METHYLCYCLOHEXANE IGNITION DELAY TIMES UNDER A WIDE RANGE OF CONDITIONS Thesis Submitted to The School of Engineering of the UNIVERSITY OF DAYTON In Partial Fulfillment of the Requirements for The Degree of Master of Science in Mechanical Engineering By Aditya Nagulapalli Dayton, Ohio May 2015 METHYLCYCLOHEXANE IGNITION DELAY TIMES UNDER A WIDE RANGE OF CONDITIONS Name: Nagulapalli, Aditya APPROVED BY: _____________________________ _____________________________ Sukh S. Sidhu, Ph.D. Philip. H. Taylor, Ph.D. Advisory Committee Chairman Committee Member Division Head Group Leader Distinguished Research Engineer Distinguished Research Scientist Energy Technologies & Materials Division Environmental Engineering Group University of Dayton Research Institute University of Dayton Research Institute _____________________________ Moshan Kahandawala, Ph.D. Committee Member Group Leader Senior Research Engineer Bioenergy & Carbon Mitigation Group University of Dayton Research Institute ________________________ ________________________ John G. Weber, Ph.D. Eddy M. Rojas, Ph.D., M.A, P.E Associate Dean Dean, School of Engineering School of Engineering ii © Copyright by Aditya Nagulapalli All rights reserved 2015 iii ABSTRACT METHYLCYCLOHEXANE IGNITION DELAY TIMES UNDER A WIDE RANGE OF CONDITIONS Name: Nagulapalli, Aditya University of Dayton Advisor: Dr. Sukh. S. Sidhu During the last century, our dependence on oil has increased rapidly and is projected to increase for several decades. There is a critical need to improve the design of the combustion chamber for different kinds of engines to reduce fuel consumption. Chemical kinetics of the fuel plays an important role in reducing emissions and improving engine efficiency. Studying single components of a conventional fuel allows a fuller understanding of the physical and chemical behavior of the real fuel. Many studies have been conducted on all classes of hydrocarbons, with the exception of cycloalkanes. Only a few studies exist on cycloalkanes, which is an important class of hydrocarbons. Methylcyclohexane (MCH), which is widely used as a surrogate to represent the cycloalkane portion of a fuel, was chosen as the subject of this study. The shock tube is an established tool used for measuring the ignition delay, and was used as the experimental apparatus. Ignition delay was measured using the end-plate pressure rise, the OH* and CH* chemiluminescence and white light emission. iv In addition, experimental results were compared with kinetic modeling data using detailed MCH mechanisms developed by Pitz et al. and Orme et al. Different modeling approaches, such as constant volume and internal energy (with and without experimental pressure profiles) and constant pressure, were used to validate the models by comparing against experimental ignition delay data. It was observed that the equivalence ratio affects the ignition delay time. For the lower argon concentration (Ar = 93%) and higher pressure (P ~ 16 atm), ignition delay times were longest for rich conditions. Additionally, they were shorter at lower temperatures (T ≤ 1250 K) for stoichiometric conditions in comparison to lean values, but the opposite trend was observed at the higher temperatures (T > 1250 K). Ignition delay times of stoichiometric mixtures were longer than lean mixtures across the studied temperature range for low pressure (P = 2 atm) and argon concentration (Ar = 93%), as well as high pressure (P ~ 16 atm) and argon concentration (Ar = 98%). The Orme et al. model using the approach of constant U,V assumption with experimental pressure profile showed a better agreement with experimental results at low temperatures than the approach without experimental pressure profile. Both models and approaches underestimate the experimental ignition delay times at high temperatures. v DEDICATION Dedicated to Family and Friends vi ACKNOWLEDGMENTS I would like to express my sincere gratitude to my research advisor, Dr. Sukhjinder S. Sidhu, for his substantial support and motivation throughout my master’s work done at the Shock Tube Research Laboratory. Besides my advisor, I want to extend my earnest thanks to Dr. Moshan Kahandawala for his guidance, inspiration and efforts throughout my research work. I am indebted to the University of Dayton Research Institute for providing a stimulating environment, as well as the Air Force Research Laboratory for their generous support. Specifically, I would like to express my appreciation for the contract monitor of this project, Mr. Edwin Corporan. I consider it an honor to work on this project as a member of the Sustainable Environmental Technologies Group, and thank them for their continued support. The help of Dr. Saumitra Saxena and Mr. Giacomo Flora in their in-depth guidance and constant availability were of great value during this work. Thesis editing by Dr. Jeremy Cain is also greatly appreciated. Finally, this effort would have been incomplete without the encouragement and the abundant love of my parents, brother and friends. I thank them for their support and understanding during the long years of my education. vii TABLE OF CONTENTS ABSTRACT ....................................................................................................................... iv DEDICATION ................................................................................................................... vi ACKNOWLEDGMENTS ................................................................................................ vii TABLE OF CONTENTS ................................................................................................. viii LIST OF FIGURES .......................................................................................................... xii LIST OF TABLES .......................................................................................................... xvii LIST OF SYMBOLS ..................................................................................................... xviii LIST OF ABBREVIATIONS .......................................................................................... xix CHAPTER 1 ....................................................................................................................... 1 INTRODUCTION .............................................................................................................. 1 1.1 Background ............................................................................................................. 1 1.2 Ignition Delay Time ............................................................................................... 3 1.3 Shock Tube ............................................................................................................ 5 1.4 Methylcyclohexane ................................................................................................ 7 1.5 Current Study ....................................................................................................... 10 CHAPTER 2 ..................................................................................................................... 12 EXPERIMENTAL SETUP AND PROCEDURE ............................................................ 12 viii 2.1 Shock Tube Components ..................................................................................... 12 2.2 Operation of Shock Tube ..................................................................................... 17 CHAPTER 3 ..................................................................................................................... 20 CALCULATIONS ............................................................................................................ 20 3.1 End Plate Velocity Calculation ............................................................................ 20 3.2 Post-Reflected Temperature and Pressure Calculations ...................................... 22 3.3 Uncertainties of Post-Reflected Pressures and Temperatures ............................. 22 3.4 Calculation of the Uncertainties Using the Perturbation Method ........................ 23 3.4.1 Example of Uncertainty Propagation .......................................................... 24 3.5 Fuel Mixture Calculation ..................................................................................... 24 3.6 Fuel Mixture Preparation ..................................................................................... 26 CHAPTER 4 ..................................................................................................................... 27 RESULTS AND DISCUSSION ....................................................................................... 27 4.1 Overview of Results ............................................................................................. 27 4.1.1 Ignition Delay Correlation .......................................................................... 32 4.1.2 Uncertainty Analysis ................................................................................... 36 4.1.3 Modeling ..................................................................................................... 37 4.1.4 Modeling Approach .................................................................................... 38 4.2 Discussion ............................................................................................................ 39 ix 4.2.1 Ignition Delay Trends at Different Conditions ........................................... 39 4.2.2 Impact of Pressures, Equivalence Ratios