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 atomisers (PSA) 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-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 atomiser sprayed water into cross-flowing air at varying flow velocities. The tests were provided 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 us 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. CEJPEK Ondřej, University of Technology, 2020

Nomenclature


Symbol

Description

A

cross-section

AT

arrival time to the measurement volume

Bo

Bond number

c

droplet concentration


discharge coefficient

D

mean droplet diameter

d

diameter


arithmetic mean diameter


surface mean diameter


Sauter mean diameter

F

force acting on a liquid element

Fr

Froude number

G

gravitational acceleration

K

nozzle dimension constant

L

characteristic distance


break-up distance

LDA1

velocity in Z-direction

LDA4

velocity in Y-direction

n

wave number

Oh

Ohnesorge number

p

pressure

Q

flow rate

q

liquid-to-air momentum ratio

r

radius

Re

Reynolds number

S

swirl number

Stk

Stokes number

SCA

spray cone angle

t

time

TT

transit time through the measurement volume

Tu

turbulence intensity

u

velocity

U12

phase shift between photomultipliers 1 and 2

U13

phase shift between photomultipliers 1 and 3

w

swirl component of the velocity

We

Weber number

X, Y, Z

Cartesian coordinates



Greek symbols



difference between the gas and droplet velocity


nozzle efficiency


dynamic viscosity

ρ

liquid density

σ

surface tension



Indices


a

aerodynamic

ac

air core

c

swirl chamber

cf

cross-flow

Cr

critical

D

droplet

g

gas

i

index number of a droplet

in

atomiser inlet (inlet ports)

l

liquid

m

inertia

n

total number of droplets

o

exit orifice

p

pressure

r

relative

v0.1, v0.5, v0.9

volumetric fractions 0.1, 0.5 and 0.9 of the total droplet volume

µ

related to dynamic viscosity

σ

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 atomiser

RSF

relative diameter span factor




Contributed by: Ondrej Cejpek, Milan Maly, 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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