Three-dimensional imaging of swirled spray injection in a generic aero engine burner under realistic operating conditions

Medientyp: E-Artikel
Titel: Three-dimensional imaging of swirled spray injection in a generic aero engine burner under realistic operating conditions
Beteiligte: Klinner, Joachim; Willert, Christian E.
Erschienen: Springer Science and Business Media LLC, 2022
Erschienen in: Experiments in Fluids
Sprache: Englisch
DOI: 10.1007/s00348-021-03343-z
ISSN: 0723-4864; 1432-1114
Schlagwörter: Fluid Flow and Transfer Processes ; General Physics and Astronomy ; Mechanics of Materials ; Computational Mechanics
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Beschreibung: <jats:title>Abstract</jats:title><jats:p>Tomographic shadowgraph imaging is applied to reconstruct the instantaneous three-dimensional spray field immediately downstream of a generic aero engine fuel injector. Within the swirl passage of the injector model, a single kerosene jet undergoes air-blast atomization in a cross-flow configuration at Weber numbers of <jats:inline-formula><jats:alternatives><jats:tex-math>$$\text {We}=360-770$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mtext>We</mml:mtext> <mml:mo>=</mml:mo> <mml:mn>360</mml:mn> <mml:mo>-</mml:mo> <mml:mn>770</mml:mn> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>, air pressures of <jats:inline-formula><jats:alternatives><jats:tex-math>$$p_a=4-7\,\text{ bar }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>p</mml:mi> <mml:mi>a</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>4</mml:mn> <mml:mo>-</mml:mo> <mml:mn>7</mml:mn> <mml:mspace /> <mml:mspace /> <mml:mtext>bar</mml:mtext> <mml:mspace /> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> and air temperatures of <jats:inline-formula><jats:alternatives><jats:tex-math>$$T_a=440-570\,\text{ K }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>T</mml:mi> <mml:mi>a</mml:mi> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>440</mml:mn> <mml:mo>-</mml:mo> <mml:mn>570</mml:mn> <mml:mspace /> <mml:mspace /> <mml:mtext>K</mml:mtext> <mml:mspace /> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>. High-speed, high magnification shadowgraphy is used to visualize the initial fuel atomization stages within the fuel injector before the spray enters the spray chamber. The 4-camera tomographic measurement setup is described in detail and includes a depth-of-field analysis with respect to droplet size based on Mie simulations and calibration data of the point-spread function. For a volume size of <jats:inline-formula><jats:alternatives><jats:tex-math>$$16\times 13\times 10\,\text{ mm}^3$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mn>16</mml:mn> <mml:mo>×</mml:mo> <mml:mn>13</mml:mn> <mml:mo>×</mml:mo> <mml:mn>10</mml:mn> <mml:mspace /> <mml:mspace /> <mml:msup> <mml:mtext>mm</mml:mtext> <mml:mn>3</mml:mn> </mml:msup> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> , the smallest resolvable droplet diameter is estimated to be <jats:inline-formula><jats:alternatives><jats:tex-math>$$d=10\,\mu \text{ m }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>d</mml:mi> <mml:mo>=</mml:mo> <mml:mn>10</mml:mn> <mml:mspace /> <mml:mi>μ</mml:mi> <mml:mspace /> <mml:mtext>m</mml:mtext> <mml:mspace /> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> within the focal plane and increases to <jats:inline-formula><jats:alternatives><jats:tex-math>$$d \approx 20\,\mu \text{ m }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>d</mml:mi> <mml:mo>≈</mml:mo> <mml:mn>20</mml:mn> <mml:mspace /> <mml:mi>μ</mml:mi> <mml:mspace /> <mml:mtext>m</mml:mtext> <mml:mspace /> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> toward the edges of the volume. Droplet velocities above the resolution limit were retrieved by 3-d cross-correlation of two volumetric reconstructions recorded at two consecutive time-steps. This is accompanied by an error analysis on the random error dependency on the camera viewing geometry. The results indicate increasing motion and fluctuations of the spray tail with increasing temperature and Weber number. Validation against PDA data further downstream of the burner plate revealed consistency for size classes <jats:inline-formula><jats:alternatives><jats:tex-math>$$d=10\,\mu \text{ m }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>d</mml:mi> <mml:mo>=</mml:mo> <mml:mn>10</mml:mn> <mml:mspace /> <mml:mi>μ</mml:mi> <mml:mspace /> <mml:mtext>m</mml:mtext> <mml:mspace /> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula> and <jats:inline-formula><jats:alternatives><jats:tex-math>$$d=15\,\mu \text{ m }$$</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:mi>d</mml:mi> <mml:mo>=</mml:mo> <mml:mn>15</mml:mn> <mml:mspace /> <mml:mi>μ</mml:mi> <mml:mspace /> <mml:mtext>m</mml:mtext> <mml:mspace /> </mml:mrow> </mml:math></jats:alternatives></jats:inline-formula>. Deviations from PDA occur in regions with strong velocity gradients due to different spatial resolutions, the presence of reconstruction ambiguities (ghost particles), uncertainties inherent to the two-frame cross-correlation of spray volumes and the finite LED pulse duration.</jats:p> <jats:p><jats:bold>Graphical Abstract</jats:bold></jats:p>

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