Development of a direct fuel injector for a two stroke gasoline engine

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"I hereby declare that I have read this thesis and in my opinion

this thesis is sufficient in terms of scope and quality for

the award of the degree of Master of Engineering (Mechanical)"

Signature

Name of Supervisor

Date

Prof. Ir 1\zhar Abdul Aziz

BAHAGIAN A - Pengesahan Kerjasama*

Adalah disahkan bahawa projek penyelidikan tesis ini telah dilaksanakan melalui

kerjasama antara __________ dengan _________ _

Disahkan oleh: Tandatangan Nama Jawatan (Cop rasmi)

* Jika penyediaan tesis/projek melibatkan kerjasama.

Tarikh:

BAHAGIAN B - Untuk Kegunaan Pejabat Fakulti Kejuruteraan Mekanikal

Tesis ini telah diperiksa dan diakui oleh:

Nama dan Alamat

Pemeriksa Luar Technical Advisor Dr. Victor Chelliah Blok K, PSSS

Lots 3288 & 3289, Off Jalan Ayer Hitam Kawasan Perindustrian Bangi

Nama dan Alamat Pemeriksa Dalam I

Pemeriksa Dalam II (Tiada)

Nama Penyelia lain (jika ada)

43000 Kajang Selangor

Dr. Jamaluddin bin Md Sheriff Jabatan Termo Bendalir Fakulti Kejuruteraan Mekanikal UTM, Skudai

Disahkan oleh Timbalan Pendafta di Fakulti Kejuruteraan Mekanikal:

DEVELOPMENT OF A DIRECT FUEL INJECTOR FOR

A TWO-STROKE GASOLINE ENGINE

MAS FAWZI BIN MOHD ALI

A thesis submitted in fulfillment of the

requirements for the award of the degree of

Master of Engineering (Mechanical)

Faculty of Mechanical Engineering

Universiti Teknologi Malaysia

11

DECLARATION

I declare that this thesis entitled "Development of a Direct Fllel Injector for a

Two-stroke Gasoline Engine" is the result of my own research except as cited in the references. The thesis has not been accepted for any degree and is not concurrently

submitted in candidature of any other degree .

Signature

....

~

... .

Ma~l~~~'i'JMohd

Ali Name

DEDICATION

To my beloved family, friends

and to all mankind.

i\'

ACKNOWLEDGEMENT

ABSTRACT

A prototype pressure-swirl injector was designed to suit an arbitrary

two-stroke, gasoline direct injection engine requirement. A commercial computational

fluid dynamics software FLUENT was used as a tool to analyze the performance of

the conceptual design. A prototype injector was fabricated once the conceptual

design met the requirements. The fabricated prototype injector was then subjected to

a series of specification tests such as leak test, static flow rate test and discharge

coefficient test. A dedicated test rig was set up to evaluate the performance of the

prototype injector. The spray images at specified time frame were illuminated by

Nd:Y AG laser sheet and captured using a high-speed digital camera. The stored

images were analyzed to give data of spray angle, and droplet Sauter mean diameter

at fuel-air pressure differential ranging from 1.0 to 5.0 MPa, with a step size of 1.0

MPa. From the tests, the prototype injector static flow rate, half spray cone angle

and the droplet Sauter mean diameter at fuel injection pressure of 5.0 MPa was found

to comply with the outlined requirements, which are approximately 475 cc/min, 32°

and 19 11m respectively. Finally, the experimental data was compared with the

calculated data. It was found that the measured data of static flow rate, discharge

coefficient, and droplet Sauter mean diameter were higher than the computed data at

fuel-air pressure differential between 1.0 and 3.0 MPa. In contrast, the calculated

initial spray angle was overestimated by 3% at all tested fuel-air pressure

vi

ABSTRAK

Sebuah prototaip penyuntik tekanan-pusaran telah direkacipta untuk mencpati

kepcrluan sebuah enjin petrol dua lejang suntikan terus. Scbuah pcrisian komcrsial

pengkomputeran mekanik bendalir FLUENT telah digunakan scbagai alat untuk

menganalisa prestasi rekabentuk konsep tersebut. Scbuah prototaip telah difabrikasi

bilamana rekabentuk konsep tersebut memcnuhi kesemua kchendak yang telah

digariskan. Prototaip berkenaan kemudiannya melalui beberapa ujian spcsifikasi

sepcrti ujian kebocoran, ujian kadar aliran statik dan ujian pckali semburan. Sebuah

radas ujikaji khusus telah dibina untuk menilai prestasi prototaip tcrsebut. Imcj

semburan yang disinari dengan helaian laser Nd:Y AG pada ketika tertcntu telah

dirakam menggunakan kamera digital berkelajuan tinggi. Imej tersebut telah

dianalisa untuk mendapatkan data sudut semburan dan purata diameter Sauter titisan

pada beza tckanan bahanapi-udara dari 1.0 hingga 5.0 MPa dcngan kenaikan 1.0

MPa. Daripada ujian-ujian tersebut, prototaip tersebut telah mcnepati kehendak yang

telah digariskan iaitu kadar aliran statik sebanyak 475 cc/min, scparuh sudut

semburan bersaiz 32° dan purata diameter Sauter titisan bersaiz 19 flm. Akhir sekali,

data eksperimen berkenaan telah dibandingkan dengan data pengiraan yang telah

dibuat terdahulu. Didapati bahawa data cksperimen untuk kadar aliran statik, pckali

semburan, dan purata diameter Sauter adalah lebih tinggi daripada hasil pengiraan

pada beza tekanan bahanapi-udara diantara 1.0 hingga 3.0 MPa. Sebaliknya, data

pengiraan sudut semburan melebihi jangkaan sebanyak 3% pad a kesemua beza

CHAPTER

TABLE OF CO\TE\TS

TITLE

DECLARATION

DEDICATION

ACKNO\\,LEDGEl\IENT

ABSTRACT

ABSTRAK

TABLE OF CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF SYMBOLS

LIST OF ABBREVIA TIONS

LIST OF APPENDI CES

INTRODucnON

1.1 Problem Background

1.--1

Research Objecti\"es and Sc()pe

Importance of the Study and P(1tential Contributions

Contents of Thesis

'. :t

ii

iii

\"II

:xii

:x:xii

\'i i i

2 LITERA TURE REVIEW 7

2.1

Overview

7

2.2

Gasoline Direct Injection

7

2.3

Atomization Approach II

2.4

Pressure-swirl or Simplex Atomizer

14

2.4.1

Discharge Coefficient

16

2.4.2

Initial Spray Angle

19

2.4.3

Liquid Sheet Thickness

21

2.4.4

Mean Droplet Size

22

2.5

CFD Assisted Analysis

25

2.5.1

CFD Codes

26

2.5.2

Single-component Test Fluid 27

2.5.3

Internal Flow Calculation

29

2.5.4

Discrete Spray Prediction

32

2.6

Testing and Measuring Standard

33

2.7

Droplet Size Measurement

34

2.7.1

Spatial and Temporal Sampling

Techniques

36

2.7.2

Sample Size

37

2.7.3

Sampling Location

37

2.7.4

High-speed Photography

38

2.8

Summary

39

3 METHODOLOGY 41

3.1

Overview

41

IX

3.3

Determining Specific Requirements

..+4

3.3.1

Injector Duty Cycle

..+5

3.3.2

Injector Static Flow Rate

47

3.3.3

Spray Angle

49

3.3.4

Mean Droplet Size

50

3.3.5

Fuel Operating Pressure

5 I

3.3.6

Spray Pattern

52

3.3.7

Special Features

53

3.4

CFD Calculations

54

3.4.1

Eulerian Multiphase

55

3.4.2

Lagrangian Discrete Phase

59

3.5

Specification Test

63

3.6

Spray Performance Test

66

3.6.1

Basic Operation

68

3.6.2

High Pressure Fuel Pump

70

3.6.3

Laser Illumination

70

3.6.4

Droplet Size Analysis

71

3.6.5

Experiment Procedure

71

4 PROTOTYPE DEVELOPMENT

74

4.1

Overview

74

4.2

Initial Conceptual Design

74

4.2.1

The Nozzle

75

4.2.2

The Swirler 77

4.2.3

The Needle

78

4.3

Prototype Fabrication and Assembly

79

4.4

Leak Test

80

4.5

Prototype Evolution

81

4.5.1

Needle Evolution

83

4.5.2

Solenoid Evolution

84

4.5.3

Injector Driver Circuit Upgrade

86

4.5.4

Swirler Evolution

87

4.5.5

Nozzle Evolution

88

4.6

Final Design

89

5 RESULTS AND DISCUSSIONS 91

5.1

Overview

91

5.2

CFD Multiphase

92

5.3

CFD Discrete Phase

97

5.3.1

Free Spray

98

5.3.2

In-cylinder Spray

103

5.4

Static Flow Rate and Discharge

Coefficient

105

5.5

Spray Performance

108

5.5.1

Initial Spray Angle

109

5.5.2

Mean Droplet Size

109

5.6

Computational and Experimental

Comparison

110

5.7

SMD Prediction Approaches Comparison 115

6 CONCLUSIONS 118

Xl

6.2 Future Works 119

6.2.1 A Two-stroke ODI Engine

Performance Test 119

6.2.2 2D versus 3D Eulerian Multiphase

CFD Calculation 120

6.2.3 Effect of Fuel Temperature on

Atomization 120

6.2.4 Effect of Fuel Surface Tension on

Atomization 121

6.2.5 Liquid Sheet Thickness of a

Pressure-swirl Atomizer 121

6.2.6 Droplet SMD Prediction

Approaches - A Critical Review 122

6.2.7 In-cylinder Droplet SMD 123

6.2.8 Discrete Phase Prediction from a

Multiphase Calculation 124

REFERENCES 125

XII

LIST OF TABLES

TABLE NO. TITLE PAGE

2.1 Features comparison between several atomizing

techniques used in ODI applications (Liu, 2000) 14

2.2 Empirical correlations for mean droplet size generated by pressure-swirl atomizers (Lefebvre,

1989; Liu, 2000) 24

2.3 Factors affecting droplet size (Schick, 1997) 25

2.4 Some of the CFD codes used in the development

of two-stroke ODI engine 26

2.5 Test fluid properties at 293 K (ILemmon cl al.,

2005; 2Bauer, 2000) 28

2.6 Droplet size measurement techniques adapted from Chigier (1983), Lefebvre (1989), Williams

(1990), or Liu (2000) 35

2.7 Influence of sample size on the accuracy of

droplet size measurements (Lefebvre, 1989) 37

3.1 Engine platform specifications (Aziz cl al., 2005) 43

3.2 Flexible control strategy for the prototype injector 54

3.3 Conceptual injector specification for a 125 cc

two-stroke gasoline engine 54

3.4 Eulerian multi phase calculation setting 58

3.5 Inlet swirl intensity unit vector components 59

X 111

3.7 Free spray discrete phase calculation injection

inputs 61

3.8 In-cylinder discrete phase calculation setting 63

3.9 List of apparatus for static flow rate test 64

3.10 List of apparatus for performance test 67

4.1 Evolution of prototype injector components 82

4.2 Improvements and weaknesses of prototype

injector mark 0 to VI 82

4.3 A comparison of needle material and weight 84

4.4 Calculated specification of solenoid B 85

4.5 A maximum ratings comparison between Darlington transistor BDX53C and BDW42 (STMicroelectronics, 1999; ON Semiconductor,

2002) 86

5.1 Result analysis for static flow rate test 107

5.2 Measured spray half-cone angle,

e

(0) 109

5.3 Droplet SMD measurements result 110

5.4 Droplet SMD prediction approaches 115

xiv

LIST OF FIGURES

FIGURE NO. TITLE PAGE

l.1 Problems of two-stroke engine in comparison with similar four-stroke counterparts (Heywood,

1988; Blair, 1996; Stone, 1997) 2

2.1 Most important GDI developments in the past five decades (Iwamoto et al., 1997; Queiroz and Tomanik, 1997; Zhao et al., 1997; Houston and Cathcart, 1998; Brooke, 1999; Sogawa and Kato,

2001) 8

2.2 Enhanced version of Preussner et al. (1998) mixture formation mechanism system analysis

adapted for two-stroke engine application 10

2.3 (a) Cross-section of a GDI injector, (b)

geometrical region that has great influence on the spray characteristics, (c) volume of fluid of the tangential swirl slots, swirl chamber, and final

orifice 16

2.4 (a) Evolution of liquid spray structure with injection pressure (Lefebvre, 1989), and (b) Evolution of discharge coefficient and cone angle

for a pressure-swirl atomizer (Cousin et al., 1998) 17

2.5 Effect of several combinations of needle-tip shapes and swirl intensities on discharge

coefficient (Aziz and Ali, 2006c) 18

2.6 A sketch of three stages in LISA spray model

(Suh and Rutland, 1999) 19

2.7 Metric for spray cone angle determination using (a) imagery of backlit spray, and (b) spray waist diameter along with spray penetration (Zhao et

xv

2.8 Liquid sheet breakup nomenclature (Cousin and

Nuglisch,2001) 22

2.9 Representation of droplet sampling techniques:

(a) Spatial, and (b) Temporal (Schick, 1997) 36

3.1 Research methodology flow diagram 42

3.2 Cross-section of two-stroke compound-piston

gasoline engine (Aziz et al., 2005) 44

3.3 Seven important areas that constitute to a

pressure-swirl injector specification 45

3.4 Typical port timing of a two-stroke engine 46

3.5 Static allowable injection period for the prototype

step-piston two-stroke gasoline engine 46

3.6 Combustion chamber cross-section geometry 49

3.7 Theoretical optimum spray angle, 80PI 50

3.8 Mapping of Lefebvre (1983) droplet SMD

correlation for pressure-swirl atomizer 51

3.9 Exhaust emissions by various combination of combustion chamber configuration and injector

orientation (Sogawa and Kato, 2001) 53

3.10 (a) Volume of fluid of the tangential swirl slots, swirl chamber, and final orifice, and (b) 2D

swirling section of the calculated region 56

3.11 (a) Representation of fuel inlet vector entering needle seat passage from angled tangential slots, viewed from Nozzle Exit, and (b) boundaries of a

2D rotating region 57

3.12 2D domain for Eulerian multiphase calculation, (a) CINJ-0500, (b) CINJ-0600, and (c) MitslIbishi

GDI injector 59

3.13 In-cylinder calculation domain 62

3.14 Schematic apparatus setup for static flow rate test 64

xvi

3.16 Schematic apparatus setup for spray performance

test 68

3.17 Part of the dedicated spray performance test rig 69

3.18 Spray performance test procedure flow diagram 72

3.19 Five spatial droplet-sampling regions 73

4.1 Exploded isometric view of prototype injector

mark 0 (CINJ-0100) 75

4.2 Mapping of correlation between nozzle orifice diameter and static flow rate with a given discharge coefficient CD. The formula was obtained from Heywood (1988) where A is the

76 cross section area of the nozzle orifice

4.3 Injector assembly (CINJ-0100)

+

wire harness

+

o-ring 79

4.4 Injector assembly (CINJ-OI00) 79

4.5 Nozzle (PNZL-O 1 00) 80

4.6 Swirler (PSWL-O 1 00) 80

4.7 (Left) Needle (PNDL-OIOO), sub-assembly of

Nozzle

+

Swirler 80

4.8 (Left) sub-assembly of injector Body (CBDY-0100)

+

Solenoid (CSNDA0100), and Lock

(PLCK-0100) 80

4.9 (Left to right) CNDL-OIOO, CNDL-0200, and

CNDL-0300 84

4.10 (Left) PBDY-OIOO and PBDY-0101 85

4.11 (Left) Abdullah (2003) original injector driver

circuit, and upgraded driver circuit 87

4.12 (Left) PSWL-0100 and PSWL-0200 88

4.13 (Left) PNZL-OI00 and PNZL-0200 89

4.14 Schematic of injector mark VI (CINJ-0600) 90

xvii

5.1 Contour of fuel volume fraction at several pressure differentials for: (top to bottom)

CINJ-0500, CINJ-0600, and MitslIbishi GDI injector 93

5.2 Computed liquid sheet thicknesses, t f at several

pressure differentials 95

5.3 Computed initial spray angles,

e

at several

pressure differentials 96

5.4 Computed theoretical droplet SMD using Wang-Lefebvre correlation at several pressure

differentials 97

5.5 CINJ -0500 free spray at 0.5, 1.0 and 1.5 ms after SOl with pressure differential of 1.0, 3.0 and 5.0

MPa 99

5.6 CINJ-0600 free spray at 0.5, 1.0 and 1.5 ms after SOl with pressure differential of 1.0, 3.0 and 5.0

MPa 100

5.7 MitslIbishi GDI free spray at 0.5, 1.0 and 1.5 after SOl with pressure differential of 1.0, 3.0 and 5.0

MPa 101

5.S Spray images of a pressure-swirl injector at several time steps captured with a high-speed

camera (Kawahara et at., 2004) 102

5.9 Computed droplet SMD using Lagrangian

discrete phase approach 102

5.10 In-cylinder spray during compression stroke at

3333 RPM 103

5.11 In-cylinder spray during compression stroke at

6666 RPM 104

5.12 Graph of dynamic flow, Q" against injector pulse

width, PW 106

5.13 Measured droplet SMD 110

5.14 Computed and measured static mass flow rates 111

5.15 Computed and estimated liquid sheet thicknesses,

5.17

5. IS

6.1

Computed and mea\urcd drnpict S\ 1 D

A comparison or se\·cral dropict S\lD plctiicti(1n approaches

LOlliS I:nginl'l"ring optical accc\\ cn~inc (Lotu\ Engincering.20()(1)

\ '.; 11

1 1.~

II·!

LIST OF SYMBOLS English Symbols FN I Ie k krmx

lQ,dQ

ls,ds

-11

N

Cross-section area of final orifice [mm2 ]

Total inlet port area [mm2]

Cross-section area of wire [mm2]

Magnetic field [mTesla]

Discharge coefficient [-]

Spray angle correction factor [-]

Droplet mean diameter [!-lm]

Diameter of wire [mm]

Flow number, JilL /(M_{L PL)Q5} [-]

Current [A]

Collector current [A]

Turbulence kinetic energy [m2/s2]

Wave number of the dominant perturbation [-]

Length and diameter of final orifice [mm]

Length and diameter of swirl chamber [mm]

Mass flow rate [g/s]

No. of droplets [-]

Engine speed [RPM]

No. of turns (wire) [turns]

Pressure [MPa]

Total power dissipation [Watts]