Internal Modifications to Optimize Pollution and Emissions of Internal Combustion Engines through Multiple-Criteria Decision-Making and Artificial Neural Networks

[Abstract] The present work proposes several modifications to optimize both emissions and consumption in a commercial marine diesel engine. A numerical model was carried out to characterize the emissions and consumption of the engine under several performance parameters. Particularly, five internal modifications were analyzed: water addition; exhaust gas recirculation; and modification of the intake valve closing, overlap timing, and cooling water temperature. It was found that the result on the emissions and consumption presents conflicting criteria, and thus, a multiple-criteria decision-making model was carried out to characterize the most appropriate parameters. In order to analyze a high number of possibilities in a reasonable time, an artificial neural network was developed

Analysis of a nature-inspired shape for a vertical axis wind turbine

[Abstract] Wind energy is gaining special interest worldwide due to the necessity of reducing pollutant emissions and employ renewable resources. Traditionally, horizontal axis wind turbines have been employed but certain situations require vertical axis wind turbines. With a view to improve the efficiency of a vertical axis wind turbine Savonius type, the present work proposes a bioinspired design blade profile relying on the Fibonacci spiral. This shape is repeatedly presented in nature and thus it leads to a bio-inspired blade profile. A numerical model was carried out and it was found that the Fibonacci shape improves the performance of the original Savonius shape, based on semicircular blade profiles. Particularly, the Fibonacci blade profile increases around 14% the power in comparison with the Savonius blade profile. Besides this comparison between Savonius and Fibonacci, a research study was carried out to improve the efficiency of the Fibonacci turbine. To this end, the effect of several parameters was analyzed: number of blades, aspect ratio, overlap, separation gap, and twist angle. Improvements on the average power greater than 30% were obtained

Numerical analysis of emissions from marine engines using alternative fuels

The current restrictions on emissions from marine engines, particularly sulphur oxides (SOx ), nitrogen oxides (NOx ) and carbon dioxide (CO2 ), are compelling the shipping industry to a change of tendency. In the recent years, many primary and secondary reduction techniques have been proposed and employed in marine engines. Nevertheless, the increasingly restrictive legislation makes it very difficult to continue developing efficient eduction procedures at competitive prices. According to this, the paper presents the possibility to employ alternative fuels. A numerical model was developed to analyze the combustion process and emissions using oil fuel, natural gas and hydrogen. A commercial marine engine was studied, the Wärtsilä 6L 46. It was found, that hydrogen is the cleanest fuel regarding CO2 , hydrocarbons (HC) and carbon monoxide (CO). Nevertheless, it is very expensive for marine applications. Natural gas is cheaper and cleaner than fuel oil regarding CO2 and CO emissions. Still, natural gas emits more NOx and HC than oil fuel. SOx depends basically on the sulphur content of each particular fuel.S

Optimization of a nature-inspired shape for a vertical axis wind turbine through a numerical model and an artificial neural network

[Abstract] The present work proposes an artificial neural network (ANN) to analyze vertical axis wind turbines of the Savonius type. These turbines are appropriate for low wind velocities due to their low starting torque. Nevertheless, their efficiency is too low. In order to improve the efficiency, several modifications are analyzed. First of all, an innovative blade profile biologically inspired is proposed. After that, the influence of several parameters such as the aspect ratio, overlap, and twist angle was analyzed through a CFD (computational fluid dynamics) model. In order to characterize the most appropriate combination of aspect ratio, overlap, and twist angle, an artificial neural network is proposed. A data set containing 125 data points was obtained through CFD. This data set was used to develop the artificial neural network. Once established, the artificial neural network was employed to analyze 793,881 combinations of different aspect ratios, overlaps, and twist angles. It was found that the maximum power coefficient, 0.3263, corresponds to aspect ratio 7.5, overlap/chord length ratio 0.1125, and twist angle 112. This corresponds to a 32.4% increment in comparison to the original case analyzed with aspect ratio 1, overlap 0, and twist angle 0

Optimización de los procesos de evaluación de riesgos por atmósferas explosivas : aplicación a industrias agroalimentarias y otras de eliminación de residudos

[Resumen] El objetivo de la presente tesis es el estudiar diferentes metodologías para valorar atmósferas explosivas, bien sean por gases, vapores o nieblas y/o por polvos combustibles. Las metodologías propuestas se encuentran basadas en la norma UNE 60079-10 y norma italiana CEI 91-95, ambas normas son de reconocido prestigio y de aplicación en multitud de escenarios. En nuestro caso ambas son comparadas mediante la aplicación a casos prácticos de una industria láctea y a una planta de tratamiento de residuos. Asimismo, han sido elaborados varios modelos CFD simplificados, mediante el código comercial FLUENT, capaz de predecir el comportamiento de la propagación de los escapes de gas y de la propagación de las llamas y variación de presiones para las atmósferas pulverulentas. Los modelos utilizados incluyen diferentes geometrías, condiciones iniciales y de contorno. También se analizan las normas de dimensionamiento más utilizadas para la protección de silos mediante sistemas de venteo, la norma americana NFPA 68 y la europea EN 14491 y su aplicación a los ejemplos estudiados. Por último se hace uso de la técnica de la termografía mediante cámara infrarroja para el estudio de diferentes fuentes de ignición debidas a superficies calientes. Los resultados obtenidos contribuyen a comprender mejor la extensión de las atmósferas explosivas y el desarrollo de las explosiones.[Resumo] O obxectivo da presente tese é estudar diferentes metodoloxías para valorar atmósferas explosivas, ben sexan por gases, vapores ou néboas e/ou por pos combustibles. As metodoloxías propostas encóntranse baseadas na norma UNE 60079-10 e na norma italiana CEI 91-95, ambas normas son de recoñecido prestixio e de aplicación en multitude de escenarios. No noso caso ambas as dúas son comparadas mediante a aplicación a casos prácticos dunha industria láctea e a unha planta de tratamento de residuos. Así mesmo, foron elaborados varios modelos CFD simplificados, mediante o código comercial FLUENT, capaz de predicir o comportamento da propagación dos escapes de gas e da propagación das chamas e variación de presións para as atmósferas pulverulentas. Os modelos utilizados inclúen diferentes xeometrías, condicións iniciais e de contorno. Tamén se analizan as normas de dimensionamento máis utilizadas para a protección de silos mediante sistemas de vento, a norma americana NFPA 68 e a europea EN 14491 e a súa aplicación aos exemplos estudados. Por último faise uso da técnica da termografía mediante cámara infravermella para o estudo de diferentes fontes de ignición debidas a superficies quentes. Os resultados obtidos contribúen a comprender mellor a extensión das atmósferas explosivas e o desenvolvemento das explosións.[Abstract] The objective of this thesis is to study different methodologies to value explosive atmospheres, whether by gases, vapours or mists or combustible dusts. The proposed methodologies are based on the norm UNE 60079-10 and Italian norm CEI 91-95, both standards are prestigious and application in a variety of scenarios. In our case, both are compared by the application to practical cases of a milk industry and waste treatment plant. Several simplified CFD models through the commercial code FLUENT, able to predict the behavior of the spread of the leakage of gas and the spread of the flames and variation of pressures for pulverulentas atmospheres have also been elaborated. The models used include different geometries, initial and boundary conditions. Also sizing standards used to protect silos through systems analyses of venting, the American standard NFPA 68 and the European EN 14491 and its application to the studied examples. Finally makes use of the technique of thermography by infrared camera for the study of different ignition sources due to hot surfaces. The results obtained contribute to better understand the extent of explosive atmospheres and the development of the explosions

Internal modifications to reduce pollutant emissions from marine engines. A numerical approach

Taking into account the increasingly stringent legislation on emissions from marine engines, this work aims to analyze several internal engine modifications to reduce NOx (nitrogen oxides) and other pollutants. To this end, a numerical model was employed to simulate the operation cycle and characterize the exhaust gas composition. After a preliminary validation process was carried out using experimental data from a four-stroke, medium-speed marine engine, the numerical model was employed to study the influence of several internal modifications, such as water addition from 0 to 100% water to fuel ratios, exhaust gas recirculation from 0 to 100% EGR rates, modification of the overlap timing from 60 to 120°, modification of the intake valve closing from 510 to 570°, and modification of the cooling water temperature from 70 to 90 o C. NOx was reduced by nearly 100%. As expected, it was found that, by lowering the combustion temperature, there is a notable reduction in NOx, but an increase in CO (carbon monoxide), HC (hydrocarbons) and consumption.S