Cavitation in Two-Dimensional Asymmetric Nozzles

Schmidt, David P.; Rutland, Christopher J.; Corradini, Michael L.; Roosen, Peter; Genge, O.

doi:10.4271/1999-01-0518

Cited by 72 publications

(25 citation statements)

References 10 publications

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“…In contrast, single-fluid cavitation models, which are sometimes referred to as homogeneous Eulerian models, treat the fluid as a continuous mixture of liquid and vapor solving a single set of constitutive equations characterized by average mixture properties, such as mixture density and mixture viscosity. Although not necessary, the void fraction can be transported separately as with Volume-of-Fluid (VOF) methods, 25 allowing for inclusion of non-equilibrium phase transition effects as proposed by Kunz et al 26 or Yuan et al 27 Assuming the liquid and gaseous phases to be in thermal and mechanical equilibrium, Schmidt et al 28,29 and Schnerr et al 30 developed a model in which the two phases are uniformly distributed within each cell without slip between the liquid and vapor phases, neglecting surface tension and buoyancy effects. Thermodynamic equilibrium models exhibit an intrinsic length-scaling capability 31 and thus are particularly suitable for application to complex flows in conjunction with subgrid-scale (SGS) models for non-resolved flow scales.…”

Section: -2 öRley Et Almentioning

confidence: 99%

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

et al. 2015

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We employ a barotropic two-phase/two-fluid model to study the primary break-up of cavitating liquid jets emanating from a rectangular nozzle, which resembles a high aspect-ratio slot flow. All components (i.e., gas, liquid, and vapor) are represented by a homogeneous mixture approach. The cavitating fluid model is based on a thermodynamic-equilibrium assumption. Compressibility of all phases enables full resolution of collapse-induced pressure wave dynamics. The thermodynamic model is embedded into an implicit large-eddy simulation (LES) environment. The considered configuration follows the general setup of a reference experiment and is a generic reproduction of a scaled-up fuel injector or control valve as found in an automotive engine. Due to the experimental conditions, it operates, however, at significantly lower pressures. LES results are compared to the experimental reference for validation. Three different operating points are studied, which differ in terms of the development of cavitation regions and the jet break-up characteristics. Observed differences between experimental and numerical data in some of the investigated cases can be caused by uncertainties in meeting nominal parameters by the experiment. The investigation reveals that three main mechanisms promote primary jet break-up: collapse-induced turbulent fluctuations near the outlet, entrainment of free gas into the nozzle, and collapse events inside the jet near the liquid-gas interface. C 2015 AIP Publishing LLC. [http://dx

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Section: -2 öRley Et Almentioning

confidence: 99%

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

et al. 2015

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“…During the last two decades, the focus of research in quantifying nozzle flow and spray characteristics was on diesel injectors [3][4][5][6][7][8][9][10][11][12] using both experimental and CFD techniques capable of visualizing, measuring and calculating the internal flow characteristics of injectors and, in particular, describing the cavitation process which is associated with the local pressure distribution inside the sac volume and adjacent holes. Different types of cavitation have been identified: (i) geometrically induced cavitation which occurs in flow areas with sharp corners such as at the entrance into the nozzle holes, (ii) 'string' or 'vortex' type cavitation [3,9,12] which is the main source of instability in the sprays exiting the nozzle holes and (iii) 'needle' cavitation [13] which initiates in the vicinity of the needle and extends to the opposite nozzle hole when it is fully developed.…”

Section: Introductionmentioning

confidence: 99%

Internal Flow and Cavitation in a Multi-Hole Injector for Gasoline Direct-Injection Engines

Nouri

Mitroglou

Yan

et al. 2007

SAE Technical Paper Series

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A transparent enlarged model of a six-hole injector used in the development of emerging gasoline directinjection engines was manufactured with full optical access. The working fluid was water circulating through the injector nozzle under steady-state flow conditions at different flow rates, pressures and needle positions. Simultaneous matching of the Reynolds and cavitation numbers has allowed direct comparison between the cavitation regimes present in real-size and enlarged nozzles. The experimental results from the model injector, as part of a research programme into second-generation direct-injection spark-ignition engines, are presented and discussed. The main objective of this investigation was to characterise the cavitation process in the sac volume and nozzle holes under different operating conditions. This has been achieved by visualizing the nozzle cavitation structures in two planes simultaneously using two synchronised high-speed cameras.Imaging of the flow inside the injector nozzle identified the formation of three different types of cavitation as a function of the cavitation number, C N . The first is needle cavitation, formed randomly at low C N (0.5-0.7) in the vicinity of the needle, which penetrates into the opposite hole when it is fully developed. The second is the well known geometric cavitation originating at the entrance of the nozzle hole due to the local pressure drop induced by the nozzle inlet hole geometry with its onset at around C N =0.75. Finally, and at the same time as the onset of geometric cavitation, string type cavitation can be formed inside the nozzle sac and hole volume having a strong swirl component as a result of the large vortical flow structures present there; these become stronger with increasing C N . Its link with geometric cavitation creates a very complex two-phase flow structure in the nozzle holes which seems to be responsible for holeto-hole and cycle-to-cycle spray variations.

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“…For high pressure injection systems cavitation may occur in the injectors [31]. Cavitating sprays have characteristics significantly different from the non cavitating ones.…”

Section: Modified Turbulence Induced Atomization Modelmentioning

confidence: 99%

Modeling the atomization of high-pressure fuel spray by using a new breakup model

Wang

et al. 2016

Applied Mathematical Modelling

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a b s t r a c tThe main objective of this research is to develop a new breakup model and investigate the influence of cavitation, turbulence on processes of high-pressure diesel sprays. The model distinguishes between jet primary atomization and droplet secondary atomization. The primary atomization was simulated based on a modified turbulence induced atomization model taken into account the coupling effects of the relaxation of the velocity profile, cavitation and turbulent fluctuation based on the principle of conservation of energy. The growth time scale of surface waves was provided by Kelvin-Helmholtz (K-H) instability theory on an infinite length cylinder for an inviscid liquid jet. The time scale of initial surface waves based on K-H instability theory on an infinite plane jet is much larger than that based on infinite length cylindrical jet. Based on the present modified model, the weighting coefficients of turbulence and cavitation on the overall atomization can be distinguished clearly. There was remarkable variation in simulated spray shape with present models. It could be seen that the original turbulence induced atomization model results in a shorter spray penetration and smaller drops near the spray core than the modified model. When applying the turbulent weighting coefficient C t in the determination of the spray angle, the resultant value of spray angle gradually drops due to the reduction of C t . However, the spray angle increases with increasing the cavitation weighting coefficient C cav . Comparing the experimental results (such as spray angle, tip penetration and spray shape) with the theoretical ones for different injection pressure, gives a reasonable agreement.

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Cavitation in Two-Dimensional Asymmetric Nozzles

Cited by 72 publications

References 10 publications

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

Large-eddy simulation of cavitating nozzle flow and primary jet break-up

Internal Flow and Cavitation in a Multi-Hole Injector for Gasoline Direct-Injection Engines

Modeling the atomization of high-pressure fuel spray by using a new breakup model

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