The influence of in-nozzle cavitation on flow characteristics and spray break-up

Lešnik, Luka; Kegl, Breda; Bombek, Gorazd; Hočevar, Marko; Biluš, Ignacijo

doi:10.1016/j.fuel.2018.02.144

Cited by 41 publications

(17 citation statements)

References 22 publications

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“…These simulations showed complex vapor structures formed due to the sudden flow blockage caused by the needle closing, even for a condition and nozzle geometry that usually does not exhibit cavitation. The strong correlation between internal nozzle flow and primary spray atomization was shown by various authors in [29,30,31,32]. The location of cavitating vortices inside the nozzle was shown to affect the instantaneous spray pattern.…”

Section: Introductionmentioning

confidence: 80%

A numerical study on the effect of cavitation erosion in a diesel injector

Cristofaro

Edelbauer

Koukouvinis

et al. 2020

Applied Mathematical Modelling

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The consequences of geometry alterations in a Diesel injector caused by cavitation erosion are investigated with numerical simulations. The differences in the results between the nominal design geometry and the eroded one are analyzed for the internal injector flow and spray formation. The flow in the injector is modeled with a 3-phase Eulerian approach using a compressible pressure-based multiphase flow solver. Cavitation is simulated with a non-equilibrium mass transfer rate model based on the simplified form of the Rayleigh-Plesset equation. Slip velocity between the liquid-vapor mixture and the air is included in the model by solving two separate momentum conservation equations. The eroded injector is found to result to a loss in the rate of injection but also lower cavitation volume fraction inside the nozzle. The injected sprays are then simulated with a Lagrangian method considering as initial conditions the predicted flow characteristics at the exit of the nozzle. The obtained results show wider spray dispersion for the eroded injector and shorter spray tip penetration.

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Section: Introductionmentioning

confidence: 80%

A numerical study on the effect of cavitation erosion in a diesel injector

Cristofaro

Edelbauer

Koukouvinis

et al. 2020

Applied Mathematical Modelling

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“…Concerns of environmental protection and fossil fuel shortage have stimulated the studies on high-efficiency engines. 1–4 Many researchers have devoted to improving the diesel engine performance, and their results confirmed that the flow characteristics inside diesel nozzles and the near-nozzle spray breakup process were crucial to subsequent far-field spray, combustion and emissions. 5–7 Moreover, cavitating flow, a common flow phenomenon occurring in engine nozzles, has been confirmed to enhance the production of turbulence intensity near nozzle exit that contributes to the primary disintegration of the liquid jet and increase spray cone angle, 8–10 especially the higher injection pressures for better spray characteristics.…”

Section: Introductionmentioning

confidence: 97%

Visual experimental investigations of string cavitation and residual bubbles in the diesel nozzle and effects on initial spray structures

Guo

Zhang

et al. 2018

International Journal of Engine Research

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In this article, optical experiments on string cavitation and residual bubbles inside the real-size transparent tapered diesel nozzle and near-nozzle spray structures were performed based on a high-pressure common rail fuel injection system with a high-speed camera. The tapered nozzle which has high flow efficiency with weak or even no geometric cavitation has been widely used in commercial injectors, while there still exists string cavitation which may also influence the in-nozzle flow and subsequent spray. This article put focus on the tapered nozzle and the result indicated that the in-nozzle string cavitation provided a reasonable explanation for the two bumps of spray cone angles during the opening and closing stages of needle of real diesel engine injection processes. The suction and compression of air bubbles at the start and end stages of injection processes, and the various shot-to-shot near-nozzle spray patterns were captured and analyzed. These different near-nozzle spray patterns were attributed to the distribution of residual bubbles inside the nozzle orifice. The residual bubbles were survived from the last injection or sucked into the nozzle during needle opening stages. Stagnant bubbles were compressed and then accelerated the residual fuel which was close to the injector tip, leading to the formation of mushrooms. This study confirmed that the initial mushroom and the tail were generated by the interactions between the residual/sucked bubbles and the residual/initial fuel, and the leading mushroom was incurred by the combination of the transverse expansion of the jet and the laminar layer theory. This work pointed out and analyzed the new sources of the cycle-to-cycle variation of air/fuel mixture and spray.

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“…In the present work, the turbulence modeling was done using a standard k-ε turbulence model. The model was selected based on works presented in [21,25,29,34]. Hybrid wall treatment, suitable for all y+ values, was used to compute the near wall region's turbulent flow.…”

Section: Mathematical Modelsmentioning

confidence: 99%

“…Similar to X-ray imaging methods, these programs allow us to determine fuel flow conditions like velocity, cavitation inception, etc., in a non-intrusive way. When using numerical simulation, RANS, LES, or DNS approaches can be used [21]. Simulations can be performed at fixed or transient needle positions.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Effect of the In-Cylinder Back Pressure on the Injection Process and Fuel Flow Characteristics in a Common-Rail Diesel Injector Using GTL Fuel

et al. 2021

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The presented paper aims to study the influence of mineral diesel fuel and synthetic Gas-To-Liquid fuel (GTL) on the injection process, fuel flow conditions, and cavitation formation in a modern common-rail injector. First, the influence on injection characteristics was studied experimentally using an injection system test bench, and numerically using the one-dimensional computational program. Afterward, the influence of fuel properties on internal fuel flow was studied numerically using a computational program. The flow inside the injector was considered as multiphase flow and was calculated through unsteady Computational Fluid Dynamics simulations using a Eulerian–Eulerian two-fluid approach. Finally, the influence of in-cylinder back pressure on the internal nozzle flow was studied at three distinctive back pressures. The obtained numerical results for injection characteristics show good agreement with the experimental ones. The results of 3D simulations indicate that differences in fuel properties influence internal fuel flow and cavitation inception. The location of cavitation formation is the same for both fuels. The cavitation formation is triggered regardless of fuel properties. The size of the cavitation area is influenced by fuel properties and also from in-cylinder back pressure. Higher values of back pressure induce smaller areas of cavitation and vice versa. Comparing the conditions at injection hole exit, diesel fuel proved slightly higher average mass flow rate and velocities, which can be attributed to differences in fluid densities and viscosities. Overall, the obtained results indicate that when considering the injection process and internal nozzle flow, GTL fuel can be used in common-rail injection systems with solenoid injectors.

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The influence of in-nozzle cavitation on flow characteristics and spray break-up

Cited by 41 publications

References 22 publications

A numerical study on the effect of cavitation erosion in a diesel injector

A numerical study on the effect of cavitation erosion in a diesel injector

Visual experimental investigations of string cavitation and residual bubbles in the diesel nozzle and effects on initial spray structures

Effect of the In-Cylinder Back Pressure on the Injection Process and Fuel Flow Characteristics in a Common-Rail Diesel Injector Using GTL Fuel

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