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Journal Article

Enhanced Lateral and Roll Stability Study for a Two-Axle Bus via Hydraulically Interconnected Suspension Tuning

2018-11-19
Abstract The suspension system has been shown to have significant effects on vehicle performance, including handling, ride, component durability, and even energy efficiency during the design process. In this study, a new roll-plane hydraulically interconnected suspension (HIS) system is proposed to enhance both roll and lateral dynamics of a two-axle bus. The roll-plane stability analysis for the HIS system has been intensively explored in a number of studies, while only few efforts have been made for suspension tuning, especially considering lateral plane stability. This article aims to explore the integrated lateral and roll dynamics by suspension tuning of a two-axle bus equipped with HIS system. A ten-degree-of-freedom (DOF) lumped-mass vehicle model is integrated with either transient mechanical-hydraulic model for HIS or the traditional suspension components, namely, shock absorber and anti-roll bar (ARB).
Journal Article

A Review on Physical Mechanisms of Tire-Pavement Interaction Noise

2019-05-16
Abstract Tire-pavement interaction noise (TPIN) dominates for passenger cars above 40 km/h and trucks above 70 km/h. Numerous studies have attempted to uncover and distinguish the basic mechanisms of TPIN. However, intense debate is still ongoing about the validity of these mechanisms. In this work, the physical mechanisms proposed in the literature were reviewed and divided into three categories: generation mechanisms, amplification mechanisms, and attenuation mechanisms. The purpose of this article is to gather the published general opinions for further open discussions.
Journal Article

Semiconductor Safety Concepts for the Power Distribution of Automated Driving

2019-12-18
Abstract Automated driving is a highly complex idea. It involves mechanics, electronics and chemistry, artificial intelligence, human intelligence and high computational efforts. Apart from those aspects, the automated intelligence is run using electricity. An unintended interrupt can easily lead to a hazard. Therefore, a highly reliable power distribution has to be developed. This work focuses on the reliability calculation of such a power distribution concept. It points out what is required and will be in future such that the algorithms for the path planning and control are running in a safe environment according to the ISO 26262 standard.
Journal Article

Active Safety System for Connected Vehicles

2019-10-14
Abstract The development of connected-vehicle technology, which includes vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) communications, opens the door for unprecedented active safety and driver-enhanced systems. In addition to exchanging basic traffic messages among vehicles for safety applications, a significantly higher level of safety can be achieved when vehicles and designated infrastructure locations share their sensor data. In this article, we propose a new system where cameras installed on multiple vehicles and infrastructure locations share and fuse their visual data and detected objects in real time. The transmission of camera data and/or detected objects (e.g., pedestrians, vehicles, cyclists, etc.) can be accomplished by many communication methods. In particular, such communications can be accomplished using the emerging Dedicated Short-Range Communications (DSRC) technology.
Journal Article

Cooperative Ramp Merging System: Agent-Based Modeling and Simulation Using Game Engine

2019-05-16
Abstract Agent-based modeling and simulation (ABMS) has been a popular approach for modeling autonomous and interacting agents in a multi-agent system. Specifically, ABMS can be applied to connected and automated vehicles (CAVs) since CAVs can operate autonomously with the help of onboard sensors, and cooperate with each other through vehicle-to-everything (V2X) communications. In order to improve energy efficiency and mobility of traffic, we have developed an online feedforward/feedback longitudinal controller for CAVs to cooperatively merge at ramps. Agent-based CAV models were built in the Unity3D environment, where vehicles are given connectivity and autonomy through C#-based scripting API. Agent-based infrastructure model is also built as a Unity3D simulation network based on the city of Mountain View, California.
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

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

Exploring the Potential of Combustion on Titan

2018-04-07
Abstract Significant attention has been focused on Mars due to its relative proximity and possibility of sustaining human life. However, its lack of in-situ sources of energy presents a challenge to generate needed energy on the surface. Comparatively, Titan has a nearly endless source of fuel in its atmosphere and lakes, but both are lacking in regards to their oxidizing capacity. The finding of a possible underground liquid ammonia-water lake on Titan suggests that oxygen might actually be within reach. This effort provides the first theoretical study involving a primary energy generation system on Titan using the atmosphere as a fuel and underground water as the source for the oxygen via electrolysis from wind generated electricity.
Journal Article

High Power-Density, High Efficiency, Mechanically Assisted, Turbocharged Direct-Injection Jet-Ignition Engines for Unmanned Aerial Vehicles

2019-05-02
Abstract More than a decade ago, we proposed combined use of direct injection (DI) and jet ignition (JI) to produce high efficiency, high power-density, positive-ignition (PI), lean burn stratified, internal combustion engines (ICEs). Adopting this concept, the latest FIA F1 engines, which are electrically assisted, turbocharged, directly injected, jet ignited, gasoline engines and work lean stratified in a highly boosted environment, have delivered peak power fuel conversion efficiencies well above 46%, with specific power densities more than 340 kW/liter. The concept, further evolved, is here presented for unmanned aerial vehicle (UAV) applications. Results of simulations for a new DI JI ICE with rotary valve, being super-turbocharged and having gasoline or methanol as working fuel, show the opportunity to achieve even larger power densities, up to 430 kW/liter, while delivering a near-constant torque and, consequently, a nearly linear power curve over a wide range of speeds.
Journal Article

Improving the Modelling of Dissociating Hydrogen Nozzles

2019-11-21
Abstract While the design of nozzles for diatomic gases is very well established and covered by published works, the case of a diatomic gas dissociating to monatomic along a nozzle is a novel subject that needs a proper mathematical description. These novel studies are relevant to the definition of nozzles for gas-core Nuclear Thermal Rockets (NTR) that are receiving increased attention for the potential advantages they may deliver versus current generation rockets. The article thus reviews the design of the nozzles of gas-core NTR that use hydrogen as the propellant. Propellant temperatures are expected to reach 9,000-15,000 K. Above 1500 K, hydrogen begins to dissociate at low pressures, and around 3000 K dissociation also occurs at high pressures. At a given temperature, the lower the gas pressure the more molecules dissociate, and H2 → H + H. The properties of the gas are a function of the mass fractions of diatomic and monatomic hydrogen x H2 and x H = 1 − x H2.
Journal Article

Mathematical Model of Heat-Controlled Accumulator (HCA) for Microgravity Conditions

2020-01-20
Abstract It is reasonable to use a two-phase heat transfer loop (TPL) in a thermal control system (TCS) of spacecraft with large heat dissipation. One of the key elements of TPL is a heat-controlled accumulator (HCA). The HCA represents a volume which is filled with vapor and liquid of a single working fluid without bellows. The pressure in a HCA is controlled by the heater. The heat and mass transfer processes in the HCA can proceed with a significant nonequilibrium. This has implications on the regulation of TPL. This article presents a mathematical model of nonequilibrium heat and mass transfer processes in an HCA for microgravity conditions. The model uses the equations of mass and energy conservation separately for the vapor and liquid phases. Interfacial heat and mass transfer is also taken into account. It proposes to use the convective component k for the level of nonequilibrium evaluation.
Journal Article

Parametric Studies on Airfoil-Boundary Layer Ingestion Propulsion System

2020-03-11
Abstract From the fact that a propulsor consumes less power for a given thrust if the inlet air is slower, simulations are conducted for a propulsor imposed behind an airfoil as ideal boundary layer ingestion (BLI) propulsor to stand on the benefits of this configuration from the point of view of power and efficiency and to get a closer look on the mutual interaction between them. This interaction is quantified by the impact on three main sets of parameters, namely, power consumption, boundary layer properties, and airfoil performance. The position and size of the propulsor have great influence on the flow around the airfoil. Parametric studies are carried out to understand their influence. BLI propulsor directly affects the power saving and all of the pressure-dependent parameters, including lift and drag. For the present case, power saving reached 14.4% compared to the propeller working in freestream.
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

Onboard Natural Gas Reforming for Heavy Duty Vehicles

2019-01-07
Abstract Powertrain simulations and catalyst studies showed the efficiency credits and feasibility of onboard reforming as a way to recover waste heat from heavy duty vehicles (HDVs) fueled by natural gas (NG). Onboard reforming involves 1) injecting NG into the exhaust gas recycle (EGR) loop of the HDV, 2) reforming NG on a catalyst in the EGR loop to hydrogen and carbon monoxide, and 3) combusting the reformed fuel in the engine. The reformed fuel has increased heating value (4-10% higher LHV) and flame speed over NG, allowing stable flames in spark ignition (SI) engines at EGR levels up to 25-30%. A sulfur-tolerant reforming catalyst was shown to reform a significant amount of NG (15-30% conversion) using amounts of precious metal near the current practice for HDV emissions control (10 g rhodium). Engine simulations showed that the high EGR levels enabled by onboard reforming are used most effectively to control engine load instead of waste-gating or throttling.
Journal Article

Assessing Road Load Coefficients of a Semi-Trailer Combination Using a Mechanical Simulation Software with Calibration Corrections

2019-01-07
Abstract The study of road loads on trucks plays a major role in assessing the effect of heavy-vehicle design on fuel conservation measures. Coastdown testing with full-scale vehicles in the field offers a good avenue to extract drag components, provided that random instrumentation faults and biased environmental conditions do not introduce errors into the results. However, full-scale coastdown testing is expensive, and environmental biases which are ever-present are difficult to control in the results reduction. Procedures introduced to overcome the shortcomings of full-scale field testing, such as wind tunnels and computational fluid dynamics (CFD), though very reliable, mainly focus on estimating the effects of aerodynamic drag forces to the neglect of other road loads which should be considered.
Journal Article

Empirical Investigation on the Effects of Rolling Resistance and Weight on Fuel Economy of Medium-Duty Trucks

2019-08-28
Abstract Vehicle rolling resistance and weight are two of the factors that affect fuel economy. The vehicle tire rolling resistance has a more significant influence than aerodynamics drags on fuel economy at lower vehicle speeds, particularly true for medium- and heavy-duty trucks. Less vehicle weight reduces inertia loads, uphill grade resistance, and rolling resistance. The influence of weight on the fuel economy can be considerable particularly in light- to medium-duty truck classes because the weight makes up a larger portion of gross vehicle weight. This article presents an empirical investigation and a numerical analysis of the influences of rolling resistance and weight on the fuel economy of medium-duty trucks. The experimental tests include various tires and payloads applied on a total of 21vehicle configurations over three road profiles. These tests are used to assess the sensitivity of rolling resistance and weight to the vehicle fuel economy.
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

Implementation and Optimization of a Variable-Speed Coolant Pump in a Powertrain Cooling System

2020-02-07
Abstract This study investigates methods to precisely control a coolant pump in an internal combustion engine. The goal of this research is to minimize power consumption while still meeting optimal performance, reliability and durability requirements for an engine at all engine-operating conditions. This investigation achieves reduced fuel consumption, reduced emissions, and improved powertrain performance. Secondary impacts include cleaner air for the earth, reduced operating costs for the owner, and compliance with US regulatory requirements. The study utilizes mathematical modeling of the cooling system using heat transfer, pump laws, and boiling analysis to set limits to the cooling system and predict performance changes.
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

A Study of Low Temperature Plasma-Assisted Gasoline HCCI Combustion

2019-01-29
Abstract In this study low temperature plasma technology was applied to expand auto-ignition operation region and control auto-ignition phasing of the homogeneous charge compression ignition (HCCI) combustion. The low temperature plasma igniter of a barrier discharge model (barrier discharge igniter (BDI)) with high-frequency voltage (15 kHz) was provided at the top center of the combustion chamber, and the auto-ignition characteristics of the HCCI combustion by the low temperature plasma assistance was investigated by using a single-cylinder gasoline engine. HCCI combustion with compression ratio of 15:1 was achieved by increasing the intake air temperature. The lean air-fuel (A/F) ratio limit and visualized auto-ignition combustion process on baseline HCCI without discharge assistance, spark-assisted HCCI, and BDI-assisted HCCI were compared.
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