Problem № 2 “Aerosol” презентация

Review
IYPT , 2019
Introduction to the production and properties of the aerosol
Assemble an experimental setup
Studying of the break-up mechanisms of the jet into drops. The role of air.
Aerosol properties.
Analysis of the work and conclusions.

Experimental Setup
Theory Model
Optimization
IYPT
Basic concepts
Aerosol is a dispersed system which consists of small particles suspended in a gaseous medium. Size of particles in aerosols vary from a few millimeters to ten to the power of minus 7 m.

The method of producing aerosol
Condensation aerosol
Cooling and the formation of supersaturated vapor, some chemical reactions
Dispersing aerosols
Disintegration of solid and liquid substances
The type of aerosol and the way of it`s producing uniquely defined by the condition of the problem - spraying a jet of water as it passes through a small aperture.(dispersing aerosol)

Scheme of jet disintegration
Fath, A., Fettes, C., and Leipetz, A. 1998. Investigation of the Diesel Break - up Close to the Nozzle at Different Injection Conditions, The Fourth International Symposium COMODIA 98, p.p. 429 - 434, Kyoto, Japan
Vapor bubbles and turbulence
Waves on the free surface of the fluid
The gaseous bubbles
Droplets
several sticky droplets
Reasons:
Instabilities and perturbations, which arise in the jet itself:
Cavitation
Turbulent flows
Jet disintegration due to interaction with the air

Aerodynamic regimes
*Ohnesorge V.W. Anwendung eines kinematographischen Hochfrequenzaparates mit mechanischer Regelung der Belichtung zur Aufnahme der Tropfenbildung und des Zerfalls flüssiger Strahlen//Dissertation Techn. Hochschule Berlin 1937
*Reitz R.D. Atomization and other Breakup Regimes of a liquid jet//
Ph.D. Thesis, Princeton University, 1978
Different sizes of the particles
Relay-Plato break-up mode
First aerodynamic regime
Second aerodynamic regime
Spray

REVIEW OF INVESTIGATION
Process of disintegration of the jet into droplets, depending on the flow rate;
Find out the role of air;
Determination of droplet size in an aerosol;
Optical and electrical properties of aerosol

nozzle
Experimental setup
tripod
tube
pump

The depth of field
DETERMINATION OF DROPLET SIZE
15 – 20 сm
3 – 5 mm

IYPT

Jet flow mode
Viscous friction force and dynamic pressure force of liquid jet

INVESTIGATING JET`S BREAK-UP PROCESS
Laminar flow
Semi-turbulent flow
Turbulent flow
Experimental Setup
Theory Model
Optimization
IYPT
Re < 2100
2100 < 2300
Re >2300

Rayleigh-Plateau instabilities
The jet devides into separate drops.
Laminar flow
The characteristic time of jet disintegration of the initial radius Rₒ is equal to
The length of the unbroken jet is equal to
**Atomization and Sprays
Arthur H. Lefebvre and Vincent G. McDonell
L

Quality explanation of the Rayleigh-Plateau instability
14
Experimental Setup
Theory Model
Optimization
IYPT

Experimental Setup
Theory Model
Optimization
IYPT
L is the length of the unbroken part of the jet
INVESTIGATION OF THE PROCESS OF DISINTEGRATION INTO DROPS. LAMINAR FLOW.
L

Experimental Setup
Theory Model
Optimization
IYPT
INVESTIGATION OF THE PROCESS OF DISINTEGRATION INTO DROPS. SEMI-TURBULENT FLOW.

Experimental Setup
Theory Model
Optimization
IYPT
U,m/s
2100 < Re <2300
L,m
Diameter of aperture
Density of the fluid
Surface tension
coefficient
INVESTIGATION OF THE PROCESS OF DISINTEGRATION INTO DROPS. SEMI-TURBULENT FLOW.
L
U

INVESTIGATION OF THE PROCESS OF DISINTEGRATION INTO DROPS. TURBULENT FLOW.

Qualitative explanation of the turbulent jet
21
Experimental Setup
Theory Model
Optimization
IYPT

Experimental Setup
Theory Model
Optimization
IYPT
Зависимость угла разлёта от скорости при турбулетном течении

Qualitative explanation of the angle of expansion

d=0,8mm
Turbulent flow
INVESTIGATION OF THE PROCESS OF DISINTEGRATION INTO DROPS
22
Experimental Setup
Theory Model
Optimization
IYPT

The role of air(assumptions)
for the diameter of the jet:
2.5 mm the velocity is 10m/s
1 mm the velocity is 16 m / s
Effect of entrainment of water by air flow is significant
An estimation for the airflow velocity required for this situation is approximately 830 m/s.
air flow is capable of deforming the jet, thereby increasing the disturbance that has arisen.
23
Experimental Setup
Theory Model
Optimization
IYPT

Why can the jet be devideed into small drops? why do droplet sizes depend on the jet velocity?
Internal perturbations (turbulent motion) are required to break up the droplet
Number of Weber is necessary.
24
Experimental Setup
Theory Model
Optimization
IYPT
Surface tension and dynamic pressure force of liquid jet

Воропай П.И., Шленов А.А. Повышение надежности поршневых насосов. М., Недра, 1980, 359 с.
Why can the jet be devided into small drops? why do droplet sizes depend on the jet velocity?
Internal perturbations (turbulent motion) are required to break up the droplet

Average diameter is 0,129 mm
26
Experimental Setup
Theory Model
Optimization
IYPT
Aerosol isn’t monodispersed
Probability
Size of the droplets, mm

DETERMINATION OF THE DROPLET`S SIZE
d=2,5мм, water
d=0,8мм, water
d=0,8мм, glycerin
f
27
Experimental Setup
Theory Model
Optimization
IYPT

The booger — Lambert — ber law will determine the attenuation of a monochromatic beam of light when passing through an absorbing medium.
aerosol
х
I0
I(х)
Source of the light
photosensor
kλ – the absorption rate depends on the wavelength λ of the absorbed light and the aerosol concentration
х
Source of the light
photosensor
OPTICAL PROPERTIES OF AN AEROSOL

OPTICAL PROPERTIES OF AN AEROSOL
29
Experimental Setup
Theory Model
Optimization
IYPT

Experimental Setup
Theory Model
Optimization
IYPT
ELECTRICAL PROPERTY

Conclusions:
a method of obtaining aerosol by simple mechanical spraying destruction through a small aperture;
the mechanism of the jet disintegration into droplets and the dependence of droplet sizes on the liquid velocity was studied;
at the qualitative level, the influence of air flows is understood and estimates are made for speeds in situation when the aerodynamic effect is significant;
a technique for estimating the size of droplets, studied the optical and electrical properties of the aerosol.

7. Fath, A., Fettes, C., and Leipetz, A. 1998. Investigation of the Diesel Break - up Close to the Nozzle at
Different Injection Conditions, The Fourth International Symposium COMODIA 98, p.p. 429 - 434, Kyoto, Japan
8. Воропай П.И., Шленов А.А. Повышение надежности поршневых насосов. М., Недра, 1980, 359 с.
9. РАСЧЕТ ТРАЕКТОРИИ ДВИЖЕНИЯ КАПЛИ ЖИДКОСТИ В ГАЗОВОМ ПОТОКЕ
С УЧЕТОМ ЕЕ ДЕФОРМАЦИи.В.И. Рублев, В.В. Логинов
10. Study of the effects of the injector length/diameter ratio on the surface properties of
turbulent liquid jets in still air using X-ray imaging
A.R. Osta a, J. Lee a, K.A. Sallam a,, K. Fezzaa b Break-up length of liquid jets produced by short nozzles
M. Etzold ∗, A. Deswal , L. Chen , F. Durst
11. Atomization and Sprays
Arthur H. Lefebvre and Vincent G. McDonell
1. Береснев С.А., Грязин В.И.
Физика атмосферных аэрозолей: Курс лекций. – Екатеринбург:
Изд-во Урал. ун-та, 2008.
2. Фукс Н.А. Механика аэрозолей. М.: Изд. АН СССР, 1955.
3. К.И. Белоусов, А.А. Евстрапов,
И.В. Кухтевич, Я.С. Посмитная
ОСНОВЫ НАНОТЕХНОЛОГИЙ. ЧАСТЬ 1
4. A.R. Osta a, J. Lee a, K.A. Sallam a,, K. Fezzaa b Break-up length of liquid jets produced by short nozzles
M. Etzold ∗, A. Deswal , L. Chen , F. Durst
5. Sustainable Solutions for Energy and Environment, EENVIRO - YRC 2015, 18-20 November2015, Bucharest, Romania
Breakup of Liquid Jets
Ioana Laura Omoceaa*, Claudiu Patrascua, Mihaela Turcanua, Corneliu Balana
6. Manuel A. Reddemann · Florian Mathieu ·Reinhold Kneer «Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet»
Bibliography:

There are some interesting things…(done, but not shown)
Estimation for the number of Weber for droplet which rotate;
The measurements of the velocity of the laminar jet; for turbulent jet;
Droplet divide;
Instability of the Rayleigh- plateau;
The losses of energy;
The device of the spray;
The determination of the average diameter of the particles;
lifetime of the aerosol and droplet. The estimation of the critical radius for evaporation and condensation;
The concentration of the droplets.

***Manuel A. Reddemann · Florian Mathieu ·Reinhold Kneer «Transmitted light microscopy for visualizing the turbulent primary breakup of a microscale liquid jet»
Theory of Castleman

F
h
We move in frame of reference associated with the jet. Select the item Δm
AERODYNAMIC EFFECTS
the jet is compressed by the air flow
jet diameter grows
forces in equilibrium, critical flow velocity
gas
gas
sur
sur
sur
sur

critical velocities significantly lower than velocities that we working with.
Not our effect
thickness of the reduced mass layer (cylinder)
crit
crit
crit
gas
Aerodynamic effects

Consider the effect of entrainment of liquid air flow. Let the jet arose disturbance
thickness of the reduced mass layer (cylinder)
Aerodynamic effects
fr
sur