Quantification of coflow effects on primary atomization of pressure swirl atomizers

Petry, Niklas; Schäfer, Dominik; Lammel, Oliver; Hampp, Fabian

doi:10.1016/j.ijmultiphaseflow.2021.103946

Cited by 11 publications

(2 citation statements)

References 52 publications

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“…Droplet horizontal velocity corresponds approximately to the projection of the droplet radial and tangential velocities. These horizontal velocity profiles are consistent with those described in the literature using the PIV technique [32][33][34]. The horizontal velocity projection is approximately zero when ∆P = 0.2 MPa.…”

Section: Resultssupporting

confidence: 89%

Comparative study of droplet and liquid film velocities in sprays

Machado¹,

Costa²,

Andrade³

et al. 2023

Meas. Sci. Technol.

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This study presents a comparative analysis of droplet and conical liquid film velocities in sprays by a pressure swirl injector with Abramovich geometric constant K = 1.986. The velocities were measured simultaneously by schlieren image velocimetry (SIV) and sequential images of the liquid film, using a high-speed camera with 8192 fps and shutter of 2 μs. Other parameters, such as discharge coefficients, spray cone angles and breakup lengths were also determined, using water as test fluid, for injection pressures from 0.05 to 0.5 MPa. Experimental velocity data were compared to results from different semi-empirical equations. The breakup lengths decreased continuously from around 20 mm to 15 mm for injection pressures from 0.1 to 0.5 MPa, while spray cone angles increased continuously from about 42o to 53o, for pressures from 0.2 to 0.5 MPa. Mean axial droplet velocities varied from 4.7 m/s to 14.5 m/s, while the mean total droplet velocities varied from 5 m/s to 16.2 m/s and the total liquid film velocity increased from 5.7 m/s to 20.2 m/s, approximately, for increasing injection pressure. Liquid film velocities were about 15 % to 28 % higher than the droplet velocities in the pressure range considered, due to the energy required for liquid film breakup and the air drag on the droplets. The current findings underscore that significant discrepancies may arise when relying on inadequate velocity data, particularly when employed in the computation of key parameters such as the Reynolds and Weber numbers.

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Section: Resultssupporting

confidence: 89%

Comparative study of droplet and liquid film velocities in sprays

Machado¹,

Costa²,

Andrade³

et al. 2023

Meas. Sci. Technol.

View full text Add to dashboard Cite

show abstract

“…The results presented in figure 7( a – d ) feature a mean velocity deficit near , which is due to the wake of the spray injector, similar to the results presented by Petry et al. (2022). Also, the mean velocity profiles are nearly symmetric for the test conditions without a perforated plate; however, these profiles are nearly asymmetric for test conditions with one and two perforated plates, which are similar to those reported by Kheirkhah & Gülder (2015).…”

Section: Resultssupporting

confidence: 86%

Separate and joint clustering characteristics of large-Stokes-number sprays subjected to turbulent co-flows

Rostami

Kheirkhah

2023

J. Fluid Mech.

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Separate and joint droplets, clusters, and voids characteristics of sprays injected in a turbulent co-flow are investigated experimentally. Simultaneous Mie scattering and interferometric laser imaging for droplet sizing along with separate hotwire anemometry are performed. The turbulent co-flow characteristics are adjusted using zero, one or two perforated plates. The Taylor-length-scale-based Reynolds number varies from 10 to 38, and the Stokes number estimated based on the Kolmogorov time scale varies from 3 to 25. The results show that the mean length scale of the clusters normalized by the Kolmogorov length scale varies linearly with the Stokes number. However, the mean void length scale is of the order of the integral length scale. It is shown that the number density of the droplets inside the clusters is approximately 7 times larger than that in the voids. The ratios of the droplets number densities in the clusters and voids to the total number density are independent of the test conditions and equal 5.5 and 0.8, respectively. The joint probability density function of the droplets diameter and clusters area shows that the droplets with the most probable diameter are found in the majority of the clusters. It is argued that intensifying the turbulence broadens the range of turbulent eddy size in the co-flow which allows for accommodating droplets with a broad range of diameters in the clusters. The results are of significance for engineering applications that aim to modify the clustering characteristics of large-Stokes-number droplets sprayed into turbulent co-flows.

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Schlieren Image Velocimetry of Swirl Sprays

Machado¹,

Costa²,

Andrade³

et al. 2022

Flow Turbulence Combust

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Schlieren image velocimetry is based on light de ection through ow heterogeneities and image crosscorrelations. This is a low-cost and relatively low complexity technique that allows measurement of the droplet velocity eld in a large region of a spray. A Z-type Toepler schlieren system with a high-speed camera was used to determine mean vertical and horizontal droplet velocities, as well as the cone angles of sprays produced by a pressure swirl injector with characteristic geometric constant K = 2. Different LEDs and digital lters were evaluated for edge detection and improvement of image contrast. Open software was adopted for digital image processing and velocimetry. Interrogation windows and overlaps of different sizes were tested to obtain an appropriate correlation for determination of the velocity eld.The digital images were obtained with 5×10 3 fps and a resolution of 2.77 pixels/mm. Since the swirl sprays analysed presented instabilities, a number of 100 cross-correlations of images was required to reduce mean velocity uctuations. Injection pressures varied from 0.05 to 7 bar and mass ow rates varied from 1.389 to 13.89 g/s, using water as test uid. The wideband warm white LED with Laplacian or high-pass lters provided velocity data for a larger range of injection pressures. Mean axial velocities varied from 3.3 to 11.3 m/s, approximately, with mean horizontal velocities varying from around 0.17 to 3.3 m/s for pressures from 0.05 to 3.22 bar. The velocity data were compared to microscopic shadowgraphy results, showing a good agreement. Spray cone angles ranged from about 32.5 o to 69.5 o , for injection pressures from 0.05 to 7 bar, and results of triangulation with a blue LED were closer to semiempirical data.

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Quantification of coflow effects on primary atomization of pressure swirl atomizers

Cited by 11 publications

References 52 publications

Comparative study of droplet and liquid film velocities in sprays

Comparative study of droplet and liquid film velocities in sprays

Separate and joint clustering characteristics of large-Stokes-number sprays subjected to turbulent co-flows

Schlieren Image Velocimetry of Swirl Sprays

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