bluuebunny/crossref_metadata_2025 huggingface dataset:
Fatigue Crack Growth in an Al-Mg-Si Alloy under Negative Load Ratio
Authors: Torres Marcelo A.S. , Silva B.R.L. , Costa D.H.S. , Baptista C.A.R.P. , Pastoukhov V.
Published: September 2017

The usual approaches for Fatigue Crack Growth (FCG) assessment are based on semi-empirical models that consider the stress intensity factor range of fracture mechanics, ΔK, as the governing driving force for crack propagation. However, FCG data incorporating compressive loads have brought discussions and controversies. The compressive loads are not taken into account in the usual life prediction codes and the negative portion of the loading cycle is neglected. In the present work, constant amplitude fatigue crack growth tests with load ratios-1 and 0 are performed, for two diferent stess levels, in AA 6005 alloy centre-notched middle tension M(T) specimens and the obtained results are discussed. It is shown that the crack closure concept, that usually work well for positive ratios, is not enough to satisfactorily explain the negative load ratio effects. The results also showed how the negative part of the load affected the propagation rate of the crack, mainly for larger cracks and smaller loads. Finally, it is shown that a previously proposed expression for the stress distribution ahead of the crack can shed some light on this question.
Creep Damage Tolerance Factor λ of Selected Creep-Resistant Steels
Authors: Sklenička Václav , Kuchařová Květa , Dvořák Jiří , Kvapilová Marie , Král Petr
Published: September 2017

The creep damage tolerance factor λ as an important outcome of the continuum damage mechanics approach has been used to asses the creep fracture mode and the susceptibility of material to localized cracking at strain concentrations. In this work, using sets of our earlier published creep data of three advanced ferritic creep-resistant steels (T23 low alloy steel, P91 and P92 chromium steels) are analysed in terms of the creep damage tolerance factor λ. It was found that the value of the creep damage factor λ is not constant and depends on the creep loading conditions. The data analysis is followed by fractographic investigations, which is used to identify the creep fracture mode (s) experimentally.
Descrizione di una nuova specie di Pectocera Hope del sud della Cina: Pectocera hainana n. sp. (Coleoptera, Elateridae, Pityobiinae)
Authors: Riese Sergio
Published: September 2017

Viene descritta una nuova specie di Elateridae del sud della Cina (Isola di Hainan): Pectocera hainana n. sp. (♂♀) (Coleoptera: Elateridae, Pityobiinae), loc. typ.: Cina – Hainan, Sanya city, mt. Jiangfengling. Presenta lo stesso habitus di P. jiangxiana Kishii & Jiang, 1994, ma è facilmente distinguibile per la colorazione, gli angoli posteriori del pronoto carenati e lo scutello submitrale nettamente inciso alla base.
Indagine conoscitiva della lepidotterofauna presente nella riserva naturale regionale Ripa Bianca di Jesi (Ancona, Marche, Italia)
Authors: Teobaldelli Adriano
Published: September 2017

Negli anni 2012-2013 è stata effettuata una sistematica indagine conoscitiva sui Lepidotteri presenti nella Riserva Naturale Regionale “Ripa Bianca” di Jesi (Ancona, Marche). Le specie accertate sono 184, tra cui alcune entità poco note e localizzate nel territorio regionale. Il rilevante numero di specie censite in rapporto alla limitata estensione dell’Area protetta di soli 18 ettari, evidenzia la ricchezza della biodiversità e l’interesse scientifico sul piano faunistico e zoogeografico della Riserva. Vengono esaminate le entità raccolte per categoria corologica, riportando i dati percentuali dei vari elementi faunistici. Si evidenzia che la maggior parte delle specie sono a diffusione Eurasiatica, Eurosibirica e Mediterranea.
The Macrocoma Chapuis from the Canary Islands, with description of a new species (Coleoptera Chrysomelidae Eumolpinae)
Authors: Zoia Stefano
Published: September 2017

The known species of Macrocoma from the Canary Islands are reviewed and the aedeagi illustrated. Macrocoma pelikani n. sp. is described from Gran Canaria, Barranco de Guayadeque. M. franzi Palm, 1976 is downgraded to subspecies of M. splendidula (Wollaston, 1862) and the following nomenclatural changes are proposed: M. splendidula ssp. franzi Palm, 1976 n. stat., M. splendidula ssp. palmaensis Palm, 1977 n. stat. a key to species identification and a catalogue with new locality data are also provided.
End-stage renal disease in children on maintenance dialysis in Benghazi, Libya
Authors: Barakat Ben Sauod Ekram , Aklifa Ahmed
Published: September 2017

Background: End-stage renal disease (ESRD) is a major cause of morbidity and mortality worldwide. Understanding the risk factors of ESRD can help identify preventive strategies and is critical for planning interventions to minimize the disease morbidity and mortality. Objectives: The aim is to identify the demographic and clinical characteristics and risk factors that contribute to ESRD 2005–2016. Settings: The dialysis unit of Benghazi Pediatric Hospital, Benghazi, Libya. Patients and Methods: This is a descriptive case series of all children with ESRD on maintenance dialysis (hemodialysis or peritoneal dialysis) between January 2006 and June 2016. Data were collected from patients' charts and the statistics department of the hospital. Demographic information, the age of onset, duration, and type of dialysis, likely etiology (if documented), complications and comorbidities were all documented and outcome including the cause of death. Results: The mean age of onset of ESRD was 8.5 years; nearly 41% of patients started dialysis at 6–10 years. The majority of patients (72%) resided locally. Male to female ratio was 1.5:1. Consanguinity of parents and family history of renal disease were reported by 12% and 16% of patients, respectively. More than half of patients (51.3%) had had no complications from dialysis. The most common known cause of ESRD was glomerulopathy (18.4%); including glomerulonephritis and nephrotic syndrome. Congenital and hereditary disorders involved 17.1% of cases. These were obstructive uropathy in 9.2% of the patients. The cause was not known in a large proportion (52.6%). Nearly 80% of the patients were alive during the study. Encephlophay (10.5%) and sepsis (6.5%) are the most common causes of death. Conclusions: The clinical profiles, causes, and outcome of ESRD in a specialized center in Benghazi were documented. The study is limited by the high proportion of unknown etiology. Full documentation of underlying etiology is a good clinical practice that should produce better epidemiological studies.
Periodic Solutions of Second Order Degenerate Differential Equations with Delay in Banach Spaces
Authors: Bu Shangquan , Cai Gang
Published: September 2017

We give necessary and sufficient conditions of the Lp-well-posedness (resp. -wellposedness) for the second order degenerate differential equation with finite delays

with periodic boundary conditions (Mu)(0) = (Mu)(2π), (Mu)′ (0) = (Mu)′ (2π), where A, B, and M are closed linear operators on a complex Banach space X satisfying D(A) ∩ D(B) ⊂ D(M), F and G are bounded linear operators from into X.
Интегрируемая иерархия, включающая иерархию Абловица-Каупа-Ньюэла-Сигура и ее строгую версию
Authors: Helminck Gerard F
Published: September 2017

Представлена интегрируемая иерархия, которая включает в себя и иерархию Абловица-Каупа-Ньюэла-Сигура, и ее строгую версию. Проведено разложение пространства петель $\mathfrak g$ для алгебры $gl_2$ на подалгебры Ли $\mathfrak g_{\geq 0}$ и $\mathfrak g_{<0}$ всех петель с положительными степенями петельного параметра и всех петель со строго отрицательными степенями петельного параметра соответственно. Выбрана коммутативная подалгебра Ли $C$ во всем пространстве петель $\mathfrak s$ для алгебры $sl_2$, она представлена как $C=C_{\geq 0}\oplus C_{<0}$. Выполнена деформация подалгебры Ли $C_{\geq 0}$ группой, соответствующей $\mathfrak g_{<0}$, а подалгебры Ли $C_{<0}$ - группой, соответствующей $\mathfrak g_{\geq 0}$. Используется требование, чтобы эволюционные уравнения деформированных образующих элементов $C_{\geq 0}$ и $C_{<0}$ имели форму Лакса, определяемую исходным разложением. Доказаны совместность этой системы уравнений Лакса и ее эквивалентность множеству соотношений нулевой кривизны для проекций определенных произведений образующих элементов. Также определены подходящие модули петель и множество уравнений в этих модулях, называемое линеаризацией системы, из которого могут быль получены уравнения Лакса для иерархии. Проведена полезная характеризация особых элементов, появляющихся в линеаризации, - так называемых волновых матриц. Предлагается способ построения достаточно широкого класса решений смешанной иерархии Абловица-Каупа-Ньюэла-Сигура.
Поведение плазмы с произвольной степенью вырождения электронного газа в слое проводящей среды
Authors: Latyshev Anatolii Vasil'evich , Gordeeva Nadezhda Mikhailovna
Published: September 2017

Получено аналитическое решение граничной задачи о поведении (колебаниях) электронной плазмы с произвольной степенью вырождения электронного газа в слое проводящей среды, находящемся во внешнем электрическом поле. Применяются кинетическое уравнение Власова-Больцмана с интегралом столкновений типа Бхатнагара-Гросса-Крука и уравнение Максвелла для электрического поля. Используются зеркальные граничные условия отражения электронов от границы слоя. Граничная задача сводится к одномерной и односкоростной. Для этого применяется метод последовательных приближений, линеаризация уравнений относительно абсолютного распределения электронов Ферми-Дирака и закон сохранения числа частиц. Затем разделение переменных сводит уравнения задачи к характеристической системе уравнений. В пространстве обобщенных функций находятся собственные решения исходной системы, отвечающие непрерывному спектру (моды Ван Кампена). Далее путем решения дисперсионного уравнения находятся собственные решения, отвечающие присоединенному и дискретному спектрам (моды Друде и Дебая). Затем составляется общее решение граничной задачи в виде разложения по собственным решениям. Коэффициенты разложения находятся из граничных условий. Это позволяет в явном виде получить разложения функции распределения и электрического поля в явном виде.
Собственные значения векторов Бете в модели Годена
Authors: Molev Alexander Ivanovich , Mukhin Evgenii Evgen'evich
Published: September 2017

По теореме Фейгина-Френкеля-Решетихина собственные значения высших гамильтонианов Годена на векторах Бете могут быть найдены с использованием центра аффинной вертексной алгебры на критическом уровне. В нашей недавней работе были вычислены явные образы Хариш-Чандры образующих центра во всех классических типах. Объединение этих результатов приводит к явным формулам для собственных значений высших гамильтонианов Годена на векторах Бете. Образы Хариш-Чандры можно интерпретировать как элементы классических $\mathcal W$-алгебр. Путем вычисления классических пределов соответствующих скриннинговых операторов выявлена прямая связь между кольцами $q$-характеров и классическими $\mathcal W$-алгебрами.
Структуры Ли-Пуассона над дифференциальными алгебрами
Authors: Zharinov Viktor Viktorovich
Published: September 2017

На основе ключевых элементов подхода Олвера к гамильтоновым эволюционным уравнениям в частных производных предложена алгебраическая конструкция, пригодная для представления гамильтоновых эволюционных систем со связями.
High Speed X-Ray Imaging for Nozzle Exit Velocity and Density Distribution Measurements of GDI Nozzles
Authors: Distler Raphael , Hamann Christoph , Krämer Martin , Kull Eberhard , Wensing Michael , Li Zhilong , Gao Ya , Wang Jin
Published: September 2017

Investigation of the primary breakup region of gasoline sprays is important for future nozzle development. It improvesthe principal understanding of inner nozzle flow and spray breakup. It also allows validating and developingCFD models. Due to the high optical density common measurement techniques like Phase Doppler Anemometryreach their limit in optical dense sprays as in the primary breakup region. High Speed X-Ray Imaging is capable tomeasure 2D velocity distributions directly at the spray hole exit. For generating the intense X-Ray beam the synchrotronAdvanced Photon Source at Argonne National Laboratory is used. Passing through the spray the X-Raybeam is changed by two different physical principles: absorption and phase contrast. Absorption can be applied tomeasure the density of the spray. Phase contrast is used to visualize the borders of droplets and ligaments withhigh contrast. The accelerated electron bunches inside the synchrotron have a constant period length to each other.This leads to an accurate pulsed X-Ray beam (periodicity: 68 ns). The use of multi exposure with very short X-Raypulses (17 ns) shows the traveled distance of the spray droplets and ligaments. The spray speed (150-250 m/s) iscalculated by dividing these distances with the time gap between two X-Ray pulses. The X-Ray measured densitydistributions and velocity distributions are combined to calculate the spray force rate. The so gained force rate isvalidated with a spray force measurement performed at the Spray Momentum Test Bench (SMTB) at ContinentalAutomotive GmbH. The study is focusing on the measurement setup of High Speed X-Ray Imaging at ArgonneNational Laboratory and the evaluation algorithms.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4598
Primary breakup of liquids using a high-speed rotary bell atomizer for spray painting processes
Authors: Shen Bo , Ye Qiaoyan , Tiedje Oliver , Domnick Joachim
Published: September 2017

The present contribution deals with numerical studies of the primary liquid breakup process using a commercialhigh-speed rotary bell atomizer. The first part of the investigations focuses on the film formation on the distributor disk and the inner surface of the rotary bell. Numerical simulations using the volume of fluid (VOF) approach were carried out. A non-Newtonian liquid is used to investigate the effect of the viscosity on the initial wetting, the film formation process and the film thickness distribution on the bell. The Herschel-Bulkley model is considered to describe the shear-thinning (pseudoplastic) behavior of the fluid. A non-homogeneous film structure is found on the inside surface of the rotary bell. This is also observed in experimental investigations using a high-speed camera.The following disintegration process is studied by applying an appropriately fine computational mesh. The VOF method and Reynolds stress model are used to calculate the disintegration process and the two-phase flow field.The numerical results are compared with images which are recorded by means of a high-speed camera.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4611
Analytical / Computational Approach to Liquid Spray Heating and Vaporization at Supercritical Pressures
Authors: Sirignano William A , Jorda Juanos Albert
Published: September 2017

Our findings from two areas of background research will define an approach to the study of liquid spray heating andvaporization in gases at supercritical pressure: (i) vaporizing droplets at supercritical pressure and (ii) supercritical combustion in simple configurations, e.g., counterflow. The a priori conclusion that only one phase exists at super- critical pressure is based on false “lore” and not physical law. The question about the phases must be left open until the analysis reaches a conclusion; a proper approach will be defined. Proper equations of state for density and en- thalpy and the determination of phase equilibrium, liquid composition due to dissolved gas, energy of vaporization, surface tension, and transport properties for high pressures will be discussed. The case of an isolated droplet will be reviewed and origin of the transcritical concept will be explained. A counterflow spray configuration at pressures above the liquid critical pressure will be analyzed. The concept of shifting phase equilibrium will be applied as the droplets in the spray heat. Hydrocarbon liquids and oxidizing gaseous environments will be studied. Differences between real fluids and ideal fluids at high pressures will be emphasized. Proper rules for gaseous mixtures andliquid solutions will be discussed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4615
Numerical and Experimental Investigations on rotary Bell Atomizers with predominant Air Flow Rates
Authors: Guettler Nico , Paustian Stephan , Ye Qiaoyan , Tiedje Oliver
Published: September 2017

For high-quality spray painting of small parts, a rotary bell atomizer with a narrow spray pattern is used in the automotive industry. The required unusual high shaping air flow rate yields in an atomization process predominated by a pneumatic atomization and rather than by a rotary atomization, called hybrid bell atomizer in this article. Numerical and experimental investigation on typical high-speed rotary bell atomizers, with rotation type of high rotational speed 40000-60000 rpm of the bell, were already successful demonstrated. For these high-speed rotary bell atomizer for painting bigger areas the ratio between tangential velocity at the bell edge and axial shaping air velocity at the bell edge is in the range of 0.8 and 4, depending on the process parameter. At the hybrid bell atomizer (10000-20000 rpm), this ratio is between 0.2 and 0.4.The first step of the present study includes the theoretical characterization of spray cone velocity profile using two definitions of swirl-number compared to experimental measurements of particle velocities using Laser-Doppler-Velocimetry (LDV). This study was carried out on varying shaping air settings and rotational speeds. The results show that the the swirl of the main airflow field is dominated by the secondary airflow, which is induced coaxial in an angle of 45°. The influence of the circumferential speed of the bell cup on the swirl of the main airflow field plays a subordinate role, so the resulting spray pattern is only weakly influenced by the number of revolutions of the bell-cup.In the second step, the hybrid bell atomizer was examined numerically. In order to implement the hybrid atomization concept in the simulation correctly, methods for creating droplet initial conditions in the trajectory calculation was developed. The simulation results were verified through comparisons of calculated and measured velocity profiles inside the spray cone and calculated and measured film thickness distributions on the work piece. In the present investigations of the atomizer, it has been demonstrated numerically and experimentally that the airflow field of this hybrid bell atomizer is strongly impacted by the secondary shaping air and both the circumferential speed of the bell cup and the direct electrostatic charge on the bell have only a minor effect on the generated spray pattern and the resulting transfer efficiency.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4650
A quantitative analysis of nozzle surface bound fuel for diesel injectors
Authors: Turner Jack , Sykes Dan , De Sercey Guillaume , Stetsyuk Viacheslav , Gold Martin , Pearson Richard , Crua Cyril
Published: September 2017

In a fuel injector at the end of the injection, the needle descent and the rapid pressure drop in the nozzle leads todischarge of large, slow-moving liquid structures. This unwanted discharge is often referred as fuel ‘dribble’ and results in near-nozzle surface wetting, creating fuel-rich regions that are believed to contribute to unburnt hydrocarbon emissions. Subsequent fluid overspill occurs during the pressure drop in the expansion stroke when residual fluid inside the nozzle is displaced by the expansion of trapped gases as the pressure through the orifices is equalised, leading to further surface wetting. There have been several recent advancements in the characterisation of these near nozzle fluid processes, yet there is a lack of quantitative data relating the operating conditions and hardware parameters to the quantity of overspill and surface-bound fuel. In this study, methods for quantifying nozzle tip wetting after the end of injection were developed, to gain a better understanding of the underlying processes and to study the influence of engine operating conditions. A high-speed camera with a long- distance microscope was used to visualise fluid behaviour at the microscopic scale during, and after, the end of injection. In order to measure the nozzle tip temperature, a production injector was used which was instrumented with a type K thermocouple near one of the orifices. Image post-processing techniques were developed to track both the initial fuel coverage area on the nozzle surface, as well as the temporal evolution and spreading rate of surface-bound fluid. The conclusion presents an analysis of the area of fuel coverage and the rate of spreading and how these depend on injection pressure, in-cylinder pressure and in-cylinder temperature. It was observed that for this VCO injector, the rate of spreading correlates with the initial area of fuel coverage measured after the end of injection, suggesting that the main mechanism for nozzle wetting is through the impingement of dribble onto the nozzle. However, occasional observations of the expansion of orifice-trapped gas were made that lead to asignificant increase in nozzle wetting.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4661
A new approach to modelling the two way coupling for momentum transfer in a hollow-cone spray
Authors: Papoutsakis Andreas , Sazhin Sergei , Begg Steven , Danaila Ionut , Luddens Francky
Published: September 2017

A new approach to modelling the interaction between droplets and the carrier phase is suggested. The new model isapplied to the analysis of a spray injected into a chamber of quiescent air, using an Eulerian-Lagrangian approach. The conservative formulation of the equations for mass, momentum and energy transport is used for the analysis of the carrier phase. The dispersed phase is modelled using the Lagrangian approach with droplets represented by individual parcels.The implementation of the Discontinuous Galerkin method (ForestDG), based on a topological representation of the computational mesh by a hierarchical structure consisting of oct- quad- and binary trees, is used in our analysis. Adaptive mesh refinement (h-refinement) enables us to increase the spatial resolution for the computational mesh in the vicinity of the points of interest such as interfaces, geometrical features, or flow discontinuities. The local increase in the expansion order (p-refinement) at areas of high strain rates or vorticity magnitude results in an increase of the order of the accuracy of discretisation of shear layers and vortices.The initial domain consists of a graph of unitarian-trees representing hexahedral, prismatic and tetrahedral elements. The ancestral elements of the mesh can be split into self-similar elements allowing each tree to grow branches to an arbitrary level of refinement. The connectivity of the elements, their genealogy and their partitioning are described by linked lists of pointers. These are attached to the tree data structure which facilitates the on-the-fly splitting, merging and repartitioning of the computational mesh by rearranging the links of each node of the tree. This enables us to refine the computational mesh in the vicinity of the droplet parcels aiming to accurately resolve the coupling betweenthe two phases.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4671
Where does the drop size distribution come from?
Authors: Canu Romain , Dumouchel Christophe , Duret Benjamin , Essadki Mohamed , Massot Marc , Ménard Thibault , Puggelli Stefano , Reveillon Julien , Demoulin François-Xavier
Published: September 2017

This study employs DNS of two-phase flows to enhance primary atomization understanding and modelling to beused in numerical simulation in RANS or LES framework. In particular, the work has been aimed at improving the information on the liquid-gas interface evolution available inside the Eulerian-Lagrangian Spray Atomization (ELSA) framework. Even though this approach has been successful to describe the complete liquid atomization process from the primary region to the dilute spray, major improvements are expected on the establishment of the drop size distribution (DSD). Indeed, the DSD is easily defined once the spray is formed, but its appearance and even the mathematical framework to describe its creation during the initial breakup of the continuous liquid phase in a set of individual liquid parcels is missing. This is the main aim of the present work to review proposals to achieve a continuous description of the DSD formation during the atomization process.The attention is here focused on the extraction from DNS data of the behaviour of geometrical variable of the liquid- gas interface, such as the mean and Gauss surface curvatures. A DNS database on curvature evolution has been generated. A Rayleigh-Plateau instability along a column of liquid is considered to analyse and to verify the capabilities of the code in correctly predicting the curvature distribution. A statistical analysis on the curvatures data, in terms of probability density function, was performed in order to determine the physical parameters that control the curvatures on this test case. Two different methods are presented to compute the curvature distribution and in addition, the probability to be at a given distance of the interface is studied. This approach finally links the new toolsproposed to follow the formation of the spray with the pioneering work done on scale distribution analysis.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4706
Drop Stream – Immiscible Jet Collisions: Regimes and Fragmentation Mechanisms
Authors: Planchette Carole , Hinterbichler Hannes , Brenn Günter
Published: September 2017

We investigate the collision of a continuous liquid jet with a regular stream of immiscible droplets. The immiscible liquids, namely silicon oil for the continuous jet and an aqueous glycerol solution for the drop stream, are selected to enable the total wetting of the drops by the jet liquid. Four different regimes are experimentally identified: drops in jet, encapsulation without satellites, encapsulation with satellites from the jet liquid and mixed fragmentation. The drops in jet regime, potentially of great interest for new applications, corresponds to a regular stream of drops embedded in a continuous jet and is described and reported for the first time. Using well known aspects of drop collision and jet stability, we propose to model the transition between the drops in jet regime and the others. Two dimensionless parameters are derived from this analysis which are thus used to produce a simple regime map where the drops in jet regime can be well distinguished from the other outcomes.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4707
An Experimental Study of Diesel Spray Impingement on a Flat Plate: Effects of Injection Conditions
Authors: Zhu Xiucheng , Zhao Le , Zhao Zhihao , Ahuja Nitisha , Naber Jeffrey , Lee Seong-Young
Published: September 2017

Advanced injection strategies for internal combustion engines have been extensively studied although there stillexists a significant fundamental knowledge gap on the mechanism for high-pressure spray interaction with the piston surface and chamber wall in the internal combustion engine. The current study focuses on providing qualitative and quantitative information on spray-wall impingement and its characteristics by expanding the range of operating parameters under engine-like conditions. Parameters considered in the experiment are ambient gas and fuel injection conditions. The test included the non-vaporizing spray at the different ambient density (14.8, 22.8 and 30 kg/m3) and injection pressure (1200, 1500 and 1800 bar) with the isothermal condition (ambient, and plate temperatures of 423 K). The test was conducted in the constant-volume vessel with the 60-degree impinging spray angle relative to the plate. The free spray and impinged spray properties were qualitatively analysed based on Mie and schlieren images. The results showed that the lower ambient density and higher injection pressure tended to result in relatively higher impinged spray height. The expanding shape of the impinged spray on the wall showedthe oval shape.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4733
Measurement of a Direct Water-Gasoline-Emulsion-Injection
Authors: Wagner Thilo , Rottengruber Hermann , Beyrau Frank , Dragomirov Plamen , Schaub Maximilian
Published: September 2017

The investigation focus for combustion engines is on reduction of emissions as well as fuel consumption. By introducing the gasoline direct injection combined with downsizing the efficiency and the fuel consumption of gasoline engines has been optimized. An additional potential to the previous solutions provides the water injection. The article include the results of the fundamental research of water injection for combustion engines, it shows the influence of the amount of water in a water-gasoline-emulsion on the spray in a high pressure injection chamber. Therefor the spray of a gasoline direct injection injector is visualized by a high speed camera using the shadowgraph technique.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4753
Maximum entropy method for biodiesel spray droplet distribution
Authors: Kolodnytska Ruslana , Skurativskyi Sergiy , Moskvin Pavel
Published: September 2017

The efficiency of combustion process in diesel engine depends on the spray characteristics. The most importantof them are droplet size and velocity distributions. There are four methods which are used for describing the droplet size distributions: empirical, maximum entropy formalism (MEF), discrete probability function (DPF) and stochastic method. The MEF assumes that spray formation is a random process that can be described using the principle of maximum entropy. DPF method is a combination of random and non-random processes when the drop-size distribution appears from fluctuations in the initial conditions. Under the DPF approach the spray formation is divided into following steps: liquid breakup, ligaments separation, breakup of ligaments into fragments, fragment breakup into droplets. The stochastic breakup model assumes that the probability  of formation of daughter droplet breakup size is independent of its parent size (a fractal scaling of breakup has been identified). This paper presents an investigation into the application of MEF model for distribution of biodiesel droplets. We used the model approach with the constraints: normalization, mass conservation, momentum conservation and surface energy conservation. The resulting probability density function (PDF) for velocity and droplet size is obtained by maximizing the Shannon entropy. We also used the new numerical algorithm to improve the model accuracy. The PDF for droplets diameters with different Weber numbers were calculated for both diesel and biodiesel fuels. The MEF predictions were compared against the experimental data for diesel and biodiesel droplet distribution with different injection pressure. According to the maximum entropy method, the influence of fuel thermodynamic properties on the parameters of drop-size and velocity distribution function forfuel sprays has been analysed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4769
Effect of Prefilmer Edge Thickness on Breakup Phenomena of Liquid Film in Prefilming Airblast Atomizer
Authors: Okabe Takahiro , Katagata Naoki , Sakaki Toshihiro , Inamura Takao , Fumoto Koji
Published: September 2017

This paper describes the investigation of the effect of a prefilmer edge thickness on the breakup phenomena of aliquid film in a prefilmer airblast atomizer. The breakup phenomena of the liquid film at five prefilmer edge thicknesses (160, 500, 1250, 2000, and 3000 μm) under various conditions was observed using a high-speed camera. The breakup length of the liquid film was calculated by an image processing technique developed in this study. In order to quantitatively evaluate the effect of the prefilmer edge thickness on the breakup frequency, the Fast Fourier Transformation (FFT) analysis was conducted based on the time evolution of the breakup length. The results indicated that the breakup length increase and the breakup frequency decreases by increasing prefilmer edge thickness due to a larger volume of a liquid accumulation attaching to the prefilmer edge. The FFT analysis showed that the increase in prefilmer edge thickness causes the transition of the maximal power spectrum to a lower frequency (i.e. less than 100 Hz) due to the increase in the liquid accumulation at the edge as well. Finally, adimensionless correlation has been proposed for the breakup length of a liquid film.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4931
Properties of Fuel Spray Obtained by Electrohydrodynamic Atomization
Authors: Daaboul Michel , Saba Nicolas , Rishmany Jihad , Louste Christophe
Published: September 2017

Airblast atomization is com monly used to atomize fuel in aircraft engines. An annular liquid sheet is atomized bythe shear forces exerted by the co-flowing air stream. Nevertheless, this technique is less effe ctive 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 electricallycharging 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 reco rded with the help of a high speed camera. Primary atomization is only studied, secondaryatomization 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, thedroplet count, etc.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5018
Numerical Investigation of Droplet Impact on Smooth Surfaces with Different Wettability Characteristics: Implementation of a dynamic contact angle treatment in OpenFOAM.
Authors: Georgoulas Anastasios , Vontas Konstantinos , Andredaki Manolia , Nikas Konstantinos Stefanos , Marengo Marco
Published: September 2017

The “Direct Numerical Simulations” (DNS) of droplet impact processes is of great interest and importance for a variety of industrial applications, where laboratory experiments might be difficult, costly and time-consuming. Furthermore, in most cases after validated against experimental data, they can be utilised to further explain the experimental measurements or to extend the experimental runs by performing “virtual” numerical experiments.  In such “DNS” calculations of the dynamic topology of the interface between the liquid and gas phase, the selected dynamic contact angle treatment is a key parameter for the accurate prediction of the droplet dynamics. In the present paper, droplet impact phenomena on smooth, dry surfaces are simulated using three different contact angle treatments. For this purpose, an enhanced VOF-based model, that accounts for spurious currents reduction, which has been previously implemented in OpenFOAM CFD Toolbox, is utilised and further enhanced. Apart from the already implemented constant and dynamic contact angle treatments in OpenFOAM, the dynamic contact angle model of Kistler, that considers the maximum advancing and minimum receding contact angles, is implemented in the code. The enhanced VOF model predictions are initially compared with literature available experimental data of droplets impacting on smooth surfaces with various wettability characteristics. The constant contact angle treatment of OpenFOAM as well as the Kistler’s implementation show good qualitative and quantitative agreement with experimental results up to the point of maximum spreading, when the spreading is inertia dominated. However, only Kistler’s model succeeds to accurately predict both the advancing and the recoiling phase of the droplet impact, for a variety of surface wettability characteristics. The dynamic contact angle treatment fails to predict almost all stages of the droplet impact. The optimum version of the model is then applied for 2 additional series of parametric numerical simulations that identify and quantify the effects of surface tensionand viscosity, in the droplet impact dynamics.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5020
LIF/Mie Droplet Sizing of Water Sprays from SCR System Injector using Structured Illumination
Authors: Kapusta Łukasz Jan
Published: September 2017

Recent trends in SCR (Selective Catalytic Reduction) systems development increase requirements for UWS (UreaWater Solution) injection. Close-coupled SCR system designs decrease the distance available for water evaporation and urea decomposition. Due to that, much effort is put into static mixing elements design improvement and injection process enhancement. So far, most experimental studies on UWS spray formation were based on Mie scattering visualization using global illumination and shadowgraphy imaging. High speed imaging of Mie signal with global illumination allows to determine global spray parameters such as penetration and angle but does not give information on droplet sizes. Droplet size determination, due to relatively large droplets generated by SCR injectors, can be done with Mie scattering or backlight imaging methods. Then the visualized area becomes narrowed since high magnification is required. Determination of droplet size distribution across whole spray in such arrangement requires number of measurements. LIF/Mie (Laser Induced Fluorescence/Mie scattering) technique provides an attractive alternative for rapid determination of droplet size distribution across the whole spray. This method however suffers from multiple scattering effects which might affect droplet size distribution results even in relatively dilute sprays.In this study, LIF/Mie ratio distribution across sprays from commercial automotive injector for SCR systems was determined by simultaneous LIF and Mie detection using structured illumination. Moreover, the results were compared with conventional LIF/Mie imaging. Nd:YAG pulse laser was used as a light source. Second harmonic beam of 532 nm was used to illuminate the sprays. Instead of UWS pure water doped with Eosin Y was used. The results showed that conventional images exhibited much stronger background signal. Moreover, the conventional imaging was sensitive to reflections from experimental setup elements, specifically reflections from LIF camera filter. These two observations prove the importance of using SLIPI for LIF/Mie droplets sizing in sprays for SCR systems. At the same time the obtained results showed that under certain conditions (no accidental reflections in the background) conventional imaging provides similar LIF/Mie ratio as structured illumination. The results showed that the LIF/Mie ratio remains unchanged over the spray cloud. This suggests that SMD remains unchanged as well. The slight increase of LIF/Mie ratio far from the injector outlet could be caused by absence of small droplets due to lower momentum and thus lower penetration distance. This assumption however should be verified with PIVmeasurement.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5031
Liquid-Liquid Secondary Fragmentation with Solidification
Authors: Rimbert Nicolas , Hadj-Achour M. , Gradeck M.
Published: September 2017

In the event of a hypothetical core disruptive accident in nuclear power plants, the molten core may flow out thereactor 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 bathtemperature considered.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.5034
Characteristics of Control Piston Motion and Pressure Inside of a Common Rail Diesel Injector
Authors: Schuckert Sebastian , Wachtmeister Georg
Published: September 2017

In this paper the experimental setup of a commercial third generation common rail solenoid injector with advancedmeasurement is discussed. The motion of the control piston is measured while performing injection rate investigations using a purpose-built injection rate analyzer of the Bosch type. At the same time fuel pressure in the feed line of the nozzle is gauged and contrasted to fuel pressure before the inlet connector.In contrast to the steady rise observed in a similar study, the motion of the control piston in this case is characterized by a changing gradient in the upward movement. The magnitude of the negative displacement of the upper part of the control piston due to the fuel pressure in the control volume corresponds to simulation results of the elastic deformation.Pressure before the inlet connector and pressure in the feed line exhibit a similar course with a difference in magnitude that is rising with higher rail pressures. Precisely with the end of injection the pressure in the feed line surpasses the pressure before the inlet connector for a short moment. The measurement results of control piston motion and pressure inside the injector are of particular interest because these parameters are to serve as indicatorsfor changes in the injection rate caused by phenomena like wear and coking amongst others.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.6454
Actividad insecticida e insectistática de Beauveria bassiana en Bradysia impatiens (Diptera: Sciaridae)
Authors: Marín-Cruz Víctor H. , Rodríguez-Navarro Silvia , Barranco-Florido Juan E. , Cibrián-Tovar David
Published: September 2017

Introducción: Bradysia impatiens causa pérdidas significativas en viveros e invernaderos de México.Objetivo: El efecto insecticida e insectistático de Beauveria bassiana se evaluó sobre B. impatiens.Materiales y métodos: El efecto insecticida e insectistático de conidios (107 conidios·mL-1), enzimas (10 000 ppm), metabolitos (10 000 ppm) y extracto crudo de B. bassiana se evaluó a los 8 y 20 días. Los datos de mortalidad corregida de larvas y pupas de B. impatiens y emergencia relativa de adultos, transformados con la función arcoseno, se sometieron a un análisis de varianza y comparación de medias de Tukey (P < 0.05).Resultados y discusión: En el día 8, los conidios tuvieron la mayor actividad insecticida con 31.1 % de mortalidad corregida, mientras que la actividad de las enzimas fue nula. A los 20 días, los tratamientos de metabolitos y conidios tuvieron el mayor efecto en la mortalidad, 47.5 y 42.1 %, respectivamente. Dichos tratamientos tuvieron la mayor actividad insectistática. La emergencia de adultos a los 20 días fue menor con los conidios (6 %), mientras que con las enzimas fue de 100 %. Los metabolitos provocaron que 65 % de los adultos mostraran malformaciones.Conclusión: Los metabolitos y conidios de B. bassiana podrían emplearse para el control de larvas y pupas de B. impatiens.
Caracterización molecular mediante iniciadores ISSR de Magnolia mexicana DC. de dos regiones de Zongolica, Veracruz, México
Authors: Medrano-Hernández Jessica M. , Rodríguez de la O José L. , Reyes-Trejo Benito , Peña-Ortega M. Gisela
Published: September 2017

Introducción: Magnolia mexicana DC. es una especie amenazada según la NOM-059-SEMARNAT-2010, situación atribuida a la fragmentación y destrucción del hábitat. No existen estudios sobre la diversidad genética de M. mexicana, a pesar de que es endémica de nuestro país.Objetivo: Evaluar la variabilidad genética en dos poblaciones de M. mexicana mediante marcadores moleculares tipo ISSR.Materiales y métodos: Las colectas provienen de Amatitla y Zapotla en Zongolica, Veracruz. El ADN se extrajo de las hojas jóvenes. Se probaron 55 iniciadores ISSR, se seleccionaron los 10 que produjeron mayor número de bandas con polimorfismo y se amplificaron por PCR.Resultados y discusión: Los iniciadores ISSR mostraron 86 % de polimorfismo. El análisis de agrupamiento, con el método de varianza mínima de Ward, fue capaz de separar las colectas por su procedencia geográfica. El análisis de varianza molecular demostró que la mayor variabilidad (90.88 %) se encuentra dentro de cada población. El índice de diversidad de Shannon-Weaver fue de 0.47 y 0.41 para Amatitla y Zapotla, respectivamente.Conclusión: Las poblaciones de M. mexicana no han sufrido cambios en su estructura genética; no hay evidencia, a nivel genético, de alteraciones ocasionadas por la reducción de poblaciones o fragmentación del hábitat.