Congresos. Editorial UPV

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Congresos realizados en la UPV publicados por la Editorial Universitat Politècnica de València.

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An innovative concrete-steel structural system allowing for a fast and simple erection
(Editorial Universitat Politècnica de València, 2018-06-05) Lepourry, Clemence; Somja, Hugues; Keo, Pisey; Heng, Piseth; Palas, Franck; Agence Nationale de la Recherche, Francia
[EN] In usual concrete buildings, medium to long span slabs can only be achieved by using prestressed beams. However, these elements are heavy, making their handling expensive; the cladding of these beams to vertical elements creates several difficulties, particularly in case of moment resisting frames; at last, their precamber implies a cautious management of the concreting and is a source of defects. Steel-concrete composite beams may offer an alternative, with similar performances. However they are not considered by concrete builders, because specific tools and skills are needed to erect them on site. Moreover usual composite members require a supplementary fire protection, which is costly and unsightly. This article presents an innovative steel-concrete moment resisting portal frame that overcomes these difficulties. It is based on composite tubular columns, and a composite beam made of a U-shaped steel profile used as permanent formwork to encase a concrete beam. This steel-concrete duality of beams allows an erection on site without any weld or bolt by a wise positioning of the construction joints. Moreover, as the resistance to fire is ensured by the concrete beam, the system does not require any additional fire protection. Finally, as only steel elements have to be handled on site, there is no need of heavy cranes. This system has been used to build a research center near Rennes, in France. As it is not covered in present norms, an experimental validation was required. After a detailed description of the structural system, the full-scale tests which have been performed are presented : - A series of asymmetrical push-out tests in order to determine the behaviour and resistance of shear connectors; - One 6-point bending test made to investigate the resistance of the USCHB under sagging bending moment; Two tests of the beam-column joint.
Behaviour of free falling viscoelastic liquid jets
(Editorial Universitat Politècnica de València, 2017-07-28) Tirel, Christophe; Renoult, Marie-Charlotte; Dumouchel, Christophe; Blaisot, Jean-Bernard; Agence Nationale de la Recherche, Francia
[EN] In a recent work, a protocol to measure the relaxation time of dilute polymer solutions, known to be challenging, has been established [1]. This protocol is based on a 2D multi-scale description of free-falling low velocity viscoelastic liquid jets. Although the relaxation time reached an asymptotic value for high jet velocities, a significant dependence with the jet velocity is observed for low velocities. The present work reconsiders these previous experimental data using a 3D multi-scale analysis in order to identify the origin of the dependence between the relaxation time and the jet velocity. The 3D analysis demonstrates the importance of a velocity–dependent coalescence mechanism in the jet behaviour. Thanks to a simple model of jet deformation it is demonstrated that this coalescence mechanism prevents the elasto-capillary contraction of the smallest scales from occurring when the jet velocity is reduced.
Direct numerical simulation of an atomizing biodiesel jet: Impact of fuel properties on atomization characteristics
(Editorial Universitat Politècnica de València, 2017-07-28) Ling, Yue; Legros, Guillaume; Popinet, Stéphane; Zaleski, Stéphane; Agence Nationale de la Recherche, Francia; Très Grand Centre de calcul du CEA
[EN] The utilization of biodiesel is an effective approach to reduce pollution from internal combustion engines and thus has attracted steadily increasing interest in the recent years. As the viscosity of biodiesel is much higher than that of standard diesel, the atomization characteristics of a biodiesel jet can significantly deviate from those of a standard diesel jet under identical injection conditions. Since atomization of the injected fuel has a strong impact on fuel-air mixing and the following combustion processes, it is important to investigate the atomization of biodiesel and in particular to understand how the fuel properties affect the atomization process and the resulting spray characteristics. In the present study, three-dimensional direct numerical simulations are conducted to investigate atomizing biodiesel and diesel jets. The novel adaptive multiphase solver Basilisk is used for simulations. The statistics of droplets formed in the biodiesel jet is compared to the diesel jet under identical injection conditions.
Effect of geometry of real-size transparent nozzles on cavitation and on the atomizing jet in the near field
(Editorial Universitat Politècnica de València, 2017-07-28) Cao, Yujun; Idlahcen, Said; Blaisot, Jean-Bernard; Rozé, Claude; Méès, Loïc; Maligne, David; Agence Nationale de la Recherche, Francia
[EN] Cavitation inception is very sensitive to the nozzle geometry. Two diesel-like transparent nozzles with sharp and round inlet edge were investigated under moderate injection pressure. By means of backlight imaging technique, images were recorded in two regions near the orifice: within ten orifice diameter downstream the nozzle and inside the nozzle, for different times after start of the injection. A cross-correlation technique was applied to images downstream the orifice to estimate the average velocity of the spray. The development of the spray was studied at the transient and full-opened stage, related to the needle lift motion. To analyse the flow inside the nozzle, the relative size of the vapour pockets was measured on the image and the relative frequency of the occurrence of cavitation was determined over image series. This approach permits to examine the time variation of the cavitation occurrence from the inlet to the outlet of the orifice. The results highlight the sensitivity of the cavitating flow to the shape of the inlet edge. Moreover, the trends of the variation over time of the velocity and of the cavitation frequency are very similar to each other but different for each geometry, indicating that the characteristics of the diesel spray in the near field is closely affected by the way cavitation is developing in the nozzle.
Experimental investigation of Ethane and Propane injection under sub- and super-critical conditions
(Editorial Universitat Politècnica de València, 2017-07-28) Vallee, Nathalie; Ribert, Guillaume; Blaisot, Jean-Bernard; Lisiecki, Denis; Agence Nationale de la Recherche, Francia
[EN] Studying a fluid flow under high-pressure conditions through reliable experiments is still nowadays a challenge. When the chamber pressure exceeds the critical pressure of working fluids the supercritical state of matter is reached and the distinction between gas and liquid becomes blurred. For such special conditions, experimental data are scarce and need to be consolidated. Indeed, the modification of the local refractive index induced by density gradient needs to be analyzed with appropriate image-based technique. In the present study, the REFINE test bench (Real-gas Effect on Fluid Injection: a Numerical and Experimental study) has been designed at CORIA Lab to study the non-reactive injection of Ethane and Propane into Nitrogen under sub- and supercritical conditions. The ambient gas pressure can be raised up to 6 MPa and warmed up to 573 K to scan sub- and trans-critical injections. The chamber is equipped with two perpendicular optical axes allowing simultaneously different optical diagnostics. Experimental data are collected from shadowgraph and diffused backlight illumination techniques. Quantitative measurements of jet spreading angle and breakup length are compared to results coming from literature exhibiting multiple flows topologies.
Large eddy simulations of atomisation and sprays: application to a high pressure multihole injector
(Editorial Universitat Politècnica de València, 2017-07-28) Chausserie-Laprée, Paul; Hélie, Jérome; Chesnel, Jeremy; Demoulin, François-Xavier; Agence Nationale de la Recherche, Francia
[EN] A weak coupling strategy is proposed to simulate the pressurised spray without any empirical readjustment. Volume Of Fluid is used to simulate the nozzle internal flow with cavitation and its primary atomization into ligaments. Lagrangian simulations are then used to get the spray evolution, even temporal. Large Eddy Simulations are used for these two simulations types. The coupling between both is realized by a recording and an analysis of the ligaments with local break up modelling into drops. Two test cases are presented, the second one deals with full, complex geometry, 6-holes Gasoline Direct Injection nozzle. Such approach shows a huge potential for prediction of the final spray from the nozzle geometry.
Liquid-Liquid Secondary Fragmentation with Solidification
(Editorial Universitat Politècnica de València, 2017-07-28) Hadj-Achour, M.; Rimbert, Nicolas; Gradeck, M.; Agence Nationale de la Recherche, Francia
[EN] In the event of a hypothetical core disruptive accident in nuclear power plants, the molten core may flow out the reactor vessel and interact with the cold water. The evolution of the accident is strongly affected by the fragmentation of the jet of molten metallic fuel due to its interaction with the water (i.e. this situation is known as fuel coolant interaction, FCI). In order to evaluate and predict the various consequences of a FCI, many researches are conducted with either corium or high melting temperature molten metal, where premixing stage evolves with an important production of steam. This steam production that is unavoidable because the high temperature of corium leads to difficulties for using optical diagnostics. Hence, in our case, we use a eutectic alloy (Field’s metal) with a low melting point (62°C) in order to be able to visualize correctly the droplet fragmentation processes. The present work focuses on the fragmentation of a single Field’s metal liquid droplet with mass equals to 0.27g (±0.01g). The liquid droplet interacts with a water pool whose temperature range between 20°C to 60°C. According to its Weber number, it fragments in different ways. For each experiment, a single droplet has been visualized using a high-speed camera (at 8000 fps). All measurements (drop size, velocity, impact parameter and geometrical properties of the drops after the penetration) into the pool are evaluated using an open source image processing. Solidified fragments can then be sieved and the size PDF determined. Focus of the present work is put on the evolution of the Sauter Mean Diameter with increasing Weber number and varying bath pool temperature. It is shown that using a simple crust model during solidification and defining an effective Weber number which include the crust elasticity all the curves collapse on the same master curve for all the water bath temperature considered.
Resistance of a steel-concrete hybrid thermal break system to low cycle fatigue under thermal actions
(Editorial Universitat Politècnica de València, 2018-06-05) Le Gac, Benoit; Keo, Pisey; Somja, Hugues; Palas, Franck; Agence Nationale de la Recherche, Francia
[EN] External insulation is the most widely used technique in Northern and Continental Europe. This technique generates thermal bridges where the building facade has some projecting element like balconies. The thermal requirements of actual standards lead to restore the continuity of the insulation at the interfaces by using thermal break systems (TBS). They are usually made of a box containing the insulation material, and a minimalist structural system able to transmit the shear force and the bending moment from the balcony to the wall. In most cases, structural elements are made of stainless steel, as it is less heat-conducting than normal steel. The paper focuses on a specific TBS, that uses shear keys and steel profiles to ensure the transfer of forces. TBS are also submitted to important horizontal cyclic shear deformations, provoked by the variations of the dimensions of the balconies due to climatic effects. The objective of the study presented in the paper is to show that significant yielding under these cyclic actions can be accepted during service life. First experimental cyclic loading tests have been performed in order to characterize the behaviour of the TBS, as well as its fatigue strength. Then the loading has been defined on the basis of the database of the ECA&D, the European Climate Assessment and Dataset. Finally, the fatigue resistance of the system has been verified. It is shown that the developed TBS can resist to fatigue loading for large lengths of balconies, while exhibiting significant yielding during service life.
Spray and Combustion Characterizations of Acetone-Butanol-Ethanol (ABE) blend at High-Pressure and High-Temperature Conditions
(Editorial Universitat Politècnica de València, 2017-07-28) Nilaphai, Ob; Ajrouche, Hugo; Hespel, Camille; Moreau, Bruno; Chanchaona, Somchai; Foucher, Fabrice; Mounaïm-Rousselle, Christine; Agence Nationale de la Recherche, Francia; European Regional Development Fund
ÈN] Abstract The intermediate fermentation mixture of butanol production, Acetone, Butanol and Ethanol (ABE), is increasingly considered as a new alternative fuel in CI engines due to its physical and chemical properties, which are similar to those of butanol, and its advantages of no additional cost or energy consumption due to butanol separation. In a previous study, the High-Pressure and High-Temperature (HPHT) chamber, called ‘New One Shot Engine” (NOSE), was used to investigate macroscopic spray-combustion parameters by validating Spray-A conditions of the Engine Combustion Network. The present study concerns the spray-combustion characteristics of the ABE mixture (volume ratio 3:6:1), blended with n-dodecane at a volumetric ratio of 20% (ABE20), compared to n-dodecane as reference fuel. The macroscopic spray and combustion parameters were investigated, for non-reactive conditions, in pure Nitrogen and for reactive conditions, in 15% oxygen, at ambient pressure (60 bar), ambient density (22.8 kg/m3 ) and different ambient temperatures (800 K, 850 K and 900 K). The liquid and vapor spray penetrations were investigated by the Diffused Back Illumination (DBI) and Schlieren techniques in non-reactive conditions. In reactive conditions, the lift-off length was measured by OH* chemiluminescence images at 310 nm. The Schlieren technique was also used to verify the choice of detection criterion. The ignition delay results of the two fuels were compared. It was found that the behavior of the two fuels as a function of temperature was similar even if the liquid length of ABE20 was shorter than that of n-dodecane at all ambient temperatures. On the other hand, no real difference in vapor spray penetration between the two fuels was observed. The vaporization properties and the lower autoignition ability of ABE20 led to longer ignition delays and lift-off length.
Spray ignition and local flow properties in a swirled confined spray-jet burner: experimental analysis
(Editorial Universitat Politècnica de València, 2017-07-28) Marrero Santiago, Javier; Verdier, Antoine; Vandel, Alexis; Godard, Gilles; Cabot, Gilles; Renou, Bruno; Agence Nationale de la Recherche, Francia
[EN] Laser ignition was investigated in the swirled, confined CORIA Rouen Spray Burner under ultra-lean conditions (=0.61) with n-heptane as the liquid fuel. Ignition probability was calculated for different spark locations and compared to the non-ignited local flow properties. Mean velocity components of the carrier flow were measured by PDA under spray presence and without spray, and are compared to mean values from PIV. PIV measurements provide information on the instantaneous airflow and the total strain rate. Fuel droplet size-velocity data was measured by PDA. Toluene-PLIF images were acquired to provide information on the local equivalence ratio and the flammability factor. Results show that the outer recirculation zone (ORZ) has a flammability factor close to 1 and the highest ignition probability (~80%). These results have a high correlation with the air velocity field and turbulent kinetic energy. Instantaneous equivalence ratio images and shear rate-velocity fields give important information on local segregation of the flow properties that help to understand the ignition process. The present work provides a useful database for numerical simulations and industry, plus new insight on spray ignition.
Spreading model for wall films generated by high-pressure sprays
(Editorial Universitat Politècnica de València, 2017-07-28) Lamiel, Quentin; Lamarque, Nicolas; Hélie, Jérome; Legendre, Dominique; Agence Nationale de la Recherche, Francia; Association Nationale de la Recherche et de la Technologie, Francia
[EN] This paper presents a new model developed to predict the area of wall films that may develop in gasoline direct injection engines (GDI). In a always more restrictive legislation on gas emissions the injection process in internal combustion (IC) engines has been highlighted as a domain of great concern in order to satisfy these requirements. Many spray wall interactions models exist in literature and are included in different CFD tools. Most often they are based on the sum of single drop-wall impacts. The specificity of the present model lies in its simplicity and the way the film is treated globally. Here its propagation is predicted using a balance between the momentum given by the spray and the viscous shear stress. Jointly with the theoretical model, an experimental set-up has been built up, an optical measurement technique called Refractive Index Matching method is used to follow the development of the wall film. It has been found that the area of the wall film is proportional to the duration of injection, while the distance between the injector and the wall has not shown many influence on the evolution of area. The influence of the injection pressure has also been identified, when the pressure is doubled the radius of the film is multiplied by √3 2. Eventually the model predicts that film thickness decreases as fuel pressure rises.
Synthesis of titanium dioxide precursor by the hydrolysis of titanium oxychloride solution
(Editorial Universitat Politècnica de València, 2018-09-07) Le Bideau, Pascal; Richard-Plouet, Mireille; Glouannec, Patrick; Magueresse, Anthony; Iya-Sou, D.; Brohan, L.; Agence Nationale de la Recherche, Francia
[EN] This communication focuses on the development of an approach to improve the synthesis of [Ti8O12(H2O)24]Cl8.HCl.7H2O crystals which is one of the precursor for titanium dioxide TiO2 particles. This study provides a significant improvement in crystallization kinetics with a production rate increased by a factor nineteen by intensifying heat and mass transfers compared to the process in a close vessel. This enhancement was made possible by the development of a new reactor to control the heat and mass transfers involved. In parallel with the experimental set-up, a numerical model representative of the transfer phenomena was initiated. The first numerical results are encouraging and present a good agreement with the measurements.
X-ray diagnostics of dodecane jet in spray A conditions using the new one shot engine (NOSE)
(Editorial Universitat Politècnica de València, 2017-07-28) Chiboud, Ibrahim; Arjouche, Hugo; Nilaphai, Ob; Dozias, Sebastian; Moreau, Bruno; Hespel, Camille; Foucher, Fabrice; Mounaïm-Rousselle, Christine; Pouvelse, Jean-Michel; Robert, Eric; Agence Nationale de la Recherche, Francia
[EN] Quantifying liquid mass distribution data in the dense near nozzle area to develop and optimize diesel spray by optical diagnostic is challenging. Optical methods, while providing valuable information, have intrinsic limitations due to the strong scattering of visible light at gas-liquid boundaries. Because of the high density of the droplets near the nozzle, most optical methods are ineffective in this area and prevent the acquisition of reliable quantitative data. X-ray diagnostics offer a solution to this issue, since the main interaction between the fuel and the X-rays is absorption, rather than scattering, thus X-ray technique offers an appealing alternative to optical techniques for studying fuel sprays. Over the last decade, x-ray radiography experiments have demonstrated the ability to perform quantitative measurements in complex sprays. In the present work, an X-ray technique based on X-ray absorption has been conducted to perform measurements in dodecane fuel spray injected from a single-hole nozzle at high injection pressure and high temperature. The working fluid has been doped with DPX 9 containing a Cerium additive, which acts as a contrast agent. The first step of this work was to address the effect of this dopant, which increases the sensitivity of X-ray diagnostics due its strong photon absorption, on the behavior and the physical characteristics of n-dodecane spray. Comparisons of the diffused back illumination images acquired from ndodecane spray with and without DPX 9 under similar operating conditions show several significant differences. The current data show clearly that the liquid penetration length is different when DPX 9 is mixed with dodecane. To address this problem, the dodecane was doped with a several quantities of DPX containing 25% ± 0.5 of Cerium. Experiments show that 1.25% of Ce doesn’t affect the behaviour of spray. Radiography and density measurements at ambient pressure and 60 bars are presented. Spray cone angle around 5° is obtained. The obtained data shows that the result is a compromise between the concentration of dopant for which the physical characteristics of the spray do not change and the visualization of the jet by X-ray for this concentration.

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