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=Pressure-swirl spray in a low-turbulence cross-flow=
=Pressure-swirl spray in a low-turbulence cross-flow=
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<div id="figure1">
<div id="figure1">
<gallery mode=nolines class="center" widths=500px heights=200px>
<gallery mode=nolines class="center" widths=500px heights=200px>
File:spray_image_hs_im.png|'''Figure 1a''': Spray image in cross flow from high-speed imaging
File:spray_image_hs_im.png|'''Figure 1a''': Illustrative image of spray in cross flow from high-speed imaging
File:opti_meas_wt_section.png|'''Figure 1b''': Optical measurement using PDA (taken from <ref name="CEJPEK 1"> O. Cejpek, Design and realization of an aerodynamic tunnel for spraying nozzles [online]. Brno, 2020 [cit. 2023-04-18]. Available from: https://www.vutbr.cz/studenti/zav-prace/detail/124871. Master thesis. Brno university of Technology </ref>)
File:opti_meas_wt_section.png|'''Figure 1b''': Atomizer in the test section of the wind tunnel, optical measurement of the spray using PDA (taken from <ref name="CEJPEK 1"> O. Cejpek, Design and realization of an aerodynamic tunnel for spraying nozzles [online]. Brno, 2020 [cit. 2023-04-18]. Available from: https://www.vutbr.cz/studenti/zav-prace/detail/124871. Master thesis. Brno university of Technology </ref>)
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<references/>
<references/>


= Nomenclature =
{| class="wikitable"  style="text-align:center; vertical-align:middle;margin:auto"
|-
! <br />Symbol
! <br />Description
|-
| <br /><math>A</math>
| <br />Cross-section
|-
| <br />AT
| <br />Arrival time to the measurement volume
|-
| <br /><math>Bo</math>
| <br />Bond number; <math>B o=\Delta \rho g D^2 / \sigma</math>
|-
| <br /><math>c</math>
| <br />Droplet concentration
|-
| <br /><math>C_D</math>
| <br />Discharge coefficient; <math> C_D = Q_l \sqrt \rho / A_{o} \sqrt { 2 p_in } </math>
|-
| <br /><math>D</math>
| <br />Mean droplet diameter
|-
| <br /><math>d</math>
| <br />Diameter
|-
| <br /><math>D_{10}</math>
| <br />Arithmetic mean diameter; <math>D_{10}={\sum_{i=1}^n d_i / n}</math>
|-
| <br /><math>D_{20}</math>
| <br />Surface mean diameter; <math>D_{20}=\sqrt{\sum_{i=1}^n d_i^2 / n}</math>
|-
| <br /><math>D_{32}</math>
| <br />Sauter mean diameter; <math>D_{32}={\sum_{i=1}^n d_i^3 / \sum_{i=1}^n d_i^2}</math>
|-
| <br /><math>F</math>
| <br />Force acting on a liquid element
|-
| <br /><math>Fr</math>
| <br />Froude number; <math>Fr=\frac{u}{\sqrt{gL}}</math>
|-
| <br /><math>G</math>
| <br />Gravitational acceleration
|-
| <br /><math>k</math>
| <br />Nozzle dimension constant; <math> k = A_{in} / 4r_{c}r_{o} </math>
|-
| <br /><math>L</math>
| <br />Characteristic distance or dimension
|-
| <br /><math>l_{b}</math>
| <br />Break-up distance
|-
| <br />LDA1
| <br />Velocity in Z-direction
|-
| <br />LDA4
| <br />Velocity in Y-direction
|-
| <br /><math>n</math>
| <br />Wave number, number of samples
|-
| <br /><math>Oh</math>
| <br />Ohnesorge number; <math>O h=\sqrt{W e} / \operatorname{Re}</math>
|-
| <br /><math>p</math>
| <br />Pressure
|-
| <br /><math>Q</math>
| <br />Volumetric flow rate
|-
| <br /><math>q</math>
| <br />Liquid-to-air momentum ratio; <math>q=\frac{\rho_lu_l^2}{\rho_gu_{cf}^2}
</math>
|-
| <br /><math>r</math>
| <br />Radius
|-
| <br /><math>Re</math>
| <br />Reynolds number; <math>R e=\rho u L / \mu</math>
|-
| <br /><math>S</math>
| <br />Swirl number; <math>S = \frac{wr_{c}}{u_{o}r_{o}} </math>
|-
| <br /><math>Stk</math>
| <br />Stokes number; <math>S t k=\rho_l \bar{D}_p^2 \Delta \bar{v} / 18 \mu_g L</math>
|-
| <br /><math>SCA</math>
| <br />Spray cone angle
|-
| <br /><math>t</math>
| <br />Time
|-
| <br />TT
| <br />Transit time  through the measurement volume
|-
| <br /><math>Tu</math>
| <br />Turbulence intensity; <math>Tu=v_{rms}/ \bar{v}  </math>
|-
| <br /><math>u</math>, <math>v</math>
| <br />Velocity
|-
| <br />U12
| <br />Phase shift  between photomultipliers 1 and 2
|-
| <br />U13
| <br />Phase shift  between photomultipliers 1 and 3
|-
| <br /><math>w</math>
| <br />Swirl component of the velocity
|-
| <br /><math>We</math>
| <br />Weber number; <math>W e=\rho u^2 L / \sigma</math>
|-
| <br /><math>X, Y, Z</math>
| <br />Cartesian coordinates
|-
| <br />
| <br />
|- style="font-weight:bold;"
| <br />Greek symbols
| style="font-weight:normal;" | <br />
|-
| <br /><math>\Delta v </math>
| <br />Difference between the gas and droplet velocity
|-
| <br /><math>\eta_{n}</math>
| <br />Nozzle efficiency
|-
| <br /><math>\mu</math>
| <br />Dynamic viscosity
|-
| <br /><math>\rho</math>
| <br />Liquid density
|-
| <br /><math>\sigma</math>
| <br />Surface tension
|-
| <br />
| <br />
|- style="font-weight:bold;"
| <br />Indices
| style="font-weight:normal;" | <br />
|-
| <br /><math>a</math>
| <br />Aerodynamic
|-
| <br /><math>ac</math>
| <br />Air core
|-
| <br /><math>c</math>
| <br />Swirl chamber
|-
| <br /><math>cf</math>
| <br />Cross-flow
|-
| <br /><math>Cr</math>
| <br />Critical
|-
| <br /><math>D</math>
| <br />Droplet
|-
| <br /><math>g</math>
| <br />Gas
|-
| <br /><math>i</math>
| <br />Index number of a droplet
|-
| <br /><math>in</math>
| <br />Atomizer inlet (inlet ports)
|-
| <br /><math>l</math>
| <br />Liquid
|-
| <br /><math>m</math>
| <br />Inertia
|-
| <br /><math>n</math>
| <br />Total number of droplets
|-
| <br /><math>o</math>
| <br />Exit orifice
|-
| <br /><math>p</math>
| <br />Pressure
|-
| <br /><math>r</math>
| <br />Relative
|-
| <br /><math>v0.1, v0.5, v0.9</math>
| <br />Volumetric fractions 0.1, 0.5 and 0.9 of the total  droplet volume
|-
| <br /><math>\mu</math>
| <br />Related to dynamic viscosity
|-
| <br /><math>\sigma</math>
| <br />Related to surface tension
|-
| <br /><math> \tau </math>
| <br />Liquid film thickness
|-
| <br />
| <br />
|- style="font-weight:bold;"
| <br />Abbreviations
| style="font-weight:normal;" | <br />
|-
| <br />AC
| <br />Air core
|-
| <br />fps
| <br />Frames per second
|-
| <br />GT
| <br />Gas turbine
|-
| <br />HSC
| <br />High-speed camera
|-
| <br />HSV
| <br />High-speed vizualization
|-
| <br />LDA
| <br />Laser Doppler anemometry,
|-
| <br />PDA
| <br />Phase Doppler anemometry
|-
| <br />PSA
| <br />Pressure-swirl atomizer
|-
| <br />RSF
| <br />Relative diameter span factor
|}
<br/>
----
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|organisation=Brno University of Technology
|organisation=Brno University of Technology
}}
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Latest revision as of 08:19, 17 August 2023

Pressure-swirl spray in a low-turbulence cross-flow

Front Page

Introduction

Review of experimental studies

Description

Experimental Set Up

Measurement Quantities and Techniques

Data Quality and Accuracy

Measurement Data and Results


Abstract

Pressure-swirl atomizers (PSAs) produce fine spray and are used in many industrial, chemical and agricultural applications of sprays in flowing environments. The study examines spray from a small low-pressure PSA exposed to low-turbulence cross-flowing air. The PSA spray was investigated experimentally using phase Doppler anemometry (PDA) and high-speed visualisation (HSV). The atomizer sprayed water into cross-flowing air at varying flow velocities. The tests were performed at a newly developed wind tunnel facility in the Spray laboratory at Brno University of Technology. PDA results contain information on the size and velocity of individual droplets in multiple positions of the developed spray (after the liquid break-up is completed). A high-speed camera (HSC) documented the complexity of the liquid discharge, the formation and break-up of the liquid film, and the spray morphology. The data is relevant to CFD engineers and scientists involved in modelling as they can highlight the crucial phenomena to be considered in numerical simulations of the disperse two-phase flow case. The case allows to study 1) liquid discharge and sheet formation, the primary break-up of the liquid sheet, 2) secondary break-up and spray formation and 3) the interaction of the sprayed liquid with surrounding air: gas–liquid mixing, droplet collisions, droplet clustering and droplet reposition.

  • Figure 1a: Illustrative image of spray in cross flow from high-speed imaging

    Figure 1a: Illustrative image of spray in cross flow from high-speed imaging

  • Figure 1b: Atomizer in the test section of the wind tunnel, optical measurement of the spray using PDA (taken from [1])

    Figure 1b: Atomizer in the test section of the wind tunnel, optical measurement of the spray using PDA (taken from [1])

References

  1. ↑ O. Cejpek, Design and realization of an aerodynamic tunnel for spraying nozzles [online]. Brno, 2020 [cit. 2023-04-18]. Available from: https://www.vutbr.cz/studenti/zav-prace/detail/124871. Master thesis. Brno university of Technology


Contributed by: Ondrej Cejpek, Milan Maly, Ondrej Hajek, Jan Jedelsky — Brno University of Technology

Front Page

Introduction

Review of experimental studies

Description

Experimental Set Up

Measurement Quantities and Techniques

Data Quality and Accuracy

Measurement Data and Results


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