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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

Numerical and Experimental Investigation of the Optimization of Vehicle Speed and Inter-Vehicle Distance in an Automated Highway Car Platoon to Minimize Fuel Consumption

2018-06-22
Abstract The development of the technology of automated highways promises the opportunity for the vehicles to travel safely at a closer distance concerning each other. As such, vehicles moving in the wake of others experience a reduction in fuel consumption. This article investigates the effect of longitudinal distance between two passenger cars on drag coefficients numerically and experimentally. For the numerical analysis, the fluid flow at car speeds of 70, 90 and 110 km/h were examined. The Artificial Intelligence coding was applied to train an Artificial Neural Network to extend the calculated data. The optimum values for the inter-vehicle distance and the vehicle speed to assure the least drag coefficient are obtained. To support the numerical results an instrument designed and built particularly to accurately measure the fuel consumption was installed on a midsize sedan car and some field tests were carried out.
Journal Article

Multi-Chamber Tire Concept for Low Rolling-Resistance

2019-04-08
Abstract Rolling-resistance is leading the direction of numerous tire developments due to its significant effect on fuel consumption and CO2 emissions considering the vehicles in use globally. Many attempts were made to reduce rolling-resistance in vehicles, but with no or limited success due to tire complexity and trade-offs. This article investigates the concept of multiple chambers inside the tire as a potential alternative solution for reducing rolling-resistance. To accomplish that, novel multi-chamber designs were introduced and numerically simulated through finite-element (FE) modeling. The FE models were compared against a standard design as the baseline. The influences on rolling-resistance, grip, cornering, and mechanical comfort were studied. The multi-chambers tire model reduced rolling-resistance considerably with acceptable trade-offs. Independent air volumes isolating tread from sidewalls would maintain tire’s profile effectively.
Journal Article

Limitations of Two-Stage Turbocharging at High Flight Altitudes

2018-09-17
Abstract High-altitude long-endurance (HALE) unmanned aerial vehicles (UAVs) are used for high flight altitudes, which enable low drag and fast flight with minimal fuel consumption. Two-stage turbocharging is necessary to sustain sea-level power at high flight altitudes. In this study, the limitations of two-stage turbocharging at high flight altitudes typical for HALE UAVs are analyzed for the first time. The obtained results show that the minimum available engine power increases as the altitude rises. This will limit the ability of the aircraft to descend rapidly. Furthermore, at high altitudes, if a lower operating point is required for a fast descent, further recovery to full power for climbing or cruising could be unavailable. In the latter cases, a lower altitude must be reached before full power would be available again. A basic algorithm for the assessment and analysis of the limitations of UAV engines with two-stage turbochargers operating at high altitudes is suggested.
Journal Article

Introducing the Modified Tire Power Loss and Resistant Force Regarding Longitudinal Slip

2018-04-18
Abstract Investigation of vehicle resistant forces and power losses is of crucial importance owing to current state of energy consumption in transport sector. Meanwhile, considerable portion of resistant forces in a ground vehicle is traced back to tires. Pneumatic tires are known to be a source of energy dissipation as a consequence of their viscoelastic nature. The current study aims to provide a modification to tire resistance by considering the power loss in a tire due to longitudinal slip. The modified tire resistance is comprised of rolling resistance and a newly introduced resistance caused by tire slip, called slip resistance. The physical model is chosen for parameters sensitivity study since the tractive force is described in this model via tangible physical parameters, e.g. tire tangential stiffness, coefficient of friction, and contact patch length.
Journal Article

Fueling an Engine by Ultrasonic Atomization, and Its Control

2018-08-08
Abstract This article presents work carried out on a small, 4-stroke, SI engine, incorporated with an ultrasonic atomizer-based fueling system. A disc-type ultrasonic atomizer having good atomization characteristics was incorporated in the air intake path of a single cylinder, two-wheeler engine, replacing the conventional carburetor. This new fueling system was introduced with the aim of reducing the engine fuel consumption, while looking for a possible reduction in exhaust emissions. An electronic control mechanism was devised to change the atomization rate, in order to set the desired equivalence ratio for optimum engine operation. Test results indicate a significant improvement in fuel consumption and brake thermal efficiency, with a good control over the equivalence ratio. The system also allows engine operation at equivalence ratios as low as 0.5, and hence could be adopted for ultra-lean engines.
Journal Article

Experimental Investigation of the Influence of Engine Operating Parameters on a Rankine Based Waste Heat Recovery System in a SI Engine

2018-04-18
Abstract One of the most promising techniques to reduce carbon dioxide (CO2) emissions of future combustion engines is the use of waste heat from exhaust gas with a Rankine cycle. The target of this study was to investigate the influence of engine operating parameters such as ignition timing, coolant temperature and injection parameters on the efficiency and performance of Rankine based waste heat recovery systems (WHR). This was done to gain basic knowledge about the influences of the engine operating parameters which helps to explain the system behavior under different operating conditions and second to identify the operating parameters with the highest overall system efficiency which can be used to highlight the impact of changes in engine application on the car. These first of a kind tests were performed on a state-of-the-art gasoline engine equipped with a prototype Rankine-system.
Journal Article

Experimental Investigation of Ethanol-Diesel-Butanol Blends in a Compression Ignition Engine by Modifying the Operating Parameters

2018-10-31
Abstract The rapid utilization of fossil fuels has triggered the finding of alternative renewable fuel that replaces or reduces the consumption by alternative fuels for fueling compression ignition (CI) engines. One such renewable fuel is ethanol which can be manufactured from biomass. The present study details the utilization of an optimum amount of ethanol in CI engine by modifying the operating parameters. It was already published in the previous paper that 45% ethanol can be utilized along with diesel using 10% butanol as cosolvent. This fuel is also meeting the minimum requirement with respect to properties as per ASTM standards. This experimental study was performed to investigate the influence of modifying the engine operating parameters on the performance, combustion, and emission parameters fueled with the blend containing 45% ethanol under various load conditions.
Journal Article

Direct Versus Indirect Acting Piezoelectric CR Injectors: Comparison of Hydraulic Performance, Pollutant Emissions, Combustion Noise, and Fuel Consumption

2018-11-08
Abstract A comprehensive comparison between a direct acting and an indirect acting piezoelectric injector has been carried out both at the hydraulic rig and at the dynamometer cell. The working principle of these injector typologies is illustrated, and their hydraulic performance has been analyzed and discussed on the basis of experimental data collected at a hydraulic test rig. The injector characteristics, nozzle opening and closure delays, injector leakages, injected flow-rate profiles, injector-to-injector variability in the injected mass, injected volume fluctuations with the dwell time (DT), and minimum DT for fusion-free multiple injections have been compared in order to evaluate the impact of the injector driving system on the injection apparatus performance. The direct acting and indirect acting piezoelectric injectors have been installed on a Euro 5 diesel engine, which has been tested at a dynamometer cell.
Journal Article

Combined Battery Design Optimization and Energy Management of a Series Hybrid Military Truck

2018-10-31
Abstract This article investigates the fuel savings potential of a series hybrid military truck using a simultaneous battery pack design and powertrain supervisory control optimization algorithm. The design optimization refers to the sizing of the lithium-ion battery pack in the hybrid configuration. The powertrain supervisory control optimization determines the most efficient way to split the power demand between the battery pack and the engine. Despite the available design and control optimization techniques, a generalized mathematical formulation and solution approach for combined design and control optimization is still missing in the literature. This article intends to fill that void by proposing a unified framework to simultaneously optimize both the battery pack size and power split control sequence. This is achieved through a combination of genetic algorithm (GA) and Pontryagin’s minimum principle (PMP) where the design parameters are integrated into the Hamiltonian function.
Journal Article

Analysis of Regulated Pollutant Emissions and Aftertreatment Efficiency in a GTDi Engine Using Different SOI Strategies

2018-06-25
Abstract In order to improve performance and minimize pollutant emissions in gasoline turbocharged direct-injection (GTDi) engines, different injection strategies and technologies are being investigated. The inclusion of exhaust gas recirculation (EGR) and the variation of the start of injection (SOI) are some of these strategies that can influence the air-to-fuel (AF) mixture formation and consequently in the combustion process and pollutant emissions. This paper presents a complete study of the engine performance, pollutant emissions and aftertreatment efficiency that produces the SOI variation with a fixed EGR rate in a 4-cylinder, turbocharged, gasoline direct-injection engine with 2.0 L displacement. The equipment used in this study are TSI-EEPS for particle measurement and HORIBA MEXA 1230-PM for soot measurement being HORIBA MEXA 7100-DEGR with a heated line selector the system employed for regulated gaseous emission measurement and aftertreatment evaluation.
Journal Article

Adaptive Transmission Shift Strategy Based on Online Characterization of Driver Aggressiveness

2018-06-04
Abstract Commercial vehicles contribute to the majority of freight transportation in the United States. They are also significant fuel consumers, with over 23% of fuel used in transportation in the United States. The gas price volatility and increasingly stringent regulation on greenhouse-gas emissions have driven manufacturers to adopt new fuel-efficient technologies. Among others, an advanced transmission control strategy, which can provide tangible improvement with low incremental cost. In the commercial sector, individual drivers have little or no interest in vehicle fuel economy, contrary to fleet owners. Aggressive driving behavior can greatly increase the real-world vehicle fuel consumption. However, the effectiveness of transmission calibration to match the shift strategy to the driving characteristics is still a challenge.
Journal Article

Active Control of Cylinder Charge Motion Using Vortex Generating Jets (VGJs) on Generic Intake Port Geometries

2018-08-08
Abstract Swirl is known to have impact on the combustion process and the engine emission performance. Generally the swirl flows are generated on engines by e.g. helical or tangential intake ports. However, such features of intake ports constrict the airflow, resulting in raising pumping losses and thus higher fuel consumption. This article introduces a further possibility to generate and regulate the swirl flow by injecting air directly into the intake ports using Vortex Generating Jets (VGJs). The effect of air injection was studied by means of experimental investigations regarding swirl generation and flow rate improvement. The optimization of VGJ diameters, positions as well as injection airflow rate was carried out with respect to energy efficiency of swirl generation.
Journal Article

A Novel Approach towards Stable and Low Emission Stratified Lean Combustion Employing Two Solenoid Multi-Hole Direct Injectors

2018-04-18
Abstract Stratified lean combustion has proven to be a promising approach for further increasing the thermal efficiency of gasoline direct injection engines in low load conditions. In this work, a new injection strategy for stratified operation mode is introduced. A side and a central-mounted solenoid multi-hole injector are simultaneously operated in a single-cylinder engine. Thermodynamic investigations show that this concept leads to improved stability, faster combustion, reduced particle number emissions, and lower fuel consumption levels compared to using only one injector. Experiments at an optical engine and three-dimensional computational fluid dynamics (CFD) simulations explain the improvements by a more compact mixture and reduced piston wetting with two injectors. Finally, the application of external EGR in combination with the above concept allows NOx emissions to be effectively kept at a low level while maintaining a stable operation.
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