Simulation of cavitation in outward-opening piezo-type pintle injector nozzles

Giannadakis, E.; Papoulias, D.; Theodorakakos, A.; Gavaises, Manolis

doi:10.1243/09544070jauto728

Cited by 12 publications

(8 citation statements)

References 27 publications

(39 reference statements)

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“…As mentioned, there is no cavitation for the same lift when tapered holes are employed, so in this case only one horizontal bar is depicted. Overall, model predictions are close to the experimental values and thus model predictions can be considered reliable for providing more detailed information about the flow distribution inside the nozzle; more thorough validation of the CFD model used can be found in reference [17] and more recently in reference [30].…”

Section: Test Casessupporting

confidence: 53%

Flow in valve covered orifice nozzles with cylindrical and tapered holes and link to cavitation erosion and engine exhaust emissions

Gavaises

2008

International Journal of Engine Research

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Citation: Gavaises, M. (2008). Flow in valve covered orifice nozzles with cylindrical and tapered holes and link to cavitation erosion and engine exhaust emissions. International Journal of Engine Research, 9(6), doi: 10.1243/14680874JER01708 This is the accepted version of the paper.This version of the publication may differ from the final published version. Results from a research programme addressing the development, testing, and production of valve covered orifice (VCO) nozzles operating with current production Tier 3 offhighway diesel engines are reviewed. The common rail injectors operate at pressures exceeding 1300 bar and include pilot and main injection events. Although acceptable engine exhaust emissions can be obtained with conventional VCO nozzles, cavitation erosion may lead to mechanical failure of the nozzle. Redesigning the injector in terms of its durability against surface erosion has been obtained through use of a computational fluid dynamics (CFD) flow solver incorporating a two-phase cavitation model and flow visualization in enlarged transparent nozzle replicas. The model has provided evidence of the flow distribution under realistic pressure and needle lift opening scenarios while at the same time it has been calibrated to indicate the locations where the possibility of cavitation erosion may become significant. The experiments performed in enlarged transparent nozzle replicas have provided evidence of the string cavitation structures formed inside the different nozzle designs. Crosscorrelation with engine emission tests indicates that string cavitation may be associated with increased engine exhaust emissions. Proposed injector designs with geometric modification easily implemented in the production series have been proved to be erosion-free while at the same time have improved the engine exhaust emissions. Permanent

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Section: Test Casessupporting

confidence: 53%

Flow in valve covered orifice nozzles with cylindrical and tapered holes and link to cavitation erosion and engine exhaust emissions

Gavaises

2008

International Journal of Engine Research

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“…In two-fluid nozzle flow models the liquid and vapour phases are treated separately, i.e. two sets of governing equations (one for each phase) are solved and interactions between the phases are modelled by an additional source term [14][15][16][17][18]. 2.…”

Section: Cavitation Modellingmentioning

confidence: 99%

Numerical simulation and extended validation of two-phase compressible flow in diesel injector nozzles

Salvador

Hoyas

Novella

et al. 2011

Proceedings of the Institution of Mechanical Engineers, Part D:

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In this paper, the ability of a computational fluid dynamics code to reproduce cavitation phenomena accurately is checked by comparing data acquired by numerical simulations against those obtained from different experiments involving the mass flow, the momentum flux, and the effective injection velocity. Cavitation is modelled using a single-phase cavitation model based on a barotropic equation of state together with a homogeneous equilibrium assumption. In the research reported in this paper, the ability to use the code for actual diesel injector nozzle geometries and conditions has been checked and validated. The main contribution of the present investigation and what makes it different from previous work in the literature is the consideration of extended experimental data for validation purposes: the mass flow, the momentum flux at the nozzle exit, and the effective injection velocity. These are unique features in contrast with other publications, which normally take into account at the most, if at all, the cavitation morphology or the mass flow. The results obtained and their comparison with available experimental data show how the model is able to predict the behaviour of the fluid in such conditions with a high level of confidence.

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“…After estimating the distance function from equation (12), the mask function a IB is calculated using equation ( 14):…”

Section: Immersed Boundary Methodsmentioning

confidence: 99%

Numerical simulation of fuel dribbling and nozzle wall wetting

Gavaises

Murali-Girija

Rodríguez

et al. 2021

International Journal of Engine Research

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The present work describes a numerical methodology and its experimental validation of the flow development inside and outside of the orifices during a pilot injection, dwelt time and the subsequent start of injection cycle. The compressible Navier-Stokes equations are numerically solved in a six-hole injector imposing realistic conditions of the needle valve movement and considering in addition a time-dependent eccentric motion. The valve motion is simulated using the immersed boundary method; this allows for simulations to be performed at zero lift during the dwelt time between successive injections, where the needle remains closed. Moreover, the numerical model utilises a fully compressible two-phase (liquid, vapour) two-component (fuel, air) barotropic model. The air’s motion is simulated with an additional transport equation coupled with the VOF interface capturing method able to resolve the near-nozzle atomisation and the resulting impact of the injected liquid on the oleophilic nozzle wall surfaces. The eccentric needle motion is found to be responsible for the formation of strong swirling flows inside the orifices, which not only contributes to the breakup of the injected liquid jet into ligaments but also to their backwards motion towards the external wall surface of the injector. Model predictions suggest that such nozzle wall wetting phenomena are more pronounced during the closing period of the valve and the re-opening of the nozzle, due to the residual gases trapped inside the nozzle, and which contribute to the poor atomisation of the injected fluid upon re-opening of the needle valve in subsequent injection events.

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Simulation of cavitation in outward-opening piezo-type pintle injector nozzles

Cited by 12 publications

References 27 publications

Flow in valve covered orifice nozzles with cylindrical and tapered holes and link to cavitation erosion and engine exhaust emissions

Flow in valve covered orifice nozzles with cylindrical and tapered holes and link to cavitation erosion and engine exhaust emissions

Numerical simulation and extended validation of two-phase compressible flow in diesel injector nozzles

Numerical simulation of fuel dribbling and nozzle wall wetting

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