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Journal Article

U.S. Light-Duty Vehicle Air Conditioning Fuel Use and Impact of Solar/Thermal Control Technologies

2018-12-11
Abstract To reduce fuel consumption and carbon dioxide (CO2) emissions from mobile air conditioning (A/C) systems, “U.S. Light-Duty Vehicle Greenhouse Gas Emissions and Corporate Average Fuel Economy Standards” identified solar/thermal technologies such as solar control glazings, solar reflective paint, and active and passive cabin ventilation in an off-cycle credit menu. National Renewable Energy Laboratory (NREL) researchers developed a sophisticated analysis process to calculate U.S. light-duty A/C fuel use that was used to assess the impact of these technologies, leveraging thermal and vehicle simulation analysis tools developed under previous U.S. Department of Energy projects. Representative U.S. light-duty driving behaviors and weighting factors including time-of-day of travel, trip duration, and time between trips were characterized and integrated into the analysis.
Journal Article

Transient Operation and Over-Dilution Mitigation for Low-Pressure EGR Systems in Spark-Ignition Engines

2018-09-17
Abstract Low-Pressure cooled Exhaust Gas Recirculation (LP-cEGR) is proven to be an effective technology for fuel efficiency improvement in turbocharged spark-ignition (SI) engines. Aiming to fully exploit the EGR benefits, new challenges are introduced that require more complex and robust control systems and strategies. One of the most important restrictions of LP-cEGR is the transient response, since long air-EGR flow paths introduce significant transport delays between the EGR valve and the cylinders. High dilution generally increases efficiency, but can lead to cycle-by-cycle combustion variation. Especially in SI engines, higher-than-requested EGR dilution may lead to combustion instabilities and misfires. Considering the long EGR evacuation period, one of the most challenging transient events is throttle tip-out, where the engine operation shifts from a high-load point with high dilution tolerance to a low-load point where EGR tolerance is significantly reduced.
Journal Article

Toward Improving Vehicle Fuel Economy with ADAS

2018-10-29
Abstract Modern vehicles have incorporated numerous safety-focused advanced driver-assistance systems (ADAS) in the last decade including smart cruise control and object avoidance. In this article, we aim to go beyond using ADAS for safety and propose to use ADAS technology to enable predictive optimal energy management and improve vehicle fuel economy (FE). We combine ADAS sensor data with a previously developed prediction model, dynamic programming (DP) optimal energy management control, and a validated model of a 2010 Toyota Prius to explore FE. First, a unique ADAS detection scope is defined based on optimal vehicle control prediction aspects demonstrated to be relevant from the literature. Next, during real-world city and highway drive cycles in Denver, Colorado, a camera is used to record video footage of the vehicle environment and define ADAS detection ground truth. Then, various ADAS algorithms are combined, modified, and compared to the ground truth results.
Journal Article

The Key Role of Advanced, Flexible Fuel Injection Systems to Match the Future CO2 Targets in an Ultra-Light Mid-Size Diesel Engine

2019-01-23
Abstract The article describes the results achieved in developing a new diesel combustion system for passenger car application that, while capable of high power density, delivers excellent fuel economy through a combination of mechanical and thermodynamic efficiencies improvement. The project stemmed from the idea that, by leveraging the high fuel injection pressure of last generation common rail systems, it is possible to reduce the engine peak firing pressure (pfp) with great benefits on reciprocating and rotating components’ light-weighting and friction for high-speed light-duty engines, while keeping the power density at competitive levels. To this aim, an advanced injection system concept capable of injection pressure greater than 2500 bar was coupled to a prototype engine featuring newly developed combustion system. Then, the matching among these features has been thoroughly experimentally examined.
Journal Article

Steady Aeroelastic Response Prediction and Validation for Automobile Hoods

2018-07-10
Abstract The pursuit of improved fuel economy through weight reduction, reduced manufacturing costs, and improved crash safety can result in increased compliance in automobile structures. However, with compliance comes an increased susceptibility to aerodynamic and vibratory loads. The hood in particular withstands considerable aerodynamic force at highway speeds, creating the potential for significant aeroelastic response that may adversely impact customer satisfaction and perception of vehicle quality. This work seeks an improved understanding in computational and experimental study of fluid-structure interactions between automobile hoods and the surrounding internal and external flow. Computational analysis was carried out using coupled CFD-FEM solvers with detailed models of the automobile topology and structural components. The experimental work consisted of wind tunnel tests using a full-scale production vehicle.
Journal Article

Speed Planning and Prompting System for Commercial Vehicle Based on Real-Time Calculation of Resistance

2019-06-25
Abstract When commercial vehicles drive in a mountainous area, the complex road condition and long slopes cause frequent acceleration and braking, which will use 25% more fuel. And the brake temperature rises rapidly due to continuous braking on the long-distance downslopes, which will make the brake drum fail with the brake temperature exceeding 308°C [1]. Meanwhile, the kinetic energy is wasted during the driving progress on the slopes when the vehicle rolls up and down. Our laboratory built a model that could calculate the distance from the top of the slope, where the driver could release the accelerator pedal. Thus, on the slope, the vehicle uses less fuel when it rolls up and less brakes when down. What we do in this article is use this model in a real vehicle and measure how well it works.
Journal Article

Performance, Fuel Economy, and Economic Assessment of a Combustion Concept Employing In-Cylinder Gasoline/Natural Gas Blending for Light-Duty Vehicle Applications

2019-04-25
Abstract In current production natural gas/gasoline bi-fuel vehicles, fuels are supplied via port fuel injection (PFI). Injecting a gaseous fuel in the intake port significantly reduces the volumetric efficiency and consequently torque as compared to gasoline. In addition to eliminating the volumetric efficiency challenge, direct injection (DI) of natural gas (NG) can enhance the in-cylinder flow, mixing, and combustion process resulting in improved efficiency and performance. A computational fluid dynamics (CFD) approach to model high-pressure gaseous injection was developed and validated against X-ray data from Argonne’s Advanced Photon Source. NG side and central DI of various designs and injection strategies were assessed experimentally along with CFD correlation. Significant effects on combustion metrics were quantified and explained via improved understanding of the in-cylinder flow effects due to NG injection.
Journal Article

Modeling and Optimal Design of All-Wheel-Drive Hybrid Light Trucks

2019-06-06
Abstract Fuel economy and performance are both important in the design of hybrid pickup trucks. All-wheel drive is essential to ensure superior performance compared to two-wheel-drive designs. In this article, as a comprehensive extension work to the article published in ASME Dynamic Systems and Control Conference [1] on all-wheel-drive (AWD) hybrid truck, we investigate the modeling, design, and control problem of AWD hybrid vehicles and develop a methodology to identify optimal designs. This methodology 1) formulates an automated modeling process, 2) searches exhaustively through all possible AWD designs, and 3) employs a near-optimal energy management strategy, to obtain a family of designs with superior performance and fuel economy. A design case study for a hybrid Ford F-150 is conducted, to showcase this design process.
Journal Article

Energy Consumption Test and Analysis Methodology for Heavy-Duty Vehicle Engine Accessories

2018-10-03
Abstract Fuel economy is a crucial parameter in long-haulage heavy-duty vehicles. Researchers tended to focus initially on engine combustion efficiency, while modern researchers turn their attention to the energy consumption of engine accessories in an attempt to enhance fuel economy. The accessories investigated in this study include the cooling fan, water pump, air compressor, power steering pump, air-conditioning (AC) compressor, and generator. Normally, accessory energy consumption analysis is based on rig data and simulation results. Here, we focus on the disparate test environments between the rig and vehicle to establish a novel steady power test method; the proposed method provides accurate accessory power data under different working conditions. A typical highway driving cycle is selected to collect accessory duty-cycle. The heavy-duty vehicle accessories’ energy consumption distribution under highway road conditions is obtained through the repeated road tests.
Journal Article

Development of an Overhead Camshaft System Adapted to an SAE Supermileage Single-Person Vehicle in a Fuel Economy Perspective

2018-06-18
Abstract This article presents a comparative study between two camshafts systems adapted to the single cylinder engine of a Supermileage vehicle in a fuel economy perspective. One system is from a Honda AF70E engine and the other is a new design. The new camshaft system was improved for fuel economy by developing a new camshaft that enhances volumetric efficiency while reducing friction losses. The comparison was made by measuring the efficiency of the engine in the speed range where the engine was used by the Supermileage vehicle and a calculation was made to show which of the configuration is best for the vehicle.
Journal Article

Development of a New Neutral Coasting Control Utilizing ADAS and GPS

2019-01-23
Abstract It has been discussed in numerous prior studies that in-neutral coasting, or sailing, can accomplish considerable amount of fuel saving when properly used. The driving maneuver basically makes the vehicle sail in neutral gear when propulsion is unnecessary. By disengaging a clutch or shifting the gear to neutral, the vehicle may better utilize its kinetic energy by avoiding dragging from the engine side. This strategy has been carried over to series production recently in some of the vehicles on the market and has become one of the eco-mode features available in current vehicles. However, the duration of coasting must be long enough to attain more fuel economy benefit than deceleration fuel cutoff (DFCO)-which exists in all current vehicle powertrain controllers-can bring. Also, the transients during shifting back to drive gear can result in a drivability concern.
Journal Article

Artificial Lightning Tests on Metal and CFRP Automotive Bodies: A Comparative Study

2019-01-07
Abstract Carbon fiber reinforced plastic (CFRP) has been used in automobiles as well as airplanes. Because of its light weight and high strength, CFRP is a good choice for making vehicle bodies lighter, which would improve fuel economy. Conventional metal bodies provide a convenient body return for electric wiring and offer good shielding against electromagnetic fields. Although CFRP is a conductor, its conductivity is much lower than that of metals. Therefore, CFRP bodies are usually not useful for electric wiring. In thunderstorms, an automotive body is considered to be a Faraday cage that protects the vehicle’s occupants from the potential harms of lightning. Before CFRP becomes widely applied to automotive bodies, its electric and electromagnetic properties need to be investigated in order to determine whether it also works as a Faraday cage against lightning. In this article, CFRP and metal body vehicles were tested under artificial lightning.
Journal Article

A Study of an Integrated HVAC-Vehicle Model for Automotive Vehicles

2018-04-18
Abstract The objective of this work is to develop an integrated HVAC-VEHICLE model for climate control studies. A published lumped parameter based HVAC model has been used as the framework for the HVAC modeling with some modifications to realize the climate control and to improve the robustness of the model. R134a (1,1,2,2-Tetrafluoroethane) has been used as the refrigerant fluid in this study. The stand-alone HVAC model has been compared qualitatively with the experimental works available in the literature. The experimental trends of the thermodynamic and performance related parameters of HVAC are reasonably well captured by the HVAC model. In particular, Coefficient of Performance (CoP) was found to decrease with increase in compressor speed and increase in ambient temperature but increase with increase in evaporator blower mass flow rate.
Journal Article

A Review of Sensor Technologies for Automotive Fuel Economy Benefits

2018-12-11
Abstract This article is a review of automobile sensor technologies that have the potential to enhance fuel economy. Based on an in-depth review of the literature and demonstration projects, the following sensor technologies were selected for evaluation: vehicular radar systems (VRS), camera systems (CS), and vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) systems. V2V and V2I systems were found to have the highest merit in improving fuel economy over a wide range of integration strategies, with fuel economy improvements ranging from 5 to 20% with V2V and 10 to 25% for V2I. However, V2V and V2I systems require significant adoption for practical application which is not expected in this decade. Numerous academic studies and contemporary vehicular safety systems attest VRS as more technologically mature and robust relative to other sensors. However, VRS offers less fuel economy enhancement (~14%).
Journal Article

A Method for Turbocharging Single-Cylinder, Four-Stroke Engines

2018-07-24
Abstract Turbocharging can provide a low cost means for increasing the power output and fuel economy of an internal combustion engine. Currently, turbocharging is common in multi-cylinder engines, but due to the inconsistent nature of intake air flow, it is not commonly used in single-cylinder engines. In this article, we propose a novel method for turbocharging single-cylinder, four-stroke engines. Our method adds an air capacitor-an additional volume in series with the intake manifold, between the turbocharger compressor and the engine intake-to buffer the output from the turbocharger compressor and deliver pressurized air during the intake stroke. We analyzed the theoretical feasibility of air capacitor-based turbocharging for a single-cylinder engine, focusing on fill time, optimal volume, density gain, and thermal effects due to adiabatic compression of the intake air.
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