bluuebunny/crossref_metadata_2025_split huggingface dataset:
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
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
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
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
Statistical methods of images analysis as an essential tool in the assessment process of computer methods intended for numerical simulations of cavitating flows
Authors: Niedźwiedzka Agnieszka , Lipiński Seweryn 
Published: September 2017

Cavitation, because of its negative effects, like e.g. erosion, noise or vibration, is usually an undesirablephenomenon. However, in devices where spraying and atomization are expected, cavitation is required. This group of devices includes e.g. diesel injectors. Appearance of vapour bubbles results in increase of the maximum flow velocity. It is possible for the following reasons. Firstly, bubbles start to form in the throat, so its diameter reduces. Secondly, appearance of vapour bubbles along the wall results in a slip boundary condition. Moreover, cavitation has a positive influence on a spray cone angle. However, regardless of the place of occurrence, research on cavitation bases primarily on numerical simulations. The area of numerical methods intended for cavitating flows includes many solutions which differ not only in the basic assumptions, i.e. considering flow either as a multiphase mixture with the average density or just as two independent liquids, fluid and vapour, with a distinct boundary between them, but also in many methods applied in particular approaches. Currently, to choose the best way of the prediction of cavitation phenomenon for the undertaken issue, many aspects should be considered. The most important factor is the assessment level between the results of numerical simulation and experimental data. Secondary are computing time, requirements for the hardware, price of software and additional costs connected with the selected software. The final decision about the chosen way of the cavitation prediction results from all the above-considered elements. The main aim of the work is to present the methods of image analysis, which can be very helpful in this process. The main advantage of these methods is the quantitative answer about the correlation degree between analysed images. It eliminates subjective decisions based solely on a raw imaging material. The image material used in the work was obtained via numerical simulations performed in ANSYS Fluent. Presented methodology bases on their statistical analysis that considers the shape and intensity of cavitating area, as well as on basic methods of image processing and analysis. The conclusion is that the obtained results demonstrate the usefulness of the proposed methods in the aspect of a reliable comparison of images obtained in the numericalstudies of the cavitation phenomenon.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4993
Internal flow and air core dynamics in simplex and spill-return pressure-swirl atomizers
Authors: Maly Milan , Janáčková Lada , Jedelský Jan , Sláma Jaroslav , Sapík Marcel , Wigley Graham 
Published: September 2017

It is well known that the spray characteristics of pressure-swirl atomizers are strongly linked to the internal flow andthat an unstable air core may cause instabilities in the spray. In this paper, a 10:1 scale transparent Plexiglas (PMMA) model of a pressure-swirl atomizer as used in a small gas turbine is introduced. The internal flow is examined using high-speed imaging, laser-Doppler anemometry and computational fluid dynamics tools. The experimental and numerical results were analysed and compared in terms of the air core morphology and its temporal stability. Two different liquids were used, Kerosene-type Jet A-1 represented a commonly used fuel while p-Cymene (4-Isopropyltoluene) matched the refractive index of the Plexiglas atomizer body. The internal flow characteristics were set using dimensionless numbers i.e. the Reynolds number and Froude number. The flow test conditions were limited to inlet Reynolds numbers from 750 to 1750. Two atomizers were examined to represent a simplex and spill-return (SR) geometry. In a comparative manner, the SR atomizer features a central passage in the rear wall of the swirl chamber. The main advantage of this concept is that the fuel is always supplied to the swirl chamber at a high pressure therefore providing good atomization over a wide range of the injection flow rate. However, the presence of the spill orifice strongly affects the internal flow even if the spill-line is closed. The air core in the simplex atomizer was found fully developed and stable. The SR atomizer behaved differently, the air core didnot form at all, and the spray was therefore unstable.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4995
High-speed X-Ray Phase Contrast Imaging of String Cavitation in a Diesel Injector Orifice
Authors: Karathanassis Ioannis , Koukouvinis Phoevos , Lorenzi Massimo , Kontolatis Efstathios , Li Zhilong , Wang Jin , Mitroglou N. , Gavaises Manolis 
Published: September 2017

The present investigation illustrates the temporally-resolved, phase-contrast visualization of the cavitating flowwithin an enlarged injector replica conducted at the ANL Advanced Photon Source. The flow was captured through side-view, x-ray radiographies at 67890 frames per second with an exposure time of 347ns. The orifice employed for the experiments has an internal diameter of 1.5mm and length equal to 5mm. A parametric investigation was conducted considering various combinations of the Reynolds and cavitation numbers, which designate the extent of in-nozzle cavitation. Proper post-processing of the obtained radiographies enabled the extraction of information regarding the shape and dynamical behaviour of cavitating strings. The average string extent along with its standard deviation was calculated for the entire range of conditions examined (Re=18000-36000, CN=1.6-7.7). Furthermore, the effect of the prevailing flow conditions on quantities indicative of the string dynamic behaviour such as the break-up frequency and lifetime was characterized and the local velocity field in the string region was obtained.DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4996