186 research outputs found
Numerical Analysis of Methane Direct Injection in a Single-cylinder 250 cm3 Spark Ignition Engine
No full textThe paper shows the results of the numerical tasks of a study aimed to evaluate the potential of low-pressure (< 20 bar) direct injection systems for internal combustion engines fed with gaseous fuels. Starting from the geometry of a low-cost commercial injector already available for GDI uses, a 2D axisymmetric CFD analyses is performed to assess the influence of injection pressure and valve and seat-valve profiles on jet characteristics, methane-air mixing, and charge distribution at ignition time. Then 3D simulations for the motorcycle single cylinder test-engine are carried out considering as much as possible combustion chamber details and realistic boundary conditions. Although it is possible identifying which operating and geometrical details of injection system are able to support complete mixture homogeneity, this study shows tremendous difficulties, in case of gaseous fuels, to realise satisfactory stratification charges that would be required to obtain satisfactory performance at partial loads
Hydro-Pneumatic Driveline for Passenger Car Applications
No full textReal driving cycles are characterized by a sequence of accelerations, cruises, decelerations and engine idling. Recovering the braking energy is the most effective way to reduce the propulsive energy supply by the thermal engine. The fuel energy saving may be much larger than the propulsive energy saving because the ICE energy supply may be cut where the engine operates less efficiently and because the ICE can be made smaller. The present paper discusses the state of the art of hydro-pneumatic drivelines now becoming popular also for passenger cars and light duty vehicle applications permitting series and parallel hybrid operation. The papers presents the thermal engine operation when a passenger car fitted with the hydro-pneumatic hybrid driveline covers the hot new European driving cycle. From a reference fuel consumption of 4.71 liters/100 km with a traditional driveline, the fuel consumption reduces to 2.91 liters/100 km
Similarity rules and parametric design of race engines
No full textThe paper shows results fom the comparison between V10 and V12 engines for racing applications. Results are derived from a combination of experimental data and 1d simulations
"Comparison of V10 and V12 F1 Engines"
No full textThe paper compares 3.0 liter F1 engines having different architectures and developed in compliance with the 1998 FIA technical regulations. Similarity rules and non dimensional parameters from previous projects define key geometry and operating parameters for V10 and V12 engines having equal degree of sophistication. The paper presents computed classical engine outputs versus engine speed, including brake, indicated and friction values. The V12 solution shows clear advantages in terms of pure engine performances
Reassessing the projections of the World Water Development Report
No full textThe 2018 edition of the United Nations World Water Development Report stated that nearly 6 billion peoples will suffer from clean water scarcity by 2050. This is the result of increasing demand for water, reduction of water resources, and increasing pollution of water, driven by dramatic population and economic growth. It is suggested that this number may be an underestimation, and scarcity of clean water by 2050 may be worse as the effects of the three drivers of water scarcity, as well as of unequal growth, accessibility and needs, are underrated. While the report promotes the spontaneous adoption of nature-based-solutions within an unconstrained population and economic expansion, there is an urgent need to regulate demography and economy, while enforcing clear rules to limit pollution, preserve aquifers and save water, equally applying everywhere. The aim of this paper is to highlight the inter-linkage in between population and economic growth and water demand, resources and pollution, that ultimately drive water scarcity, and the relevance of these aspects in local, rather than global, perspective, with a view to stimulating debate
Electrically Driven Quantum Light Sources
No full textTypical applications of quantum light require optical sources which generate either individual photons or entangled (correlated) photons. For the sake of practicality and scalability, these quantum sources should be easily produced, operate at room temperature, and be electrically excited and controlled. Here, recent research on quantum sources obtained from electrically driven (ED) devices constructed from p-n junctions integrated in planar optical cavities, micropillars, nanowires, photonic crystals, and active plasmonic elements is reviewed. Single-photon and entangled-photon sources are distinguished by their different roles in the development of either quantum cryptography or quantum computing protocols, and the different types of devices used to produce them are highlighted, with a focus on their spectral emission, brightness, and conditions of operation. Achievements to date are summarized and compared with prerequisites for the practical use of these sources. Important recent results that could provide future novel quantum sources are also in focus, where more practical requirements could be addressed by the judicious engineering of materials and careful device design
A Preliminary Study of a Graphene Fractal Sierpinski Antenna
No full textWe provide a preliminary study of a Graphene fractal antenna operating at THz frequencies with the opportunity to modulate the emission. There are a number of advantages of the fractal design, namely multiband/wideband ability, and, a smaller, lighter and simpler configuration for higher gain, that can benefit from the coupling with Graphene, the thinnest and strongest of materials exhibiting very high electrical conductivity and tunability. This paper proposes a conceptual background for the study and presents some preliminary results on the electromagnetic emission simulations undertake
Towards Single Biomolecule Imaging via Optical Nanoscale Magnetic Resonance Imaging
No full textNuclear magnetic resonance (NMR) spectroscopy is a physical marvel in which electromagnetic radiation is charged and discharged by nuclei in a magnetic field. In conventional NMR, the specific nuclei resonance frequency depends on the strength of the magnetic field and the magnetic properties of the isotope of the atoms. NMR is routinely utilized in clinical tests by converting nuclear spectroscopy in magnetic resonance imaging (MRI) and providing 3D, noninvasive biological imaging. While this technique has revolutionized biomedical science, measuring the magnetic resonance spectrum of single biomolecules is still an intangible aspiration, due to MRI resolution being limited to tens of micrometers. MRI and NMR have, however, recently greatly advanced, with many breakthroughs in nano-NMR and nano-MRI spurred by using spin sensors based on an atomic impurities in diamond. These techniques rely on magnetic dipole-dipole interactions rather than inductive detection. Here, novel nano-MRI methods based on nitrogen vacancy centers in diamond are highlighted, that provide a solution to the imaging of single biomolecules with nanoscale resolution in-vivo and in ambient conditions. Recent measurements with near surface NV centers in diamonds have allowed high resolution nano-MRI in ambient conditions. This brings us closer to the visualization of the full 3D morphology of biomolecules. The image shows a confocal modality to sense a small ensemble of nuclear spins at nanometric distance from an NV center sensor
Nitrogen-vacancy centers in diamond for nanoscale magnetic resonance imaging applications
No full textThe nitrogen-vacancy (NV) center is a point defect in diamond with unique properties for use in ultra-sensitive, high-resolution magnetometry. One of the most interesting and challenging applications is nanoscale magnetic resonance imaging (nano-MRI). While many review papers have covered other NV centers in diamond applications, there is no survey targeting the specific development of nano-MRI devices based on NV centers in diamond. Several different nano-MRI methods based on NV centers have been proposed with the goal of improving the spatial and temporal resolution, but without any coordinated effort. After summarizing the main NV magnetic imaging methods, this review presents a survey of the latest advances in NV center nano-MRI
Recovery of exhaust and coolant heat with R245fa organic Rankine cycles in a hybrid passenger car with a naturally aspirated gasoline engine
No full textIn internal combustion engines, only a part of the fuel energy flow is transformed into power available at the crankshaft, while the most part of the fuel energy flow is lost as coolant, exhaust gases and other waste heat flows. Recovery of waste heat from the exhaust gases, and the coolant with organic Rankine cycles (ORC) is considered here for a hybrid vehicle powered by a 1.8 L naturally aspirated gasoline engine. the ORC systems fitted on the exhaust and the coolant permit an increase in fuel conversion efficiency by up to 6.4% and 2.8% individually, and by up to 8.2% combined. the average improvements all over the map are 3.4%, 1.7% and 5.1% respectively. These gross improvements do not account for the less than uniform efficiency of the mechanical-to-electric-to- chemical-to-electric-to-mechanical loop when the ORC expanders are used to charge the battery of the hybrid vehicle. Nor do they account for the reduced efficiency of the thermal engine due to the back pressure effects on the indicated mean effective pressure (exhaust ORC) and friction mean effective pressure (coolant ORC). Nevertheless, these values serve as a reference point for the assessment of the current potential of a technology that is still being developed having major downfalls in the increase of weight, costs, packaging complexity and finally in difficulty in transient operation. © 2011 Published by Elsevier Ltd. All rights reserved
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