bluuebunny/crossref_metadata_2025 huggingface dataset:
Spray/wall interaction analysis on an ECN single-hole injector at diesel-like conditions through Schlieren visualization.
Authors: Peraza Jesús Enrique , Payri Raul , Gimeno Jaime , Bazyn Tim
Published: September 2017

To continuously improve CFD models which simulate spray evolution, breakup and evaporation mechanisms, it is helpful to validate them with results obtained by experimental research. In the present study, a mono-orifice target nozzle from Engine Combustion Network, referred to as Spray D, was investigated at conditions of spray-wall interaction, which actually is a real situation in internal combustion engines that is not frequently analyzed by visualization. A Photron SA-X2 high-speed camera was employed to record the vapor phase development of the spray in an inert atmosphere using a Schlieren imaging single-pass setup. The experiments show that the spreading of the spray along the wall has a behavior fairly similar to penetration at free-jet situations, especially regarding to its susceptibility to the operating conditions and its proportionality to the square root of time once the spray reaches a steady regime interacting with the wall. Furthermore, the spray film thickness was measured at three distances from the spray-wall impact point during the injection event, thereby characterizing that parameter both spatially and temporally. The tests were carried out in a constant pressure-flow facility able to reproduce pressure and temperature conditions, similar to those seen into a diesel engine. In order to observe the behavior of the spray colliding with a wall within this test rig, a system capable to being fitted into it and to holding a fused quartz wall at different injector tip-wall distances and impingement angle configurations, was designed and employed.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4709
Detailed simulation of air-assisted spray atomization: effect of numerical scheme at intermediate Weber number
Authors: Tretola Giovanni , Vogiatzaki Konstantina , Navarro-Martinez Salvador
Published: September 2017

Numerical simulations are often used to understand spray atomisation and estimate the size of the liquid fragments.Several techniques (Level Set, Volume of Fluid, Smooth Particle Hydrodynamics, among others) exist to compute multiphase flows and potentially represent liquid-break-up. However, the complexity of the breakup process and the wide range of scales prevents the use of an unified approach to simulate the complete spray. Numerical techniques face different challenges depending on the spray characteristics. The incorrect representation of surface forces in capillary dominated flows, creates large parasitic currents that distort and in some cases destroy the interface. Methods that perform well in the capillary regime aim to capture the interface directly and the surface radius cur- vature is therefore larger than the mesh size. However, this creates large constrains on the mesh resolution and limits its applications to low Weber number flows, when there is no extensive atomization. Methods that simulate large Weber number flows (typical of industrial injectors) do not resolve the interface directly and the mesh is larger than the smallest radius of curvature. These models often have numerical or artificial diffusion that destroys small scale structures and alters the break-up. However, even at large Weber flows, the spray formation can be affected by errors due to the local imbalance between pressure and surface tension forces and interface curvature errors. Numerical schemes work around these problems by adjusting the amount of numerical diffusion of the scheme depending on the spray application. Intermediate Weber number sprays are well suited to study the performance of numerical methods as they exhibit hybrid behaviour between capillary flows and full atomization. In the present work an intermediate gas Weber of a laboratory air-blast atomiser is investigated using a volume of fluid approach. The amount of numerical diffusion is controlled by a compressive factor in the volume of fluid transport equation. The effect of the compressive term on spray atomization and droplet size distribution is explored. The results suggestthat the optimal amount of diffusion depends on the local Weber number.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4712
Expansion rates of bubble clusters in superheated liquids
Authors: Dietzel Dirk , Hitz Timon , Munz Claus-Dieter , Kronenburg Andreas
Published: September 2017

The present work analyses the growth of multiple bubbles in superheated liquid jets by means of direct numericalsimulations (DNS). A discontinuous Galerkin approach is used to solve the Euler equations and an adequate in- terface resolution is ensured by applying finite-volume sub-cells in cells with interfaces. An approximate Riemann solver has been adapted to account for evaporation and provides consistency of all conserved quantities across the interface. The setup mimics conditions typical for orbital manoeuvring systems when liquid oxygen (LOX) is injected into the combustion chamber prior to ignition. The liquid oxygen will then be in a superheated state, bubble nucleation will occur and the growth of the bubbles will determine the break-up of the liquid jet. The expansion rates of bubble groups under such conditions are not known and standard models rely on single bubble assumptions. This is a first DNS study on bubble-bubble interactions in flash boiling sprays and on the effects of these interactions on the growth rates of the individual bubbles. The present simulations resolve a small section of the jet close to the nozzle exit and the growth of bubble groups inside of the jet is analysed. The results suggest that an individual bubble within the group grows more slowly than conventional models for single bubble growth would predict. The reduction in bubble growth can amount to up to 30% and depends on the distances between the bubbles and the number of bubbles within the bubble group. In the present case, the volume expansion of the superheated liquiddecreases by approximately 50% if the distance between the bubbles is doubled.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4714
Polydisperse spray flames in vortex flows
Authors: Dagan Yuval , Katoshevski David , Greenberg Barry J
Published: September 2017

A new mathematical analysis of the dynamics of laminar spray diffusion flames in the vicinity of a vortex flow fieldis presented. The governing equations for a spray evaporating in an unsteady vortex are studied. New similarity solutions are found for the dynamics of the spray and the flame it supports. Analytical solutions for the spray flames are derived using Schvab-Zeldovich parameters, through which the radial evolution of the flames is found. The results based on the solution reveal the significant influence the droplets size has on the diffusion flame dynamicsin the vicinity of vortical flows.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4716
Comparison between numerical and experimental water-in-oil dispersion in a microchannel
Authors: Tarlet Dominique , Desjonquères Philippe , Ménard Thibault , Bellettre Jérôme
Published: September 2017

The dispersion of water inside a flow of oil is investigated in a microfluidic device, producing a water-in-oilemulsion. The liquid–liquid flow mainly differs from those presented in existing literature through its high capillary number (between 3 and 14), and in the head-on collision between water and oil streams. By comparing with experimental data, numerical simulations can provide more information about the topology of the flow. A coupled Volume of Fluid and Level Set method (CLSVOF) is used to treat the interface between both phases and incompressible Navier-Stokes equations are solved. Three set of parameters, close to those in the experimental setup, are investigated to compare experimental and numerical results. The comparison between experiments and simulation provides a precise knowledge of the liquid-liquid dispersion process and the overall flow patternwithin the microfluidic device.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4717
Modelling of spheroidal drop evaporation with non-uniform temperature conditions
Authors: Tonini Simona , Cossali Gianpietro Elvio , Ravasio Stefano
Published: September 2017

The  heating  and  evaporation  of  single  component  spherical  and  spheroidal  drops  in  gaseous  quiescentenvironment are predicted, accounting for the effect of a non-uniform distribution of the temperature at the drop surface. The analytical solution of the species conservation equations in the proper coordinate system (spherical/spheroidal) is implemented to numerically solve the energy equation in a rectangular domain. The effect  of  temperature  disuniformity  on  the  local  Nusset  number  and  global  heat  and  evaporation  rates  iscalculated for different species, drop deformation and gaseous temperature.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4721
Visualisation and quantitative analysis of the near nozzle formation and structure of a high pressure water jet in air and water.
Authors: Jasper Sarah , Hussong Jeanette , Lindken Ralph
Published: September 2017

High pressure water jets (HPWJ) are frequently used in industrial applications like cleaning, further processing of workpieces or cutting of materials. In a joint research program with the International Geothermal Centre (GZB) the HPWJ process is adapted to the field of rock drilling to develop and enhance an innovative drilling technology for geothermal applications. In this case, the HPWJ is used to cut and destroy rock in deep geothermal reservoirs to make them accessible for energy generation. This transfer requires a broad knowledge of the process and interaction between the HPWJ and the rock surface. The challenges in analysis and characterization of the process are high velocities of the water jet of several hundred meters per second based on the high pump pressure of up to 180 MPa and the very small spatial expansion of the field of interest between the nozzle outlet and the rock surface, which is within a few centimeters. The objective of the present work is the visualization of a HPWJ in diverse fluids as a first step to increase the process knowledge of waterjet cutting of rocks. Tests are performed in air, water and slurry respectively and a parametric study is carried out to examine the influence of different operating parameters on the HPWJ formation and structure. Moreover, the influence of the surrounding fluid on the HPWJ is investigated.Optical measurement techniques are applied to analyze the HPWJ and results will be presented. The high velocities, the very small spatial expansion and the dense liquid jet represent challenges to the application of these measurement techniques. High speed photography in terms of shadow experiments is used for visualization and relevant spray parameters are evaluated with common spray analysis techniques. Adopting the double frame technique, well-known with particle image velocimetry (PIV), an estimation of the fluid velocity on the boundary of the HPWJ is performed. In addition to the shadowgraph analysis, PIV in auto-correlation mode with fluorescent tracers is applied to analyze velocity fields, the dimension of the potential core as well as the interaction with the surrounding fluid.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4736
Experimental study on the effect of initial liquid droplet size on the evaporation in a heterogeneous droplet
Authors: Sung Kun Hyuk , Nam Jun Seok , Hong Gi Bae , Ryou Hong Sun
Published: September 2017

In the present work, we experimentally investigated the effect of initial liquid droplet size on the evaporation in the heterogeneous droplet. Spherical carbon and water were used for particle and liquid droplet comprising the heterogeneous droplet. four initial droplet volumes of 1, 2, 3 and 4 μl were considered when the diameter of the particle was 5 mm. The heterogeneous droplet was suspended with a rod at 20 cm away from the radiator which surface temperature was fixed to 473 K. Ambient temperature and relative humidity remained 296 K and 40 %, respectively, during the experiment. As the results, the evaporation rate of 4 μl case increased about 1.8 times compared with that of 1 μl case. The evaporation rate increased almost linearly with the volume ratio, and that is related closely with the contact surface between particle and water droplet. Contact surface area remained almost constantly with time, whereas it increased with the initial volume of water droplet. The energy from radiator can be accumulated at the contact surface at the side of particle, thereby intensifying the evaporation of water droplet because more heat transfers from particle to droplet through the contact surface. Consequently, the initial volume of liquid droplet is one of the influence factors on the evaporation rate in the heterogenous droplet.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4744
Influence of the chemical mechanism in the frame of diesel-like CFD reacting spray simulations using a presumed PDF flamelet-based combustion model
Authors: Pérez-Sánchez Eduardo Javier , Payri Francisco , García-Oliver José María , Novella Ricardo
Published: September 2017

The ability of a computational fluid dynamics (CFD) simulation to reproduce the diesel-like reacting spray ignitionprocess and its corresponding flame structure strongly depends on both the fidelity of the chemical mechanismfor reproducing the oxidation of the fuel and also on how the turbulence-chemistry interaction (TCI) is modeled.Therefore, investigating the performance of different chemical mechanisms not only in perfect stirred reactors butdirectly in the diesel-like spray itself is of great interest in order to evaluate their suitability for being further appliedto CFD engine simulations.This research work focuses on applying a presumed probability density function (PDF) unsteady flamelet combustionmodel to the well-known spray A from the Engine Combustion Network (ECN), using three chemical mechanismswidely accepted by the scientific community as a way to figure out the influence of chemistry in the keycharacteristics of the combustion process in the frame of diesel-like spray simulations. Results confirm that in spiteof providing all of them correct trends for ignition delays (ID) and lift-off lengths (LOL), when comparing with experimentalresults, the structure of the flame presents noticeable differences, especially in the low and intermediatetemperatures and high equivalence ratio regions. Consequently, the selection of the chemical mechanism has animpact on the zones of influence of key species as observed in both spatial coordinates and also in the equivalenceratio-temperature maps. These differences are expected to be relevant considering the implications when couplingpollutant emissions models. The analysis of temperature and oxygen concentration parametric studies evidenceshow the observed differences are consistent and moderately dependent on the ambient conditions.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4746
Flashboiling atomization in nozzles for GDI engines
Authors: Bornschlegel Sebastian , Conrad Chris , Eichhorn Lisa , Wensing Michael
Published: September 2017

Flashboiling denotes the phenomenon of rapid evaporation and atomization at nozzles, which occurs when fluidsare injected into ambient pressure below their own vapor pressure. It happens in gasoline direct injection (GDI) engines at low loads, when the cylinder pressure is low during injection due to the closed throttle valve. The fuel temperature at the same time approaches cylinder head coolant temperature due to the longer dwell time of the fuel inside the injector. Flash boiling is mainly beneficial for atomization quality, since it produces small droplet sizes and relative broad and homogenous droplet distributions within the spray. Coherently, the penetration depth normally decreases due to the increased aerodynamic drag. Therefore the thermal properties of injectors are often designed to reach flash boiling conditions as early as possible. At the same time, flash boiling significantly increases the risk of undesired spray collapsing. In this case, neighbouring jets converge and form a single jet. Due to the now concentrated mass, penetration depth is enhanced again and can lead to liner or piston wetting in addition to the overall diminished mixture formation.In order to understand the underlying physics, it is important to study the occurring phenomena flashboiling and jet-to-jet interacting i.e. spray collapsing separately. To this end, single hole injectors are built up to allow for an isolated investigation of flashboiling. The rapid expansion at the nozzle outlet is visualized with a microscopic high speed setup and the forces that lead to the characteristic spray expansion are discussed. Moreover, the results on the macroscopic spray in terms of penetration, cone angles and vapor phase are shown with a high speed Schlieren setup. Resulting droplet diameters and velocities are measured using LDA/PDA.As a result, we find a comprehensive picture of flash boiling. The underlying physics can be described and discussed for the specific case of high pressure injection at engine relevant nozzle geometries and conditions, but independently from neighbouring jets. These findings provide the basis to understand and investigate flashboilingand jet-to-jet interaction as distinct, but interacting subjects rather than a combined phenomenon.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4750
Models for automotive fuel droplets heating and evaporation
Authors: Al Qubeissi Mansour , Sazhin Sergei , Al-Esawi Nawar
Published: September 2017

The paper presents recent approaches to the modelling of heating and evaporation of automotive fuel droplets with application to biodiesel, diesel, gasoline, and blended fuels in conditions representative of internal combustion engines. The evolutions of droplet radii and temperatures for gasoline, diesel, and a broad range of biodiesel fuels and their selective diesel fuel blends have been predicted using the Discrete Component model (DCM). These mixtures combine up to 112 components of hydrocarbons and methyl esters. The results are compared with the predictions of the case when blended diesel-biodiesel fuel are represented by pure fossil and biodiesel fuels. In contrast to previous studies, it is shown that droplet evaporation time and surface temperature predicted for 100% biodiesel (B100) are not always close to those predicted for pure diesel fuel. Also, the previously introduced MultiDimensional Quasi-Discrete model and its application to these fuels and their mixtures are discussed. The previous application of this model has resulted in up to 96% reduction in CPU time compared to the case when all fuel components are considered using the DCM.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4754
Experimental and Computational Investigation of binary drop collisions under elevated pressure
Authors: Breitenbach Jan , Reitter Louis Maximilian , Liu Muyuan , Huang Kuan-Ling , Bothe Dieter , Brenn Günter , Pan Kuo-Long , Roisman Ilia V. , Tropea Cameron
Published: September 2017

Spray systems often operate under extreme ambient conditions like high pressure, which can have a significant influence on important spray phenomena. One of these phenomena is binary drop collisions. Such collisions, depending on the relative velocity and the impact parameter (eccentricity of the collision), can lead to drop bouncing, coalescence or breakup. This experimental and computational study is focused on the description of the phenomenon of drop bouncing, which is caused by a thin gas layer preventing the drops coalescence. To identify the main influencing parameters of this phenomenon, experiments on binary drop collisions are performed in a pressure chamber. This experimental system allows us to investigate the effect of an ambient pressure (namely the density and viscosity of the surrounding gas) on the bouncing/coalescence threshold.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4758
Microexplosion and Puffing of an Emulsion Fuel Droplet
Authors: Xia Jun , Shinjo Junji
Published: September 2017

Microexplosion is rapid disintegration of an emulsion droplet caused by explosive boiling of embedded liquid subdropletswith a lower boiling point. Microexplosion and puffing (partial microexplosion) are potentially beneficialto achieving enhanced secondary atomisation. These eruptive secondary atomisation mechanisms will help tomeet conflicting requirements for an atomising fuel spray with regard to penetration achieved by large droplets andevaporation/mixing achieved by small droplets.Although with great interest, our understanding of microexplosion is still limited and therefore optimising andcontrolling microexplosion is not feasible yet. This paper reviews our recent research outcome on microexplosionand puffing of an emulsion fuel droplet from high-fidelity interface-capturing simulation study, which directly resolvesthe dynamics of boiling and evaporating liquid/gas interfaces, immiscible liquid/liquid interfaces with jump conditionsfor mass, momentum and heat transfer across a resolved interface.We first unveiled microexplosion and puffing dynamics of an emulsion fuel droplet in a quiescent ambient.Since convective heating has important effects on temperature distribution inside a fuel droplet in realistic engineconditions, which determines the initial nucleation location and thus the microexplosion outcome, a model has beenproposed to approximate the temperature distribution inside a droplet, for which momentum and heat transport wasfound to be only moderately correlated under typical engine conditions. With this model in place that allows forsaving considerable computational cost on setting up initial conditions for microexplosion simulation, puffing effectson fuel/air mixing is then investigated, which can be quantified by the scalar dissipation rate (SDR) of the primaryfuel decane, the SDR of the secondary fuel ethanol and the cross SDR. We then further extended our simulationstudies towards reacting conditions and investigate puffing effects on a droplet wake flame.The series of high-fidelity simulation studies is believed to have considerably improved our understanding ofmicroexplosion dynamics and impact on local fuel/air mixing and combustion. Based on the improved knowledge,microexplosion induced secondary droplet breakup models can be developed and incorporated into hybrid highfidelitysimulation of spray atomisation and combustion enhanced by microexplosion.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4762
Analysis of Heat and Flow Characteristics on Spray Cooling Heat Transfer with an Optimized Hexagonal Finned Heat Sink
Authors: Yesildal Faruk , Yakut Kenan
Published: September 2017

An experimental study was carried out with a hexagonal finned heat sink to obtain valuable information about the thermal and flow characteristics on spray cooling. Water was used as the refrigerant fluid and was atomized by an air-assisted atomizer and some of the variables that affect spray cooling process, such as breakup length and Sauter Mean Diameter (SMD) were obtained using appropriate correlations. The parameters most influential on the Nusselt number were determined and analyzed. Experiments were conducted for optimized conditions. The jet diameter and spray angle were determined via image processing using macroscopic aspects. Nusselt were demonstrated of hexagonal finned heat sink which optimized according to the Taguchi optimization method. The results of the spray analysis showed that SMD decreases with an increase in either air-liquid mass ratio (ALR) or operating pressure resulting in a more uniform spray. As the liquid flow rate increases in all ALR values, the heat transfer rate also increases markedly. As a results of the experiments, Nusselt number, jet width and spray angle correlations were developed. The relationship of ALR-Nu was demonstrated according to fin height and spraying time.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4772
Mathematical models for turbulent round jets based on “ideal” and “lossy” conservation of mass and energy
Authors: Franco Fermin , Fukumoto Yasuhide
Published: September 2017

We propose mathematical models for turbulent round atomized liquid jets that describe its dynamics in a simplebut comprehensive manner with the apex angle of the cone being the main disposable parameter. The basic assumptions are that (i) the jet is statistically stationary and that (ii) it can be approximated by a mixture of two fluids with the phases in local dynamic equilibrium, or so-called locally homogeneous flow (LHF). The models differ in their particular balance of explanatory capability and precision. To derive them we impose partial conservation of the initial mass and energy fluxes, introducing loss factors again as disposable parameters. Depending on each model, the equations admit explicit or implicit analytical solutions or a numerical solution in the discretized model case. The described variables are the the two-phase fluid’s composite density and velocity, both as functions of thedistance from the nozzle, from which the dynamic pressure is calculated.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4778
Experimental investigation of size effects in colliding droplet
Authors: Pasternak Lars , Sommerfeld Martin
Published: September 2017

The present work focuses on the size effect of binary collisions of PVP droplets (viscosity 5.5 mPas). The aim was the identification of the boundaries between bouncing, coalescence, stretching and reflexive separation.These boundaries are necessary for numerical simulations of droplet collisions in spray drying processes. Therefore, droplet chains were generated by droplet generators with oscillating membrane and directed towards each other at different angles for producing binary collisions. In the experiments two droplet properties (i.e. droplet size and size ratio) were varied. Two synchronised high-speed cameras were used to observe the collision process and outcome perpendicularly and parallelly to the collision plane. The variation of the impact parameter B was performed by a frequency offset for one droplet generator. The relative velocity (i. e. 0.5 to 4.7 m/s) was set by changing the collision angle.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4781
Application of dry-ice for transient spray cooling
Authors: Panao Miguel , Costa José , Bernardo Mário
Published: September 2017

Spray cooling systems are able to remove large amounts of heat due to phase-change. Although vaporization is themost common phase-change process used in applications requiring thermal management, the use of liquids often implies the presence of a liquid film which is known to mitigate cooling performance. Thus, it is worth exploring other approaches for spray cooling avoiding liquid films. The work presented here explores sublimation using CO2 particles (dry-ice) formed through the Joule-Thomson effect. The application of interest is the molding industry, where reducing the cycle time taking advantage of the time-frame available between the mold opening and closing during the part’s extraction, allows a production increase and, consequently, a higher competitive advantage in the market. The purpose of the experiments performed in dry-ice particle spray cooling is to investigate the effect of the impingement distance (350-450mm), and injection duration, on the total energy flux removed from the surface, and cooling efficiency, in order to assess the performance of sublimation spray cooling. The results show an evolution of temperature distribution from a more homogeneous pattern with shorter pulses to a heterogeneous one for pulse durations longer than 1 s. This is particularly useful in hotspot cooling. In terms of changing the spray impact distance, the higher particle dispersion achieved with a larger distance led to a decrease in thermal performance, probably due to the saturation of CO2 close to the impact surface. However, the pattern observed for the evolution of the total energy flux removed, with a maximum around an injection duration of 0.5 s, remains unaltered. The maximum cooling efficiency, obtained for the shortest distance, is up to 30%, which is comparable to spray coolingsystems based on vaporization.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4784
Numerical analysis of sprays with an advanced collision model
Authors: Sommerfeld Martin , Lain Santiago
Published: September 2017

Modelling of collisions between liquid droplets in the frame of a Lagrangian spray simulation has still many openissues, especially when considering higher viscous droplets and if colliding droplets have a large size difference. A generalisation of the collision maps is attempted based on the behaviour of characteristic points, namely the triple point where bouncing, coalescence and stretching separation coincide and the critical Weber-number where reflexive separation first occurs in head-on collisions. This is done by correlating experimental data with respect to the Capillary number with the Ohnesorge-number for the triple point and the critical Weber-number is also well described by a correlation the Ohnesorge-number. Based on these results the boundary line between stretching separation and coalescence is found by adapting the Jiang et al. (1992) correlation. For the upper boundary of reflexive separation the shifted Ashgriz and Poo (1990) correlation is used. It was however so far not possible to predict the lower bouncing boundary through the Estrade et al. (1999) boundary line correctly. The proposed boundary-line models were validated for various liquid, however still considering only a size ratio of one. With the developed three-line boundary model Euler/Lagrange numerical calculations for a simple spray system were conducted and the droplet collisions were analysed with respect to their occurrence. Droplet collision modelling is performed on the basis of the stochastic droplet collision  model,  also considering the influence  of impact efficiency, which so far was neglected for most spray simulations. The comparison with measurements showedreasonable good agreement for all properties.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4785
Generalized analysis of the deposition/splashing limit for one- and two-component droplet impacts upon thin films
Authors: Bernard Ronan , Foltyn Patrick , Geppert Anne , Lamanna Grazia , Weigand Bernhard
Published: September 2017

Single drop impacts on thin liquid layers are of particular interest because of the ejection of secondary droplets, theso-called splashing. Only a few studies handle the deposition/splashing limit for two-component interaction, where the liquid properties of the impacting drop and wall film differ significantly.This study aims at identifying a unified approach for one- and two-component interactions to determine the deposi- tion/splashing limit. Therefore, a large database of both interactions is considered, which includes data from litera- ture for one-component interactions plus the following binary combinations: hyspin-hexadecane, diesel-hexadecane and diesel-motor oil. Furthermore, a systematic study of two-component interactions with several silicon oils and hexadecane is performed. To map the outcomes, the Ohnesorge number Oh and the Reynolds number Re calcu- lated with arithmetically averaged fluid properties between droplet and wall film fluid are chosen. The dimensions- less film thickness δ is added to form a 3D plot, where one- and two-component experiments are combined.Existing correlations from the literature are revised regarding both interactions and their consistency is checked. The investigated range of high viscosity fluids allow us to propose an improvement of the correlation for high Oh. Our results show that the arithmetically averaged fluid properties lead to a good repartition of both one- and two- components interactions toward the deposition/splashing limit. They also corroborate the previous findings that an increase of δ inhibits splashing but its influence is decreasing with increasing Oh.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4810
Spray and Combustion Characterizations of Acetone-Butanol-Ethanol (ABE) blend at High-Pressure and High-Temperature Conditions
Authors: Ob Nilaphai , Hugo Ajrouche , Camille Hespel , Bruno Moreau , Somchai Chanchaona , Fabrice Foucher , Christine Mounaim-Rousselle
Published: September 2017

The intermediate fermentation mixture of butanol production, Acetone, Butanol and Ethanol (ABE), is increasinglyconsidered as a new alternative fuel in CI engines due to its physical and chemical properties, which are similar to those of butanol, and its advantages of no additional cost or energy consumption due to butanol separation. In a previous study, the High-Pressure and High-Temperature (HPHT) chamber, called ‘New One Shot Engine” (NOSE), was used to investigate macroscopic spray-combustion parameters by validating Spray-A conditions of the Engine Combustion Network. The present study concerns the spray-combustion characteristics of the ABE mixture (volume ratio 3:6:1), blended with n-dodecane at a volumetric ratio of 20% (ABE20), compared to n-dodecane as reference fuel. The macroscopic spray and combustion parameters were investigated, for non-reactive conditions, in pure Nitrogen and for reactive conditions, in 15% oxygen, at ambient pressure (60 bar), ambient density (22.8 kg/m3) and different ambient temperatures (800 K, 850 K and 900 K). The liquid and vapor spray penetrations were investigated by the Diffused Back Illumination (DBI) and Schlieren techniques in non-reactive conditions. In reactive conditions, the lift-off length was measured by OH* chemiluminescence images at 310 nm. The Schlieren technique was also used to verify the choice of detection criterion. The ignition delay results of the two fuels were compared. It was found that the behavior of the two fuels as a function of temperature was similar even if the liquid length of ABE20 was shorter than that of n-dodecane at all ambient temperatures. On the other hand, no real difference in vapor spray penetration between the two fuels was observed. The vaporization properties and the lower auto-ignition ability of ABE20 led to longer ignition delays and lift-off length.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4852
Oxygenated fuels properties and its relationship with engine performance in port fuel injection engines.
Authors: Gonzalez Uriel , Schifter Isaac
Published: September 2017

Gasoline oxygenating agents (alcohols, ethers and a carbonate) were used to formulate gasoline at different oxygencontents up to 20 wt.% and compared with commercial Premium gasoline.The performance of each fuel was investigated in a port fuel injected, single cylinder, spark-ignited engine at different stages i.e. air fuel mixture preparation, combustion behavior and exhaust emissions. In all cases, the intake cooling effect (related mainly to fuel properties like latent heat of vaporization and Reid Vapor Pressure), shows an important relationship with engine performance and emissions, probably due to reductions in heat losses associated with decreases in charge temperature at compression stroke before ignition. This results was confirmed by means of vehicle FTP-75 test.The high RVP promotes high intake manifold evaporation rate, and the high HoV is related to important cooling effect as the fuel absorbs heat during evaporation. If the fuel evaporates faster upstream intake valves, the advantages of high HoV as a way to reduce compression work and heat transfer fallen.The quantification of the charge cooling effect was done by means of precision intake air temperature control and the instrumentation of a temperature downstream the injector at intake port and as close as possible to the intake valves.The use of oxygenates reduce the hydrogen and carbon fuel contents as a result of fuel dilution. For a given level of oxygenation as lower is the molecular oxygen content in the additive, higher will be the fuel dilution.For 10 wt.% oxygen and more, fuel performance in port engines depends mainly on oxygenate contents and its relationship with HoV and RVP. For oxygenated gasolines, fuel sensitivity have a direct relationship with latent heatls increase RON. In the other hand, MON is almostinsensible to high heat of vaporization, because the intake air is heated to 159 C as a test requirement.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4855
Vapor phase penetration measurements with both single and double-pass Schlieren for the same injection event
Authors: Payri Raul , Salvador Francisco Javier , Bracho Gabriela , Viera Alberto
Published: September 2017

Schlieren imaging has been adopted as a standard optical technique for the analysis of diesel sprays under enginelike conditions. A single-pass Schlieren arrangement is typically used for the study of single-orifice nozzles, asvessels with multiple optical accesses regularly allow line of sight visualization. Contrarily, for multi-spray nozzles,measurements are commonly performed through a single optical access, in which case a double-pass arrangementis employed. As a consequence, the light beams pass through the test section twice, increasing the optical sensitivityof the Schlieren setup. However, the impact this has on the macroscopic spray characteristics is still unclear.The scope of this study is to analyze the differences in vapor phase penetration for the same injection event,through high-speed imaging, for both single and double-pass Schlieren configurations. Experiments were carriedout with a three hole nozzle with a nominal orifice diameter of 90 μm, named Spray B from the Engine CombustionNetwork, using commercially available diesel fuel and in non-reactive conditions. The impact of different injectionpressures and chamber densities on the spray captured by each setup was assessed. On the results, vapor phasepenetration followed the expected trend found in the literature, as it increases with increasing injection pressure anddecreasing chamber density. Comparing the optical setups, vapor phase penetration obtained with the double-passarrangement was marginally higher. The deviation was observed throughout all tested conditions. Although thediscrepancy was approximately constant for different injection pressures and chamber temperature, it increasedwith increasing density. These results highlight the importance of a proper understanding regarding the limitationsof optical diagnostics, in particular for results used in calibration of computational models.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4884
Effect of geometry of real-size transparent nozzles on cavitation and on the atomizing jet in the near field
Authors: Cao Yujun , Idlahcen Said , Blaisot Jean-Bernard , Rozé Claude , Méès Loïc , Maligne David
Published: September 2017

Cavitation inception is very sensitive to the nozzle geometry. Two diesel-like transparent nozzles with sharp andround inlet edge were investigated under moderate injection pressure. By means of backlight imaging technique,images were recorded in two regions near the orifice: within ten orifice diameter downstream the nozzle and insidethe nozzle, for different times after start of the injection. A cross-correlation technique was applied to imagesdownstream the orifice to estimate the average velocity of the spray. The development of the spray was studiedat the transient and full-opened stage, related to the needle lift motion. To analyse the flow inside the nozzle, therelative size of the vapour pockets was measured on the image and the relative frequency of the occurrence ofcavitation was determined over image series. This approach permits to examine the time variation of the cavitationoccurrence from the inlet to the outlet of the orifice. The results highlight the sensitivity of the cavitating flow to theshape of the inlet edge. Moreover, the trends of the variation over time of the velocity and of the cavitation frequencyare very similar to each other but different for each geometry, indicating that the characteristics of the diesel sprayin the near field is closely affected by the way cavitation is developing in the nozzle.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4938
Fuel spray vapour distribution correlations for a high pressure diesel fuel spray cases for different injector nozzle geometries.
Authors: Njere Darlington , Emekwuru Nwabueze
Published: September 2017

The evolution of diesel fuel injection technology, to facilitate strong correlations of in-cylinder spray propagation with injection conditions and injector geometry, is crucial in facing emission challenges. More observations of spray propagation are, therefore, required to provide valuable information on how to ensure that all the injected fuel has maximum contact with the available air, to promote complete combustion and reduce emissions. In this study, high pressure diesel fuel sprays are injected into a constant-volume chamber at injection and ambient pressure values typical of current diesel engines. For these types of sprays the maximum fuel liquid phase penetration is different and reached sooner than the maximum fuel vapour phase penetration. Thus, the vapour fuel could reach the combustion chamber wall and could be convected and deflected by swirling air. In hot combustion chambers this impingement can be acceptable but this might be less so in larger combustion chambers with cold walls. The fuel-ambient mixture in vapourized fuel spray jets is essential to the efficient performance of these engines. For this work, the fuel vapour penetration values are presented for fuel injectors of different k-factors. The results indicate that the geometry of fuel injectors based on the k-factors appear to affect the vapour phase penetration more than the liquid phase penetration. This is a consequence of the effects of the injector types on the exit velocity of the fuel droplets.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4951
Effects of Injection Nozzle Geometry on Spray Characteristics for Direct Injection Diesel Engines
Authors: Tamaki Nobushige , Harada Takato
Published: September 2017

Sprayatomization of the multi-hole atomization enhancement nozzle, which was invented in previous studies, is explored. The aim is to improve and obtain excellent spray characteristics. The effects of different nozzle geometries and dimensions on spray characteristics are investigated, including chamfered and rounded nozzle hole inlets and a multi-hole atomization enhancement nozzles.  It is found that the multi-hole atomization enhancement nozzle with a rounded chamfered inlet is effective in achieving a high-dispersion spray, a large spray angle and small droplets. However, it should be noted that the spray is significantly atomized and a large number of small droplets as suspended as a mist. The photographic images of the spray are taken against a white background and the boundaries between the ejected spray and the background are indistinct.  Furthermore, the breakup length is short at 3 mm for a hole diameter of 0.3 mm, the spray angle is about 70° and the Sauter mean diameter decreasesdramatically to 15 μm at a low injection pressure of 10 MPa.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4981
Break up length on Urea Water Solution jet in hot cross flow
Authors: T.N.C Anand , P Senthilkumar , Bakshi Shamit
Published: September 2017

Selective Catalytic Reduction (SCR) using Urea-Water Solution (UWS) as an ammonia precursor is consideredas one of the best choices to meet the current stringent emission norms for reduction of NOX in diesel engines. UWS sprayed in the engine exhaust line forms ammonia, and this ammonia reduces NOX into nitrogen. The NOX reduction efficiency depends on the mixing and evaporation behavior of the UWS spray in the hot exhaust gas. Spray characteristics decide the evaporation rate and hence the NOX reduction efficiency. The spray structure is closely related to the breakup point and breakup mode of the jet. Hence, in this study, breakup length and breakup mode were investigated by injecting UWS (32.5 % by weight) through a nozzle in a hot air cross flow. A CCD camera and pulsed Nd:Yag laser were used for capturing the images. Experiments were conducted with varying nozzle size (150, 250 and 400 micron), injection pressure (0.5 to 3 bar), temperature (32 °C,150 °C and 200 °C) and air flow rate. The effect of operating parameters (nozzle size, injection pressure, air temperature and velocity) in terms of dimensionless numbers (Weber number and momentum flux ratio) on jet breakup mode and jet breakup length was studied. It was observed that the breakup length for UWS was close to that of water. The jet breakup length increases with momentum flux ratio since a jet having a higher momentum is able to penetrate a larger distance in the cross flow. Increasing the air temperature increases the velocity of the cross flow and hence reduces the breakup length. A correlation for jet breakup length was developed. The effect of inclusion of Weber number in the breakup length correlation, in addition to the momentum flux ratio, was studied. Visual observation shows that droplet sizes obtained from the plain orifice injector without preheating is large. Preheatingthe UWS before injection is recommended to reduce the droplet size.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4982
Large eddy simulations of atomisation and sprays: application to a high pressure multihole injector
Authors: Hélie Jérome , Chausserie-Laprée Paul , Chesnel Jeremy , Demoulin François-Xavier
Published: September 2017

A weak coupling strategy is proposed to simulate the pressurised spray without any empirical readjustment. VolumeOf Fluid is used to simulate the nozzle internal flow with cavitation and its primary atomization into ligaments. Lagrangian simulations are then used to get the spray evolution, even temporal. Large Eddy Simulations are used for these two simulations types. The coupling between both is realized by a recording and an analysis of the ligaments with local break up modelling into drops. Two test cases are presented, the second one deals with full, complex geometry, 6-holes Gasoline Direct Injection nozzle. Such approach shows a huge potential for predictionof the final spray from the nozzle geometry.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4987
Evaluation of the combustion characteristics of isolated droplets of Jet A blended with ethanol and butanol
Authors: Ballester Javier , Muelas Álvaro , Remacha Pilar
Published: September 2017

In light of the potential of ethanol and butanol as alternative fuels for blending with conventional kerosene in gasturbine engines, experimental data regarding the burning characteristics of these blends are required in order tobetter understand their combustion process. In this study, free-falling droplets of Jet A, ethanol, butanol and theirmixtures (20% alcohol in Jet A by volume) were examined in a combustion chamber which providesrepresentative conditions of real flames, both in terms of temperature and oxygen availability. Results show thatthe evolution of droplet diameter for Jet A and its blends with both alcohols are very similar, regardless of theobvious compositional differences. On the other hand, sooting behaviors are found to be quite different, with aclear reduction in the sooting propensity of the Jet A/alcohol mixtures when compared to neat kerosene. Theseresults are consistent with previous studies in gas turbines, suggesting that such blends are viable alternativefuels with similar combustion characteristics to Jet A, but with much less propensity to produce soot. Moreover,this study provides new results on the combustion properties of Jet A/ethanol and Jet A/butanol mixtures, forwhich very scarce data exist in the open literature.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4990