universiti putra malaysia · 2018-04-09 · chemical mechanism for the 2-stroke engine to...

UNIVERSITI PUTRA MALAYSIA

MOHAMMAD IZADI NAJAFABADI

FK 2014 55

NUMERICAL AND EXPERIMENTAL STUDIES OF HOMOGENEOUS CHARGE COMPRESSION IGNITION ENGINE PERFORMANCE

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NUMERICAL AND EXPERIMENTAL STUDIES OF HOMOGENEOUS

CHARGE COMPRESSION IGNITION ENGINE PERFORMANCE

By


Thesis Submitted to the School of Graduate Studies, Universiti Putra Malaysia, in

Fulfilment of the Requirements for the Degree of Master of Science

February 2014

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Abstract of thesis presented to the Senate of Universiti Putra Malaysia

In fulfilment of the requirement for the degree of Master of Science

NUMERICAL AND EXPERIMENTAL STUDIES OF HOMOGENEOUS

CHARGE COMPRESSION IGNITION ENGINE PERFORMANCE

By


February 2014

Chairman: Nuraini Abdul Aziz, PhD

Faculty: Engineering

During the recent decade, an alternative combustion technology, known as

Homogeneous Charge Compression Ignition (HCCI), has shown the potential to

decrease both emissions and fuel consumption. In spite of its high fuel efficiency and

low NOx emission compared to diesel and SI engines, HCCI combustion has some

critical difficulties. The main difficulty of HCCI engine is the absence of any external

control of ignition timing. Finding the effects of different parameters on the ignition

timing is vital to be able to control HCCI engines. The focus of this study was to carry

out a detailed numerical and experimental investigation into the factors affecting HCCI

ignition timing in a 2-stroke gasoline engine. As the primary objective of this study, a

Computational Fluid Dynamic (CFD) model was developed coupled to a semi-detailed

chemical mechanism for the 2-stroke engine to investigate the effects of different

variables such as intake temperature, air to fuel ratio, scavenging efficiency, and

compression ratio on the ignition timing and emissions. As the second objective, effects

of different simulation parameters such as turbulence model, grid density, and time step

size were investigated to find the best method for simulation of considered engine. As

the final objective, validation of numerical results was carried out using experimental

study on the 2-stroke engine that was modified to operate in HCCI mode. Results

confirmed that k-ε RNG model was the best turbulence model for simulation of this case

study coupled to the time step size of 0.25 crank angle degree and the grid size of around

50,000 cells. Results also demonstrated that decreasing the intake temperature,

equivalence ratio, residual gasses, and compression ratio can significantly retard the

combustion timing and experimental results confirmed that this ignition retarding can

considerably increase the engine power and torque.

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Abstrak tesis dikemukakan kepada Senat Universiti Putra Malaysia sebagai memenuhi

keperluan untuk Ijazah Master Sains

KAJIAN BERANGKA DAN EKSPERIMEN UNTUK PRESTASI ENJIN

PENCUCUHAN MAMPATAN SUAPAN HOMOGEN

Oleh


Februari 2014

Pengerusi: Nuraini Abdul Aziz, PhD

Fakulti: Kejuruteraan

Sepanjang dekad baru-baru ini, satu teknologi pembakaran dikenali sebagai

pencucuhan mampat bercaj seragam (HCCI) telah menunjukkan potensi untuk

mengurangkan gas pelepasan dan penggunaan bahan api. Walaupun ia

mempunyai kecekapan bahan api yang tinggi dan pelepasan gas NOx yang

rendah berbanding enjin diesel dan enjin palam pencucuhan, pembakaran secara

HCCI mempunyai beberapa masalah kritikal. Masalah yang utama adalah

ketiadaan kawalan luaran pemasaan penyalaan. Mencari kesan-kesan daripada

parameter enjin yang berbeza terhadap pemasaan penyalaan adalah penting untuk

membolehkan mengawal enjin HCCI. Fokus tesis ini adalah untuk menjalankan

satu penyiasatan secara pengiraan terperinci dan eksperimen terhadap faktor-

faktor yang mempengaruhi pemasaan penyalaan HCCI pada enjin gas dua lejang.

Sebagai objektif utama kajian ini, satu model Dinamik Bendalir Komputeran

(CFD) dibangunkan dan ditambah kepada satu mekanisma kimia separa

terperinci untuk enjin dua lejang bagi menyiasat kesan-kesan pembolehubah lain

seperti pengambilan suhu, nisbah udara untuk bahan api, kecekapan menghapus-

sisa dan nisbah mampatan pada masa penyalaan dan pelepasan. Sebagai objektif

kedua, kesan-kesan berbeza parameter simulasi model pergolakan, grid

ketumpatan dan saiz masa langkah disiasat untuk mencari kaedah terbaik untuk

simulasi enjin tersebut. Sebagai objektif terakhir, pengesahan keputusan daripada

model pengiraan dijalankan menggunakan kajian eksperimen terhadap enjin dua

lejang yang diubah untuk beroperasi dalam mod HCCI. Keputusan mengesahkan

yang model k-ε RNG merupakan model pergolakan terbaik untuk simulasi kajian

ini dengan saiz masa langkah sebanyak 0.25 darjah sudut engkol dan saiz grid

sebanyak 50,000 sel. Keputusan juga menunjukkan bahawa pengurangan suhu

pengambilan, nisbah setara, sisa gas dan nisbah mampatan boleh melengahkan

masa penyalaan dengan ketara dan keputusan eksperimen mengesahkan yang

pelengahan masa penyalaan ini boleh meningkatkan kuasa dan tork enjin.

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ACKNOWLEDGEMENTS

First of all, I would like to thank my dear spouse, Fahimeh, for her love, warm-

heartedness and support she has demonstrated during the past two years it has taken me

to finalize this thesis. Furthermore I would also like to thank my parents for their

countless affection and support. I am grateful for the endless sacrifices they made for

me.

I would like to thank Dr. Nuraini Abdul Aziz who has supported me throughout my

thesis with her valuable guidance and knowledge. I could not have imagined having a

better supervisor for my Master study. Also special thanks to my supervisory committee

member, Associate Professor Ir. Dr. Nor Mariah Adam, for her encouragement and

helpful advice.

The author also acknowledges the support of Universiti Putra Malaysia under Research

University Grants (RUGS), Project No. 05-05-10-1076RU and Ministry of Higher

Education under Exploratory Research Grants Scheme (ERGS), Project Code:

ERGS/1/2012/TK01/UPM/02/5 for this research.

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I certify that a Thesis Examination Committee has met on 3 February 2014 to conduct

the final examination of Mohammad Izadi Najafabadi on his thesis entitled "Numerical

And Experimental Studies Of Homogeneous Charge Compression Ignition Engine

Performance" in accordance with the Universities and University Colleges Act 1971 and

the Constitution of the Universiti Putra Malaysia [P.U.(A) 106] 15 March 1998. The

Committee recommends that the student be awarded the Master of Science.

Members of the Thesis Examination Committee were as follows:

Mohd Sapuan b. Salit, PhD

Professor Ir.

Faculty of Engineering

Universiti Putra Malaysia

(Chairman)

Kamarul Arifin Ahmad, PhD

Associate Professor



(Internal Examiner)

Nur Ismarrubie bt. Zahari, PhD

Senior Lecturer



(Internal Examiner)

Md. Mustafizur Rahman, PhD

Associate Professor

Universiti Malaysia Pahang

Malaysia

(External Examiner)

NORITAH OMAR, PhD

Associate Professor and Deputy Dean

School of Graduate Studies


Date: 17 February 2014

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This thesis was submitted to the Senate of Universiti Putra Malaysia and has been

accepted as fulfillment on the requirement for the degree of Master of Science. The

members of the supervisory committee were as follows:

Nuraini Abdul Aziz, PhD

Senior Lecturer



(Chairman)

Nor Mariah Adam, PhD, PE

Associate Professor



(Member)

BUJANG BIN KIM HUAT, PhD Professor and Dean

School of Graduate Studies


Date:

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Declaration by graduate student

I hereby confirm that:

● this thesis is my original work;

● quotation, illustration and citations have been duly referenced;

● this thesis has not been submitted previously or concurrently for any other

degree at any other institutions;

● intellectual property from the thesis and copyright of thesis are fully-owned

by University Putra Malaysia, as according to the University Putra Malaysia

(Research) Rules 2012;

● written permission must be obtained from supervisor and the office of Deputy

Vice-Chancellor (Research and Innovation) before thesis is published (in the

form of written, printed or in electronic form) including books, journals,

modules, proceedings, popular writings, seminar papers, manuscripts,

posters, reports, lecture notes, learning modules or any other materials as

stated in the Universiti Putra Malaysia (Research) Rules 2012;

● there is no plagiarism or data falsification/fabrication in the thesis, and

scholarly integrity is upheld as according to the University Putra Malaysia

(Graduate studies) Rule 2003 (Revision 2012-2013) and University Putra

Malaysia (Research) Rules 2012. The thesis has undergone plagiarism

detection software.

Signature: ______________________ Date: 20 March 2014

Name and Matric No.: MOHAMMAD IZADI NAJAFABADI, GS31644

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Declaration by Members of Supervisory Committee

This is to confirm that:

● the research conducted and the writing of this thesis was under our

supervision;

● supervision responsibilities as started in the university Putra Malaysia

(Graduate Studies) Rules 20003 (Revision 2012-2013) are adhered to.

Signature: ___________________ Signature: ___________________

Name of Name of

Chairman of Member of

Supervisory Supervisory

Committee: Nuraini Abdul Aziz, PhD Committee: Nor Mariah Adam, PhD

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TABLE OF CONTENTS

Page

ABSTRACT ..................................................................................................................... ii ABSTRAK ....................................................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................... iv APPROVAL v

DECLARATION vii

LIST OF TABLES .......................................................................................................... xi LIST OF FIGURES ....................................................................................................... xii LIST OF ABBREVIATIONS ...................................................................................... xvi

CHAPTER........................................................................................................................ 1

1. INTRODUCTION .................................................................................................... 1

1.1 Background of the Study .................................................................................... 1

1.1.1 HCCI Concept ............................................................................................. 1 1.1.2 Gasoline HCCI Combustion Engines .......................................................... 2 1.1.3 2-Sroke HCCI Combustion Engine ............................................................. 4 1.1.4 HCCI Challenges and Proposed Solutions .................................................. 5

1.2 Significance of Study .......................................................................................... 7

1.3 Problem Statement .............................................................................................. 7

1.4 Research Scope ................................................................................................... 8

1.5 Objectives ........................................................................................................... 8

1.6 Thesis Organization ............................................................................................ 9

2. LITERATURE REVIEW ...................................................................................... 10

2.1 HCCI/CAI Engine............................................................................................. 10

2.1.1 2-Stroke HCCI Engine .............................................................................. 10 2.1.2 4-Stroke HCCI Engine .............................................................................. 14

2.2 Control of HCCI Combustion ........................................................................... 15

2.2.1 Mixture Dilution for HCCI Control ........................................................ 15

2.2.1 Changing Fuel Properties for HCCI Control ............................................. 19 2.2.2 Fast Thermal Management for HCCI Control........................................... 20 2.2.3 Direct Injection for HCCI Control ............................................................ 22

2.3 HCCI Modeling ................................................................................................ 23

2.3.1 Single-zone Thermo-kinetic Model ........................................................... 24 2.3.2 Multi-zone Models .................................................................................... 24 2.3.3 Full Integration of CFD and Chemical Kinetics Codes ............................. 26

3. MATERIALS AND METHODS .......................................................................... 27

3.1 Introduction ....................................................................................................... 27

3.2 Numerical Method ............................................................................................ 28

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3.2.1 Geometry and Grid Generation ................................................................. 29

3.2.2 Governing Equations and Solver Algorithm ............................................. 34 3.2.3 Wall Function ............................................................................................ 36 3.2.4 Chemical Reactions ................................................................................... 37 3.2.5 Dynamic Mesh........................................................................................... 42 3.2.6 Boundary and Initial Conditions ............................................................... 44

3.3 Experimental Method ....................................................................................... 45

4. RESULTS AND DISCUSSION ............................................................................ 50

4.1 Introduction ....................................................................................................... 50

4.2 Validation of Numerical Method ...................................................................... 50

4.2.1 Validation Based on the Experimental Data of the 2-stroke Engine ......... 50 4.2.2 Validation Based on the Dec Experimental Data ...................................... 52

4.3 Numerical Results ............................................................................................. 56

4.3.1 Grid Size Independence ............................................................................. 57 4.3.2 Time Step Size Independence ................................................................... 61 4.3.3 Effect of Different Turbulence models ...................................................... 65 4.3.4 Effect of Intake Temperature on Ignition Timing and Emissions ............. 67 4.3.5 Effect of Equivalence Ratio on Ignition Timing and Emissions ............... 71 4.3.6 Effect of Scavenging Factor on Ignition Timing and Emissions .............. 75 4.3.7 Effect of Compression Ratio on Ignition Timing and Emissions .............. 81

4.4 Experimental Results ........................................................................................ 85

5. CONCLUSIONS AND RECOMMENDATIONS ............................................... 88

5.1 Introduction ....................................................................................................... 88

5.2 Findings ............................................................................................................ 88

5.3 Recommendations and Future Works ............................................................... 90

REFERENCES .............................................................................................................. 91 APPENDIX A............................................................................................................... 101 BIODATA OF STUDENT .......................................................................................... 106 LIST OF PUBLICATIONS ........................................................................................ 107 PERMISSIONS............................................................................................................ 108

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