructure-to-vehicle (I2V) for safety applications based on Dedicated Short-Range Communications (DSRC) under a cooperative agreement between the Crash Avoidance Metrics Partners LLC (CAMP) and the Federal Highway Administration (FHWA). During the development of the Curve Speed Warning (CSW) and Reduced Speed Zone Warning with Lane Closure (RSZW/LC) safety applications [1], the Basic Information Message (BIM) was developed to wirelessly transmit infrastructure-centric information. The Traveler Information Message (TIM) structure, as described in the SAE J2735, provides a mechanism for the infrastructure to issue and display in-vehicle signage of various types of advisory and road sign information. This approach, though effective in communicating traffic advisories, is limited by the type of information that can be broadcast from infrastructures.
Journal Article

Benefits of Pd Doped Zeolites for Cold Start HC/NOx Emission Reductions for Gasoline and E85 Fueled Vehicles

2018-04-03
2018-01-0948
In the development of HC traps (HCT) for reducing vehicle cold start hydrocarbon (HC)/nitrogen oxide (NOx) emissions, zeolite-based adsorbent materials were studied as key components for the capture and release of the main gasoline-type HC/NOx species in the vehicle exhaust gas. Typical zeolite materials capture and release certain HC and NOx species at low temperatures (<200°C), which is lower than the light-off temperature of a typical three-way catalyst (TWC) (≥250°C). Therefore, a zeolite alone is not effective in enhancing cold start HC/NOx emission control. We have found that a small amount of Pd (<0.5 wt%) dispersed in the zeolite (i.e., BEA) can significantly increase the conversion efficiency of certain HC/NOx species by increasing their release temperature. Pd was also found to modify the adsorption process from pure physisorption to chemisorption and may have played a role in the transformation of the adsorbed HCs to higher molecular weight species.
Journal Article

Passive Hydrocarbon Trap to Enable SULEV-30 Tailpipe Emissions from a Flex-Fuel Vehicle on E85 Fuel

2018-04-03
2018-01-0944
Future LEV-III tailpipe (TP) emission regulations pose an enormous challenge forcing the fleet average of light-duty vehicles produced in the 2025 model year to perform at the super ultralow emission vehicle (SULEV-30) certification levels (versus less than 20% produced today). To achieve SULEV-30, regulated TP emissions of non-methane organic gas (NMOG) hydrocarbons (HCs) and oxygenates plus oxides of nitrogen (NOx) must be below a combined 30 mg/mi (18.6 mg/km) standard as measured on the federal emissions certification cycle (FTP-75). However, when flex-fuel vehicles use E85 fuel instead of gasoline, NMOG emissions at cold start are nearly doubled, before the catalytic converter is active. Passive HC traps (HCTs) are a potential solution to reduce TP NMOG emissions. The conventional HCT design was modified by changing the zeolite chemistry so as to improve HC retention coupled with more efficient combustion during the desorption phase.
Journal Article

Tier 2 Test Fuel Impact to Tier 3 Aftertreatment Systems and Calibration Countermeasures

2018-04-03
2018-01-0941
During the course of emissions and fuel economy (FE) testing, vehicles that are calibrated to meet Tier 3 emissions requirements currently must demonstrate compliance on Tier 3 E10 fuel while maintaining emissions capability with Tier 2 E0 fuel used for FE label determination. Tier 3 emissions regulations prescribe lower sulfur E10 gasoline blends for the U.S. market. Tier 3 emissions test fuels specified by EPA are required to contain 9.54 volume % ethanol and 8-11 ppm sulfur content. EPA Tier 2 E0 test fuel has no ethanol and has nominal 30 ppm sulfur content. Under Tier 3 rules, Tier 2 E0 test fuel is still used to determine FE. Tier 3 calibrations can have difficulty meeting low Tier 3 emissions targets while testing with Tier 2 E0 fuel. Research has revealed that the primary cause of the high emissions is deactivation of the aftertreatment system due to sulfur accumulation on the catalysts.
Journal Article

A New Catalyzed HC Trap Technology that Enhances the Conversion of Gasoline Fuel Cold-Start Emissions

2018-04-03
2018-01-0938
Passive in-line catalyzed hydrocarbon (HC) traps have been used by some manufacturers in the automotive industry to reduce regulated tailpipe (TP) emissions of non-methane organic gas (NMOG) during engine cold-start conditions. However, most NMOG molecules produced during gasoline combustion are only weakly adsorbed via physisorption onto the zeolites typically used in a HC trap. As a consequence, NMOG desorption occurs at low temperatures resulting in the use of very high platinum group metal (PGM) loadings in an effort to combust NMOG before it escapes from a HC trap. In the current study, a 2.0 L direct-injection (DI) Ford Focus running on gasoline fuel was evaluated with full useful life aftertreatment where the underbody converter was either a three-way catalyst (TWC) or a HC trap. A new HC trap technology developed by Ford and Umicore demonstrated reduced TP NMOG emissions of 50% over the TWC-only system without any increase in oxides of oxygen (NOx) emissions.
Technical Paper

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

2018-04-03
2018-01-0939
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.
Technical Paper

Impacts of Drive Cycle and Ambient Temperature on Modelled Gasoline Particulate Filter Soot Accumulation and Regeneration

2018-04-03
2018-01-0949
Gasoline particulate filters (GPF) are used as an efficient solution to reduce particulate matter (PM) emissions on gasoline vehicles. GPFs are ceramic wall-flow filters and are normally located downstream of conventional three-way catalysts (TWC) [1]. The study in this paper is intended to evaluate the impact of drive cycle and ambient temperature on modelled GPF soot accumulation and regeneration. The test data were obtained through real road testing in Chinese cities including Nanjing, Hainan and Harbin. Five 2.0 L gasoline turbo direct-injection (GTDI) prototype vehicles from several China Stage 6 applications were employed for the road tests. The results of the testing indicated that a drive cycle with low engine speed and engine load, like a typical city road in rush hour traffic in Nanjing, had a low probability of generating high GPF temperatures (> 600 °C) and sufficient oxygen to regenerate the GPF.
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