Integrated In-Cylinder / CHT Methodology for the Simulation of the Engine Thermal Field: An Application to High Performance Turbocharged DISI Engines

New SI engine generations are characterized by a simultaneous reduction of the engine displacement and an increase of the brake power; such targets are achieved through the adoption of several techniques such as turbocharging, direct fuel injection, variable valve timing and variable port lengths. This design approach, called "downsizing", leads to a marked increase in the thermal loads acting on the engine components, in particular on those facing the combustion chamber. Hence, an accurate evaluation of the thermal field is of primary importance in order to avoid mechanical failures. Moreover, the correct evaluation of the temperature distribution improves the prediction of pointwise abnormal combustion onset. The paper proposes an evolution of the CFD methodology previously developed by the authors for the prediction of the engine thermal field, which is applied to two different high performance turbocharged DISI engines: the methodology employs both in-cylinder 3D-CFD combustion simulations and CHT (Conjugate Heat Transfer) simulations of the whole engine, inclusive of both the solid components and the coolant circuit. In-cylinder analyses are used as thermal boundary conditions for the CHT simulations, which are in turn a fundamental benchmark to evaluate the accuracy of the combustion heat flux estimation by means of a combination of global engine thermal survey and local temperature measurements. A preliminary evaluation of some consolidated heat transfer models is carried out to evaluate the accuracy of the predicted gas-to-wall heat fluxes. Then, a modified heat transfer model is proposed, critically motivated and applied to the specific engine conditions under investigations. The proposed model strongly improves the predictive capability of the combined in-cylinder/CHT methodology in terms of both global thermal balance and pointwise temperature distribution for both the investigated engine

a numerical investigation on the potentials of water injection to increase knock resistance and reduce fuel consumption in highly downsized gdi engines

Abstract 3D CFD analyses are used to analyse the effects of port-injection of water in a high performance turbocharged GDI engine. Particularly, water injection is adopted to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock resistance. A full-load / maximum power engine operation of a currently made turbocharged GDI engine is investigated comparing the actual adopted fuel-only rich mixture to stoichiometric-to-lean mixtures, for which water is added in the intake port under constant charge cooling in the combustion chamber. In order to find the optimum fuel/water balance, preliminary analyses are carried out using a chemical reactor to evaluate the effects of charge dilution and mixture modification on both autoignition delays and laminar flame speeds. Thanks to the lower chemical reactivity of the diluted end gases, the water-injected engine allows the spark advance (SA) to be increased; as a consequence, engine power target is met, or even crossed, with a simultaneous relevant reduction of fuel consumption

Effects on Knock Intensity and Specific Fuel Consumption of Port Water/Methanol Injection in a Turbocharged GDI Engine: Comparative Analysis

Abstract The recent rise in fuel prices, the need both to reduce ground transport-generated emissions (increasingly constrained by legislation) and to improve urban air quality have brought fuel-efficient, low-emissions powertrain technologies at the top of vehicle manufacturers' and policy makers' agenda. To these aims, engine design is now oriented towards the adoption of the so-called downsizing and down-speeding techniques, while preserving the performance target. Therefore, brake mean effective pressure is markedly increasing, leading to increased risks of knock onset and abnormal combustions in last-generation SI engines. To counterbalance the increased risks of pre-ignition, knock or mega-knock, currently made turbocharged SI engines usually operate with high fuel enrichments and delayed (sometimes negative) spark advances. The former is responsible for high fuel consumption levels, while the latter induce an even lower A/F ratio (below 11), to limit the turbine inlet temperature, with huge negative effects on BSFC. Possible solutions to increase knock resistance are investigated in the paper by means of 3D-CFD analyses: water, water/methanol emulsion and methanol are port-fuel injected to replace mixture enrichment while preserving, if not improving, indicated mean effective pressure and knock safety margins. The aim of the work is therefore the replacement of the gasoline-only rich mixture with a global stoichiometric one while avoiding power loss and improving fuel consumption. In order to maintain the same knock tendency, water, methanol or a mixture of the two is then added in the intake port to keep the same charge cooling of the original rich mixture. Different strategies in terms of methanol/water ratios of the port injected mixture are compared in order to find the best trade-off between fuel consumption, performance and knock tendency

Numerical investigation on the effects of bore reduction in a high performance turbocharged GDI engine. 3D investigation of knock tendency

Abstract Downsizing is a must for current high performance turbocharged SI engines. This is often achieved through the reduction of cylinder number, while keeping constant unit displacement and increasing boost pressure. However, the ensuing higher loads strongly increases the risk of abnormal combustion and thermo-mechanical failures. An alternative path to downsizing is the reduction of cylinder bore: this approach is more expensive, requiring a brand new design of the combustion system, but it also provides some advantages. The goal of the present paper is to explore the potential of bore reduction for achieving a challenging downsizing target, while preserving the engine knock safety margins. A current V8 GDI turbocharged sporting engine is taken as a reference, and a preliminary CFD-3D analysis is carried out in order to define the most suitable bore-to-stroke ratio. On this basis, bore is reduced by 11% at constant stroke, thus obtaining a reduction of about 20% on the engine displacement. In order to achieve the same peak power target, both engine boost and spark advance are adjusted until the knock safety margin of the original engine is met. 3D CFD tools, accurately calibrated on the reference engine, are used to address engine design and the calibration of the operating parameters

A novel ventilated thermoplastic mesh bandage for post-operative management of large soft tissue defects: a case series of three dogs treated with autologous platelet concentrates

A ventilated thermoplastic mesh bandage was used for the post-operative management of large soft tissue defects in three dogs. Once the granulation tissue appeared, the wounds were treated with liquid or jellified autologous platelet concentrates, Platelet Rich Plasma (PRP) and Platelet Lysate (PL), to improve the wound healing process. After cleaning the wound with sterile physiological solution, a dressing was performed with several layers of cotton. A window through the layers of cotton was opened above the wound. Then, the platelet concentrate was topically applied, and the bandage was completed by placing, over the access window, a ventilated thermoplasticmeshmodeled according to the size and shape of the wound. After 24 h, it was replaced by a low adhesion bandage. The thermoplastic mesh avoids the direct contact between the wound and the external layers of the bandage, preventing the drainage of the topical agent and the removal of the growing healthy granulation tissue. The bandage proposed in this study is easily applied by the veterinarian and well-tolerated by the animal, ensuring high welfare standards in stressed patients presenting compromised clinical conditions

Impact of the Primary Break-Up Strategy on the Morphology of GDI Sprays in 3D-CFD Simulations of Multi-Hole Injectors

The scientific literature focusing on the numerical simulation of fuel sprays is rich in atomization and secondary break-up models. However, it is well known that the predictive capability of even the most diused models is aected by the combination of injection parameters and operating conditions, especially backpressure. In this paper, an alternative atomization strategy is proposed for the 3D-Computational Fluid Dynamics (CFD) simulation of Gasoline Direct Injection (GDI) sprays, aiming at extending simulation predictive capabilities over a wider range of operating conditions. In particular, attention is focused on the eects of back pressure, which has a remarkable impact on both the morphology and the sizing of GDI sprays. 3D-CFD Lagrangian simulations of two dierent multi-hole injectors are presented. The first injector is a 5-hole GDI prototype unit operated at ambient conditions. The second one is the well-known Spray G, characterized by a higher back pressure (up to 0.6 MPa). Numerical results are compared against experiments in terms of liquid penetration and Phase Doppler Anemometry (PDA) data of droplet sizing/velocity and imaging. CFD results are demonstrated to be highly sensitive to spray vessel pressure, mainly because of the atomization strategy. The proposed alternative approach proves to strongly reduce such dependency. Moreover, in order to further validate the alternative primary break-up strategy adopted for the initialization of the droplets, an internal nozzle flow simulation is carried out on the Spray G injector, able to provide information on the characteristic diameter of the liquid column exiting from the nozzle

A methodology to reduce the computational effort in 3D-CFD simulations of plate-fin heat exchangers

The analysis of a plate-fin heat exchanger performance requires the evaluation of key parameters such as heat transfer and pressure drop. In this regard, computational Fluid Dynamics (CFD) can be proficiently adopted, at the design stage, to predict the performance of plate-fin heat exchangers. However, these last are often characterized by a complex geometry, such as in the case of plate exchangers with turbulators, leading to a huge computational effort, which often exceeds the available resources. In this study, a numerical methodology for the simulation of plate heat exchangers is proposed, to bypass the limits imposed by the computational cost. The methodology relies on the simulation of a minimal portion of the exchanger (two plates, one per fluid) characterized by periodic boundary conditions (that mimic the presence of several layers). The total heat exchanged is obtained simply multiplying the calculated heat transfer by the number of plate couples composing the device. Moreover, the two plates allow to calibrate porous media which are adopted to rebuild (in a simplified version) the two fluid circuits of the whole exchanger and obtain the overall pressure drop across the device for both the hot and cold fluids. The proposed approach is validated against experimental data of an oil cooler for automotive application, that is a plate-fin heat exchanger characterized by the presence of turbulators. The numerical outcomes are compared to the experiments in terms of pressure drop and heat transfer for a wide range of volumetric flow rates. Particular attention is devoted to the mesh sensitivity and the adopted computational grid minimizes the number of cells (and, thus, the computational cost), without compromising the accuracy. Moreover, the Reynolds-Stress-Transport turbulence model is accurately selected among the most diffused ones, in order to properly match the test bench data. The proposed methodology allows to reduce of nearly one order of magnitude the total number of cells required for the simulation of the heat exchanger performance. The heat transfer is predicted with high accuracy, i.e. error is always lower than 4%. As for the pressure loss, the deviation compared to the experiments increases up to nearly 15% (for one of the simulated conditions) but it is considered still acceptable

Interplay between COVID-19, pollution, and weather features on changes in the incidence of acute coronary syndromes in early 2020

Coronavirus disease 2019 (COVID-19) has caused an unprecedented change in the apparent epidemiology of acute coronary syndromes (ACS). However, the interplay between this disease, changes in pollution, climate, and aversion to activation of emergency medical services represents a challenging conundrum. We aimed at appraising the impact of COVID-19, weather, and environment features on the occurrence of ST-elevation myocardial infarction (STEMI) and non-ST-elevation myocardial infarction (NSTEMI) in a large Italian region and metropolitan area

Mineração de Dados Educacionais e Learning Analytics no contexto educacional brasileiro: um mapeamento sistemático

A partir de um mapeamento sistemático buscou-se verificar as contribuições de Learning Analytics e Mineração de Dados Educacionais no contexto educacional brasileiro. Optou-se por fontes de busca em três revistas na área de Informática na Educação e Anais de dois eventos de relevância nacional onde foram verificados 136 artigos entre janeiro de 2008 e março de 2020. Após a aplicação dos critérios de exclusão e de qualidade foram selecionados 71 artigos. Os resultados apresentam a maior ocorrência de projetos com finalidade de analisar desempenho acadêmico e prevenção de evasão escolar, embora nos últimos anos os assuntos estejam apresentando diversificação temática. Grande parte são voltados ao Ensino Superior e na modalidade de Educação a Distância. Há variedade de tecnologias e recursos utilizados no desenvolvimento de soluções em LA ressaltando o uso de Linguagem R, MySQL e a ferramenta Weka

Production of Plant Secondary Metabolites: Examples, Tips and Suggestions for Biotechnologists

Plants are sessile organisms and, in order to defend themselves against exogenous (a)biotic constraints, they synthesize an array of secondary metabolites which have important physiological and ecological effects. Plant secondary metabolites can be classified into four major classes: terpenoids, phenolic compounds, alkaloids and sulphur-containing compounds. These phytochemicals can be antimicrobial, act as attractants/repellents, or as deterrents against herbivores. The synthesis of such a rich variety of phytochemicals is also observed in undifferentiated plant cells under laboratory conditions and can be further induced with elicitors or by feeding precursors. In this review, we discuss the recent literature on the production of representatives of three plant secondary metabolite classes: artemisinin (a sesquiterpene), lignans (phenolic compounds) and caffeine (an alkaloid). Their respective production in well-known plants, i.e., Artemisia, Coffea arabica L., as well as neglected species, like the fibre-producing plant Urtica dioica L., will be surveyed. The production of artemisinin and caffeine in heterologous hosts will also be discussed. Additionally, metabolic engineering strategies to increase the bioactivity and stability of plant secondary metabolites will be surveyed, by focusing on glycosyltransferases (GTs). We end our review by proposing strategies to enhance the production of plant secondary metabolites in cell cultures by inducing cell wall modifications with chemicals/drugs, or with altered concentrations of the micronutrient boron and the quasi-essential element silicon