Laminar Flame Speed Estimation from Experimental Data Using a Quasi-Dimensional Turbulent

125 Pages·2017·1.43 MB·English

by  Akash Desai

Clemson University
TigerPrints
All Theses Theses
12-2011
Laminar Flame Speed Estimation from
Experimental Data Using a Quasi-Dimensional
Turbulent Flame Entrainment Combustion
Simulation For Spark Ignition Engines
Akash Desai
Clemson University, [email protected]
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Recommended Citation
Desai, Akash, "Laminar Flame Speed Estimation from Experimental Data Using a Quasi-Dimensional Turbulent Flame Entrainment
Combustion Simulation For Spark Ignition Engines" (2011).All Theses. 1281.
https://tigerprints.clemson.edu/all_theses/1281
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Laminar Flame Speed Estimation from Experimental Data Using a Quasi-Dimensional
Turbulent Flame Entrainment Combustion Simulation
For Spark Ignition Engines

A Thesis
Presented to
The Graduate School of
Clemson University

In Partial Fulfillment
of the Requirements for the Degree
Master of Science
Mechanical Engineering

by
Akash Sanjay Desai
December 2011

Accepted by:
Dr. Robert Prucka, Committee Chair
Dr. John Wagner
Dr. Ardalan Vahidi

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ABSTRACT

The goal of this research is to develop a thermodynamic simulation of spark-
ignition engine combustion that uses a predictive burn-rate model. Previously done
thermodynamic engine simulations in MATLAB [1] [2] are based on a specified burn
rate model. Also, the effect of turbulence parameters on the rate of mass burn up is not
considered. A predictive burn rate model is necessary to study the effect of different fuels
on spark ignition engine combustion. The effect of laminar flame speed and turbulent
intensity on combustion is difficult to assess experimental due to the difficulty in the
measurement of these two variables. Thus, the aim of this simulation is to
thermodynamically model the spark ignition engine cycle taking into account the
turbulence parameters and their effect on the combustion process. The simulation can be
used for predictive studies of combustion of different varieties of fuels by calibration of
laminar flame speed, assuming the turbulent intensity to be a fuel-independent parameter.
The key parameters of interest are the turbulence intensity and laminar flame
speed. Both these parameters play a key role in controlling mass burn-up rate. The
simulation intends to calculate mass fraction burned profile and turbulence intensity from
a predictive combustion model based on the concept of turbulent flame entrainment and
diffusive burn-up [3] [4]. An empirical relation for laminar flame speed is used for
known fuel (gasoline) which can be later calibrated for variety of fuels. The simulation
calculates the mass fraction burned profile based on calculated cylinder pressure,
temperature and species concentration.

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The cylinder pressure and temperature predicted by the simulation match well
with the experimental data for the engine used for calibration. The MFB10, MFB50 and
MFB90 crank angle positions simulated by the predictive combustion model were
compared with those calculated from a commercially available engine thermodynamics
program (AVL Concerto) which is based on experimental data and were found within 5-
10% of each other. The turbulence parameters, laminar flame speed and the length scales
during combustion also showed results in accordance with those shown by previous
experiments / simulation [5].
The quasi-dimensional simulation is done in MATLAB for computational speed
and acceptable accuracy. Using MATLAB also makes inserting additional sub-models
easier to make the model more detailed and accurate. This simulation will serve as a
student guide to engine modeling and also can be used as a base for more advanced
simulations.

iii
ACKNOWLEDGMENTS

I would primarily like to acknowledge Dr. Robert Prucka of CU-ICAR. Without
his guidance and support, this research would not have been possible. His help during this
research and related courses has greatly improved my knowledge of the subject and I am
very thankful for that. I would also like to thank Dr. Wagner and Dr. Vahidi for their co-
operation during the final stages of the thesis.
My friends at Clemson University have given me a great deal of motivation and
support during my research work and I greatly appreciate their concern and kindness. I
would like to dedicate this thesis to my family. Without their encouragement, this thesis
would not have been possible. Thank you. Go Tigers!!
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TABLE OF CONTENTS

Page

TITLE PAGE .................................................................................................................... i

ABSTRACT ..................................................................................................................... ii

ACKNOWLEDGMENTS .............................................................................................. iv

LIST OF TABLES ......................................................................................................... vii

LIST OF FIGURES ...................................................................................................... viii

LIST OF SYMBOLS, SUBSCRIPTS AND ABBREVIATIONS ................................... x

CHAPTERS

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

1.1. Background ....................................................................................... 1
1.2. Thesis Outline ................................................................................... 3

2. THERMODYNAMIC MODEL DESCRIPTION ......................................... 4

2.1. Model Description and Assumptions ................................................ 4
2.2. Thermodynamic Analysis ................................................................. 5
2.3. Gas Exchange Model ........................................................................ 9
2.4. Turbulent Flow Model .................................................................... 10
2.5. Heat Transfer Model ....................................................................... 14
2.6. Combustion Model.......................................................................... 16
2.7. Method of Solution ......................................................................... 21

3. MATLAB SIMULATION OUTLINE ........................................................ 22

3.1. Simulation Framework.................................................................... 23
3.2. Simulation Inputs ............................................................................ 23
3.3. Simulation Output ........................................................................... 28

4. CALIBRATION OF MATLAB SIMULATION......................................... 30

4.1. Calibration Background .................................................................. 30
4.2. Description of Experimental Facility .............................................. 30
v
Table of Contents (Continued)
Page

4.3. Calibration of the Model ................................................................. 32
4.4. Validation of Calibration ................................................................ 34

5. VALIDATION OF SUB-MODELS ............................................................ 37

5.1. Introduction to Validation of Sub-Model ....................................... 37
5.2. Main Variables ................................................................................ 38
5.3. Gas Exchange Sub-Models ............................................................. 38
5.4. Turbulence Parameters.................................................................... 40

6. CONCLUSION ............................................................................................ 44

6.1. Conclusion ...................................................................................... 44
6.2. Future Work .................................................................................... 45

APPENDICES ............................................................................................................... 47

A: List of Programs ........................................................................................... 48
B: Sub-Models Used by Main Functions.......................................................... 49
C: Matlab Programs .......................................................................................... 50

REFERENCES ............................................................................................................ 110
vi
LIST OF TABLES

Table Page

3.1 Sample simulation inputs ............................................................................. 24

4.1 Engine geometry specifications ................................................................... 32

4.2 Valve timings (referenced to TDC of compression as 0o) ........................... 32

vii
LIST OF FIGURES

Figure Page

2.1 P-V diagram of SI engine showing phases of engine cycle ........................... 4
2.2 Zero-dimensional turbulent energy cascade model ..................................... 11
2.3 Schematic of turbulent flame propagation process ...................................... 17
3.1 Flowchart of the cycle simulation ................................................................ 23
3.2 Valve lift and discharge coefficient data ..................................................... 27
3.3 Flame geometry data .................................................................................... 28
3.4 Normalized flame area versus flame radius for pent roof combustion
chamber at different crank positions ...................................................... 29
4.1 Engine test cell at CU-ICAR........................................................................ 31
4.2 Measured and predicted pressure traces for GM 5.3 L
V-8 engine at 3000 RPM and spark at 22o BTDC ................................. 33
4.3 Predicted mass fraction entrained and burned profile
For GM 5.3 L V-8 engine at 3000 RPM and spark at 22o BTDC.......... 34
4.4 Measured and predicted pressure traces for GM 5.3 L
V-8 engine at 5000 RPM and spark at 35o BTDC ................................. 35
4.5 Predicted mass fraction entrained and burned profile
For GM 5.3 L V-8 engine at 5000 RPM and spark at 35o BTDC.......... 36
5.1 Predicted pressure trace for 5000 RPM (WOT) .......................................... 37
5.2 Predicted temperature trace for 5000 RPM (WOT) ..................................... 38
5.3 Mass flow rate through intake valve for 5000 RPM (WOT) ....................... 39
viii
List of Figures (Continued)

Figure Page

5.4 Mass flow rate through exhaust valve for 5000 RPM (WOT)..................... 40
5.6 Turbulence intensity (u)at 5000 RPM (WOT) .......................................... 41
5.7 Evaluation of turbulence length scales & L during combustion
stroke at 5000 RPM (WOT) ................................................................... 42
5.8 Laminar flame speed trace during combustion stroke
at 5000 RPM (WOT) ............................................................................. 43

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