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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

CFD Windshield Deicing Simulations for Commercial Vehicle Applications

2018-04-06
Abstract Windshield deicing performance is a key metric for HVAC system development and optimization within the sphere of commercial vehicle design. The primary physical parameters that drive this metric are pressure drops in the HVAC ducting, flow rate of the air through the system, and the transient vent temperature rise affected by engine coolant warm-up. However, many design engineers also have to take underhood and instrument panel (IP) space constraints into consideration while trying to optimize a new HVAC system design. This study leverages historical deicing simulation methodologies in conjunction with modern computational horsepower so as to optimize the HVAC ductwork in the studied commercial truck at the beginning of the design phase. By iterating on a design in the computational domain under steady-state and transient flow and thermal conditions, a robust HVAC system design can be created even prior to the prototyping stage of development.
Journal Article

Investigation on Underhood Thermal Analysis of Truck Platooning

2018-03-22
Abstract This paper presents a combined aero-thermal computational fluid dynamic (CFD) evaluation of platooning medium duty commercial vehicles in two highway configurations. Thermal analysis comparison is made between an approach that includes vehicle drag reduction on engine heat rejection and one that does not by assuming a constant heat rejection based on open road conditions. The paper concludes that accounting for aerodynamic drag reduction on engine heat load provides a more real world evaluation than assuming a constant heat load based on open road conditions. A 3D CFD underhood thermal simulations are performed in two different vehicle platooning configurations; (i) single-lane and (ii) two-lane traffic conditions. The vehicle platooning consists of two identical vehicles, i.e. leading and trailing vehicle. In this work, heat exchangers are modeled by two different heat rejection rate models.
Journal Article

Investigation of Passive Porosity as a Means for Bluff-Body Drag Reduction

2018-03-16
Abstract An investigation into the capability of passive porosity to reduce the drag of a bluff-body is presented. This initial work involves integrating varying degrees of porosity into the side and back faces of a small-scale model to determine optimum conditions for maximum drag reduction. Both force and pressure measurements at differing degrees of model yaw are presented, with the conditions for optimum performance, identified. At a length-based Reynolds number of 2.3 × 106, results showed a maximum drag reduction of 12% at zero yaw when the ratio of the open area on the back face relative to the side faces was between two and four. For all non-zero yaw angles tested, this ratio reduced to approximately two, with the drag benefit reducing to 6% at 10.5 degrees. From a supplementary theoretical analysis, calculated optimum bleed rate into the base for maximum drag reduction, also showed reasonable agreement to other results reported previously.
Journal Article

Aerodynamic Analysis of Cooling Airflow for Different Front-End Designs of a Heavy-Duty Cab-Over-Engine Truck

2018-04-07
Abstract Improving the aerodynamics of heavy trucks is an important consideration in the strive for more energy-efficient vehicles. Cooling drag is one part of the total aerodynamic resistance acting on a vehicle, which arises as a consequence of air flowing through the grille area, the heat exchangers, and the irregular under-hood area. Today cooling packages of heavy trucks are dimensioned for a critical cooling case, typically when the vehicle is driving fully laden, at low speed up a steep hill. However, for long-haul trucks, mostly operating at highway speeds on mostly level roads, it may not be necessary to have all the cooling airflow from an open-grille configuration. It can therefore be desirable for fuel consumption purposes, to shut off the entire cooling airflow, or a portion of it, under certain driving conditions dictated by the cooling demands. In Europe, most trucks operating on the roads are of cab-over-engine type, as a consequence of the length legislations present.
Journal Article

LSPI Durability, a Study of LSPI over the Life of a Vehicle

2018-03-01
Abstract Increasingly stringent emissions standards and the related efforts to increase vehicle fuel economy have forced the development and implementation of many new technologies. In the light-duty, passenger vehicle segment, one key strategy has been downsized, down-sped, boosted engines. Gasoline direct injection, coupled with turbocharging, have allowed for a drastic reduction in engine size while maintaining or improving engine performance. However, obtaining more power from a smaller engine has produced some consequences. One major consequence is the uncontrolled combustion known as Low Speed Pre-Ignition (LSPI). LSPI and the high energy knocking event which frequently follows have been known to result in fractured pistons and catastrophic engine failure. The propensity at which LSPI occurs has been linked to engine oil formulation.
Journal Article

Investigation into the Potentials of a Dedicated Multi-Point Injection System for a Production NG Single-Point Heavy-Duty Engine

2018-03-08
Abstract CNG is at present retaining a growing interest as a factual alternative to traditional fuels for SI engines, thanks to its high potentials in reducing the engine-out emissions. Increasing thrust into the exploitation of NG in the transport field is in fact produced by the even more stringent emission regulations that are being introduced into the worldwide scenario. Moreover, the transport sector accounts for the 27% of the overall energy consumptions and up to the 13% in terms of global emissions. The present paper aims at deeply investigating into the potentials of a heavy-duty engine running on CNG and equipped with two different injection systems, an advanced single point (SP) one and a prototype multi-point (MP) one. The considered 7.8-liter engine was designed and produced to implement a SP strategy and hence modified to run with a dedicated MP system.
Journal Article

Knock Phenomena under Very Lean Conditions in Gasoline Powered SI-Engines

2018-03-13
Abstract Homogeneous lean operation is a well-known strategy for enhancing the thermal efficiency of SI-engines. At higher load points the efficiency is often compromised by the need to suppress knock. Experiments were performed to determine the knock characteristics of SI engines using homogeneous lean operation at λ values of up to 1.8 with various hardware configurations that are commonly used to increase the lean limit. Changing λ altered the eigenfrequencies of the combustion chamber and the highest energy excitation mode. Increasing λ from 1.0 to 1.2 increased the knock tendency and led to an earlier knock onset. However, further increases in λ significantly reduced the knock tendency and retarded the knock onset. The knock signal energy increased for higher λ values and constant knock tendencies. The differences in knock characteristics between the various λ values became more pronounced upon raising the intake temperature from 40 °C to 90 °C.
Journal Article

Investigations on Drive Axle Thermal Behaviour: Power Loss and Heat-Transfer Estimations

2018-03-08
Abstract In the present study, a truck drive axle and its gear set are analysed. As the gear set is a hypoid or a spiral bevel one, sliding and so tooth friction are an important source of dissipation. Other losses are mainly due to rolling element bearings and oil churning. The power losses are first calculated according to relationships given in ISO technical report. As comparison with test results shows great discrepancies, some modifications of the previous formulae are proposed. The thermal exchanges are also reviewed. Finally, two methods to obtain the bulk temperatures of the gear set are compared: a classical approach which focuses on the gear set only and a global approach which considers the complete axle using the thermal-network method.
Journal Article

Resolution of HEV Battery Cooling System Inlet Noise Issue by Optimizing Duct Design and Fan Speed Control Strategy

2018-04-07
Abstract The power battery cooling system of a hybrid electric vehicle is composed of a fan and duct assembly with its inlet positioned inside the vehicle cabin. For the prototype vehicle considered in this work, the air inlet is positioned on the package tray due to limited feasible choices. When the battery temperature is over rated limit, the cooling fan starts to operate to cool the battery system. Propelled by the fan in the cooling system, the air in the passenger compartment enters the duct inlet, and rushes through the air duct to reach the battery pack to fulfill the intended cooling function. In this case, the rear seat occupants could clearly perceive the existence of an annoying whirring noise. In this paper, the characteristics of the battery air cooling system and its working principles are briefly described. The air inlet noise generation mechanism and its frequency characteristics are then analyzed.
Journal Article

Investigations on Spark and Corona Ignition of Oxymethylene Ether-1 and Dimethyl Carbonate Blends with Gasoline by High-Speed Evaluation of OH* Chemiluminescence

2018-03-01
Abstract Bio-fuels of the 2nd generation constitute a key approach to tackle both Greenhouse Gas (GHG) and air quality challenges associated with combustion emissions of the transport sector. Since these fuels are obtained of residual materials of the agricultural industry, well-to-tank CO2 emissions can be significantly lowered by a closed-cycle of formation and absorption of CO2. Furthermore, studies of bio-fuels have shown reduced formation of particulate matter on account of the fuels’ high oxygen content therefore addressing air quality issues. However, due to the high oxygen content and other physical parameters these fuels are expected to exhibit different ignition behaviour. Moreover, the question is whether there is a positive superimposition of the fuels ignition behaviour with the benefits of an alternative ignition system, such as a corona ignition.
Journal Article

Exploring Engine Oil Reactivity Effects on End Gas Knock in a Direct-Injection Spark Ignition Engine

2018-03-05
Abstract An experimental study was conducted in a direct-injection (DI) spark-ignited engine to determine the extent to which oil reactivity impacts combustion phasing and knock propensity. Three engine oils were examined: a baseline 20W30 oil from conventional base stock, a 5W30 oil from a synthetic base stock, and a jet oil from a hindered ester base stock. The engine was operated at a constant fueling rate of 24.7 mg/injection for two engine speed conditions (1500 and 2000 rpm) using two cam profile conditions (high and low lift), for a total of four operating conditions. Spark timing sweeps were conducted at each of the four operating conditions. Results were analyzed for an engine oil impact on combustion phasing, cycle-to-cycle variability, combustion duration, knock propensity, and knock intensity. No correlation between engine oil type and any of these performance metrics could be identified.
Journal Article

Impact of Siloxanes in Biomethane on the Performance of a CNG Vehicle

2018-03-23
Abstract In this paper, the results of experiments to determine the effects of silicon-containing compounds in biogas on the performance of spark-ignited gas engines for use in CNG vehicles are presented. Initial research was performed on micro-CHP units, which have many features common with automotive engines, to identify engine components sensitive for silica deposition prior to investigating a practical CNG engine. The experiments on the micro-CHP units revealed that the catalyst was the most sensitive part for silica fouling, with strong impact on the reduction of NOx. With the insight gained from these experiments, an 9-week endurance test was performed on a light-duty CNG vehicle.
Journal Article

Thermohydrodynamic Modeling of Squeeze Film Dampers in High-Speed Turbomachinery

2018-04-07
Abstract This work develops a comprehensive thermohydrodynamic (THD) model for high-speed squeeze film dampers (SFDs) in the presence of lubricant inertia effects. Firstly, the generalized expression for Reynolds equation is developed. Additionally, in order to reduce the complexity of the hydrodynamic equations, an average radial viscosity is defined and integrated into the equations. Subsequently, an inertial correction to the pressure is incorporated by using a first-order perturbation technique to represent the effect of lubricant inertia on the hydrodynamic pressure distribution. Furthermore, a thermal model, including the energy equation, the Laplace heat conduction equations in the surrounding solids (i.e. the journal and the bush), and the thermal boundary conditions at the interfaces is constructed. Moreover, the system of partial differential hydrodynamic and thermal equations is simultaneously solved by using an iterative numerical algorithm.
Journal Article

Compatibility Assessment of Fuel System Thermoplastics with Bio-Blendstock Fuel Candidates Using Hansen Solubility Analysis

2018-01-03
Abstract The compatibility of key fuel system infrastructure plastics with 39 bio-blendstock fuel candidates was examined using Hansen solubility analysis. Fuel types included multiple alcohols, esters, ethers, ketones, alkenes and one alkane. These compounds were evaluated as neat molecules and as blends with the gasoline surrogate, dodecane and a mix of dodecane and 10% ethanol (E10D). The plastics included polyphenylene sulfide (PPS), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyoxymethylene (POM), polybutylene terephthalate (PBT), polypropylene (PP), high density polyethylene (HDPE), along with several nylon grades. These materials have been rigorously studied with other fuel types, and their volume change results were found to correspond well with their predicted solubility levels.
Journal Article

Increased Thread Load Capability of Bolted Joints in Light Weight Design

2017-06-29
Abstract Within the scope of today’s product development in automotive engineering, the aim is to produce lighter and solid parts with higher capabilities. On the one hand lightweight materials such as aluminum or magnesium are used, but on the other hand, increased stresses on these components cause higher bolt forces in joining technology. Therefore screws with very high strength rise in importance. At the same time, users need reliable and effective design methods to develop new products at reasonable cost in short time. The bolted joints require a special structural design of the thread engagement in low-strength components. Hence an extension of existing dimensioning of the thread engagement for modern requirements is necessary. In the context of this contribution, this will be addressed in two ways: on one hand extreme situations (low strength nut components and high-strength fasteners) are considered.
Journal Article

Classification of Contact Forces in Human-Robot Collaborative Manufacturing Environments

2018-04-02
Abstract This paper presents a machine learning application of the force/torque sensor in a human-robot collaborative manufacturing scenario. The purpose is to simplify the programming for physical interactions between the human operators and industrial robots in a hybrid manufacturing cell which combines several robotic applications, such as parts manipulation, assembly, sealing and painting, etc. A multiclass classifier using Light Gradient Boosting Machine (LightGBM) is first introduced in a robotic application for discriminating five different contact states w.r.t. the force/torque data. A systematic approach to train machine-learning based classifiers is presented, thus opens a door for enabling LightGBM with robotic data process. The total task time is reduced largely because force transitions can be detected on-the-fly. Experiments on an ABB force sensor and an industrial robot demonstrate the feasibility of the proposed method.
Journal Article

Effects of Reflux Temperature and Molarity of Acidic Solution on Chemical Functionalization of Helical Carbon Nanotubes

2017-09-19
Abstract The use of nanomaterials and nanostructures have been revolutionizing the advancements of science and technology in various engineering and medical fields. As an example, Carbon Nanotubes (CNTs) have been extensively used for the improvement of mechanical, thermal, electrical, magnetic, and deteriorative properties of traditional composite materials for applications in high-performance structures. The exceptional materials properties of CNTs (i.e., mechanical, magnetic, thermal, and electrical) have introduced them as promising candidates for reinforcement of traditional composites. Most structural configurations of CNTs provide superior material properties; however, their geometrical shapes can deliver different features and characteristics. As one of the unique geometrical configurations, helical CNTs have a great potential for improvement of mechanical, thermal, and electrical properties of polymeric resin composites.
Journal Article

Lightweight Carbon Composite Chassis for Engine Start Lithium Batteries

2017-09-19
Abstract The supersession of metallic alloys with lightweight, high-strength composites is popular in the aircraft industry. However, aviation electronic enclosures for large format batteries and high power conversion electronics are still primarily made of aluminum alloys. These aluminum enclosures have attractive properties regrading structural integrity for the heavy internal parts, electromagnetic interference (EMI) suppression, electrical bonding for the internal cells, and/or electronics and failure containment. This paper details a lightweight carbon fiber composite chassis developed at Meggitt Sensing Systems (MSS) Securaplane, with a copper metallic mesh co-cured onto the internal surfaces resulting in a 50% reduction in weight when compared to its aluminum counterpart. In addition to significant weight reduction, it provides equal or improved performance with respect to EMI, structural and flammability performance.
Journal Article

Studies on Friction Mechanism of NAO Brake-Pads Containing Potassium Titanate Powder as a Theme Ingredient

2017-09-17
Abstract Potassium titanate (KT) fibers/whiskers are used as a functional filler for partial replacement of asbestos in NAO friction materials (FMs). Based on little information reported in open literature; its exact role is not well defined since some papers claim it as the booster for resistance to fade (FR), or wear (WR) and sometimes as damper for friction fluctuations. Interestingly, KT fibers and whiskers (but not powder) are proved as carcinogens by the International Agency for Research on Cancer (IARC). However, hardly any efforts are reported on exploration of influence of KT powder and its optimum amount in NAO FMs (realistic composites) in the literature. Hence a series of five realistic multi-ingredient compositions in the form of brake-pads with similar parent composition but varying in the content of KT powder from 0 to 15 wt% (in the steps of 3) were developed. These composites were characterized for physical, mechanical, chemical and tribological performance.
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