EXP 1-1

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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.

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

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

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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