Recursos de colección

Archivo Digital UPM (114.354 recursos)

This is an institutional repository providing access to the research output of the institution. Primarily contains thesis.

Materia = Mécanica

Mostrando recursos 1 - 19 de 19

  1. New reynolds equation for line contact based on the carreau model modification by bair

    Guerra Ochoa, Eduardo de la; Echávarri Otero, Javier; Chacón Tanarro, Enrique; Lafont Morgado, Pilar; Diaz Lantada, Andres; Muñoz Guijosa, Juan Manuel; Muñoz Sanz, José Luis
    This paper presents a new form of the one-dimensional Reynolds equation for lubricants whose rheological behaviour follows a modified Carreau rheological model proposed by Bair. The results of the shear stress and flow rate obtained through a new Reynolds–Carreau equation are shown and compared with the results obtained by other researchers.

  2. Influence of the rheological behaviour of the lubricant on the appearance of pitting in elastohydrodynamic eegime

    Echávarri Otero, Javier; Guerra Ochoa, Eduardo de la; Chacón Tanarro, Enrique; Lafont Morgado, Pilar; Diaz Lantada, Andres; Muñoz Guijosa, Juan Manuel; Muñoz Sanz, José Luis
    This paper analyses the influence of lubricant behaviour on the appearance of pitting. It attempts to study the effect of viscosity?pressure relation, compressibility, film thickness?roughness relation and friction coefficient on pitting failure of the contacting elements.To explain these effects, we first deal with the influence of the oil on the lubrication of the contact using elastohydrodynamic theory and secondly two multiaxial fatigue criteria are used, Crossland criterion and Dang Van criterion, to evaluate the influence of the rheology on the appearance of pitting. Finally, different applications are presented together with a discussion on the results obtained.

  3. Use of alternative fuels obtained from renowable sources in Brayton cycles

    Escudero Olano, Marcos; Jiménez Alvaro, Ángel; López Paniagua, Ignacio; Rodríguez Martín, Javier
    Analysis and simulation of the behaviour of gas turbines for power generation using different nonconventional fuels obtained from different renewable sources are presented. Three biomass-tobiofuel processes are considered: anaerobic digestion of biomass (biogas), biomass gasification (synthesis gas) and alcoholic fermentation of biomass and dehydration (bioethanol), each of them with two different biomass substrates (energy crops and municipal solid waste) as input. The gas turbine behaviour in a Brayton cycle is simulated both in an isolated operation and in combined cycle. The differences in gas turbine performance when fired with the considered biofuels compared to natural gas are studied from different...

  4. Análisis de la influencia de los diferentes parámetros de diseño en la aparición de fatiga superficial en contactos mecánicos

    Guerra Ochoa, Eduardo de la
    La fatiga superficial es uno de los principales problemas en las transmisiones mecánicas y es uno de los focos de atención de las investigaciones de los últimos anos en Tribología. La disminución de viscosidad de los lubricantes para la mejora de la eficiencia, el aumento de las potencias a transmitir, el aumento de la vida de los componentes o la mejora de su fiabilidad han supuesto que los fenómenos de fatiga superficial hayan cobrado especial relevancia, especialmente los fenómenos de pitting y micropitting en cajas multiplicadoras/reductoras de grandes potencias de aplicación, por ejemplo, en el sector eólico. Como todo fenómeno...

  5. Desarrollo de un procedimiento para el cálculo de la fuerza de fricción en un contacto EHD. Validación experimental del procedimiento

    Fernández Ruiz-Morón, Luis
    Con objeto de minimizar la fricción y desgaste, la industria diseña sus máquinas para que estas funcionen en régimen elastohidrodinámico durante el mayor tiempo posible. Científicos de todos los tiempos han dedicado sus vidas al estudio de la lubricación en régimen de película gruesa. Con especial interés, Ingenieros del último siglo y medio han realizado multitud de experimentos y, con los medios disponibles en su momento, han analizado y tabulado resultados, con objeto de disponer de herramientas que permitieran calcular la fuerza de fricción en contactos EHD. En el presente trabajo de tesis se ha elaborado un modelo propio de...

  6. Use of alternative fuels obtained from renewable sources in brayton cycles

    Escudero Olano, Marcos; Jiménez Alvaro, Ángel; López Paniagua, Ignacio; Rodríguez Martín, Javier
    Analysis and simulation of the behaviour of gas turbines for power generation using different nonconventional fuels obtained from different renewable sources are presented. Three biomass-tobiofuel processes are considered: anaerobic digestion of biomass (biogas), biomass gasification (synthesis gas) and alcoholic fermentation of biomass and dehydration (bioethanol), each of them with two different biomass substrates (energy crops and municipal solid waste) as input. The gas turbine behaviour in a Brayton cycle is simulated both in an isolated operation and in combined cycle. The differences in gas turbine performance when fired with the considered biofuels compared to natural gas are studied from different...

  7. Estudio de las emisiones de CO2 en una instalación de turbina de gas con diferentes combustibles

    Nieto Carlier, Rafael; López Paniagua, Ignacio; Jiménez Alvaro, Ángel; Rodríguez Martín, Javier; González Fernández, M. Celina
    El uso de las turbinas de gas en ciclo combinado es una de las alternativas más aceptadas en los últimos tiempos. Existen muchas razones por las que se está investigando sobre la posibilidad de usar otro tipo de combustibles como alternativa al característico, gas natural (metano). Entre otras, se pueden citar: la evolución del precio y la disponibilidad en una zona de algún tipo de gas de síntesis [17] así como estrategias medioambientales y de emisiones [10], [18], [20]. En la bibliografía se encuentran estudios, en los que de forma rigurosa se establece la relación entre la eficiencia de una...

  8. Heat transfer in separated flows on the pressure side of turbine blades

    Calzada, Pedro de la; Valdés del Fresno, Manuel; Burgos, M.A.
    Heat transfer in separated flows on the pressure side of a typical high lift turbine profile is numerically investigated by means of an in-house CFD code. The numerical code was first validated on attached flows in turbine blades. To obtain flow separation cases, the profile is subject to large negative incidences so that a separation bubble is obtained at the pressure side. The numerical results are compared to available experimental data for code validation. It is shown how local minima and maxima values of the heat transfer coefficient are related to the separation and reattachment points, where the velocity component...

  9. On existence of trends applicable to thermoeconomic optimisation of combined cycle gas turbine power plants

    Valdés del Fresno, Manuel; Rovira de Antonio, Antonio José; Durán, María Dolores
    This paper aims at the influence of the nominal power on the design configuration of combined cycle gas turbine (CCGT) power plants. This is achieved by means of a thermoeconomic model aimed at the minimisation of the power plant cost. The present work starts with the establishment of trends in existing commercial gas turbines. Based on these, other trends are found for the design of the whole CCGT, leading to the assessment of the most suitable heat recovery steam generator type and the optimal design parameters. Finally, an analysis of the influence of fuel price on the design configuration is...

  10. Cálculo de la resistencia a la fatiga superficial en superficies con lubricación elastohidrodinámica mediante el criterio de Dang Van

    Guerra Ochoa, Eduardo de la; Chacón Tanarro, Enrique; Lafont Morgado, Pilar; Echávarri Otero, Javier; Muñoz Guijosa, Juan Manuel; Muñoz Sanz, José Luis; Diaz Lantada, Andres
    Los fenómenos de fatiga superficial en sus diferentes escalas (micropitting, pitting, spalling), aparecen en multitud de elementos mecánicos en contacto lubricado como pueden ser los engranajes o rodamientos o en elementos con contacto seco como son las ruedas de ferrocarril. Los defectos que aparecen en las superficies en contacto debidos a estos fenómenos empeoran las condiciones de funcionamiento, provocando vibraciones, desgaste prematuro y en los casos más extremos el fallo de la máquina. El procedimiento que se sugiere en este artículo se inicia con el cálculo de los parámetros que definen el contacto elastohidrodinámico y que tienen influencia en la...

  11. Optimizador Multicriterio de la Velocidad de un Vehículo de Carretera

    Jiménez, Felipe; Tapia Fernández, Santiago; Cabrera, Wilmar
    Entre los objetivos de los sistemas inteligentes de transporte se encuentra la mejora de la seguridad, la reducción del consumo y el impacto medioambiental, aumentar la satisfacción de los usuarios, etc. Estos sistemas están basados en la captación, procesamiento y uso de la información, con lo que se podrían adoptar acciones con anticipación. Dentro de los ITS, un campo muy relevante lo constituyen los sistemas de control de la velocidad que suelen considerar, en general, únicamente los límites legales. Los sistemas más sofisticados, incluyen límites adicionales por condicionamientos de seguridad en puntos singulares como curvas, cruces, incorporaciones, etc. Un paso...

  12. A model to predict the behaviour at part load operation of once-through heat recovery steam generators working with water at supercritical pressure

    Rovira de Antonio, Antonio José; Valdés del Fresno, Manuel; Durán, María Dolores
    This paper describes a one-dimensional mathematical model that allows simulating the heat exchange in a steam generator working with water at supercritical pressure. The model has been developed in order to simulate the full and part load behaviour of heat recovery steam generators (HRSGs) of combined cycle gas turbine (CCGT) power plants. It takes into account the strong variation of some of the thermal and transport properties of fluids at supercritical pressure and discusses what parameters may be considered as constant along the heat exchanger. On the one hand, the model is useful because going supercritical is considered a way to...

  13. Influence of the stop/start system on CO2 emissions of a diesel vehicle in urban traffic

    Fonseca González, Natalia Elizabeth; Casanova Kindelán, Jesús; Valdés del Fresno, Manuel
    This paper presents measurements of CO2 emission and efficiency of stop/start technology on a diesel vehicle in urban traffic. Two four-wheel-drive diesel vehicles with on-board exhaust emission and vehicle activity measurement systems were tested in two urban driving circuits representative of downtown Madrid. The vehicles had similar turbocharged and intercooled diesel engines fulfilling the same Euro 4 emissions regulation; but one had an improved engine incorporating stop/start technology. CO2 emission reduction of more than 20% for the car equipped with the stop/start system was obtained. Regardless of the variability in driving style, the grade and type of streets, traffic congestion,...

  14. Material selection for spallation neutron source windows. Application to PDS-XADS and XT-ADS prototypes

    Sordo Balbín, Fernando; Abánades Velasco, Alberto; Lafuente Mazuecos, Antonio; Martínez-Val Peñalosa, José María; Perlado Martín, José Manuel
    High performance neutron sources are being proposed for many scientific and industrial applications, ranging from material studies, hybrid reactors and transmutation of nuclear wastes. In the case of transmutation of nuclear wastes, accelerator driven systems (ADS) are considered as one of the main technical options for such purpose. In ADS a high performance spallation neutron source becomes an essential element for its operation and control. This spallation source must fulfil very challenging nuclear and thermo-mechanical requirements, because of the high neutron rates needed in ADS. The material selection for this key component becomes of paramount importance, particularly the source window...

  15. Solar multiple optimization for a solar-only thermal power plant, using oil as heat transfer fluid in the parabolic trough collectors

    Montes Pita, María José; Abánades Velasco, Alberto; Martínez-Val Peñalosa, José María; Valdés del Fresno, Manuel
    Usual size of parabolic trough solar thermal plants being built at present is approximately 50 M We. Most of these plants do not have a thermal storage system for maintaining the power block performance at nominal conditions during long non-insolation periods. Because of that, a proper solar field size, with respect to the electric nominal power, is a fundamental choice. A too large field will be partially useless under high solar irradiance values whereas a small field will mainly make the power block to work at part-load conditions. This paper presents an economic optimization of the solar multiple for a...

  16. The Evolution and Development of Mechanical Engineering through large cultural areas

    Muñoz Sanz, José Luis; Bautista Paz, Emilio; Ceccarelli, Marco; Echávarri Otero, Javier; Lafont Morgado, Pilar; Diaz Lantada, Andres; Leal Wiña, María del Pilar; Lorenzo Yustos, Héctor; Muñoz Guijosa, Juan Manuel; Muñoz García, Julio
    Mechanical Engineering is probably the forerunner of many branches of Engineering and has persistently been their companion up to the present. For this reason, the History of Machines embraces a very broad period of the History of Mankind, and can be studied from many perspectives. This paper attempts to link progress in Mechanical Engineering to the great cultures that have arisen throughout the History of Mankind. This paper begins with the anonymous mechanical developments that appeared in Prehistory and opened up the way to the first civilisations, marked to a large extent, maybe, by Greco-Roman culture in Europe and by...

  17. Models for predicting friction coefficient and parameters with influence in elastohydrodynamic lubrication

    Lafont Morgado, Pilar; Echávarri Otero, Javier; Muñoz Sanz, José Luis; Diaz Lantada, Andres; Muñoz Guijosa, Juan Manuel; Lorenzo Yustos, Héctor; Leal Wiña, María del Pilar; Muñoz García, Julio
    This article shows different friction prediction models applicable to lubricants in point contacts under an elastohydrodynamic regime. The types of models used are two variations of the Newtonian theory, the Limiting Shear Stress model and the one based on Carreau's equation. The article sets out the theoretical calculation procedures and the ensuing equations for calculating the friction coefficient. The aims of the article are to study the effect of the parameters with influence on friction and to compare the model's results with those given by an experimental stage performed on a mini traction machine. This test system allows the measurement...

  18. A dislocation dynamics study of the strength of stacking fault tetrahedra. Part II: interactions with mixed and edge dislocations

    Martínez Sáez, Enrique; Marian, Jaime; Perlado Martín, José Manuel
    In this paper we present the sequel to Part I and present a comprehensive dislocation dynamics study of the strength of stacking fault tetrahedra to mixed and edge dislocation glides in fcc Cu.

  19. A dislocation dynamics study of the strength of stacking fault tetrahedra. Part I: interactions with screw dislocations

    Martínez Sáez, Enrique; Marian, Jaime; Arsenlis, A.; Victoria, Maximo Pedro; Perlado Martín, José Manuel
    We present a comprehensive dislocation dynamics (DD) study of the strength of stacking fault tetrahedra (SFT) to screw dislocation glide in fcc Cu. Our methodology explicitly accounts for partial dislocation reactions in fcc crystals, which allows us to provide more detailed insights into the dislocation– SFT processes than previous DD studies. The resistance due to stacking fault surfaces to dislocation cutting has been computed using atomistic simulations and added in the form of a point stress to our DD methodology. We obtain a value of 1658.9 MPa, which translates into an extra force resolved on the glide plane that dislocations...

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