COMPARISON FINE SPRAY NOZZLE FOR TWO PHASE FLOW ...

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COMPARISON FINE SPRAY NOZZLE FOR TWO PHASE FLOW WITHIN

EXPERIMENTAL AND SIMULATION

HAFIZ AIZAT BIN ALI

A thesis submitted in

fulfillment of the requirement for the award of the

Master in Mechanical Engineering with Honour

Faculty of Mechanical and Manufacturing Engineering

Universiti Tun Hussein Onn Malaysia

DISEMBER 2015

iv

ABSTRACT

The conversion of bulk liquid into fine spray is very important nowadays in several

industrial process and has many application in agriculture, meteorology, and medicine.

So, the design to develop a fine spray nozzle was varies according to the application.

However, new development in fine spray nozzle have been achieved and implement

better than fine spray nozzle from Halton Group Asia Sdn. Bhd. Currently, the nozzle

from Halton Group used are produce in bulk liquid condition. The improvement that

make are the nozzle use low pressure with very fine water spray. This research was

focused on comparison for fine spray nozzle between simulation and experimental. The

observation focused on flow characteristic that produce by mist spray. Multiphase

nozzle were used with air and water as a medium . Six pressure inlet different are used

during the experiment. They are 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 bar. They are three type of

nozzles been tested Nozzle A, Nozzle B and Nozzle C. Nozzle A have eight air inlet slot

which give a better performance compared to other nozzles. The result evaluated from

this experiment are spray angle and the penetration. Nozzle A was sprayed with 3.0 bar

of water and air pressure. Mass flowrate for this pressure are 5.67x10-3

kgs-1

for water

and 2.698x10-4

kgs-1

for air. The angle of spray between experimental and simulation are

35.54° and 33.5° respectively. As a result, the percentage of similarity are 94.26%. High

speed camera are used to visualize the result an the software were used to simulate the

fine spray ANSYS FLUENT version 14.5. By using fine spray technology, it can trap

dust and small particle in air inside kitchen hood more effective and can consume less

water.

v

ABSTRAK

Pada masa sekarang, proses penukaran cecair kepada semburan halus amat penting di

dalam beberapa proses industri dan aplikasinya banyak di dalam aplikasi pertanian,

meteorologi dan perubatan. Maka, reka bentuk nozzle semburan halus berbeza mengikut

aplikasinya. Walau bagaimanapun, sebuah nozzle semburan halus telah dibina semula

bagi menambah baik nozzle milik Halton Group Asia Sdn Bhd. Nozzle milik Halton

hanya menghasilkan semburan kasar. Penambah baikkan yang dibuat adalah nozzle

tersebut menggunakan tekanan udara yang rendah untuk menghasilkan semburan halus.

Fokus untuk kajian ini adalah bagi membandingkan nozzle semburan halus di antara

eksperimen dan simulasi. Nozzle ini merupakan jenis multiphase di mana air dan udara

digunakan. Enam jenis tekanan telah digunakan di dalam eksperimen ini. Ia adalah 0.5,

1.0, 1.5, 2.0, 2.5 dan 3.0 bar. Terdapat tiga jenis nozzle telah dikaji iaitu Nozzle A,

Nozzle B, dan Nozzle C dan Nozzle A yang mempunyai lapan slot masukkan udara

memberi prestasi yang lebih baik dari nozzle yang lain. Keputusan yang telah diambil

adalah sudut semburan dan penembusan. Nozzle A telah menggunakan tekanan udara

dan air sebanyak 3.0 bar. Kadar alir jisim air yang dihasilkan adalah 5.67x10-3

kgs-1

dan

bagi udara pula adalah 2.698x10-4

kgs-1

. Sudut semburan di antara eksperimen dan

simulasi adalah 35.54° dan 33.5°. Hasilnya, peratusan persamaan adalah sebanyak

94.26%. Kamera halaju tinggi telah diguna untuk mendapatkan imej semburan dan

perisian yang digunakan untuk simulasi adalah ANSYS FLUENT versi 14.5.

Penggunaan teknologi semburan halus ini dapat memerangkap habuk dan partikel halus

udara di dalam hud dapur dengan lebih berkesan dan penggunaan air untuk bekalan

nozzle semburan halus juga dapat dijimatkan.

vi

CONTENT

TITLE i

CONFESSION ii

ACKNOWLEDGEMENT iii

ABSTRACT iv

ABSTRAK v

CONTENT vi

LIST OF TABLE x

LIST OF FIGURE xi

CHAPTER 1 INTRODUCTION 1

1.1 Background of study 1

1.2 Problem Statement 2

1.3 Objectives 2

1.4 Scope of Study 2

1.5 Significant of Study 3

CHAPTER 2 LITERATURE REVIEW 4

2.1 Atomization 4

2.1.1 Droplet Size Classification 5

2.1.2 Factors of Droplet Size 6

2.1.3 Small Droplets Increase Drift 6

2.1.4 How to Reduce Drift 7

2.2 Nozzle 8

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2.2.1 Flow Principle 8

2.2.2 Techniques for Spray Production 9

2.2.3 Spray Pattern 10

2.2.3.1 Full Cone Pattern 10

2.2.3.2 Flat Jet Spray Pattern 13

2.2.3.3 Hollow Cone Spray Pattern 15

2.3 Fugitive Emissions to air and Odor 17

2.4 Comparison of Droplet Size with Other Parameters 17

2.4.1 Effect of Droplet Size with Pressure 17

2.4.2 Effect of Droplet Size with Flow Rate 18

2.4.3 Effect of Spray Inclination Angle with Injection 19

Area and Axis Length

2.4.4 Effect of Injection Pressure and the Number of 20

Inlet Slot on Spray Cone Angle

CHAPTER 3 METHODOLOGY 21

3.1 Introduction 21

3.2 Experimental procedure 24

3.2.1 Apparatus and equipment 24

3.2.2 Schematic diagram for experimental setup 28

3.2.3 Experimental setup procedure 28

3.2.4 Experimental for spray pattern procedure 31

3.3 Mass flowrate calculation 31

3.4 Modelling and simulation 32

3.4.1 Internal domain design geometry for fine spray 32

nozzle and spray chamber

3.4.2 Computational fluid dynamics 33

CHAPTER 4 RESULTS AND DISCUSSION 38

4.1 Introduction 38

viii

4.2 Multiphase volume of fluid (VOF) 39

4.3 Results of spray pattern within experimental and 40

simulation

4.3.1 Comparison for nozzle A at 0.5 bar 40






4.3.7 Comparison for nozzle B at 0.5 bar 48






4.3.13 Comparison for nozzle C at 0.5 bar 56






4.4 Discussion 64

4.4.1 Effect of pressure with Angle of Attack Between 64

Experimental and Simulation

4.4.2 Effect of Nozzle Geometry with Spray 66

CHAPTER 5 CONCLUSION AND RECOMMENDATION 69

5.1 Conclusion 69

ix

5.2 Recommendation 70

REFERENCES 71

APPENDIX 74

x

LIST OF TABLE

TABLE TITLE PAGE

2.1 Spray droplet and distance traveled 7

4.1 Mass flowrate for water and air inlet of nozzles 39

xi

LIST OF FIGURE

FIGURE TITLE PAGE

2.1 Atomization 4

2.2 Categories of spray droplet size in micron 5

2.3 Flow principle for nozzle 9

2.4 Standard full cone 11

2.5 Spiral full cone (deflection nozzle) 12

2.6 Multiple full cone (turbulence nozzle, air atomizer) 13

2.7 In flat jet (pressure nozzle) 14

2.8 Spoon flat jet (deflection nozzle) 15

2.9 Hollow cone (turbulence nozzle) 16

2.10 Hollow cone (deflection nozzle) 16

2.11 Relationship between droplet size and pressure of nozzles 17

2.12 Drop size and spray flow rates for exit orifice diameters of 0.2 and 18

0.3mm at two supply pressures and with variation of spill orifice

diameter

2.13 The relation of spray inclination angle with axis length of spray 19

injection zone and spray injection area

2.14 Effect of injection pressure and the number of inlet slot on spray 20

cone angle

3.1 Experimental flowchart 22

3.2 Modelling flowchart 23

xii

3.3 High speed camera 24

3.4 Air compressor 25

3.5 Holder 25

3.6 Water tank pressure 26

3.7 Water flowrate 26

3.8 Pressure gauge 27

3.9 Schematic diagram of experimental set-up 28

3.10 Grid background 29

3.11 Water and air tube setup 29

3.12 Location for nozzle high speed camera 30

3.13 Camera focusing on nozzle and grid background 30

3.14 Design for nozzle A 33

3.15 The flow of components in ANSYS Fluent 34

3.16 Internal domain for fine spray nozzle 35

3.17 Meshing 36

4.1(a) Experimental result for Nozzle A at 0.5 bar 40

4.1(b) Simulation result for Nozzle A at 0.5 bar 41

4.1(c) Spray for nozzle A at 0.5 bar 41










xiii







4.7(a) Experimental result for Nozzle B at 0.5 bar 48

4.7(b) Simulation result for Nozzle B at 0.5 bar 48

4.7(c) Spray for nozzle B at 0.5 bar 48
















4.13(a) Experimental result for Nozzle C at 0.5 bar 56

4.13(b) Simulation result for Nozzle C at 0.5 bar 56

4.13(c) Spray for Nozzle C at 0.5 bar 57

xiv
















4.19 Graph pressure versus angle of attack for Nozzle A, Nozzle B, and 65

Nozzle C

4.20 Angle of attack at pressure 3.0 bar for (a) Nozzle A 35.54°, (b) Nozzle 67

B 32.24° and (c) Nozzle C 30.62°

4.21 Velocity vector at 3.0 bar for (a) Nozzle A, (b) Nozzle B 68

and (c) Nozzle C

1

CHAPTER 1

INTRODUCTION

1.1 Background of study

The transformation of bulk liquid into sprays and other physical dispersions of small

particles in a gaseous atmosphere is importance in several industrial processes and has

many other application in agriculture, meteorology, and medicine. Numerous spray

devices have been developed, and they are generally designated as atomizers or nozzles.

Many experimental and theoretical studies about the atomization method have been

carried out since the atomizer was used in the diesel engine in 1892 [1].

The importance of drop size for many combustion and industrial processes that

utilize liquid sprays is attested to by the proliferation of techniques available for drop

size measurement. No single technique is completely satisfactory but each technique has

its own advantages and drawbacks, depending on the application. Direct methods

include those in which individual drops are collected on slide for subsequent

measurement and counting or in which droplets are frozen and sized as solid particles.

With the impaction methods the drop are sorted on the basis of inertial differences.

Depending on its size, a droplet may impact or fail to impact on a solid surface or may

follow a different trajectory. This allows all the drops in a spray to be sorted into

different size and categories.

The conversion of bulk liquid into fine spray is very important nowadays in

several industrial process and has many application in agriculture, meteorology, and

medicine. So, the design to develop a fine spray nozzle was varies according to the

application. However, new development in fine spray nozzle have been achieved and

2

implement better than fine spray nozzle from Halton Group Asia Sdn. Bhd. Currently,

the nozzle from Halton Group used are produce in bulk liquid condition. The

improvement that make are the nozzle use low pressure with very fine water spray. This

research was focused on comparison for fine spray nozzle between simulation and

experimental.

1.2 Problem Statement

Currently, majority of the users using the spray nozzle that already sold in the market.

The spray nozzle that sold in the market has a weakness such as need high pressure and

more water consumption. Using high pressure mean consume more energy usage, using

more volume of water mean the droplet size of water still large and the nozzle need

modification.

Thus we need is to produce a better type of nozzle. We need to produce the

nozzle that use low pressure with very fine water spray. Nowadays, the industrial

produce many types of spray nozzle for example air assist, air blast, rotary and pressure

atomizer. This types of nozzle have different shapes and various form of pressure

atomizer but still using a high pressure and a larger droplet size. Further research must

be done in this field to improve the spray nozzle.

1.3 Objectives

1. To observe flow characteristic that produce by mist spray.

2. Analysis flow visualization inside the nozzle.

3. Validation on mist spray between the experiment and simulation.

1.4 Scope of Study

1. Experiment have been conducted with water and air pressure 0.5, 1.0, 1.5, 2.0,

2.5, dan 3.0 bar .

2. Water were used as liquid agent.

3

3. Simulation analysis using ANSYS software.

4. Material for the nozzle is stainless steel.

5. Three different nozzle will be tested which have 4, 8 and 6 air flow holes.

6. The fine spray nozzle was followed the act of treatment of aerosol Section 2.2.4

and 2.2.6 of SGN 5.06

1.5 Significant of Study

1. Many new technologies that relate with fine spray will be developed.

2. Low pressure to produce fine spray will consume less energy require by the

system thus it reduce the cost [3].

4

CHAPTER 2

LITERATURE REVIEW

2.1 Atomization

Atomization is the process of generating drops and it begins when liquid was forcing

through a nozzle. The causes of the liquid to emerge as small ligaments when the

potential energy of the liquid (measured as liquid pressure for hydraulic nozzles or liquid

and air pressure for two-fluid nozzles) along with the geometry. Drops, droplets or

liquid particles as shown in Figure 2.1 happens when these ligaments then break up

further into very small pieces.

Figure 2.1 : Atomization [1]

This range is referred to as a drop size distribution when each spray provides a range of

drop sizes. The breakup of a liquid as it emerges from an orifice is a simple explanation

of this process. Various spray nozzles produce various spray patterns such as hollow

cone, full cone, flat spray and others when it have different shaped orifices. It will vary

significantly from one type to another and the drop size distribution will be dependent

5

on the nozzle type. The drop size also was affected to the factors such as the liquid

properties, nozzle capacity, spraying pressure and spray angle.

During the last decade, the importance of drop size information has increased

considerably. Information for effective use was important to the many spray applications

such as evaporative cooling, gas conditioning, fire suppression, spray drying and

agricultural spraying [1].

2.1.1 Droplet Size Classification

The size of the spray droplets created during an application plays a crucial role efficacy

of the application. Diameter is the measurement for spray droplets and micron (1 micron

equal to 0.0001cm) was used for the unit of measurement. Smallest to the largest is a

range of droplet sizes. It is referred to as the categories of droplet size when the nozzle

produce this range of droplet sizes. The best method for achieving a specific droplet size

with application are to categories the droplet size [6].

Figure 2.2: Categories of spray droplet size in micron [5]

6

2.1.2 Factors of Droplet Size

According to the following factors, the size of droplets sprayed from a spray nozzle was

varies [9].

1. Types of nozzles: Full cone type nozzles produce smaller droplets than flat spray

types even the pressure and flowrate inlet are the same. The former that produced

the diameter of droplets can sometimes be several times smaller than those

produced by the latter.

2. Pressure: The smaller droplets was appeared when pressure increase at inlet. For

example, a spray nozzle that produces droplets of 1,000 microns at 1Mpa will

produce much smaller droplets (of several tens of microns) if pressure is

increased to 10MPa.

3. Flow rate: The smaller droplets was appeared when the value flow rate are

reduced. For example, a spray nozzle that delivers very small volume of liquid,

such as 10ml/min, produces droplets of several tens of microns. A spray nozzle

that delivers high volumes of liquid, such as 1,000 l/min, produces (at the same

pressure) droplets of several thousands of microns. When flow rate is increased

or decreased droplet diameter can, therefore, be several hundred times greater or

smaller.

4. Fluid: Two mixed fluids (including gas) sprayed by a nozzle can produce far

finer droplets than a nozzle that sprays only liquid. Furthermore, droplet size can

be reduced if the gas flow rate of the former spray nozzle is increased. Normal

nozzles that spray two mixed fluids normally produced the mean droplet

diameter several tens of microns.

2.1.3 Small Droplets Increase Drift.

The potential for evaporation, drift, canopy penetration, and deposition of the spray

particles need to be considered even atomizing is the spray solution into very small

droplets that increased the coverage possible. Drift is the greater risk to the smaller

7

droplet. As shown in Table 2.1, 1 inch in less than one second was traveled by a 20

micron droplet before the water droplet evaporates.

It reach a horizontal trajectory in a very short time and evaporate rapidly when

droplets less than 100 microns in size. Rather than reaching the target, the pesticide

contained in these water droplets become very small aerosols, which remain in the air

until picked up in falling rain. Because of their large surface area, droplets over 150

microns in size resist evaporation much more than smaller droplets. Therefore, when the

diameter of droplets is increased to about 150 microns, the potential for drift rapidly

decreases [10].

Table 2.1: Spray droplets and distance traveled [10].

2.1.4 How to Reduce Drift

1. Select a nozzle that produces coarse droplets: To provide necessary coverage,

use droplets that are as coarse as practical.

2. Use the lower end of the pressure range: Many more small droplets (less than

100 microns) was generated by a high pressure generate. Do not exceed 40 to 45

psi under most conditions.

3. Lower boom height: Height was increases with wind speed. Off-target drift is

reduced if boom height is a few inches lower.

8

4. Increase nozzle size: Drift was reduced by a larger capacity of nozzles. Increase

to nozzles that put out 15 to 20 GPA if the nozzles that output 10 to 15 gallons

per acre (GPA).

5. Spray when wind speeds are less than 10 m.p.h.: The increases of wind will

make a spray move off-target.

6. Spray when wind is moving away from sensitive crops: If sensitive plants are

downwind, leave a buffer zone. When the wind changes direction, spray the

buffer zone.

7. Do not spray when the air is very calm: Spray can move slowly downwind

during calm air, or an inversion and reduces air mixing. Early morning or near

bodies of water generally inversions generally occur.

8. Use a drift control additive when needed: Average droplet size produced by

nozzles increased when using the drift control additives.

2.2 Nozzle

A device which makes use of the pressure energy of a liquid to increase its speed

through an orifice and break it into drops called as a nozzle. Most important physical

aspects firstly an overview of the of the internal flow through a nozzle will be given. The

definition of at least two phases are requirement for the multiphase simulation of nozzle

flow which is liquid and vapourization, and eventually air for the boundary conditions in

the atmosphere [4].

2.2.1 Flow Principle

Tight control of drop size and spray coverage was controlled by a high efficiency

nozzles. To achieve this very small drop size, a multi-stage atomization process must be

used as shown in Figure 2.3 [3].

9

1. Stage one : Primary Fluid Breakup

Behind the air guide, air and liquid combine. Primary atomization of the liquid stream

will be provide when the pressure drop across the air guide orifice.

2. Stage two : Secondary Fluid Breakup

Additional mechanical breakup happen when focused stream impacts the target bolt.

3. Stage three : Final Mixing

Air cap acts as a final mixing chamber. An additional, pressure drop provides the final

atomization after a liquid crosses multiple orifices.

Figure 2.3: Flow principle for nozzle [3]

2.2.2 Techniques for Spray Production

To produce a spray, many different techniques can be used. The following nozzle types

can be used in industrial applications to generate a liquid spray based on the different

techniques [8].

1. Pressure nozzles: This nozzle is the simplest type, where the liquid to be

sprayed is fed under pressure, an orifice is opened into a chamber. Spray pattern,

flow rate and spray angle produced through the orifice by a spray with depending

upon the orifice edge profile and the design of the inside pressure chamber.

2. Turbulence nozzles: The liquid moving towards the chamber preceding the

orifice is given a rotational speed component in these nozzles, so as to open up in

10

a conical shape as soon as it leaves the orifice edge because of centrifugal force.

The drops produced can be confined to the cone outer surface (hollow cone

spray) or be evenly distributed to fill the entire volume of the cone (full cone

spray based on the nozzle design and the technique used to generate the

rotational speed.

3. Impact nozzle: An impact of the liquid jet onto a properly designed surface will

produced if the desired spray shape is obtained. After leaving the nozzle edge,

the liquid jet is subsequently changed into a fluid lamina and then broken into

drops with the desired spray pattern.

4. Air assisted atomizers: By means of air assisted atomizers, working upon

various different principles, fine and very fine sprays can be obtained.

2.2.3 Spray Pattern

The shape of their spray pattern is the most basic distinguishing characteristic and there

are many types of spray nozzles. Determining the type of spray pattern required for a

particular operation is the typically beginning of nozzle selections [9].

2.2.3.1 Full Cone Pattern

The droplets are distributed into a volume which is limited by a cone in a full cone

spray, having its origin point at the nozzle orifice. In a large variety of industrial

processes this such spray pattern is commonly used, since it is the one which allows to

distribute in an even way the water flow onto a surface. To evenly spray cooling liquid

on a still surface, the full cone spray pattern is therefore useful, as a typical example.

Distribute liquid droplets within a certain volume is an another typical use, like for

example evenly distributing water droplets in the inside volume of a cooling tower

because of the wide number of processes performed by means of full cone nozzles.

Where the full cone spray pattern, or a pattern similar to a full cone one, is obtained by

different techniques, the original shape has evolved into a range of specialized types.

11

1. Standard full cone (turbulence nozzle)

Shaped vane placed at the nozzle inlet usually used by the nozzle as shown in

Figure 2.4, to give a rotational speed to the fluid flowing through the nozzle

because of the rotational speed of the fluid, water exiting the nozzle orifice is

subjected to centrifugal force and opens up in the shape of a full cone. The extent

of the angle of the cone is a function of both exit speed (created from the inlet

pressure) and the internal design of the nozzle. It can vary in practice from 15° to

120°. These nozzles can be also produced as square full cone nozzles, where the

square shape of the pyramidal spray is obtained by a special design of the outlet

orifice. Two important details have to be noted from the system designer when

using these type of nozzles is:

a) The spray angle is measured on the side of the square section

b) The square section of the spray rotates within the distance from the nozzle orifice

to the target area.

Figure 2.4: Standard full cone (turbulence nozzle) [9]

2. Spiral full cone (deflection nozzle)

The nozzle as shown in Figure 2.5 is not properly a full cone, but rather a

continuous liquid curtain evolving with the shape of a spiral inside a conical

volume. The disadvantage of a scarcely even distribution is compensated by an

exceptionally good resistance to plugging, which makes this nozzle the best

choice in those applications where safety or system reliability are the prime

concern. For example is firefighting systems.

12

Figure 2.5: Spiral full cone (deflection nozzle) [9]

3. Multiple full cone (turbulence nozzle, air atomizer)

The nozzle as shown in Figure 2.6 is used in two cases by refer their pattern, that

is:

a) When a wide spray angle is to be reached with nozzles which inherently can

only produce a narrow one, or in such cases where small size droplets and

rather high capacities are required. Therefore several nozzles are grouped in a

cluster with different spray directions: the resulting spray pattern occurs from

the additional group of single nozzle sprays and the droplet size of the spray

remains the same as one of single nozzle. It must be noted that a smaller

nozzle will normally make smaller drops as compared to a larger size nozzle

of the same type operating under the same conditions.

b) When it is necessary to obtain a wide angle jet using nozzles which

inherently deliver a limited angle spray. In the case of a wide angle air

atomizer, for example, the droplet distribution is obviously not homogeneous

and the result is rather a number of small angle sprays with different

directions, but still the liquid is atomized towards all the parts of the volume

to be treated.

13

Figure 2.6: Multiple full cone (turbulence nozzle, air atomizer) [9]

2.2.3.2 Flat Jet Spray Pattern

In a flat jet spray the liquid droplets are sprayed in the shape of a flat liquid layer, with

different thickness according to the principle used to generate the spray. A flat jet spray

nozzle serves the purpose of spraying onto a surface or an object moving in a transverse

direction with respect to the one of the jet surface, a typical example being the nozzles in

a car washing tunnel. The vast majority of flat spray nozzles used in the industry work

according to one of the following principles.

1. In line flat jet (pressure nozzle)

This is the general purpose flat jet nozzle as shown in Figure 2.7, where the

liquid enters the nozzle in line with the axis length and is fed to a pressure

chamber, from where it is ejected through the nozzle orifice. Flow value and

spray angle are determined respectively from the orifice cross section and the

orifice edge profile.

14

Figure 2.7: In line flat jet (pressure nozzle) [9]

2. In line straight jet (pressure nozzle)

These nozzles can be considered a special kind of flat jet nozzle, with naught

degree spray angle. They are designed to produce a sharp stable stream, with

powerful impact on a given point, and serve normally to perform cleaning

processes or to cut soft materials.

3. Spoon flat jet (deflection nozzle)

In this type of nozzle as shown in Figure 2.8, the liquid is fed under pressure to a

round outlet orifice, and then deflected onto a smooth profiled surface so as to

assume a flat jet shape. This sophisticated design is of advantage since it offers a

stronger jet impact using the same feed pressure. Higher efficiency comes from

the very little energy required to just change the direction of the liquid flow, this

being the only energy required to generate the flat jet.

15

Figure 2.8: Spoon flat jet (deflection nozzle) [9]

2.2.3.3 Hollow Cone Spray Pattern

A hollow cone spray pattern consists of droplets concentrated onto the outer surface of a

conical shape volume, with no droplets contained in the inside of the conical jet shape.

These nozzles are normally used for smoke washing or gas cooling applications in

several industrial processes.

1. Hollow cone (turbulence nozzle)

These nozzles as shown in Figure 2.9 use a tangential injection of liquid into a

whirling chamber to generate centrifugal forces which break up the liquid vein as

soon as it leaves the orifice. Precisely designed orifice profiles, making use of the

Coanda effect, provides the ability to obtain very large spray angles.

16

Figure 2.9: Hollow cone (turbulence nozzle) [9]

2. Hollow cone (deflection nozzle)

A hollow cone as shown in Figure 2.10 can also be obtained taking a liquid flow

to change direction onto a properly designed surface, in order to break the liquid

into droplets and distributing them as a hollow cone spray pattern. This kind of

nozzle is mainly used for applications in dust control and firefighting systems.

Figure 2.10: Hollow cone (deflection nozzle) [9]

17

2.3 Fugitive emissions to air and odor

Likely sources of fugitive emissions include open containers, storage areas, leaking

canisters, pipework and associated connections, seals on enclosed equipment, spillages,

washing activities, open conveyors and plant failures. Fugitive emissions to air may be

odorous, therefore preventing fugitive releases, by following the requirements in Section

2.2.4 and 2.2.6 of SGN 5.06 [24].

2.4 Comparison of Droplet Size with Other Parameters

2.4.1 Effect of Droplet Size with Pressure

The relationship between the droplet size (SMD and DV0.99) and the pressure is

presented in Figure 2.11. It is obvious that the values of SMD and DV0.99 decrease with

the increase in the pressure. In the range of p < 8 MPa, they decline obviously. When p

> 8 MPa, the further increase in the pressure has little effect on the size and distribution

of droplets. However, the droplet sizes increase slightly with the spray cone angle. The

reason may be that, the diameter of orifice increases due to the increase in spray angle

and then the decrease in axial velocity for the same flow rate. The diameter of droplet

depends on the relative velocity of droplet to air [15], so the water sheet at the nozzle

orifice disintegrates into much bigger droplets due to the much lower relative velocity.

Figure 2.11: Relationship between droplet size and pressure of nozzles [11]

18

2.4.2 Effect of Droplet Size with Flow Rate

Figure 2.12 summarizes a large body of experiments for two exit orifice diameters, 0.2

and 0.3mm, and for spill orifices from 0.2mm to 1.0mm in steps of 0.1mm. It is seen that

D32 <15μm is achieved at flow rates around 0.2 l/min for the 0.2mm exit orifice. In al

cases drop sizes are finer than for the modified commercial atomizers operating at

similar flow rates and pressures. It is clear that exit orifice diameter is important in

determining drop size at a given spray flow rate. However the 0.3mm exit orifice was

very much less liable to blockage than the 0.2mm orifice and thus the larger orifice was

used in most subsequent experiments. As can be seen in Figure 2.13, the SMD deceases,

as the spray flow rates increases. This is because at the higher spray flow rates for a

given supply pressure, the spill orifices are smaller so that there is an increase in the

axial velocity component of the liquid at the exit. In most applications that the authors

have reported separately [7, 16], flow rates around 0.2-0.3 l/min, and supply pressures of

9-12MPa have been used with exit orifice diameter 0.3mm and spill return orifice

0.5mm.

Figure 2.12: Drop size and spray flow rates for exit orifice diameters of 0.2 and 0.3mm,

at two supply pressures and with variation of spill orifice diameter. [12]

19

2.4.3 Effect of spray inclination angle with injection area and axis length

The relations of spray injection angle with axis length and the injection area are shown

in Figure 2.13. As the spray injection angle increases, the injection area and the longer

axis increase, but the shorter axis decreases. When the spray inclination angle is 0°, the

lengths of longer and shorter axis and the injection area are 51.6 mm, 49.8 mm, and

2018.2 mm2 respectively, which agree with the results obtained by Mudawar and

Estates [17]. As the spray angle increases, the transverse velocity of cooling medium

increases, and the residence time of the cooling medium decreases.

Figure 2.13: The relations of spray inclination angle with axis length of spray injection

zone and spray injection area [18].

20

2.4.4 Effect of injection pressure and the number of inlet slot on spray cone angle

The relationships between the numbers of inlet slots with spray cone angle for all

atomizers are shown in Figure 2.14. Atomizer A which has the most numbers of inlet

slots produces the widest spray cone angle while the atomizer with the least numbers

inlet slots produces the narrowest spray, which is in agreement with the work done by

[19]. This observation can be attributed to the fact that more inlet slot tends to increase

the azimuthal velocity inside the swirl chamber. However, the increment of spray cone

angle as the inlet slot number increased becomes less significant at lower injection

pressure. For example, the spray cone angle increases by only 5.4% as the inlet slot

number increased from 2 to 5 for an injection pressure of 2 bar, but increases by 10.7%

for an injection pressure of 8 bar. Furthermore, the variation of spray cone angle with

respect to injection pressure shows a almost linear trend for all atomizers at an injection

pressure below 6 bar. The graph also shows that an increasing injection pressure leads to

wider spray formation for each atomizer tested, which is in agreement with previous

works [20-22].

Figure 2.14: Effect of injection pressure and the number of inlet slot on spray

cone angle [23].

21

CHAPTER 3

METHODOLOGY

3.1 Introduction

The methodology of the whole research is outlined in Figure 3.1 and Figure 3.2,

focusing towards achieving the specified research goals. This chapter will describes the

methods used to carry out simulation and experimental for fine spray nozzle. ANSYS

FLUENT version 14.5 software will be used to make a simulation and high speed

camera will be used for experimental part to visualize the spray pattern. Simulation is

the way to show the characteristic of nozzle spray and experiments will be conduct in

the aerodynamics laboratory. All devices used for experiment and experimental

procedures were arranged sequentially. The research methodology will be further

discussed in this chapter.

22

Figure 3.1: Experimental flowchart

Set up the experiment

for fine spray nozzle

Test the fine spray

nozzle performance

Performance

approval

Record the video for

spray by using high

speed camera

Data analysis

Collecting data

Start

End

No

Yes

23

Figure 3.2: Modelling flowchart

Start

Geometry

Meshing

Boundary

condition

Solver

Post

processing

Data analysis

End

Result

No

Yes

24

3.2 Experimental procedure

There are a few steps must be ready before start the experiment. Firstly, identified every

single of the apparatus and equipment that need to used. Make a schematic diagram for

experimental setup as a first idea before move on into the real experiment. Finally, set

the procedure to get the spray pattern.

3.2.1 Apparatus and equipment

It is very important to know the function of all equipment that will be used to ensure that

equipment being used is suitable for experiments to be carried out. All equipment should

be in good condition and equipment operator must know how to operate the equipment

that will be used for experiments.

a) High speed camera

High speed camera are shown in Figure 3.3 was used for recording fast-moving

objects like an image of spray onto a storage medium. After recording, the

images stored on the medium can be played back in slow-motion. So, the particle

of spray droplet can visualize clearly.

Figure 3.3: High speed camera

http://en.wikipedia.org/wiki/Slow_motion

71

REFERENCES

[1] Arthur H. Lefebvre. Atomization and Sprays. Florida. Taylor & Francis Group.

1989.

[2] Mohd. Syazwan Bin Zulkipli. Development of a New Type of Sprayer Head of a

Water Mist System. Bachelor Thesis. Universiti Malaysia Pahang. 2012

[3] Spraying System Co. A Guide and Conditioning in Cement Manufacturing.

USA: Trade Brochure. 2004.

[4] Dipl. Ing Danielle Suzi. Diesel Nozzle Flow and Spray Formation: Coupled

Simulations with Real Engine Validation. Ph.D. Universitat Stuttgart. 2009

[5] Ikeuchi USA, Inc. Spray Nozzles Technical Information. Catalogue. 2008

[6] Scott Bretthauer. Spray Droplet Size Monitor. Retrieved on December, 2013,

http://web.extension.illinois.edu/ipr/i8793_829.html

[7] Nasr G.G., Yule A.J., Lloyd S.E., Whitehead A., Utilisation and Performance

Analysis of Fine Sprays for Disinfection within Healthcare, Proceedings of the

21st ILASS-EuropeConference, Turkey 2007.

[8] PNR. Spray Engineering Handbook. Europe. Commercial Catalogues. 2007

[9] Nozzle Network Co. Ltd. The World of Nozzles: Practical Edition Valuable Tips

on Selecting Nozzle. Retrieved on March, 2011,

http://www.nozzlenetwork.com/knowledge/know_practical_7.html

[10] Kansa State University State University Agricultural Experiment Station and

Cooperative Extension Service. United States. Commercial Catalogue. March

2000

http://web.extension.illinois.edu/ipr/i8793_829.html

http://www.nozzlenetwork.com/knowledge/know_practical_7.html

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[11] Liu Yinshui, Jiang Zhuo, Wang Dan, Li Xiaohui. Experimental research on the

water mist fire suppression performance in an enclosed space by changing the

characteristics of nozzles. 2014. 52 :174-181

[12] G.G. Nasr, A.J. Yule, S.E. Lloyd. The characterization of the spray from a new

fine spray spill return swirl atomizer. 2007. ILAAS

[13] Bjarne Paulsen Husted, Per Peterson, Ivar Lund, Goran Holmstedt. Comparison

of PIV and PDA droplet velocity measurement techniques on two high pressure

water mist nozzles. 2009. 44: 1030-1045

[14] Paolo E. Santangelo. Characterization of high pressure water mist sprays:

Experimental analysis of droplet size and dispersion. 2010. 34 :1353-1366

[15] S.P. Lin, R.D. Reitz, Drop and spray formation from a liquid jet, Annu. Rev.

Fluid Mech. 30 (1998) 85–105.

[16] Nasr G.G., Yule A.J., Lloyd S.E., The application of fine sprays for Chemical,

Biological, Radiological and Nuclear (CBRN) Decontamination, Proceedings of

the 21st ILASSEurope Conference, 2007, Turkey 2007.

[17] Mudawar, K.A. Estes, Optimizing and predicting CHF in spray cooling of a

square surface, Int. J. Heat Transfer 111 (1996) 672e679.

[18] T.L. Fu, Z.D. Wang, X.T. Deng, G.H. Liu, G.D. Wang, The influence of spray

inclination angle on the ultra-fast cooling of steel plate in spray cooling

condition, 2015. 78: 500-506.

[19] Hamid, A. H. A., Atan R., Noh, M. H. M., Rashid, H., 2011. Spray cone angle

and air core diameter of hollow cone swirl rocket injector. IIUM Engineering

Journal. Special Issue on Mechanical Engineering. 12, No 3.

[20] Hamid, A. H. A., Atan R. Spray characteristics of jet-swirl nozzles for thrust

chamber injector. Journal of Aerospace Science and Technology. 2009. 13,p

192-196.

[21] Yule, A.J., Widger, I. R . Swirl atomizer operating at high water pressure.

International Journal Mechanical Science. 1996. 38, no 8-9, pp 981-999.

[22] Halder, M.R., Dash, S.K., Som, S.K. A numerical and experimental investigation

on the coefficients of discharge and the spray cone angle of a solid cone swirl

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nozzle. Journal of Experimental Thermal and Fluid Science. 2004. 28, p 297-

305.

[23] Mohd Syazwan, Ahmad Hussein, Ow Chee Sheng, Zulkifli. Effect of inlet slot

number on the spray cone angle and discharge coefficient of swirl atomizer.

2012. 1781-1786.

[24] Environment Agency. Sector Guidance Note: Recovery and Disposal of

Hazardous and Non-Hazardous Waste. S5.06. 2013

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