EXP 1-1
Pressure-swirl spray in a low-turbulence cross-flow
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 1b: Optical measurement using PDA (taken from [1])
References
- ↑ 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
Nomenclature
Symbol |
Description |
---|---|
Cross-section | |
AT |
Arrival time to the measurement volume |
Bond number; | |
Droplet concentration | |
Discharge coefficient; | |
Mean droplet diameter | |
Diameter | |
Arithmetic mean diameter; | |
Surface mean diameter; | |
Sauter mean diameter; | |
Force acting on a liquid element | |
Froude number; | |
Gravitational acceleration | |
Nozzle dimension constant; | |
Characteristic distance or dimension | |
Break-up distance | |
LDA1 |
Velocity in Z-direction |
LDA4 |
Velocity in Y-direction |
Wave number, number of samples | |
Ohnesorge number; | |
Pressure | |
Flow rate | |
Liquid-to-air momentum ratio; | |
Radius | |
Reynolds number; | |
Swirl number; | |
Stokes number; | |
Spray cone angle | |
Time | |
TT |
Transit time through the measurement volume |
Turbulence intensity; | |
, |
Velocity |
U12 |
Phase shift between photomultipliers 1 and 2 |
U13 |
Phase shift between photomultipliers 1 and 3 |
Swirl component of the velocity | |
Weber number; | |
Cartesian coordinates | |
Greek symbols |
|
Difference between the gas and droplet velocity | |
Nozzle efficiency | |
Dynamic viscosity | |
Liquid density | |
Surface tension | |
Indices |
|
Aerodynamic | |
Air core | |
Swirl chamber | |
Cross-flow | |
Critical | |
Droplet | |
Gas | |
Index number of a droplet | |
Atomizer inlet (inlet ports) | |
Liquid | |
Inertia | |
Total number of droplets | |
Exit orifice | |
Pressure | |
Relative | |
Volumetric fractions 0.1, 0.5 and 0.9 of the total droplet volume | |
Related to dynamic viscosity | |
Related to surface tension | |
Liquid film thickness | |
Abbreviations |
|
AC |
Air core |
fps |
Frames per second |
GT |
Gas turbine |
HSC |
High-speed camera |
HSV |
High-speed vizualization |
LDA |
Laser Doppler anemometry, |
PDA |
Phase Doppler anemometry |
PSA |
Pressure-swirl atomizer |
RSF |
Relative diameter span factor |
Contributed by: Ondrej Cejpek, Milan Maly, Ondrej Hajek, Jan Jedelsky — Brno University of Technology
© copyright ERCOFTAC 2024