Articles de revista
http://hdl.handle.net/2117/3481
2016-09-27T12:16:18ZReliability versus mass optimization of CO2 extraction technologies for long duration missions
http://hdl.handle.net/2117/89135
Reliability versus mass optimization of CO2 extraction technologies for long duration missions
Detrell Domingo, Gisela; Griful Ponsati, Eulàlia; Messerschmid, Ernst
The aim of this paper is to optimize reliability and mass of three CO2 extraction technologies/components: the 4-Bed Molecular Sieve, the Electrochemical Depolarized Concentrator and the Solid Amine Water Desorption. The first one is currently used in the International Space Station and the last two are being developed, and could be used for future long duration missions. This work is part of a complex study of the Environmental Control and Life Support System (ECLSS) reliability. The result of this paper is a methodology to analyze the reliability and mass at a component level, which is used in this paper for the CO2 extraction technologies, but that can be applied to the ECLSS technologies that perform other tasks, such as oxygen generation or water recycling, which will be a required input for the analysis of an entire ECLSS. The key parameter to evaluate any system to be used in space is mass, as it is directly related to the launch cost. Moreover, for long duration missions, reliability will play an even more important role, as no resupply or rescue mission is taken into consideration. Each technology is studied as a reparable system, where the number of spare parts to be taken for a specific mission will need to be selected, to maximize the reliability and minimize the mass of the system. The problem faced is a Multi-Objective Optimization Problem (MOOP), which does not have a single solution. Thus, optimum solutions of MOOP, the ones that cannot be improved in one of the two objectives, without degrading the other one, are found for each selected technology. The solutions of the MOOP for the three technologies are analyzed and compared, considering other parameters such as the type of mission, the maturity of the technology and potential interactions/synergies with other technologies of the ECLSS.
2016-07-25T10:43:03ZDetrell Domingo, GiselaGriful Ponsati, EulàliaMesserschmid, ErnstThe aim of this paper is to optimize reliability and mass of three CO2 extraction technologies/components: the 4-Bed Molecular Sieve, the Electrochemical Depolarized Concentrator and the Solid Amine Water Desorption. The first one is currently used in the International Space Station and the last two are being developed, and could be used for future long duration missions. This work is part of a complex study of the Environmental Control and Life Support System (ECLSS) reliability. The result of this paper is a methodology to analyze the reliability and mass at a component level, which is used in this paper for the CO2 extraction technologies, but that can be applied to the ECLSS technologies that perform other tasks, such as oxygen generation or water recycling, which will be a required input for the analysis of an entire ECLSS. The key parameter to evaluate any system to be used in space is mass, as it is directly related to the launch cost. Moreover, for long duration missions, reliability will play an even more important role, as no resupply or rescue mission is taken into consideration. Each technology is studied as a reparable system, where the number of spare parts to be taken for a specific mission will need to be selected, to maximize the reliability and minimize the mass of the system. The problem faced is a Multi-Objective Optimization Problem (MOOP), which does not have a single solution. Thus, optimum solutions of MOOP, the ones that cannot be improved in one of the two objectives, without degrading the other one, are found for each selected technology. The solutions of the MOOP for the three technologies are analyzed and compared, considering other parameters such as the type of mission, the maturity of the technology and potential interactions/synergies with other technologies of the ECLSS.A meshless finite point method for three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
http://hdl.handle.net/2117/86276
A meshless finite point method for three-dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.
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2016-04-27T14:59:20ZOrtega, EnriqueOñate Ibáñez de Navarra, EugenioIdelsohn Barg, Sergio RodolfoFlores Le Roux, Roberto MauriceA finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.Three-dimensional numerical simulation of an external gear pump with decompression slot and meshing contact point
http://hdl.handle.net/2117/85440
Three-dimensional numerical simulation of an external gear pump with decompression slot and meshing contact point
Castilla López, Roberto; Gámez Montero, Pedro Javier; Campo Sud, David del; Raush Alviach, Gustavo Adolfo; García Vilchez, Mercedes; Codina Macià, Esteban
Recently several works have been published on numerical simulation of an external gear pump (EGP). Such kinds of pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the gearing mechanism between gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal-metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a LINUX cluster with a solver developed with the OPENFOAM Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.
2016-04-08T14:13:47ZCastilla López, RobertoGámez Montero, Pedro JavierCampo Sud, David delRaush Alviach, Gustavo AdolfoGarcía Vilchez, MercedesCodina Macià, EstebanRecently several works have been published on numerical simulation of an external gear pump (EGP). Such kinds of pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the gearing mechanism between gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal-metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a LINUX cluster with a solver developed with the OPENFOAM Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.A meshless finite point method for three dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
http://hdl.handle.net/2117/28569
A meshless finite point method for three dimensional analysis of compressible flow problems involving moving boundaries and adaptivity
Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
A finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.
2015-07-13T10:44:47ZOrtega, EnriqueOñate Ibáñez de Navarra, EugenioIdelsohn Barg, Sergio RodolfoFlores Le Roux, Roberto MauriceA finite point method for solving compressible flow problems involving moving boundaries and adaptivity is presented. The numerical methodology is based on an upwind-biased discretization of the Euler equations, written in arbitrary Lagrangian–Eulerian form and integrated in time by means of a dual-time steeping technique. In order to exploit the meshless potential of the method, a domain deformation approach based on the spring network analogy is implemented, and h-adaptivity is also employed in the computations. Typical movable boundary problems in transonic flow regime are solved to assess the performance of the proposed technique. In addition, an application to a fluid–structure interaction problem involving static aeroelasticity illustrates the capability of the method to deal with practical engineering analyses. The computational cost and multi-core performance of the proposed technique is also discussed through the examples provided.Pressure effects on the performance of external gear pumps under cavitation
http://hdl.handle.net/2117/25113
Pressure effects on the performance of external gear pumps under cavitation
Campo Sud, David del; Castilla López, Roberto; Raush Alviach, Gustavo Adolfo; Gámez Montero, Pedro Javier; Codina Macià, Esteban
The numerical analysis of an external gear pump with cavitation effects has been validated with experimental data obtained by applying Time-Resolved Particle Image Velocimetry. The effect of inlet and outlet pressure on volumetric efficiency has been studied numerically. First, the Particle Image Velocimetry method was used to analyze the two-dimensional velocity field in the middle plane of the suction chamber of the gear pump. The main improvement, with respect to previous similar analysis is the use of alginate micro particles as tracers. It is seen that the two-dimensional model is able to characterize the flow field of the real pump in the region of the inlet chamber in which cavitation is expected. In a previous study, it was seen that a cavitation cloud acted as a virtual contact point at low pressure, being responsible for an increase on the volumetric efficiency. The first set of simulations represents the pump working with high outlet pressure. Now, the cavitation cloud is not present and cavitation no longer helps to improve the efficiency of the pump. The second set of simulations represents the pump with an inlet loss factor, which implies a mean inlet pressure below atmospheric conditions. This allows cavitation clouds to propagate upstream. Despite the larger cavitation clouds, volumetric efficiency only drops at high operating velocities, when some clouds become trapped between gears and casing and are transported to the pressure side.
2014-12-19T16:57:53ZCampo Sud, David delCastilla López, RobertoRaush Alviach, Gustavo AdolfoGámez Montero, Pedro JavierCodina Macià, EstebanThe numerical analysis of an external gear pump with cavitation effects has been validated with experimental data obtained by applying Time-Resolved Particle Image Velocimetry. The effect of inlet and outlet pressure on volumetric efficiency has been studied numerically. First, the Particle Image Velocimetry method was used to analyze the two-dimensional velocity field in the middle plane of the suction chamber of the gear pump. The main improvement, with respect to previous similar analysis is the use of alginate micro particles as tracers. It is seen that the two-dimensional model is able to characterize the flow field of the real pump in the region of the inlet chamber in which cavitation is expected. In a previous study, it was seen that a cavitation cloud acted as a virtual contact point at low pressure, being responsible for an increase on the volumetric efficiency. The first set of simulations represents the pump working with high outlet pressure. Now, the cavitation cloud is not present and cavitation no longer helps to improve the efficiency of the pump. The second set of simulations represents the pump with an inlet loss factor, which implies a mean inlet pressure below atmospheric conditions. This allows cavitation clouds to propagate upstream. Despite the larger cavitation clouds, volumetric efficiency only drops at high operating velocities, when some clouds become trapped between gears and casing and are transported to the pressure side.Holistic indices for productivity control assessment, applied to the comparative analysis of PID and fuzzy controllers within an Isasmelt furnace
http://hdl.handle.net/2117/23378
Holistic indices for productivity control assessment, applied to the comparative analysis of PID and fuzzy controllers within an Isasmelt furnace
Ojeda Sarmiento, Juan Manuel; Fuertes Armengol, José Mª; Griful Ponsati, Eulàlia
This research aims to contribute to the analysis of control performance assessment in extractive metallurgy. Productivity-based indices are proposed in addition to current measuring techniques. Such criteria are employed to compare conventional PID and fuzzy-based controllers in copper smelting. This process is mathematically modeled in order to be simulated. The comparison confirms a better performance of the fuzzy controller in dealing with the molten bath temperature within an Isasmelt furnace. In normal operating conditions (online tests), the proposed controller achieves a consistent mean square relative error reduction of 72% between measured values and the temperature setpoint and standard deviation of approximately 60% (from 27.8 degrees C to 11.1 degrees C). The productivity criteria establish a lower consumption of raw materials (13%) and energy supply (29%).
2014-07-02T09:23:03ZOjeda Sarmiento, Juan ManuelFuertes Armengol, José MªGriful Ponsati, EulàliaThis research aims to contribute to the analysis of control performance assessment in extractive metallurgy. Productivity-based indices are proposed in addition to current measuring techniques. Such criteria are employed to compare conventional PID and fuzzy-based controllers in copper smelting. This process is mathematically modeled in order to be simulated. The comparison confirms a better performance of the fuzzy controller in dealing with the molten bath temperature within an Isasmelt furnace. In normal operating conditions (online tests), the proposed controller achieves a consistent mean square relative error reduction of 72% between measured values and the temperature setpoint and standard deviation of approximately 60% (from 27.8 degrees C to 11.1 degrees C). The productivity criteria establish a lower consumption of raw materials (13%) and energy supply (29%).Building evacuation: principles for the analysis of basic structures through dynamic flow networks
http://hdl.handle.net/2117/23352
Building evacuation: principles for the analysis of basic structures through dynamic flow networks
Casadesús Pursals, Salvador; Garriga Garzón, Federico
Purpose: The main purpose of this paper is to perform an analysis of the factors determining the architectural configuration of buildings for the mobility of people, using dynamic flow networks and considering group formation in the evacuation process.
Design/methodology/approach: For a long time it has been considered that once an evacuation begins, movement on the evacuation route mainly obeys mechanical factors; people occupy the free spaces which lead to evacuation more or less automatically. However, recent research has emphasized the need to consider people’s behavior; one of the aspects considered in this work is group formation, with its significant influence on the evacuation process. In positions of convergence and their branches things become considerably more complicated; as well as occupants’ behavioral aspects other relevant factors such as the geometry of the premises are critical in this process. Authors propose models, in which nodes are strategically placed, besides taking into consideration aspects of behavior. Several cases are analyzed.
Findings: The solution proposed in this paper is to analyze the problem through dynamic flow networks, using a macroscopic model in a deterministic environment in which the evolution of the quantities characterizing the problem at regular intervals is represented, obtaining a reasonably accurate and reliable understanding of the development of the evacuation.
Originality/value: A precise model of evacuation routes, convergence points and branches which includes a consideration of occupants’ behavior is obtained using stochastic models with microscopic analysis, in which people’s behavior is considered individually, this solution is complex, difficult to apply with many occupants and in large enclosures, and also, this way does not lead to optimal solutions.
2014-07-01T09:52:42ZCasadesús Pursals, SalvadorGarriga Garzón, FedericoPurpose: The main purpose of this paper is to perform an analysis of the factors determining the architectural configuration of buildings for the mobility of people, using dynamic flow networks and considering group formation in the evacuation process.
Design/methodology/approach: For a long time it has been considered that once an evacuation begins, movement on the evacuation route mainly obeys mechanical factors; people occupy the free spaces which lead to evacuation more or less automatically. However, recent research has emphasized the need to consider people’s behavior; one of the aspects considered in this work is group formation, with its significant influence on the evacuation process. In positions of convergence and their branches things become considerably more complicated; as well as occupants’ behavioral aspects other relevant factors such as the geometry of the premises are critical in this process. Authors propose models, in which nodes are strategically placed, besides taking into consideration aspects of behavior. Several cases are analyzed.
Findings: The solution proposed in this paper is to analyze the problem through dynamic flow networks, using a macroscopic model in a deterministic environment in which the evolution of the quantities characterizing the problem at regular intervals is represented, obtaining a reasonably accurate and reliable understanding of the development of the evacuation.
Originality/value: A precise model of evacuation routes, convergence points and branches which includes a consideration of occupants’ behavior is obtained using stochastic models with microscopic analysis, in which people’s behavior is considered individually, this solution is complex, difficult to apply with many occupants and in large enclosures, and also, this way does not lead to optimal solutions.Minimum-fuel escape from two body sun-earth system
http://hdl.handle.net/2117/23186
Minimum-fuel escape from two body sun-earth system
Colasurdo, Guido; Casalino, Lorenzo; Fantino, Elena
Escaping from the solar system by receiving
gravity assist from the Earth is considered
in this paper. A simple procedure,which
neglects the eccentricity of the Earth’s orbit and uses the two-body problem equations
and the patched-conic approximation, provides
near-optimal trajectories using either a
single or multiple Earth flybys. The analysis
shows that the amount of propellant required
to escape from the solar system decreases
with the number of flybys, but the mission
time increases. The same approach is also
used to find near-optimal trajectories that
use a single powered flyby. The eccentricity
of the Earth’s orbit can be exploited to
reduce the characteristic velocity; an
indirect optimization procedure provides
the most favorable locations where the Earth
should be intercepted.
2014-06-08T11:50:22ZColasurdo, GuidoCasalino, LorenzoFantino, ElenaEscaping from the solar system by receiving
gravity assist from the Earth is considered
in this paper. A simple procedure,which
neglects the eccentricity of the Earth’s orbit and uses the two-body problem equations
and the patched-conic approximation, provides
near-optimal trajectories using either a
single or multiple Earth flybys. The analysis
shows that the amount of propellant required
to escape from the solar system decreases
with the number of flybys, but the mission
time increases. The same approach is also
used to find near-optimal trajectories that
use a single powered flyby. The eccentricity
of the Earth’s orbit can be exploited to
reduce the characteristic velocity; an
indirect optimization procedure provides
the most favorable locations where the Earth
should be intercepted.Application of the finite point method to high- Reynolds number compressible flow problems
http://hdl.handle.net/2117/23168
Application of the finite point method to high- Reynolds number compressible flow problems
Ortega, Enrique; Oñate Ibáñez de Navarra, Eugenio; Idelsohn Barg, Sergio Rodolfo; Flores Le Roux, Roberto Maurice
In this work, the finite point method is applied to the solution of high-Reynolds compressible viscous flows. The aim is to explore this important field of applications focusing on two main aspects: the easiness and automation of the meshless discretization of viscous layers and the construction of a robust numerical approximation in the highly stretched clouds of points resulting in such domain areas. The flow solution scheme adopts an upwind-biased scheme to solve the averaged Navier-Stokes equations in conjunction with an algebraic turbulence model. The numerical applications presented involve different attached boundary layer flows and are intended to show the performance of the numerical technique. The results obtained are satisfactory and indicative of the possibilities to extend the present meshless technique to more complex flow problems. Copyright (c) 2014 John Wiley & Sons, Ltd.
2014-06-05T15:13:58ZOrtega, EnriqueOñate Ibáñez de Navarra, EugenioIdelsohn Barg, Sergio RodolfoFlores Le Roux, Roberto MauriceIn this work, the finite point method is applied to the solution of high-Reynolds compressible viscous flows. The aim is to explore this important field of applications focusing on two main aspects: the easiness and automation of the meshless discretization of viscous layers and the construction of a robust numerical approximation in the highly stretched clouds of points resulting in such domain areas. The flow solution scheme adopts an upwind-biased scheme to solve the averaged Navier-Stokes equations in conjunction with an algebraic turbulence model. The numerical applications presented involve different attached boundary layer flows and are intended to show the performance of the numerical technique. The results obtained are satisfactory and indicative of the possibilities to extend the present meshless technique to more complex flow problems. Copyright (c) 2014 John Wiley & Sons, Ltd.Las promesas de la nanotecnología
http://hdl.handle.net/2117/22577
Las promesas de la nanotecnología
Sureda Anfres, Miquel; Casals Terré, Jasmina
No cabe duda de que el camino que nos depara la nanotecnología es muy prometedor. Ropa de repelerá el agua, ordenadores quánticos, píldoras inteligentes o teléfonos móviles cargados con el calor humano. Todos estos desarrollos son el futuro de una revolución que empezó con un sueño: reducir los dispositivos hasta chocar con la escala del átomo. Pero no podemos olvidar que, en la gran mayoría de los campos indicados, faltan por comprender aspectos importantes, como la física básica de muchos fenómenos, o la repetitividad y la durabilidad de los procesos.
2014-04-09T13:02:29ZSureda Anfres, MiquelCasals Terré, JasminaNo cabe duda de que el camino que nos depara la nanotecnología es muy prometedor. Ropa de repelerá el agua, ordenadores quánticos, píldoras inteligentes o teléfonos móviles cargados con el calor humano. Todos estos desarrollos son el futuro de una revolución que empezó con un sueño: reducir los dispositivos hasta chocar con la escala del átomo. Pero no podemos olvidar que, en la gran mayoría de los campos indicados, faltan por comprender aspectos importantes, como la física básica de muchos fenómenos, o la repetitividad y la durabilidad de los procesos.