Cavitation Inside High-Pressure Optically Transparent Fuel Injector Nozzles

Falgout, Zachary; Linne, Mark

doi:10.1088/1742-6596/656/1/012082

Cited by 7 publications

(5 citation statements)

References 4 publications

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“…Plastics are also damaged due to the heat load from the incident x-ray beam, and this shortens their operating life. Recent optical experiments using sapphire nozzles have shown promise for high-pressure optical imaging 26 but these are unsuitable for x-ray experiments. Prior x-ray measurements of cavitation in steel nozzles 27 have been limited to phase-contrast imaging at higher x-ray energies (above 25 keV).…”

Section: Introductionmentioning

confidence: 99%

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X-ray radiography of cavitation in a beryllium alloy nozzle

Duke

Matusik

Kastengren

et al. 2017

International Journal of Engine Research

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Making quantitative measurements of the vapor distribution in a cavitating nozzle is difficult, owing to the strong scattering of visible light at gas-liquid boundaries and wall boundaries, and the small length and time scales involved. The transparent models required for optical experiments are also limited in terms of maximum pressure and operating life. Over the past few years, xray radiography experiments at Argonne's Advanced Photon Source have demonstrated the ability to perform quantitative measurements of the line of sight projected vapor fraction in submerged, cavitating plastic nozzles. In this paper, we present the results of new radiography experiments performed on a submerged beryllium nozzle 520 microns in diameter, with a length/diameter ratio of 6. Beryllium is a light, hard metal that is very transparent to x-rays due to its low atomic number. We present quantitative measurements of cavitation vapor distribution conducted over a range of non-dimensional cavitation and Reynolds numbers, up to values typical of gasoline and diesel fuel injectors. A novel aspect of this work is the ability to quantitatively measure the area contraction along the nozzle with high spatial resolution. Analysis of the vapor distribution, area contraction and discharge coefficients are made between the beryllium nozzle, and plastic nozzles of the same nominal geometry. When gas is dissolved in the fuel, the vapor distribution can be quite different from that found in plastic nozzles of the same dimensions, although the discharge coefficients are unaffected. In the beryllium nozzle, there were substantially fewer machining defects to act as nucleation sites for the precipitation of bubbles from dissolved gases in the fuel, and as such its effect on the vapor distribution was greatly reduced.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

X-ray radiography of cavitation in a beryllium alloy nozzle

Duke

Matusik

Kastengren

et al. 2017

International Journal of Engine Research

View full text Add to dashboard Cite

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“…However, there is evidence that scaling up the nozzle geometry while holding the Reynolds and cavitation numbers constant produces different cavitation structures [15]. To circumvent this scaling issue, nozzles manufactured from sapphire have been used due to the material's similarity in strength to steel and ability to withstand engine-relevant injection pressures [16].…”

Section: Operating Conditionmentioning

confidence: 99%

Fuel Nozzle Geometry Effects on Cavitation and Spray Behavior at Diesel Engine Conditions

Sforzo

Matusik

Powell

et al. 2018

Proceedings of the 10th International Symposium on Cavitation (CAV2018)

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Cavitation dynamics of diesel and gasoline injection nozzles has been a topic of ongoing research due to the effect of cavitation on the characteristics of the fuel spray, including the discharge coefficient, outlet velocity, spray angle, and atomization process. Additionally, repeated collapse of vapor cavities can damage nozzle surfaces, permanently changing the boundary conditions of the fluid flow field. Understanding the evolution and behavior of cavitation can therefore allow more precise control over its presence, as well as improved predictability of the corresponding fuel spray distribution. Studies have shown that the inception and persistence of fuel vapor inside the spray hole is sensitive to geometric features of the injection nozzle, such as the degree of taper and inlet corner radius of curvature. For example, a hole with a cylindrical profile and sharp inlet corner more readily supports cavitation formation as compared to a monotonically converging hole with a rounded inlet. To better understand the effect of these geometric features on cavitation formation, and by extension, on the associated fuel spray, we compare the nozzle geometry and spray characteristics of two single-hole diesel injectors procured through collaboration with the Engine Combustion Network (ECN). The Spray C injector, specifically designed by the ECN for the express purpose of studying cavitating flows, features a cylindrical hole with a slight divergence near the outlet and a relatively sharp inlet corner. Its non-cavitating analog, the Spray D injector, contains a rounded inlet corner and a gently converging hole profile. High-resolution x-ray tomography measurements coupled with optical microscopy images of both injectors provide the nozzle geometry with O(1) µm spatial resolution. Analysis of the measured geometries reveal that the radius of curvature of the hole inlet varies azimuthally for the modestly hydroground Spray C injector. To elucidate the effect that this asymmetric inlet condition has on cavitation formation during operando conditions, the fuel flow inside the nozzle hole was recorded using high-speed x-ray phase contrast imaging. These images reveal the formation of an asymmetric sheath of fuel vapor that persists throughout the injection event. Complementary x-ray and optical diagnostics of the downstream fuel spray further highlight the effect that this cavitation layer has on the spreading angle of the spray in comparison to the non-cavitating Spray D injector.

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“…Glass is a material that imposes limitations to the length to diameter ratio that can be achieved. Due to the brittleness of glass very short nozzles would require some kind of support as was done by [6] for acrylic nozzles for diesel injection. In the present paper a first step to develop a nozzle type and methodology that allows to study real size GDI nozzle flow.…”

Section: Introductionmentioning

confidence: 99%

“…There have been some real size transparent nozzles for Diesel injector geometries, e.g. [6][7][8]. However, the geometry of multi-hole GDI injectors is more complex and what is more demanding is that gasoline is an aggressive medium for acrylics.…”

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confidence: 99%

Binary cavitation in a transparent three hole GDI nozzle

Chaves¹,

Donath²

2017

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

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A more or less real size three hole (0.1 mm diameter) transparent injection nozzle was made with 120° between the orifices and an inclination of 20° to the injector axis. The geometry is similar to that of a multi hole GDI injector. Experiments are performed using n-pentane and -methyl-naphtalene mixtures in varying composition. The flow in the orifices is observed under submerged injection conditions from downstream looking in direction of the injector using a beam splitter plate for illumination with the light from a Minilite NdYag laser that was made incoherent by fluorescence in a cuvette filled with a dilute rhodamine-ethanol mixture. The images show the appearance of cavitation depending on the cavitation number as well as on the composition of the mixture. The behaviour is not what can be expected from equilibrium thermodynamics. Due to the transient nature of the flow the n-pentane concentration cannot attain the equilibrium value one would expect and cavitation occurs at higher cavitation values. Diffusion appears to play a role in the onset appearance of cavitation for binary mixtures. KeywordsBinary cavitation, real size transparent nozzle, fuel injection. IntroductionThe internal flow of gasoline direct injection nozzles has been investigated in the last years intensively. X-ray phase contrast imaging [1] allows visualizing the density gradients in the nozzle orifices of aluminium nozzles using very short high energy x-ray pulses from the APS Electron Storage Ring, Argonne National Laboratory. These images have shown that the flow can show hydraulic flip and cavitation in real size geometries. These results corroborate the results obtained in large scaled up transparent acrylic models of GDI multi-hole injectors, [2]. Characteristic for multi-hole injectors is the small length to diameter ratio of the orifices. The counter bore with a larger diameter does not have a direct contact with the fluid, [1] and is therefore mainly important for reducing the L/D ratio. Already in the early work with cavitating nozzles Lichtarowicz [3] noted "The function of the orifice bore, which must be at least one diameter long, is to stabilize the cavitation bubble. If the bore length is insufficient and the orifice tends to be a plate orifice cavitation occurs in bursts." This result is found in new results for GDI nozzles [4] that show flapping in timescales "in the order of a hundredth of a millisecond ". In the case of longer orifices the length of the cavitation zone in the orifice also fluctuates [5] with frequencies of about 29 kHz. Therefore, when taking instantaneous images of cavitation there will be large scatter of the cavitation length within the nozzle. There have been some real size transparent nozzles for Diesel injector geometries, e.g. [6][7][8]. However, the geometry of multi-hole GDI injectors is more complex and what is more demanding is that gasoline is an aggressive medium for acrylics. This is more so when ethanol is contained in the fuel. Therefore, transparent nozzles for gasoline fue...

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Cavitation Inside High-Pressure Optically Transparent Fuel Injector Nozzles

Cited by 7 publications

References 4 publications

X-ray radiography of cavitation in a beryllium alloy nozzle

X-ray radiography of cavitation in a beryllium alloy nozzle

Fuel Nozzle Geometry Effects on Cavitation and Spray Behavior at Diesel Engine Conditions

Binary cavitation in a transparent three hole GDI nozzle

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