Air Entrainment in High Pressure Multihole Gasoline Direct Injection Sprays

Khan, Muhammad Mahabat; Hélie, Jérôme; Gorokhovski, Mikhael; Sheikh, Nadeem Ahmad

doi:10.18869/acadpub.jafm.73.241.27628

Cited by 15 publications

(9 citation statements)

References 12 publications

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“…The distance between the injection holes is also an important parameter that play a crucial role in spray characteristics [8]. The spray characteristics based on the gas entrainment of a three hole injector is compared with 6 hole injector in [11]. It was observed that six-hole injector partially collapsed under moderate evaporating conditions while three-hole injector did not collapse.…”

Section: Injector Designmentioning

confidence: 99%

“…However, the chamber pressures are much higher in comparison to the gasoline engine condition due the difference of compression ignition in diesel engines and spark ignition is gasoline engines. GDI sprays have been observed to show a collapsing effect under highly evaporating conditions [11,12]. The collapsing effect has been observed to be more pronounced in flash boiling conditions where the super-heated fuel causes the spray to expand instantly during the spray injection process especially under low chamber pressure [13].…”

Section: Introductionmentioning

confidence: 99%

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Experimental characterization of gasoline sprays under highly evaporating conditions

et al. 2017

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An experimental investigation of multistream gasoline sprays under highly evaporating conditions is carried out in this paper. Temperature increase of fuel and low engine pressure could lead to flash boiling. The spray shape is normally modified significantly under flash boiling conditions. The spray plumes expansion along with reduction in the axial momentum causes the jets to merge and creates a low-pressure area below the injector's nozzle. These effects initiate the collapse of spray cone and lead to the formation of a single jet plume or a big cluster like structure. The collapsing sprays reduces exposed surface and therefore they last longer and subsequently penetrate more.Spray plume momentum increase, jet plume reduction and spray target widening could delay or prevent the closure condition and limit the penetration (delayed formation of the cluster promotes evaporation). These spray characteristics are investigated experimentally using shadowgraphy, for five and six hole injectors, under various boundary conditions. Six hole injectors produce more collapsing sprays in comparison to five hole injector due to enhanced jet to jet interactions. The spray collapse tendency reduces with increase in injection pressure due high axial momentum of spray plumes. The spray evaporation rates of five hole injector are observed to be higher than six hole injectors. Larger spray cone angles of the six hole injectors promote less penetrating and less collapsing sprays.

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Section: Injector Designmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental characterization of gasoline sprays under highly evaporating conditions

et al. 2017

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“…By definition, flashboiling is referred to as superheated injections, whereas spray collapse is referred to as the spatial contraction of nominal spray targetings of gasoline sprays. Spray collapse can be affected or induced by flashboiling, but also be enforced at non-superheated conditions by a simple increase in the flow hole number at multihole injectors (see Lenz 44 and Khan et al 45 ). From phenomenological point of view, very often no differentiation is made and spray collapse is equalized with flashboiling.…”

Section: Jet-to-jet Interactionsmentioning

confidence: 99%

Flashboiling-induced targeting changes in gasoline direct injection sprays

Krämer

Kull

Wensing

2015

International Journal of Engine Research

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By definition, flashboiling is referred to as superheated injections. The sudden occurrence of boiling inside the fuel can change the spray structure dramatically. Up to 99% of all injection processes during the New European Driving Cycle and 95% during 'Real Driving Emissions' tests are, with respect to mid-range cars, in a state of thermodynamic nonequilibrium below the specific vapor pressure of gasoline. Considering this fact, the scientific question is not the appearance of flashboiling during the operation of stoichiometric homogeneous charge direct injection gasoline engines but the intensity of occurring spray processes and their influence on nominal spray designs. As a consequence of induced targeting changes, the positive influence of flashboiling on the droplet size distribution and the penetration depth can be counteracted. As main driving factors for targeting changes, jet-to-jet interactions can be identified. By applying appropriate nozzle design features, the potential of flashboiling can be exploited and the targeting changes of the nominal spray designs, considered negatively, are avoided mostly. This work focuses on flashboiling-induced targeting changes, the socalled phenomenon of ''spray collapse'': its root cause, development and avoidance.

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“…A recent study indicated that the difference of spray collapse cause under flashing and non-flashing conditions [8]. The subcooled spray generally became collapse under high ambient pressure conditions due to the air entrainment causing and enhancing the central low-pressure zone [9,10]. However, a recent study has considered that the massive production of vapor counteracts the low-pressure tendency, explaining the cause of flash boiling spray collapse is different to the subcooled condition [11].…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on flash boiling GDI spray collapse process using HRM model

Zhang

Yang

et al. 2021

ICLASS

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Further investigation into the collapse mechanism of multi-jet flash boiling sprays is crucial to improve the mixture formation in gasoline direct injection (GDI) engines. Herein, n-hexane flash boiling sprays from a five-hole GDI injector have been numerically studied using the homogeneous relaxation model (HRM). The collapse process has been validated by the experimental data in terms of spray penetration length and spray width. For the given case, as the individual jets were discharged from the nozzle, they became under-expanded, where a typical shock structure (primary cell) can be well observed for each individual jets. Then, strong interactions were found between the adjacent jets leading to the formation of secondary cells. It was found the jet-to-jet structure did not form a closed ring, indicating that the closedring jet-to-jet structure might be not the necessity for the flash boiling spray collapse. The pressure distribution by two cross-sections revealed the low-pressure region development process and the shock structure vibration characteristic. The initial generation reason for the crown structure in the spray tip was considered the flow separation of the different near-field collapse levels in this process.

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Air Entrainment in High Pressure Multihole Gasoline Direct Injection Sprays

Cited by 15 publications

References 12 publications

Experimental characterization of gasoline sprays under highly evaporating conditions

Experimental characterization of gasoline sprays under highly evaporating conditions

Flashboiling-induced targeting changes in gasoline direct injection sprays

Numerical Investigation on flash boiling GDI spray collapse process using HRM model

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