Matthew Thornton

Using Global Positioning System Travel Data to Assess Real-World Energy Use of Plug-In Hybrid Electric Vehicles

Plug-in hybrid electric vehicles (PHEVs) have received considerable recent attention for their potential to reduce petroleum consumption significantly and quickly in the transportation sector. Analysis to aid the design of such vehicles and predict their real-world performance and fuel displacement must consider the driving patterns the vehicles will typically encounter. This paper goes beyond consideration of standardized certification cycless by leveraging state-of-the-art travel survey techniques that use Global Positioning System (GPS) technology to obtain a large set of real-world drive cycles from the surveyed vehicle fleet. This study specifically extracts 24-h, second-by-second driving profiles from a set of 227 GPS-instrumented vehicles in the St. Louis, Missouri, metropolitan area. The performance of midsize conventional, hybrid electric, and PHEV models is then simulated over the 227 full-day driving profiles to assess fuel consumption and operating characteristics of these vehicle technologies over a set of real-world usage patterns. In comparison to standard cycles used for certification procedures, the travel survey duty cycles include significantly more aggressive acceleration and deceleration events across the velocity spectrum, which affect vehicle operation and efficiency. Even under these more aggressive operating conditions, PHEVs using a blended charge-depleting energy management strategy consume less than 50% of the petroleum used by similar conventional vehicles. Although true prediction of the widespread real-world use of these vehicles requires expansion of the vehicle sample size and a refined accounting for the possible interaction of several variables with the sampled driving profiles, this study demonstrates a cutting-edge use of available GPS travel survey data to analyze the (highly drive cycle–dependent) performance of advanced technology PHEVs. This demonstration highlights new opportunities for using innovative GPS travel survey techniques and sophisticated vehicle system simulation tools to guide vehicle design improvements and to maximize the benefits offered by energy efficiency technologies.

Technology Improvement Pathways to Cost-effective Vehicle Electrification

Electrifying transportation can reduce or eliminate dependence on foreign fuels, emission of green house gases, and emission of pollutants. One challenge is finding a pathway for vehicles that gains wide market acceptance to achieve a meaningful benefit. This paper evaluates several approaches aimed at making plug-in electric vehicles (EV) and plug-in hybrid electric vehicles (PHEVs) cost-effective including opportunity charging, replacing the battery over the vehicle life, improving battery life, reducing battery cost, and providing electric power directly to the vehicle during a portion of its travel. Many combinations of PHEV electric range and battery power are included. For each case, the model accounts for battery cycle life and the national distribution of driving distances to size the battery optimally. Using the current estimates of battery life and cost, only the dynamically plugged-in pathway was cost-effective to the consumer. Significant improvements in battery life and battery cost also made PHEVs more cost-effective than todays hybrid electric vehicles (HEVs) and conventional internal combustion engine vehicles (CVs).

Impacts of Biodiesel Fuel Blends Oil Dilution on Light-Duty Diesel Engine Operation

Assesses oil dilution impacts on a diesel engine operating with a diesel particle filter, NOx storage, a selective catalytic reduction emission control system, and a soy-based 20% biodiesel fuel blend.

Integrated Vehicle Thermal Management for Advanced Vehicle Propulsion Technologies

Techniques for evaluating and quantifying integrated transient and continuous heat loads of combined systems incorporating electric drive systems operating primarily under transient duty cycles.

Effects of Biodiesel Operation on Light-Duty Tier 2 Engine and Emission Control Systems

This paper documents the impact of biodiesel blends on engine-out emissions as well as overall system performance in terms of emissions control system calibration and overall system efficiency.

Development of a Diesel Passenger Car Meeting Tier 2 Emissions Levels

Increasing fuel costs, the need to reduce dependence on foreign oil as well as the high efficiency and the desire for superior durability have caused the diesel engine to again become a prime target for light-duty vehicle applications in the United States. In support of this the U.S. Department of Energy (DOE) has engaged in a test project under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity to develop a passenger car with the capability to demonstrate compliance with Tier 2 Bin 5 emission targets with a fresh emission control catalyst system. In order to achieve this goal, a prototype engine was installed in a passenger car and optimized to provide the lowest practical level of engine-out emissions. While this optimized calibration proved capable of meeting Euro 4 emission regulations for nitrogen oxides (NO x ) on an engine-out basis, a further reduction of 85% in both NO x and particulate matter (PM) emissions was necessary to meet the stringent Tier 2 Bin 5 emission levels. The emission control system was subsequently optimized in the test cell under steady-state and transient conditions. A rapid warm-up strategy was developed to achieve the fastest possible catalyst light-off under cold start conditions. The catalyst performance was mapped and optimized under numerous load and speed conditions with different lean-rich modulation approaches. Finally, diesel particulate filter (DPF) regeneration as well as desulfurization strategies were developed under this project. Vehicle tests with development emission control systems proved that the combination of low engine-out emissions, in conjunction with a sophisticated regeneration strategy, were able to meet Tier 2 Bin 5 emission levels.

Achieving Tier 2 Bin 5 Emission Levels with a Medium Duty Diesel Pick-Up and a NOX Adsorber, Diesel Particulate Filter Emissions System-Exhaust Gas Temperature Management

Increasing fuel costs and the desire for reduced dependence on foreign oil has brought the diesel engine to the forefront of future medium-duty vehicle applications in the United States due to its higher thermal efficiency and superior durability. The main obstacle to the increased use of diesel engines in this platform is the upcoming extremely stringent, Tier 2 emission standard. In order to succeed, diesel vehicles must comply with emissions standards while maintaining their excellent fuel economy. The availability of technologies such as common rail fuel injection systems, low sulfur diesel fuel, NO x adsorber catalysts (NAC), and diesel particle filters (DPFs) allow the development of powertrain systems that have the potential to comply with these future requirements. In meeting the Tier 2 emissions standards, the heavy light-duty trucks (HLDTs) and medium-duty passenger vehicles (MDPVs) will face the greatest technological challenges. In support of this, the U.S. Department of Energy (DOE) has engaged in several test projects under the Advanced Petroleum Based Fuels-Diesel Emission Control (APBF-DEC) activity. The primary technology being addressed by these projects is the sulfur tolerance of the NAC/DPF system and the durability implications of varying fuel sulfur levels. The test bed for one project in this activity is a 2500 series Chevrolet Silverado equipped with a 6.6L Duramax diesel engine certified to 2002 model year (MY) Federal heavy-duty and 2002 MY California medium-duty emission standards While NAC systems have demonstrated extremely high levels of NO x reduction in steady-state laboratory evaluations, the application of a NAC system to an actual transient engine application requires the development of an integrated engine/emissions management system [1,2,3,4,5,6,7,8,9,10]. This paper discusses the integrated engine/emissions system management and regeneration control strategies that were developed. The final control strategies achieved over 98% reductions in tailpipe NO x mass emissions over the hot-start portion of the light-duty Federal Test Procedure (FTP-75). This paper discusses thermal management of exhaust gas temperature to maintain the high efficiency window for NAC operation through the use of a diesel-fueled burner. The discussion will cover cold-start strategies and low exhaust gas temperature operation.

Simulated fuel economy and performance of advanced hybrid electric and plug-in hybrid electric vehicles using in-use travel profiles

As vehicle powertrain efficiency increases through electrification, consumer travel and driving behavior have significantly more influence on the potential fuel consumption of these vehicles. Therefore, it is critical to have a good understanding of in-use or “real world” driving behavior if accurate fuel consumption estimates of electric drive vehicles are to be achieved. Regional travel surveys using Global Positioning System (GPS) equipment have been found to provide an excellent source of in-use driving profiles. In this study, a variety of vehicle powertrain options were developed and their performance was simulated over GPS-derived driving profiles for 783 vehicles operating in Texas. The results include statistical comparisons of the driving profiles versus national data sets, driving performance characteristics compared with standard drive cycles, and expected petroleum displacement benefits from the electrified vehicles given various vehicle charging scenarios.

Biodiesel Effects on U.S. Light-Duty Tier 2 Engine and Emission Control Systems – Part 2

Raising interest in Diesel powered passenger cars in the United States in combination with the government mandated policy to reduce dependency of foreign oil, leads to the desire of operating Diesel vehicles with Biodiesel fuel blends. There is only limited information related to the impact of Biodiesel fuels on the performance of advanced emission control systems. In this project the implementation of a NOx storage and a SCR emission control system and the development for optimal performance are evaluated. The main focus remains on the discussion of the differences between the fuels which is done for the development as well as useful life aged components. From emission control standpoint only marginal effects could be observed as a result of the Biodiesel operation. The NOx storage catalyst results showed lower tailpipe emissions which were attributed to the lower exhaust temperature profile during the test cycle. The SCR catalyst tailpipe results were fuel neutral. The engine-out emissions formation showed increased NOx and decreased HC emissions with the Biodiesel blend. The observed effect specifically on NOx was up to 10% increase with the B20 blend. There was some impact on fuel economy which was attributed to higher combustion efficiency resulting in approximately 2% improved fuel economy with Biodiesel. There was no measurable impact of Biodiesel operation on the engine mechanics including fuel injection system.

FREEWAY SPEED ZONES: SAFETY AND COMPLIANCE ISSUES

The effectiveness and appropriateness of establishing speed limits on freeways and the spatial extent of the zones were studied. Of particular interest were 55-mph (88-km/hr) speed zones that exist in the transition between urban and rural areas (determined according to urban area boundaries). Three types of freeway segments (urban-55, fringe-55, and rural-65) were analyzed, and although the study was of comparatively small scale, the results generally showed that higher speeds do not lead to more numerous or serious accidents. Moreover, compliance with speed limits is not necessarily a good measure of safety. On the other hand, motorists are self-policing to a certain degree in that they drive at reasonable speeds given the design of the different types of freeways. It is suggested that artificially lowered speed limits without a clear need being established from engineering and safety perspectives will not yield impressive safety benefits.