On the formation of string cavitation inside fuel injectors

Reid, Benjamin; Gavaises, Manolis; Mitroglou, Nicholas; Hargrave, Graham K.; Garner, Colin P.; Long, Edward J.; McDavid, Robert M.

doi:10.1007/s00348-013-1662-8

Cited by 35 publications

(9 citation statements)

References 17 publications

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“…Reid et al used sapphire plates to create a simplified version of the geometry found in valve-covered-orifice injectors. 9,10 They achieved injection pressures of 2000 bars with the design. The orifice was constructed by stacking sapphire plates with holes of various sizes on top of each other.…”

Section: B Past Studiesmentioning

confidence: 99%

Novel design for transparent high-pressure fuel injector nozzles

Falgout

Linne

2016

Review of Scientific Instruments

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The efficiency and emissions of internal combustion (IC) engines are closely tied to the formation of the combustible air-fuel mixture. Direct-injection engines have become more common due to their increased practical flexibility and efficiency, and sprays dominate mixture formation in these engines. Spray formation, or rather the transition from a cylindrical liquid jet to a field of isolated droplets, is not completely understood. However, it is known that nozzle orifice flow and cavitation have an important effect on the formation of fuel injector sprays, even if the exact details of this effect remain unknown. A number of studies in recent years have used injectors with optically transparent nozzles (OTN) to allow observation of the nozzle orifice flow. Our goal in this work is to design various OTN concepts that mimic the flow inside commercial injector nozzles, at realistic fuel pressures, and yet still allow access to the very near nozzle region of the spray so that interior flow structure can be correlated with primary breakup dynamics. This goal has not been achieved until now because interior structures can be very complex, and the most appropriate optical materials are brittle and easily fractured by realistic fuel pressures. An OTN design that achieves realistic injection pressures and grants visual access to the interior flow and spray formation will be explained in detail. The design uses an acrylic nozzle, which is ideal for imaging the interior flow. This nozzle is supported from the outside with sapphire clamps, which reduces tensile stresses in the nozzle and increases the nozzle's injection pressure capacity. An ensemble of nozzles were mechanically tested to prove this design concept.

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Section: B Past Studiesmentioning

confidence: 99%

Novel design for transparent high-pressure fuel injector nozzles

Falgout

Linne

2016

Review of Scientific Instruments

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“…Cavitation in true-scale injectors operating under realistic injection pressures has been also studied, for example see selectively Andriotis et al [24], Giannadakis et al [25], Mitroglou et al [26,27], and Reid et al [28,29]. Out of those, the study from Reid et al [28] has been the only one to visualize cavitation at pressures up to 2050 bars.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, it was shown that longitudinal vortices detected as string cavitation formed at the axes of the two parallel holes, whereas an additional cavitating vortex of horseshoe shape was found to "bridge" the two holes. In a subsequent study [29] referring to the same nozzle layout, it was pointed out that the secondary flow topology exhibits significant discrepancies in the cases of steady state and transient fuel injection conditions. The significance of this study lies on the fact that the same macroscopic flow features that have been observed in transparent nozzles operating at much lower pressures (from a few bar up to 600bar) are present at pressure levels similar to those in real metallic nozzles.…”

Section: Introductionmentioning

confidence: 99%

Cloud cavitation vortex shedding inside an injector nozzle

Mitroglou

Stamboliyski

Karathanassis

et al. 2017

Experimental Thermal and Fluid Science

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This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract. The development and collapse of cloud cavitation and its link to surface erosion within a transparent test single-orifice nozzle operating with a closed Diesel fuel hydraulic circuit, has been characterized using high-speed imaging. Data have been obtained for a range of cavitation and Reynolds numbers under fixed lift positions. Post processing of a large number of images acquired with short exposure time (1μs) allowed the elucidation of the distinct flow phenomena associated with the highly transient two-phase flow. At the inlet of the flow orifice, the vapour cloud was found to occupy the largest part of the nozzle hole crosssection. Coherent vortical structures of a hairpin shape have been detected to onset at the closure region of this vapour cloud and shed downstream in a fully transient manner. The effect of the operating parameters on the temporal and spatial characteristics with regards to the emergence and collapse of the hairpin vortices has been quantified. It has been established that the cavitation-vortex shedding was taking place in a periodical manner, characterized by a Strouhal number. Permanent repository link

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“…The results distinguished the formation process of cavitation for two different flow conditions. With a detailed comparison between the vortex string observed in experiments and the flow streamlines of numerical simulation, Reid et al (2014) succeeded in interpreting the origin of the cavitating lobes in a diesel fuel injector. Koukouvinis et al (2017) proposed a similar numerical method, and studied the correlation between the cavitation evolution and turbulence distribution.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation into the cavitating jet inside water poppet valves with varied valve seat structures

Yuan

Zhu

et al. 2021

Engineering Applications of Computational Fluid Mechanics

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Owing to the strong three-dimensionality and transient evolution, the flow dynamics of a cavitating jet inside a water poppet valve is poorly understood, leading to insufficient basis for exploring the governing mechanism of cavitation effects. In this paper, a three-dimensional simulation considering the compressibility of each constituent phase is performed, to clarify the governing mechanisms under the cavitating flow inside two water poppet valves. The cavitation structures inside the poppet valves are primarily located at three regions and triggered by different mechanisms. The vortex cavitation, mainly confined within the free shearing layer, is due to vortex dynamics, while the attached cavitation at the poppet trailing edge and within the chamfered groove arises from flow separation. The fast laminar-turbulent transition process contributes to the three-dimensionality within the free shearing layer and the rear part of the chamfered groove. The flow separation due to the chamfered groove leads to increased velocity of the central potential core, contributing to a different flow discharge performance from that of the poppet valves with a sharp seat. In addition, the periodic variation in cavitation reveals the significant interaction between the shed cavitating vortex and attached cavitation at the poppet trailing edge. In conclusion, the change in velocity distribution due to different poppet valve seat structures leads to variation in flow discharge performance, and the vortex dynamics makes sense for all three kinds of cavitation occurring inside poppet valves.

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On the formation of string cavitation inside fuel injectors

Cited by 35 publications

References 17 publications

Novel design for transparent high-pressure fuel injector nozzles

Novel design for transparent high-pressure fuel injector nozzles

Cloud cavitation vortex shedding inside an injector nozzle

Numerical investigation into the cavitating jet inside water poppet valves with varied valve seat structures

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