ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems
ILASS 2017 is the 28th European Conference on Liquid Atomization and Spray Systems. Following the successful 26th ILASS 2014 (Bremen) and 27th ILASS 2016 conferences, we will continue this tradition by providing a venue for industrial and academic researchers and students to engage in the scientific development and practice of Atomization and Spray Systems and to meet and share recent developments in these fields.
ILASS is the Institute for liquid atomization and spray systems. ILASS Europe has its roots in an initiative of the late Paul Eisenklam, who established the institute in 1982
URI permanente para esta colecciónhttps://riunet.upv.es/handle/10251/95642
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Item type: Capítulo de libro , Access status: Abierto , Binary cavitation in a transparent three hole GDI nozzle(Editorial Universitat Politècnica de València, 2017-07-28) Chaves, Humberto; Donath, Sebastian[EN] A more or less real size three hole (0.1 mm diameter) transparent injection nozzle was made with 120° between the orifices and an inclination of 20° to the injector axis. The geometry is similar to that of a multi hole GDI injector. Experiments are performed using n-pentane and -methyl-naphtalene mixtures in varying composition. The flow in the orifices is observed under submerged injection conditions from downstream looking in direction of the injector using a beam splitter plate for illumination with the light from a Minilite NdYag laser that was made incoherent by fluorescence in a cuvette filled with a dilute rhodamine-ethanol mixture. The images show the appearance of cavitation depending on the cavitation number as well as on the composition of the mixture. The behaviour is not what can be expected from equilibrium thermodynamics. Due to the transient nature of the flow the n-pentane concentration cannot attain the equilibrium value one would expect and cavitation occurs at higher cavitation values. Diffusion appears to play a role in the onset appearance of cavitation for binary mixtures.Item type: Capítulo de libro , Access status: Abierto , 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.Item type: Capítulo de libro , Access status: Abierto , Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries(Editorial Universitat Politècnica de València, 2017-07-28) Njere, Darlington; Emekwuru, Nwabueze[EN] The evolution of diesel fuel injection technology, to facilitate strong correlations of in-cylinder spray propagation with injection conditions and injector geometry, is crucial in facing emission challenges. More observations of spray propagation are, therefore, required to provide valuable information on how to ensure that all the injected fuel has maximum contact with the available air, to promote complete combustion and reduce emissions. In this study, high pressure diesel fuel sprays are injected into a constant-volume chamber at injection and ambient pressure values typical of current diesel engines. For these types of sprays the maximum fuel liquid phase penetration is different and reached sooner than the maximum fuel vapour phase penetration. Thus, the vapour fuel could reach the combustion chamber wall and could be convected and deflected by swirling air. In hot combustion chambers this impingement can be acceptable but this might be less so in larger combustion chambers with cold walls. The fuel-ambient mixture in vapourized fuel spray jets is essential to the efficient performance of these engines. For this work, the fuel vapour penetration values are presented for fuel injectors of different k-factors. The results indicate that the geometry of fuel injectors based on the k-factors appear to affect the vapour phase penetration more than the liquid phase penetration. This is a consequence of the effects of the injector types on the exit velocity of the fuel droplets.Item type: Capítulo de libro , Access status: Abierto , A study of the controlling parameters of fuel air mixture formation for ECN Spray A(Editorial Universitat Politècnica de València, 2017-07-28) Vogiatzaki, Konstantina; Crua, Cyril; Morgan, Robert; Heikal, Morgan; Engineering and Physical Sciences Research Council, Reino Unido; UK Research and Innovation[EN] Designing future ultra-high efficiency, ultra-low emission engines requires an in depth understanding of the multiscale, multi-phase phenomena taking place in the combustion chamber. The performance of the fuel delivery system is key in the air fuel mixture formation and hence the combustion characteristics, however in most spray modelling approaches is not considered directly. Thus, it is important to understand how the selection of models that mimic injection process affect predictions. In this paper we present an Eulerian-Lagrangian framework based on OpenFOAM libraries to model spray injection dynamics. The framework accounts for primary droplet formation (based on a parcel method with predefined initial droplet size distribution), secondary droplet breakup, evaporation and heat transfer. In order to account for the interaction of droplets with turbulence, simulations were performed within the LES context with two different turbulence models. A systematic variation of the key injection parameters (parcel number, parcel size distribution) of the parcel method as well as the grid size was considered. Varying the parcel number affects the initial droplet size distribution which in turn, depending on the selection of the turbulence and the evaporation sub-models, affects: spray dispersion; spray penetration; and subsequent droplet size distribution. Results were validated against the baseline experimental data for evaporating ECN Spray A with n-dodecane chosen as a surrogate for Diesel fuel.Item type: Capítulo de libro , Access status: Abierto , Viability of coaxial atomization for disintegration of cell solutions in cell spray applications(Editorial Universitat Politècnica de València, 2017-07-28) Bieber, Malte; Menzel, Sarah; Thiebes, Anja; Cornelissen, Christian; Jockenhoevel, Stefan; Kneer, Reinhold; Reddemann, Manuel; RWTH Aachen University[EN] Treating Leukemia with intravenous stem cell transplantation represents a well-established therapy technique. For applications, that require high local cell concentrations, transplantation by conventional intravenous injection is less potent, due to cell distribution with blood circulation. Instead, spraying them directly onto the injured or diseased area shows promising results in various applications, e.g. superficial treatment of topographically challenging wounds, in situ seeding of cells on implants, deposition of cells in tubular organs for stem cell therapy. The present work aims for a basic knowledge about viability boundaries for coaxial cell-spray atomization and the reciprocal influence between cells in solution and primary breakup mechanics. A generic modular nozzle is developed, to ensures reproducible boundary conditions. Investigations are conducted regarding primary breakup and relations between resulting droplet size distribution and cell survival. Measurements are performed, utilizing microscopic high-speed visualization with suitable image post processing. Cell viability is analyzed using phase contrast microscopy prior and after atomization. A relation between Rayleigh-Taylor instability wavelength and droplet size distributions by means of Sauter mean diameter (SMD) and cell survival rate (CSR) is suggested. A power law is presented, exclusively dependent on dimensionless measures (λ⊥ ∼ Re−1/2We−1/3 ) which is found to be proportional to SMD and CSR.Item type: Capítulo de libro , Access status: Abierto , 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.Item type: Capítulo de libro , Access status: Abierto , Models for automotive fuel droplets heating and evaporation(Editorial Universitat Politècnica de València, 2017-07-28) al Qubeissi, Mansour; Sazhin, Sergei; Al-Esawi, Nawar; Coventry University[EN] The paper presents recent approaches to the modelling of heating and evaporation of automotive fuel droplets with application to biodiesel, diesel, gasoline, and blended fuels in conditions representative of internal combustion engines. The evolutions of droplet radii and temperatures for gasoline, diesel, and a broad range of biodiesel fuels and their selective diesel fuel blends have been predicted using the Discrete Component model (DCM). These mixtures combine up to 112 components of hydrocarbons and methyl esters. The results are compared with the predictions of the case when blended diesel-biodiesel fuel are represented by pure fossil and biodiesel fuels. In contrast to previous studies, it is shown that droplet evaporation time and surface temperature predicted for 100% biodiesel (B100) are not always close to those predicted for pure diesel fuel. Also, the previously introduced MultiDimensional Quasi-Discrete model and its application to these fuels and their mixtures are discussed. The previous application of this model has resulted in up to 96% reduction in CPU time compared to the case when all fuel components are considered using the DCM.Item type: Capítulo de libro , Access status: Abierto , Statistical methods of images analysis as an essential tool in the assessment process of computer methods intended for numerical simulations of cavitating flows(Editorial Universitat Politècnica de València, 2017-07-28) Niedźwiedzka, Agnieszka; Lipiński, Seweryn[EN] Cavitation, because of its negative effects, like e.g. erosion, noise or vibration, is usually an undesirable phenomenon. However, in devices where spraying and atomization are expected, cavitation is required. This group of devices includes e.g. diesel injectors. Appearance of vapour bubbles results in increase of the maximum flow velocity. It is possible for the following reasons. Firstly, bubbles start to form in the throat, so its diameter reduces. Secondly, appearance of vapour bubbles along the wall results in a slip boundary condition. Moreover, cavitation has a positive influence on a spray cone angle. However, regardless of the place of occurrence, research on cavitation bases primarily on numerical simulations. The area of numerical methods intended for cavitating flows includes many solutions which differ not only in the basic assumptions, i.e. considering flow either as a multiphase mixture with the average density or just as two independent liquids, fluid and vapour, with a distinct boundary between them, but also in many methods applied in particular approaches. Currently, to choose the best way of the prediction of cavitation phenomenon for the undertaken issue, many aspects should be considered. The most important factor is the assessment level between the results of numerical simulation and experimental data. Secondary are computing time, requirements for the hardware, price of software and additional costs connected with the selected software. The final decision about the chosen way of the cavitation prediction results from all the above-considered elements. The main aim of the work is to present the methods of image analysis, which can be very helpful in this process. The main advantage of these methods is the quantitative answer about the correlation degree between analysed images. It eliminates subjective decisions based solely on a raw imaging material. The image material used in the work was obtained via numerical simulations performed in ANSYS Fluent. Presented methodology bases on their statistical analysis that considers the shape and intensity of cavitating area, as well as on basic methods of image processing and analysis. The conclusion is that the obtained results demonstrate the usefulness of the proposed methods in the aspect of a reliable comparison of images obtained in the numerical studies of the cavitation phenomenon.Item type: Capítulo de libro , Access status: Abierto , Simulation of droplet spreading on micro-CT reconstructed 3D real porous media using the volume-of-fluid method(Editorial Universitat Politècnica de València, 2017-07-28) Aboukhedr, Mahmoud; Mitroglou, Nicholas; Georgoulas, Anastasios; Marengo, Marco; Vogiatzaki, Konstantina[EN] Droplet impact on porous media has a broad range of applications such as material processing, drug delivery and ink injection etc. The simulation studies of such processes are rather limited. To represent the spreading and absorption process of the droplet on porous materials, robust numerical schemes capable of accurately representing wettability as well as capillary effects need to be established. The current work, presents one of the first studies of droplet impact on a real porous media geometry model extracted from a micro-CT scan. The process involves processing of CT image and subsequent threshold based on the structures segmentation. The porous geometry is extracted in the form of a STL (STereoLithography) model, which, with the aid of dedicated software like ANSA and SnappyHexMesh, is converted to an unstructured mesh for successful discretization of the flow domain. The solution algorithm is developed within the open source CFD toolbox OpenFOAM. The numerical framework to track the droplet interface during the impact and the absorption phases is based on previous work [1, 2]. The volume-of-fluid (VOF) method is used to capture the location of the interface, combined with additional sharpening and smoothing algorithms to minimise spurious velocities developed at the capillary dominated part of the phenomenon (droplet recession and penetration). A systematic variation of the main factors that affect this process are considered, i.e. wettability, porous size, impact velocity. To investigate the influence of porous structures on droplet spreading, the average porosity of the media is varied between 18.5% and 23.3% . From these numerical experiments, we can conclude that the droplet imbibition mainly depends on the porous wettability and secondly that the recoiling phase can be observed in the hydrophobic case but not in the hydrophilic case.Item type: Capítulo de libro , Access status: Abierto , Influence of the chemical mechanism in the frame of diesel-like CFD reacting spray simulations using a presumed PDF flamelet-based combustion model(Editorial Universitat Politècnica de València, 2017-07-28) Payri, F.; García-Oliver, José M; Novella Rosa, Ricardo; Pérez Sánchez, Eduardo Javier; Departamento de Máquinas y Motores Térmicos; Escuela Técnica Superior de Ingeniería Aeroespacial y Diseño Industrial; Instituto Universitario de Investigación CMT - Clean Mobility & Thermofluids; Ministerio de Educación, Cultura y Deporte; Ministerio de Economía y Competitividad[EN] The ability of a computational fluid dynamics (CFD) simulation to reproduce the diesel-like reacting spray ignition process and its corresponding flame structure strongly depends on both the fidelity of the chemical mechanism for reproducing the oxidation of the fuel and also on how the turbulence-chemistry interaction (TCI) is modeled. Therefore, investigating the performance of different chemical mechanisms not only in perfect stirred reactors but directly in the diesel-like spray itself is of great interest in order to evaluate their suitability for being further applied to CFD engine simulations. This research work focuses on applying a presumed probability density function (PDF) unsteady flamelet combustion model to the well-known spray A from the Engine Combustion Network (ECN), using three chemical mechanisms widely accepted by the scientific community as a way to figure out the influence of chemistry in the key characteristics of the combustion process in the frame of diesel-like spray simulations. Results confirm that in spite of providing all of them correct trends for ignition delays (ID) and lift-off lengths (LOL), when comparing with experimental results, the structure of the flame presents noticeable differences, especially in the low and intermediate temperatures and high equivalence ratio regions. Consequently, the selection of the chemical mechanism has an impact on the zones of influence of key species as observed in both spatial coordinates and also in the equivalence ratio-temperature maps. These differences are expected to be relevant considering the implications when coupling pollutant emissions models. The analysis of temperature and oxygen concentration parametric studies evidences how the observed differences are consistent and moderately dependent on the ambient conditions.Item type: Capítulo de libro , Access status: Abierto , Quantification of diesel injector dribble using 3D reconstruction from x-ray and DBI imaging(Editorial Universitat Politècnica de València, 2017-07-28) Sechenyh, Vitaliy; Turner, Jack; Sykes, Dan; Duke, Daniel; Swantek, Andrew; Matusik, Katarzyna; Kastengren, Alan; Powell, Christopher; Viera Sotillo, Alberto Antonio; Payri, Raul; Crua, Cyril; Departamento de Máquinas y Motores Térmicos; Instituto Universitario de Investigación CMT - Clean Mobility & Thermofluids; Escuela Técnica Superior de Ingeniería Industrial; Engineering and Physical Sciences Research Council, Reino Unido; UK Research and Innovation; U.S. Department of Energy[EN] Post-injection dribble is known to lead to incomplete atomisation and combustion due to the release of slow moving, and often surface-bound, liquid fuel after the end of the injection event. This can have a negative effect on engine emissions, performance, and injector durability. To better quantify this phenomenon we present a new image processing approach to quantify the volume and surface area of ligaments produced during the end of injection, for an ECN ‘Spray B’ 3-hole injector. Circular approximation for cross-sections was used to estimate three-dimensional parameters of droplets and ligaments. The image processing consisted in three stages: edge detection, morphological reconstruction, and 3D reconstruction. For the last stage of 3D reconstruction, smooth surfaces were obtained by computation of the alpha shape which represents a bounding volume enveloping a set of 3D points. The object model was verified by calculation of surface area and volume from 2D images of figures with well-known shapes. We show that the object model fits non-spherical droplets and pseudo-cylindrical ligaments reasonably well. We applied our processing approach to datasets generated by different research groups to decouple the effect of gas temperature and pressure on the fuel dribble process. High-speed X-ray phase-contrast images obtained at room temperature conditions (297 K) at the 7-ID beamline of the Advanced Photon Source at Argonne National Laboratory, together with diffused back-illumination (DBI) images captured at a wide range of temperature conditions (293-900 K) by CMT Motores Térmicos, were analysed and compared quantitatively.Item type: Capítulo de libro , Access status: Abierto , Modelling and validation of near-field Diesel spray CFD simulations based on the Σ -Y model(Editorial Universitat Politècnica de València, 2017-07-28) Desantes J.M.; García-Oliver, José M; Pastor Enguídanos, José Manuel; Pandal, A.; Naud, B.; Matusik, K.; Duke, D.; Kastengren, A.; Powell, C.; Schmidt, D.P.; Departamento de Máquinas y Motores Térmicos; Escuela Técnica Superior de Ingeniería Aeroespacial y Diseño Industrial; Instituto Universitario de Investigación CMT - Clean Mobility & Thermofluids; Ministerio de Economía y Competitividad; U.S. Department of Energy[EN] Diesel spray modelling still remains a challenge, especially in the dense near-nozzle region. This region is difficult to experimentally access and also to model due to the complex and rapid liquid and gas interaction. Modelling approaches based on Lagrangian particle tracking have struggled in this area, while Eulerian modelling has proven particularly useful. An interesting approach is the single-fluid diffuse interface model known as Σ-Y, based on scale separation assumptions at high Reynolds and Weber numbers. Liquid dispersion is modelled as turbulent mixing of a variable density flow. The concept of surface area density is used for representing liquid structures, regardless of the complexity of the interface. In this work, an implementation of the Σ-Y model in the OpenFOAM CFD library is applied to simulate the ECN Spray A in the near nozzle region, using both RANS and LES turbulence modelling. Assessment is performed with measurements conducted at the Advanced Photon Source at Argonne National Laboratory (ANL). The ultra-smallangle x-ray scattering (USAXS) technique has been used to measure the interfacial surface area, and x-ray radiography to measure the fuel dispersion, allowing a direct evaluation of the Σ-Y model predictions.Item type: Capítulo de libro , Access status: Abierto , 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.Item type: Capítulo de libro , Access status: Abierto , Spray/wall interaction analysis on an ECN single-hole injector at diesel-like conditions through Schlieren visualization(Editorial Universitat Politècnica de València, 2017-07-28) Payri, Raul; Gimeno, Jaime; Peraza, Jesús; Bazyn, Tim; Departamento de Máquinas y Motores Térmicos; Instituto Universitario de Investigación CMT - Clean Mobility & Thermofluids; Escuela Técnica Superior de Ingeniería Industrial; Ministerio de Economía y Competitividad[EN] To continuously improve CFD models which simulate spray evolution, breakup and evaporation mechanisms, it is helpful to validate them with results obtained by experimental research. In the present study, a mono-orifice target nozzle from Engine Combustion Network, referred to as Spray D, was investigated at conditions of spray-wall interaction, which actually is a real situation in internal combustion engines that is not frequently analyzed by visualization. A Photron SA-X2 high-speed camera was employed to record the vapor phase development of the spray in an inert atmosphere using a Schlieren imaging single-pass setup. The experiments show that the spreading of the spray along the wall has a behavior fairly similar to penetration at free-jet situations, especially regarding to its susceptibility to the operating conditions and its proportionality to the square root of time once the spray reaches a steady regime interacting with the wall. Furthermore, the spray film thickness was measured at three distances from the spray-wall impact point during the injection event, thereby characterizing that parameter both spatially and temporally. The tests were carried out in a constant pressure-flow facility able to reproduce pressure and temperature conditions, similar to those seen into a diesel engine. In order to observe the behavior of the spray colliding with a wall within this test rig, a system capable to being fitted into it and to holding a fused quartz wall at different injector tip-wall distances and impingement angle configurations, was designed and employed.Item type: Capítulo de libro , Access status: Abierto , Vapor phase penetration measurements with both single and double-pass Schlieren for the same injection event(Editorial Universitat Politècnica de València, 2017-07-28) Payri, Raul; Salvador, Francisco Javier; Bracho Leon, Gabriela; Viera Sotillo, Alberto Antonio; Departamento de Máquinas y Motores Térmicos; Escuela Técnica Superior de Ingeniería Aeroespacial y Diseño Industrial; Instituto Universitario de Investigación CMT - Clean Mobility & Thermofluids; Escuela Técnica Superior de Ingeniería Industrial; Ministerio de Economía y Competitividad; Universitat Politècnica de València[EN] Schlieren imaging has been adopted as a standard optical technique for the analysis of diesel sprays under engine like conditions. A single-pass Schlieren arrangement is typically used for the study of single-orifice nozzles, as vessels with multiple optical accesses regularly allow line of sight visualization. Contrarily, for multi-spray nozzles, measurements are commonly performed through a single optical access, in which case a double-pass arrangement is employed. As a consequence, the light beams pass through the test section twice, increasing the optical sensitivity of the Schlieren setup. However, the impact this has on the macroscopic spray characteristics is still unclear. The scope of this study is to analyze the differences in vapor phase penetration for the same injection event, through high-speed imaging, for both single and double-pass Schlieren configurations. Experiments were carried out with a three hole nozzle with a nominal orifice diameter of 90 µm, named Spray B from the Engine Combustion Network, using commercially available diesel fuel and in non-reactive conditions. The impact of different injection pressures and chamber densities on the spray captured by each setup was assessed. On the results, vapor phase penetration followed the expected trend found in the literature, as it increases with increasing injection pressure and decreasing chamber density. Comparing the optical setups, vapor phase penetration obtained with the double-pass arrangement was marginally higher. The deviation was observed throughout all tested conditions. Although the discrepancy was approximately constant for different injection pressures and chamber temperature, it increased with increasing density. These results highlight the importance of a proper understanding regarding the limitations of optical diagnostics, in particular for results used in calibration of computational models.Item type: Capítulo de libro , Access status: Abierto , Application of dry-ice for transient spray cooling(Editorial Universitat Politècnica de València, 2017-07-28) Panao, Miguel; Costa, José; Bernardo, Mário; European Commission[EN] Spray cooling systems are able to remove large amounts of heat due to phase-change. Although vaporization is the most common phase-change process used in applications requiring thermal management, the use of liquids often implies the presence of a liquid film which is known to mitigate cooling performance. Thus, it is worth exploring other approaches for spray cooling avoiding liquid films. The work presented here explores sublimation using CO2 particles (dry-ice) formed through the Joule-Thomson effect. The application of interest is the molding industry, where reducing the cycle time taking advantage of the time-frame available between the mold opening and closing during the part’s extraction, allows a production increase and, consequently, a higher competitive advantage in the market. The purpose of the experiments performed in dry-ice particle spray cooling is to investigate the effect of the impingement distance (350-450mm), and injection duration, on the total energy flux removed from the surface, and cooling efficiency, in order to assess the performance of sublimation spray cooling. The results show an evolution of temperature distribution from a more homogeneous pattern with shorter pulses to a heterogeneous one for pulse durations longer than 1 s. This is particularly useful in hotspot cooling. In terms of changing the spray impact distance, the higher particle dispersion achieved with a larger distance led to a decrease in thermal performance, probably due to the saturation of CO2 close to the impact surface. However, the pattern observed for the evolution of the total energy flux removed, with a maximum around an injection duration of 0.5 s, remains unaltered. The maximum cooling efficiency, obtained for the shortest distance, is up to 30%, which is comparable to spray cooling systems based on vaporization.Item type: Capítulo de libro , Access status: Abierto , Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays(Editorial Universitat Politècnica de València, 2017-07-28) Palmer, Johannes; Reddemann, Manuel; Kirsch, Valeri; Kneer, Reinhold; Wissenschaftsrat, Alemania[EN] A new method for instantaneous measurement of temperature, size and velocity of micro-droplets has been developed. The method is based on the well-known 2-color laser-induced fluorescence (2cLIF) technique, but uses a pulsed laser for 2-dimensional imaging without motion blur and an adjusted dye mixture for suppression of LIFMDRs by utilizing the MDR-enhanced energy transfer effect. This work presents the development steps that are necessary to verify feasibility of pulsed 2D-2cLIF-EET for micro droplet and hollow-cone spray applications.Item type: Capítulo de libro , Access status: Abierto , Properties of Fuel Spray Obtained by Electrohydrodynamic Atomization(Editorial Universitat Politècnica de València, 2017-07-28) Daaboul, Michel; Saba, Nicolas; Rishmany, Jihad; Louste, Christophe[EN] Airblast atomization is commonly used to atomize fuel in aircraft engines. An annular liquid sheet is atomized by the shear forces exerted by the co-flowing air stream. Nevertheless, this technique is less effective in some specific cases, e.g. when the external air flow velocity is relatively low. Electrohydrodynamic (EHD) atomization can constitute a solution in these cases. It consists of applying an electric field between two electrodes and electrically charging the passing carburant. This phenomenon will create instabilities within the liquid, provoking therefore its atomization. The main objective is therefore to electrically atomize a liquid sheet without the application of an external air flow like in airblast atomizers. This paper presents a novel actuator, based on dielectric barrier injection, used to induce instabilities within a plane liquid sheet of fuel similar to the annular sheet in aircraft engines. The behaviour of this atomizer was described in previous works. Several modes were observed, sometimes leading to a complete atomization, or just inducing instabilities and oscillating the liquid sheet. In the present study, only the cases where the liquid sheet is completely atomized are investigated. Images were recorded with the help of a high speed camera. Primary atomization is only studied, secondary atomization being neglected. The properties of the spray obtained by EHD atomization are investigated thoroughly, namely the breakup length, the mesh size, the drople t diameter, the droplet count, etc.Item type: Capítulo de libro , Access status: Abierto , Mathematical models for turbulent round jets based on “ideal” and “lossy” conservation of mass and energy(Editorial Universitat Politècnica de València, 2017-07-28) Franco, Fermin; Fukumoto, Yasuhide; Consejo Nacional de Ciencia y Tecnología, México; Banco de México; Kumiay International[EN] We propose mathematical models for turbulent round atomized liquid jets that describe its dynamics in a simple but comprehensive manner with the apex angle of the cone being the main disposable parameter. The basic assumptions are that (i) the jet is statistically stationary and that (ii) it can be approximated by a mixture of two fluid with the phases in local dynamic equilibrium, or so-called locally homogeneous flow (LHF). The models differ in their particular balance of explanatory capability and precision. To derive them we impose partial conservation of the initial mass and energy fluxes, introducing loss factors again as disposable parameters. Depending on each model, the equations admit explicit or implicit analytical solutions or a numerical solution in the discretized model case. The described variables are the the two-phase fluid’s composite density and velocity, both as functions of the distance from the nozzle, from which the dynamic pressure is calculated.Item type: Capítulo de libro , Access status: Abierto , Droplets heating and evaporation: an application to diesel-biodiesel fuel mixtures(Editorial Universitat Politècnica de València, 2017-07-28) al Qubeissi, Mansour; Al-Esawi, Nawar; Sazhin, Sergei; Coventry University[EN] The heating and evaporation of automotive fuel droplets are crucial to the design of internal combustion engines and to ensuring their good performance. Accurate modelling is essential to the understanding of these processes and ultimately improving engine design. The interest in fossil-biodiesel fuel blends has been mainly stimulated by depletion of fossil fuels and the need to reduce carbon dioxide emissions that contribute towards climate change. This paper presents an analytical investigation into the application of discrete component model for the heating and evaporation of multi-component fuel droplets to several blended diesel-biodiesel fuels. The model considers the contribution of all groups of hydrocarbons in diesel fuel and methyl esters in biodiesel fuels. The main features of new application to the analysis of blended-fuel droplets in engine-like conditions is described. The model is applied to several blends of diesel, combining 98 components of hydrocarbons, and 19 types biodiesel fuels, combining up to 17 species of methyl ester, considering the differences in their chemical levels of saturation, and thermodynamic and transport properties. One important finding is that some fuel blends, e.g. B5 (5% biodiesel fuel and 95% diesel fuel), can give almost identical droplet lifetimes to the one predicted for pure diesel fuel; i.e. such mixtures can be directly used in conventional diesel engines with minimal, or no, modification to the droplet break-up process.