bluuebunny/crossref_metadata_2025 huggingface dataset:
Recurrent thyrotoxicosis of extrathyroidal origin due to struma ovarii: A case report and review
Authors: Alkhumsi Soad Imhmed , Gerryo Salah , Hdia Saleh , Edra Salem , Zaidi Yonis , Khalil Abdulati
Published: September 2017

Struma ovarii (SO) is a recognized, albeit infrequent, cause of ectopic thyroid hormone secretion. Due to its rarity, only a few cases had been reported with fairly detailed information on thyroid function test (TFT) results. Furthermore, data are limited in the extent of local spread, surgical approach, and postoperative management. A 41-year-old woman from Libya presented with tremor, nervousness, weight loss, heat intolerance, and palpitation. She had also complained of lower abdominal pain and delayed periods. Two years earlier, she was diagnosed with hyperthyroidism, treated with a 12-month course of antithyroid medications resulting in full resolution of symptoms. Her TFTs revealed elevated serum triiodothyronine, thyroxine (T4), free T4, and low thyroid-stimulating hormone (TSH). Pelvic ultrasonography showed a left ovarian cystic mass and a suspicious of ectopic pregnancy was suggested. Abdominal surgical exploration with left salpingo-oophorectomy was performed. Gross and microscopic examinations confirmed the diagnosis of SO. Four weeks later, TFTs were repeated and revealed a high level of serum TSH, and low total T4 and free T4 levels. L-thyroxine replacement was started. In conclusion, Determination of the cause of thyrotoxicosis is essential for proper management. If clinical data and initial investigations are not consistent with common causes of hyperthyroidism, whole-body radioactive iodine scan should be considered. The definitive treatment for patients with SO is surgical resection via laparoscopic approach.
Адиабатическое приближение эволюции, порожденной $A$-равномерно псевдоэрмитовым гамильтонианом
Authors: Wang Wenhua , Cao Huaixin , Chen Zhengli
Published: September 2017

Обсуждается адиабатическое приближение эволюции квантовой системы, порожденной $A$-равномерно псевдоэрмитовым гамильтонианом $H(t)$. Он представляет собой зависящий от времени оператор, выражающийся через зависящий от времени эрмитов гамильтониан $G(t)$ с помощью не зависящего от времени обратимого оператора $A$. С использованием связи между решениями уравнений эволюции для $H(t)$ и $G(t)$ доказано, что $H(t)$ и $H^{\dagger}(t)$ имеют одни и те же действительные собственные значения, а соответствующие собственные векторы образуют биортогональные базисы Рисса в пространстве состояний. Для адиабатического приближенного решения в случае минимального собственного значения и основного состояния оператора $H(t)$ доказано, что это решение в каждый момент времени совпадает с состоянием системы тогда и только тогда, когда вектор основного состояния не зависит от времени. Также найдены оценки сверху для ошибки адиабатического приближения в терминах нормы разности состояний и в терминах обобщенной степени совпадения. Полученные результаты проиллюстрированы в нескольких примерах.
Числа Гурвица и произведения случайных матриц
Authors: Orlov Aleksandr Yur'evich
Published: September 2017

Изучаются многоматричные модели, которые можно рассматривать как интегралы от произведений тау-функций, зависящих от собственных значений произведений случайных матриц. Рассмотрены тау-функции двухкомпонентной иерархии Кадомцева-Петвиашвили и иерархии Кадомцева-Петвиашвили типа B, введенной Кацем и ван де Лером. В некоторых случаях эти интегралы сами являются тау-функциями. Рассмотрены модели, генерирующие числа Гурвица $H^{\mathrm E,\mathrm F}$, где $\mathrm E$ - эйлерова характеристика накрываемой поверхности, а $\mathrm F$ - число точек ветвления. Показано, что если подынтегральное выражение содержит произведение $n>2$ матриц, то интеграл порождает числа Гурвица с $\mathrm E\le 2$ и $\mathrm F\le n+2$, причем $\mathrm E$ и $\mathrm F$ зависят и от $n$, и от порядка сомножителей в произведении случайных матриц. Эйлерова характеристика $\mathrm E$ может быть четным или нечетным числом и соответственно описывает ориентируемые или неориентируемые накрываемые поверхности в зависимости от наличия тау-функции в подынтегральном выражении. Изучаются произведения комплексных и произведения унитарных матриц.
Development steps of 2-color laser-induced fluorescence with MDR-enhanced energy transfer for instantaneous planar temperature measurement of micro-droplets and sprays
Authors: Palmer Johannes , Reddemann Manuel , Kirsch Valeri , Kneer Reinhold
Published: September 2017

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 usesa pulsed laser for 2-dimensional imaging without motion blur and an adjusted dye mixture for suppression of LIFMDRsby utilizing the MDR-enhanced energy transfer effect. This work presents the development steps that arenecessary to verify feasibility of pulsed 2D-2cLIF-EET for micro droplet and hollow-cone spray applications.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4591
Experimental investigation on puffing and micro-explosion occurrence of water in rapeseed oil emulsions droplets. Effect of the surfactant concentration.
Authors: Bellettre Jerome , Melo-Espinosa Eliezer Ahmed , Tarlet Dominique , Piloto-Rodriguez Ramon , Verhelst Sebastian
Published: September 2017

In this paper, the assessment of puffing and micro-explosion occurrence in emulsion drops with differentwater percentage is studied. The emulsified fuels are formulated using micro channel emulsifier, rapeseedoil and diesel fuel as continuous phase, as well as water and Sorbitan Sesquioleate as surfactant. Theformulated dispersed systems are covered under different experimental factors such as water ratio andsurfactant percentage. The puffing occurrence is reported in all emulsified fuels tested (i.e. with andwithout surfactant). A sudden puffing and highest number of occurrence is noted when the water amountincreases in all emulsified fuels. The micro-explosion phenomenon is only noted in emulsified fuelformulated without surfactant.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4594
Determination of Heat and Flow Characteristics in Spray Cooling with Rectangular Finned Heat Sink
Authors: Karabey Altuğ , Yakut Kenan
Published: September 2017

Spray cooling process has many parameters such as extended surface, angle of inclination, effect of gravity, diameter of nozzle, angle of spray, mass flux, geometry of cooled surface, thermal performance and critical heat flux of spray etc.   Many effective parameters to carry out the experiments with conventional test methods are both expensive and time consuming. As a solution in these circumstances, Taguchi method, which is one of the modern experimental design and optimization methods and very effective in solving such problems, was used in this study. Taguchi method, as well as being in effective to improve the quality of products, also gives the opportunity to achieve better results with much less experiment. Using Taguchi method, as well as to reach the target value exactly, the sensitivity of the design against uncontrollable factors is reduced to a minimum. Thus, the optimum tolerance range in cost and quality factors is determined. When compared to conventional experimental design methods, Taguchi method has many advantages. One of them is that the test costs are minimized and the deviation around the target is kept to a minimum while in bringing targeted level of the average value of performance.  Another advantage is that the obtained results in the laboratory can be obtained in the real production environment and also saved a time of production. Nowadays, the planning of the multi-factorial experiments can be provided with great flexibility and simplicity by Taguchi method. In these experiments with using rectangular pin fin heat sinks, the effects of the longitudinal and lateral distances of the consecutively arranged nozzle or diffuser-like fin pairs, widths of the fins, angle of fins, heights of fins, spraying time, air flow rate, liquid flow rate (ALR, the ratio of air-liquid flow rate) and the ratio of the nozzle-heat sink distance to the nozzle diameter (h/d) on heat and flow characteristics have been investigated by using Taguchi experimental design method. For this reason, characteristics of flow and heat transfer are considered separately. Nusselt number considered as performance statistic, L27(311) orthogonal array has been selected as an experimental design plan for the eleven parameters mentioned above. The Nusselt number was calculated by taking into account the characteristic length of heat sink and the optimized results were found to be fin width of 45 mm, fin angle of 45o, fin height of 15 mm, x direction distance between fins of 20 mm, y direction distance between fins of 20 mm, x direction distance between slices of 15 mm, y direction distances between slices of 20 mm, air flow rate of 10-3 m3/s, liquid flow rate of 5,83*10-6 m3/s, spraying time of 5 s and the ratio of the nozzle-heat sink distance to the nozzle diameter (h/d) of 667.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4596
Selected Results of the Collaborative Research Center "Droplet Dynamics under Extreme Ambient Conditions" SFB/TRR 75
Authors: Tropea Cameron , Weigand Bernhard , Schulte Kathri
Published: September 2017

The Collaborative Research Center (CRC) SFB-TRR 75 was established in January 2010 to focus on the dynamicsof basic drop processes, and in particular on processes involving extreme boundary conditions, for example, near thermodynamic critical conditions, very low temperatures, under strong electric fields or in situations involving extremely large gradients. The CRC is a joint initiative of the University of Stuttgart, the TU Darmstadt and the German Aerospace Center (DLR) in Lampoldshausen, operating with 17 projects structured into three main research areas and involving researchers from numerous faculties: Mathematics, Chemistry, Electrical Engineering, Aerospace Engineering, Mechanical Engineering, Informatics and Computer Sciences. Some of the topics pursued at the CRC include•The behaviour of supercooled and potentially electrified droplets in clouds•The impact of Supercooled Large Droplets (SLD) on aircraft icing•The behaviour of strongly electrified drops on insulator surfaces, which can be found on high voltagepower lines, affecting the partial discharge behaviour and performance and durability of the insulator.•Trans-critical injection conditions of fuel with flash boiling in rocket combustion chambers•Atomization and vaporization of droplets at high pressures and temperature, as occurring in futurecombustion systemsThis article provides an overview of the projects being carried out at the SFB-TRR 75 and highlights scientific results from selected subprojects. The main purpose of the paper is to familiarize colleagues with this extensive and dedicated research effort in the area of drop dynamics and to motivate and initiate future collaboration with others in this field.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4597
Investigation of the effects of fluid properties representation and boundary condition selection in numerical simulations of micro scale flows with phase change
Authors: Pearce Daniel , Vogiatzaki Konstantina , Taylor A.M.K.P , Hardalupas Yannis
Published: September 2017

Cavitation is a phenomenon affected considerably by the underlying pressure waves that occur on similar timeand length scales as the bubble dynamics. Thus appropriate representation of wave dynamics within numericalframeworks is of paramount importance for the prediction of the phase change process in the nozzle as well as thesubsequent spray formation. In this paper we focus on investigating the sensitivity of the wave dynamics within acompressible Large Eddy Simulation framework with regards to downstream geometry and boundary representation.Diesel was used as working fluid and was injected at various pressures through a micro-channel. Results interms of vapour fraction, velocity and pressure are compared with the experimental data of Winklhofer [30, 31]. Thedownstream domain length and reflectivity properties are shown to exert a significant effect on in-nozzle processes.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4600
Zooming into primary breakup mechanisms of high-pressure automotive sprays
Authors: Kirsch Valeri , Reddemann Manuel A. , Palmer Johannes , Kneer Reinhold
Published: September 2017

In-cylinder mixture formation and combustion are highly influenced by primary breakup of injected fuel. Experimentalinvestigation of this phenomenon directly at the outlet of a diesel injector requires a specialized transmitted light microscopy technique combined with a constant-pressure flow microscopy vessel. The method allows verification of the existence of an intact jet core for various states of injection and different fuels. The jet core is dominated by axisymmetric surface waves during the initial injection phase. By quantification of the wavelengths and comparison with existing breakup theories, boundary layer instabilities are identified as origin of surface waves. Boundary layer wavelengths are found to be larger for a higher fuel viscosity. An occasionally appearing non-cylindrical helical jet shape is visible during the injector’s opening and closing phase. The helical jet shape is directly resulting from the nozzle outlet flow. Inner nozzle effects are found to be responsible for generation of the helical structure. A fuel dependence of the helical structure formation and its breakup could not be proved. Results also prove that fuel is exiting the nozzle even after the injector needle is closed, while air is simultaneously moving into the nozzle orifice.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4603
Experimental Characterization of Spray generated by a Rotary Atomizer Wheel
Authors: Kuhnhenn Maximilian , Luh Max Frederik , Joensen Tórstein Vincent , Roisman Ilia V. , Tropea Cameron
Published: September 2017

Rotary atomizers are widely used for spray drying processes to produce powders in various industrial applications.The atomization regime and therefore the droplet size distribution have a substantial impact on the process outcome. Depending on the intended use of the dried powder particles, various droplet size distributions are desired, which should be adjustable by the main operating parameters (e.g. mass flow rate and wheel speed). In this study the spray of a rotary atomizer wheel, operated under normal ambient conditions, is characterized for different mass flow rates, wheel speeds and viscosities with the help of a phase Doppler measurement system. Visual investigations of the spray with a high resolution camera system help to get a better understanding of the atomization process, aswell as the thickness of the liquid jets exiting the atomizer.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4610
Mechanisms of Liquid Stream Breakup: Vorticity and Time and Length Scales
Authors: Sirignano William A , Zandian Arash , Hussain Fazle
Published: September 2017

The 3D, temporal instabilities on a planar liquid jet are studied using DNS with level-set and VoF interface-capturingmethods. The λ2 method has been used to relate the vortex dynamics to the surface dynamics at different stages of the jet breakup. The breakup character depends on the Ohnesorge number (Oh) and gas-to-liquid density ratio. At high Reynolds number (Re) and high Oh, hairpin vortices form on the braid and overlap with the lobe hairpins, thinning the lobes, which then puncture creating holes and bridges. The bridges break, creating ligaments that stretch and break into droplets by capillary action. At low Oh and high Re, lobe stretching and thinning is hindered by high surface tension and splitting of the original Kelvin-Helmholtz vortex, preventing early hole formation. Corru- gations form on the lobe edges, influenced by the split vortices, and stretch to form ligaments. Both mechanisms are present in a transitional region in the We-Re map. At lower Re and not-too-large Weber number (We), lobe stretching occurs but with longer and larger ligaments in this third domain which has a hyperbolic transition to the hole formation domain as We increases. The three domains with differing breakup behaviors each occupy distinct portions of a plot of We based on gas density versus Re based on liquid properties. Characteristic times for the hole formation, as well as the lobe and ligament stretching are different - the former depending on the surface tensionand the latter on liquid viscosity. In the transitional region, both times are of the same order.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4616
Coupled study of film and spray on a basic annular prefiming airblast atomizer
Authors: Gosselin Valentin , Ferret Bernard , Bazile Rudy
Published: September 2017

One way to increase efficiency and reduce pollution in transport and energetic domain is designing fuel injectorswith better atomization. In this work, experiments were performed on a prefilming airblast atomizer often used in gas turbine engines. For this purpose, a new injector was designed to visualize the prefilming zone and the primary atomization together. The flow configuration corresponds to an annular liquid film sheared by inner high velocity airflows. High speed Shadowgraphy was used to observe film and spray, liquid film frequency, wave velocity and wave deformation, primary breakup regime. Finally, a link between liquid film and the primaryatomization are shown first qualitatively and after quantitatively.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4626
Numerical simulation of compressible cavitating two-phase flows with a pressure-based solver
Authors: Cristofaro Marco , Edelbauer Wilfried , Gavaises Manolis , Koukouvinis Phoevos
Published: September 2017

This work intends to study the effect of compressibility on throttle flow simulations with a pressure–based solver.The simple micro throttle geometry allows easier access for obtaining experimental data compared to a real injector, but still maintaining the main flow features. For this reasons it represents a meaningful and well reported benchmark for validation of numerical methods developed for cavitating injector flows.An implicit pressure–based compressible solver is used on the filtered Navier–Stokes equations. Thus, no stability limitation is applied on the time step. A common pressure field is computed for all phases, but different velocity fields are solved for each phase, following the multi–fluid approach. The liquid evaporation rate is evaluated with a Rayleigh–Plesset equation based cavitation model and the Coherent Structure Model is adopted as closure for the sub–grid scales in the momentum equation.The aim of this study is to show the capabilities of the pressure–based solver to deal with both vapor and liquid phases considered compressible. A comparison between experimental results and compressible simulations is presented. Time–averaged vapor distribution and velocity profiles are reported and discussed.  The distribution of pressure maxima on the surface and the results from a semi–empirical erosion model are in good agreement with the erosion locations observed in the experiments. This test case aims to represent a benchmark for furtherapplication of the methodology to industrial relevant cases.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4629
Experimental and Numerical Investigation of Dispersed and Continuous Liquid Film under Boiling conditions
Authors: Habchi Chaouki , Lamarque Nicolas , Helie Jerome , Jay Stéphane
Published: September 2017

In this work, both experimental and numerical investigations have been carried out in order to improve the modelling of the vaporization of wall liquid-deposits in internal combustion engines. A comprehensive model is suggested for the vaporization of liquid films in the different boiling regimes, including nucleate boiling regime, the Leidenfrost boiling regime, as well as the transition boiling regime occurring between the two latter. This work extends the validity of the Liquid Film Boiling model (Habchi, Oil & Gas Science and Technology – Rev. IFP, Vol. 65, No. 2, 2010) for dispersed liquid films that may be formed when a dilute spray impinges a wall. A sub-grid liquid film is indeed considered when the wetted-area is smaller than the wall cell-face area. A sessile droplet model is used to estimate the wall area wetted by the liquid film and whether it is resolved by the grid or located in the sub-grid scale (SGS). In addition, a novel Leidenfrost vaporization model is proposed for spray droplets located near a hot wall. The above vaporisation/boiling models has been implemented in the Large-Eddy simulation (LES) AVBP code. The validation has been carried out using two different experiments.  First, the experimental lifetime curve of a sessile droplet (Stanglmaier et al., SAE paper 2002-01-0838) has been used for a quantitative validation in the different boiling regimes. Second, the wall impingement of a heptane spray from a typical gasoline injector from Continental Automotive, has been simulated. The numerical results obtained  under boiling conditions, are compared to the liquid film footprints and lifetime provided by the Refractive Index Matching (RIM) experiment which is described in this article.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4632
Experimental Investigation of Droplet Injections in the Vicinity of the Critical Point: A comparison of different model approaches
Authors: Steinhausen Christoph , Lamanna Grazia , Weigand Bernhard , Stierle Rolf , Groß Joachim , Preusche Andreas , Dreizler Andreas
Published: September 2017

The disintegration process of liquid fuel within combustion chambers is one of the most important parameters forefficient and stable combustion. Especially for high pressures exceeding the critical value of the injected fluids the mixing processes are not fully understood yet. Recently, different theoretical macroscopic models have been introduced to understand breakdown of the classical two phase regime and predict the transition from evaporation to a diffuse-mixing process. In order to gain deeper insight into the physical processes of this transition, a parametric study of free-falling n-pentane droplets in an inert nitrogen atmosphere is presented. Atmospheric conditions varied systematically from sub- to supercritical values with respect to the fluid properties. An overlay of a diffuse lighted image with a shadowgram directly in the optical setup (front lighted shadowgraphy) was applied to simultaneously detect the presence of a material surface of the droplet as well as changes in density gradients in the surrounding atmosphere. The experimental investigation illustrates, that the presence of a material surface cannot be shown by a direct shadowgram. However, reflections and refractions caused by diffuse ambient illumination are able to indicate the presence of a material surface. In case of the supercritical droplet injections in this study, front lighted shadowgraphy clearly revealed the presence of a material surface, even when the pre-heated droplets are released into a supercritical atmosphere. This detection of the droplet interface indicates, that the droplet remains subcritical in the region of interest, even though it is injected into a supercritical atmosphere. Based on the adiabatic mixing assumption recent Raman-scattering results in the wake of the droplet are re-evaluated to compute the temperature distribution. Presented experimental findings as well as the re-evaluation of recent Raman scattering results are compared to thermodynamic models to predict the onset of diffuse-mixing and supercritical disintegration of the droplet. Additionally, a one dimensional evaporation model is used to evaluate the validity of the adiabatic mixing assumption in the estimation of the droplet temperature. The presented findings contribute to the understanding of recent theoretical models for prediction of spray and droplet disintegration and the onset of diffuse-mixing processes.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4635
Instantaneous heat transfers at the impact of a droplet onto a hot surface in the film boiling regime
Authors: Caballina Ophélie , Chaze William , Castanet Guillaume , Maillet Denis , Pierson Jean-François , Lemoine Fabrice
Published: September 2017

Heat and mass transfers at the impact of a droplet onto a hot solid surface are investigated experimentally. Millimetersizedwater droplets impinges onto a perfectly flat sapphire surface heated at 600°C. The temperature of the liquidinside the droplet is measured using the two-color laser-induced fluorescence (2cLIF) technique. Water is seededwith a temperature-sensitive fluorescent dye, while a nanosecond pulsed laser is used for the excitation of the fluorescence.The ratio of fluorescence signal detected in two appropriate spectral bands allows to determine the liquidtemperature. One advantage of this non-intrusive optical technique is that it eliminates adverse effects associatedwith signal variations caused by droplet shape during its impact. In parallel, the temperature of the solid surfaceis characterized using infrared thermography. The latter measurements are made possible by the deposition of ananosize coating of titanium aluminium nitride (TiAlN) on the upper surface of the sapphire window. Thanks to thehigh frame rate of the IR camera, the time evolution of the heat flux distribution at the solid surface can be reconstructed. A comparison of IR and 2cLIF techniques enable to correlate the heating of the liquid with the cooling ofthe wall. This reveals that most of the heat removed from the solid surface is devoted to the heating of the liquid,the energy used for liquid vaporization being significantly lower.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4636
Theory of Stagnation-Point Spray Flame Ignition
Authors: Greenberg J. Barry , Kats Gershon
Published: September 2017

A theory of stagnation-point spray flame ignition by an isothermal hot surface is presented for the first time. A mixture of fuel droplets and air flowing against an isothermal hot surface (such as a hot ignition probe) is considered. The spray of droplets is modelled using the sectional approach and a mono-sectional case is adopted for simplicity. A single global chemical reaction is assumed for the case when ignition occurs. The mathematical analysis makes use of a small parameter that is exploited for an asymptotic approach. The analysis produces a criterion for ignition that includes effects of the flow field, the reactants and the fuel spray-related parameters. Numerical computations reveal the way in which the latter impact on whether ignition will occur or not.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4643
Experimental Investigation on the Early Stage Spray Characteristics with Biodiesel and Diesel
Authors: Yu Shenghao , Yin Bifeng , Wen Shuai , Li Xifeng , Jia Hekun , Yu Jianda
Published: September 2017

The early stage spray characteristics have a great impact on the secondary atomization progress, and thus affectthe engine combustion and emission performances. The experimental investigation of the early stage spray behaviors with biodiesel and diesel was carried out by employing a laser-based Mie-scattering method. The results show that the spray tip penetration for biodiesel is higher than that for diesel at the early stage spray under the same injection pressure. Moreover, the early stage spray tip penetration can be longer under high injection pressures for two fuels. Besides, the early stage spray cone angle for biodiesel is narrower than that for diesel, and the spray cone angle is especially higher than biodiesel by 25.8% after start of injection time of 0.01ms. Furthermore, under the same injection condition, the difference of early stage spray area between diesel and biodiesel is not obvious, while the spray volume for biodiesel is larger than that for diesel, and also the sprayvolume can be enlarged by increasing injection pressure for both fuels.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4651
Development of an evaporation model for the dense spray region in Eulerian-Eulerian multiphase flow simulations
Authors: Puggelli Stefano , Palanti Lorenzo , Andreini Antonio , Demoulin François-Xavier
Published: September 2017

In the present study, a novel implicit numerical model to describe evaporation phenomena in the dense spray region is proposed. The main aim is to go beyond the limits of standard vaporization models, which are normally based on a dilute spray assumption, to deal with high liquid volume fractions. The proposed method is based on an a priori computation of steady state equilibrium conditions reached by a system composed by liquid, vapour and air at constant pressure combined with a modelled characteristic time of evaporation. Such equilibrium composition and temperature is then used inside numerical calculations to compute evaporation source terms. The new for-mulation allows to simulate evaporation process in the dense zone of the spray, where, due to the extremely low thermal relaxation time, classical explicit method can lead to unphysical results. Such innovative approach has been implemented in a multiphase solver in the framework of the CFD suite OpenFOAM. An Eulerian-Eulerian solver, de-rived from the Eulerian Lagrangian Spray Atomization (ELSA) model, has been used, in order to correctly describe the liquid-gas flow without assumptions on the topology of the liquid phase. Evaporation source terms have been modelled as function of the amount of surface available for mass and heat transfer. An analysis of the solver has been carried out in RANS framework in order to highlight the capabilities of the approach in dealing with high liquid volume fraction regions with a physically consistent representation of evaporation phenomena.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4652
Effect of excitation on gas centered swirl coaxial injectors
Authors: Yoon Youngbin , Park Gujeong , Oh Sukil , Bae Jinhyun
Published: September 2017

Studies on combustion instability in liquid rocket engines are important in improving combustion efficiency andpreventing combustion chamber losses. To prevent combustion instability, methods such as baffles and cavities are used. The injector is located in the middle of the perturbation-propagation process in the rocket engine, so it is important to study the suppression of combustion instability using the design of the injector. Much research has been focused on the study of liquid excitation in a single injector; however, the actual injector used in a liquid rocket engine is a coaxial injector. In this study, the dynamic characteristics of a gas-centred swirl coaxial injector were investigated by varying the gap thickness and momentum-flux ratio. Spray photographs were captured by synchronizing a stroboscope and digital camera, and a high-speed camera and Xenon lamp were also used. To measure the liquid film, a measurement system was implemented using the electrical conductance method. For excitation of the gas, an acoustic speaker was used to impart a frequency to the gas. The gGas velocity and effect of excitation were measured by hot-wire anemometry. A mechanical pulsator was used for liquid flow excitation. Liquid fluctuation was measured by a dynamic pressure sensor. In both gas and liquid excitation cases, the gain increased as the gap thickness decreased and the momentum-flux ratio increased. From these results, it can be concluded that gap thickness and momentum-flux ratio are major factors in suppressing combustioninstability. DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4653
Investigations on nano- and submicron-particle generation by spray painting processes
Authors: Ye Qiaoyan , Tiedje Oliver , Srinivas Shreyas Rohit , Noest Thomas , Uhrner Uhrrich
Published: September 2017

This paper presents experimental and numerical studies to determine the particle size distributions (PSD) and concentrations in paint overspray. Two kinds of paint materials, solvent borne and water borne paints, both with and without manufactured nanomaterials (pigments), and an industrial spray gun were used. Different aerosol measuring techniques, namely the Spraytec Fraunhofer type particle sizer for micro-sized droplets in the spray jet and the Scanning Mobility Particle Sizer (SMPS) for nano particles in paint overspray were applied. It was found, that solvent borne clear coats create significantly higher number concentration of nano-sized droplets than the water borneprimers. Only small differences in PSD between paints with and without manufactured nanomaterials were found. Numerical simulations of droplet trajectories within the spray booth, for both micro and nano sized droplets, were carried out. Based on the experimental and numerical results, a representative particle size distribution (smaller than 1 μm) for the given spray gun was obtained. Effects of turbulence models on the particle deposition on targets, especially for submicron particles, have been analysed in detailed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4666
Numerical simulation of superheated jets using an Eulerian method.
Authors: Lyras Konstantinos , Dembele Siaka , Madhav Rao Vendra C. , Wen Jennifer
Published: September 2017

Flash boiling is the rapid phase change of a pressurised fluid that emerges in ambient conditions below its vapourpressure. Flashing can occur either inside or outside the nozzle depending on the local pressure and geometry and the bubble formation leads to interfacial interactions that eventually influence the emerging spray. Lagrangian methods which exist in literature to simulate the flash atomisation and inter-phase heat transfer employ many sim- plifying assumptions. Typically, sub-models used for the break-up, collisions and evaporation introduce an extensive empiricism that might result in unrealistic predictions for cases like flashing. In this study, a fully Eulerian approach is selected employing the Σ − Y model proposed by Vallet and Borghi. The model tracks liquid structures of any shape and computes the spray characteristics comprising a modified version for the transport equation of the sur- face density. The main goal of this study is to investigate the performance of this model in flash boiling liquids using the Homogeneous Relaxation Model (HRM) developed by Downar-Zapolski, a model capable of capturing the heat transfer under sudden depressurisation conditions accounting for the non-equilibrium vapour generation. The model in this present study considers that the instantaneous quality would relax to the equilibrium value over a given timescale which is calculated using the flow field values. A segregated approach linking the HRM and Σ − Y is implemented in a compressible formulation in an attempt to quantify the effects of flash boiling in the spray dynamics. The developed model is naturally implemented in RANS in a dedicated solver HRMSonicELSAFoam. Results from simulations of two-phase jets of different subcooled fluids through sharp-edged orifices show that the proposed approach can accurately simulate the primary atomisation and give reliable predictions for the droplet sizes and distribution. Strong effects of the flashing and turbulent mixing on the jet are demonstrated. The model istested for turbulent flows within small nozzles and was developed within the open source code OpenFOAM.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4667
Investigation of the Influence of Microexplosions on a Laminar Premixed Water-in-Fuel Emulsion Spray Flame
Authors: Yokev Neta , Greenberg J.B.
Published: September 2017

A model is presented for a one-dimensional laminar premixed flame, propagating into a rich, off-stoichiometric, fresh homogenous mixture of water-in-fuel emulsion spray, with air and inert gas. The main purpose is to investigate the steady-state burning velocity and burnt temperature as functions of parameters such as initial water content in the emulsified droplet and total liquid droplet loading. In particular the influence of micro-explosion of the spray's droplets on the flame's characteristics will be highlighted for the first time.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4672
Influence of droplet clustering in sprays on liquid deposition rate on spherical targets
Authors: Andrade Paul , Charalampous Georgios , Hardalupas Yannis
Published: September 2017

The origin of temporal fluctuations of liquid mass deposition rates, obtained from a spray of droplets impinging on a solid spherical target, was investigated by correlation with droplet clusters in the spray. The droplet clusters were quantified using a Voronoi analysis on instantaneous images of the droplets, to obtain the number of droplet clusters, the area of the clusters and the number of droplets in each cluster. It was found that the normalised area of the droplet clusters had a distribution with a peak around 10-1 and a right tail which followed a power law of exponent -1.8. As the number density of the droplets inside the clusters increased, the temporal fluctuations of the liquid mass deposition rates increased, as a greater variation of droplet sizes impinged the target. However, as the standard deviation of the distribution of the normalised droplet cluster areas was increased, the temporal fluctuations in the liquid mass deposition rates reduced, as variations to the droplet number density and droplet sizes inside the clusters were averaged out.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4673
Comparison between analytical, numerical, and experimental results of grouping effects in droplet streams
Authors: Roth Norbert , Gomaa Hassan , Livne Alon , Katoshevski David , Weigand Bernhard
Published: September 2017

Grouping of droplets was studied in monodisperse droplet streams. This very controllable system allows to studybasic effects. In experiments droplet streams with monodisperse droplets were generated, however, with initially two different inter droplet spacing. A larger inter droplet spacing is followed by a little bit smaller one, which is followed by a larger one and so on. Due to this initial boundary condition groups of two droplets form, which approach each other and finally coagulate. It was found, that the velocity of the droplet approach is linearly dependent on the spacing between the droplets. This process was simulated by direct numerical simulation using the in-house code FS3D. The results of the simulations show the  ame linear behaviour. For larger computational domains thenumerical results approach the experimental results.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4685
Design and experiments to investigate spray and impingement characteristics of a common rail type lubrication system
Authors: Stark Matthias , De Risi Arturo , Giangreco Marcelo , Diggelmann Simon
Published: September 2017

This paper reports on the establishment of a testing facility to investigate spray and impingement characteristics ofa recently developed, fully adaptive lubrication system for large two stroke marine diesel engines. The reported part of this research relates to development steps towards the new lubrication system as well as the implementation of a dedicated testing facility and the establishment of validation approaches in order to corroborate technology developments in this context.The major objective of this development yields an optimization of lubricant utilization and at the same time a significant reduction of lubricant fraction in the exhaust gas. A requisite to obtain the desired level of flexibility calls for a revised approach in injecting the lubricant. The desired flexibility of the new lubrication approach foresees a cycle based adjustment of the injected amount of lubricant as well as the injection pressure in order to provide the possibility to shape the injection spray pattern. Concept studies nominate the application of a common rail system with integrated needle lift type injectors and adjustable injection pressure as compliant with the requisite to inject the lubricant with a high level of flexibility.This paper hence encompasses design and development aspects of the new lubrication system but most of all highlights steps in developing a validation concept in order to compare common lubrication systems with the new type of lubrication system.Initial results of the test cell provide an insight regarding relevant information on the injection spray characteristics over the full engine load range as well as the possibility to compare common lubrication system performance with the new common rail lubrication system.A comparison between measurement and simulation results provide the possibility to implement experimentallygained data in a neuronal network in order to enhance the predictive quality of the simulation tool.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4688
Spray Conditioning for the Preparation of Spray Dried Submicron Particles
Authors: Gorny Ramona Klaudia , Schaldach Gerhard , Walzel Peter , Thommes Markus
Published: September 2017

Particle size reduction down to the submicron range (0.1-1 µm) is an effective option to increase the bioavailabilityof low water soluble active pharmaceutical ingredients. According to the Nernst-Brunner equation, the preparation of submicron sized particles increases the specific surface area, thus increases the dissolution rate. Conventional spray drying devices for submicron particles show certain limitations. The main challenge is the preparation of small and uniform droplets during the atomisation step. In this work, fine droplets were generated combining a nozzle with a droplet separator. Therefore, the aerosol is generated with a pneumatic nozzle and is sprayed into a cyclone droplet separator. Depending on the characteristics of the cyclone, droplets larger than the cut-off-size were separated and returned into the liquid feed. The conditioned aerosol at the top of the cyclone separator can then be introduced into the drying chamber. With this concept the usable part is separated, thus no classification process after drying is necessary. The investigations show that the dependencies during atomisation of the droplets size on the liquid-to-gas mass flow ratio µm and the liquid properties (e.g. viscosity) do not apply to the separation step. The conditioned aerosol only depends on the separation characteristics of the cyclone droplet separator. However, the amount of droplets separated is determined by the atomisation step. Hence, the amount of droplets smaller than the cut-off-size can be increased by decreasing the droplet size of the primary aerosol. This is realised by secondary droplet fragmentation. An impact surface causes breakup of the droplets of theprimary aerosol before separation. The investigations show an increased amount of droplets <2µm.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4701
Splashing of a very viscous liquid drop impacting onto a solid wall wetted by another liquid
Authors: Kittel Hannah M , Roisman Ilia V , Tropea Cameron
Published: September 2017

In this experimental work the main focus is on the impact of a single drop of a very viscous liquid onto a thin,horizontal wall film of different liquid. Splashing resulting from drop impact onto a wetted wall occurs in many natural and engineering applications like in internal combustion engines and spray cooling. While the splashing threshold for low viscosity liquid drops has been extensively examined, impact of a very viscous drop is much less studied. The viscosities of drop and wall film liquids are varied up to kinematic viscosities of 100,000 mm²/s. The liquids used in the experiments are miscible.The impact outcome is determined by the impact parameters and fluid properties. The effect of very viscous liquids used as drop fluid and as wall film liquid on the kinematic of the corona expansion is investigated in the experiments. The results of drop impact onto solid walls are compared to obtain the limiting asymptotic values for the splashing threshold. Finally, a semi-empirical model for the splashing threshold, for the maximum spreading radius Dmax and for the maximum spreading times tmax viscous liquids.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4702
A study of the controlling parameters of fuel air mixture formation for ECN Spray A
Authors: Vogiatzaki Konstantina , Crua Cyril , Morgan Robert , Heikal Morgan
Published: September 2017

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 deliverysystem is key in the air fuel mixture formation and hence the combustion characteristics, however in most spraymodelling approaches is not considered directly. Thus, it is important to understand how the selection of modelsthat mimic injection process affect predictions. In this paper we present an Eulerian-Lagrangian framework basedon 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, evaporationand heat transfer. In order to account for the interaction of droplets with turbulence, simulations were performedwithin 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 theparcel number affects the initial droplet size distribution which in turn, depending on the selection of the turbulenceand 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-dodecanechosen as a surrogate for Diesel fuel.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4703
Experimental investigation of Ethane and Propane injection under sub- and super-critical conditions
Authors: Vallee Nathalie , Ribert Guillaume , Blaisot Jean-Bernard , Lisiecki Denis
Published: September 2017

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 den- sity 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 dif- fused backlight illumination techniques. Quantitative measurements of jet spre ding angle and breakup length arecompared to results coming from literature exhibiting multiple flows topologies.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4708