Near-Nozzle Structure of Diesel Sprays Affected by Internal Geometry of Injector Nozzle: Visualized by Single-Shot X-ray Imaging

Liu, Zunping; Im, Kyoung-Su; Wang, Yuejie; Fezzaa, Kamel; Xie, Xuelian; Lai, Ming Chia; Wang, Jin

doi:10.4271/2010-01-0877

Cited by 28 publications

(15 citation statements)

References 35 publications

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“…In support of such methods, Badock et al [7] and later Ganippa et al [8] presented results claiming that nozzle flow characteristics have negligible influence over the spray formation and that momentum is the only controlling variable for mixing. Contrasting these studies, several authors show that the flow inside the nozzle influences the nearnozzle region of the spray in terms of liquid-phase break-up, liquid length, and spray angle [9][10][11][12][13][14][15][16]. Many other studies also evidence the effects of nozzle flow characteristics over the macroscopic spray [3,4,6,11,[17][18][19][20].…”

Section: Introductionmentioning

confidence: 84%

The effect of nozzle geometry over internal flow and spray formation for three different fuels

Payri

Viera

Gopalakrishnan

et al. 2016

Fuel

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h i g h l i g h t sTwo single hole nozzle (cylindrical and convergent) are used. A complete hydraulic characterization is done along with spray visualization. A fast pulsed light source is synchronized to a fast camera working at 160 kHz. The effect of nozzle geometry is analyzed for three different fuels. A large set of experimental data was obtained, which could be used for model validation. a b s t r a c tThe influence of internal nozzle flow characteristics over macroscopic spray development is studied experimentally for two different nozzle geometries and three fuels. The measurements include a complete hydraulic characterization consisting of instantaneous injection rate and spray momentum flux measurements, followed by a high-speed visualization of isothermal liquid spray in combination with cylindrical and conical nozzle configurations. Two of the fuels are pure components-n-heptane and ndodecane-while the third fuel consists of a three-component surrogate to better represent the physical and chemical properties of diesel fuel. The cylindrical nozzle with 8.6% larger diameter, in spite of higher mass flow rate and momentum flux, shows slower spray tip penetration when compared to the conical nozzle. The spreading angle is found to be inversely proportional to the spray tip penetration. The spreading angle is largely influenced by the nozzle geometry and the ambient density. Rail pressure was found to have weak influence on the near-field spreading angle and no influence on the standard deviation of the spreading angle. n-Heptane spray shows slowest penetration rates while n-dodecane and the surrogate fuel mixture show very similar spray behavior for variations in injection pressure and back pressure. However, the surrogate fuel mixture shows higher penetration than n-dodecane when using the conical nozzle and lower penetration than n-dodecane when using cylindrical nozzle.

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Section: Introductionmentioning

confidence: 84%

The effect of nozzle geometry over internal flow and spray formation for three different fuels

Payri

Viera

Gopalakrishnan

et al. 2016

Fuel

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“…The spheroidal cap at the jet tip, with and without pre-ligaments, are also observed and described for laminar jet tips by other authors, e.g. Crua et al [11], Badock and Wirth [12], Busch [13], Liu et al [14], Hult et al [15] or Schugger [16]. Crua et al [11] explains the existence of a spheroidal cap at the jet tip by an interaction of adhesion forces at the nozzle surface and rapidly increasing axial jet velocity: fresh fuel from inside the nozzle hole pushes the jet forwards into the atmosphere until inertia of the jet tip compensates the adhesion force and the spheroidal cap detaches from the nozzle surface.…”

Section: Resultsmentioning

confidence: 56%

Zooming into primary breakup mechanisms of high-pressure automotive sprays

Kirsch

Reddemann

Palmer

et al. 2017

Proceedings ILASS–Europe 2017. 28th Conference on Liquid Atomization and Spray Systems

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In-cylinder mixture formation and combustion are highly influenced by primary breakup of injected fuel. Experimental investigation of this phenomenon directly at the outlet of a diesel injector requires a specialized transmitted light microscopy technique combined with a constant-pressure flow microscopy vessel. The method allows verification of the existence of an intact jet core for various states of injection and different fuels. The jet core is dominated by axisymmetric surface waves during the initial injection phase. By quantification of the wavelengths and comparison with existing breakup theories, boundary layer instabilities are identified as origin of surface waves. Boundary layer wavelengths are found to be larger for a higher fuel viscosity. An occasionally appearing non-cylindrical helical jet shape is visible during the injector's opening and closing phase. The helical jet shape is directly resulting from the nozzle outlet flow. Inner nozzle effects are found to be responsible for generation of the helical structure. A fuel dependence of the helical structure formation and its breakup could not be proved. Results also prove that fuel is exiting the nozzle even after the injector needle is closed, while air is simultaneously moving into the nozzle orifice.

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“…4.2 and 4.3. The wording in references (Gao et al , 2011Liu et al 2009Liu et al , 2010Moon et al 2010) can be understood to mean that the authors have successfully imaged an intact liquid core buried inside a dense spray, with very high spatial resolution and with very high dynamic range.…”

Section: Sprays Produced By a Pressure-atomized Gasoline Injectormentioning

confidence: 96%

“…More recent results (Lai et al 2011a, b) are consistent with these observations. 4.4 Phase contrast images of turbulent injector streams Moon et al (2010) present X-ray phase contrast images of ''near-nozzle jet morphology'' from a hydroground singlehole Diesel injector using biodiesel (there are a number of similar reports (Gao et al , 2011Liu et al 2009Liu et al , 2010Lai et al 2011b); this example was chosen for discussion here). An example image from Moon et al is presented in Fig.…”

Section: Sprays Produced By a Pressure-atomized Gasoline Injectormentioning

confidence: 96%

“…Somewhat more recent work by the Argonne group has involved the use of phase contrast imaging (PCI) and a faster detector Liu et al 2010;Lai et al 2011a, b), with the goal to improve spatial and temporal resolution. PCI was originally developed by Zernicke for high resolution transmission electron microscopy (HR-TEM, for which he won a Nobel prize) (Attwood 1999).…”

Section: Introductionmentioning

confidence: 98%

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Analysis of X-ray phase contrast imaging in atomizing sprays

Linne

2011

Exp Fluids

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Recent studies of spray-related flow fields using synchrotron-based X-ray phase contrast imaging have produced results that are sometimes straightforward to interpret in terms of the fluid structure, but in other cases the images do not reflect generally accepted physics of fluid motion. It has been unclear why some images have the appearance of a normal fluid stream while others depart significantly from expectation. The detailed numerical modeling presented here is meant to explain the images and resolve common questions about the technique. The simulations show that collimated X-ray beams will always contain signatures from every possible encounter, from the input plane to the exit plane, and these signatures generate overlapping phase contrast patterns that can prove at times impossible to interpret. Clouds of moderate-to large-size drops produce a complex, mottled X-ray phase contrast image indicating the presence of the cloud; but it is an image that cannot be interpreted further. Small drops generate something akin to one gray pixel image each, and their size is close to the resolution limit of the instrument, so the diffraction pattern is broadened by the instrument response into something more like a small diffuse blob. Dense clouds of small drops produce a composite image that is a fairly uniform gray mass indicating the presence of a drop cloud that cannot be interpreted further. Moreover, it is not possible to image intact liquid structures behind clouds of drops. Whenever a significant number of drops are present, therefore, X-ray phase contrast images are dominated by unavoidable artifacts of the technique. Sprays, by definition, consist of droplet clouds and this means that internal features in the spray formation region cannot be investigated using X-ray phase contrast imaging.

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Near-Nozzle Structure of Diesel Sprays Affected by Internal Geometry of Injector Nozzle: Visualized by Single-Shot X-ray Imaging

Cited by 28 publications

References 35 publications

The effect of nozzle geometry over internal flow and spray formation for three different fuels

The effect of nozzle geometry over internal flow and spray formation for three different fuels

Zooming into primary breakup mechanisms of high-pressure automotive sprays

Analysis of X-ray phase contrast imaging in atomizing sprays

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