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The constant volume combustion apparatus, known as the Ignition Quality Tester (IQT T M), is increasingly used around the world to measure the ignition delay (ID) of compression ignited fuels, and to calculate the derived cetane number (DCN) from correlations developed with the cetane number (CN). The IQT is widely used in research due to its capability to manipulate combustion controller parameters, including pressure, temperature, oxygen content and mass of injected fuel. Recently, the IQT has also been used to conduct experiments on fuels with a longer ID, such as gasoline. Most findings from I would like to greatly thank all people who either contributed to the work described with this thesis or to me personally during the working time on it. First and foremost, I would like to express my gratitude and appreciation to my supervisor professor Edgar A. Matida. His continuous support and guidance have demolished the difficulties toward gaining my PhD. I would like to acknowledge the Advanced Engine Technology (AET) Ltd. for allowing me to use their facilities and dedicating an IQT to do my research. The AET staff was wonderful and generous in providing everything for my research. I must thank Mr. Gary Webster, the principal of the AET for the opportunity to work in his laboratory, may he rest in peace. I also want to appreciate the unlimited technical support during experimental work from Luc Menard, Omar Ramadan, Dave Gardiner, and Aaron Wilcox. Without a scholarship from my home country Iraq, it was impossible to achieve this work. I hope all progress and prosperity to my country and peace to all people there. Many thanks to all friends for their emotional supports and invaluable advises. Their encouragement during difficult times of my study has inspired me and made me more productive. Finally, I dedicate this thesis to my family; my beloved mother and father whose love continues as long as my heart is beating, my lovely wife for always standing by me and my kids, my elder brothers Assim and Yasir with respect, and to all other brothers and sisters.

An experimental work has been conducted to investigate the ignition of n-heptane in the ignition quality tester (IQT TM) by using fine gage thermocouples. A set of eight buttwelded exposed junction thermocouples (TCs) were inserted inside the chamber of IQT TM at different preselected locations to get the temperature variation spatially and temporally in the period prior to the fuel injection up to the mixture ignition. The data were recorded by using a high frequency data acquisition system with a sampling rate of 10 kHz per channel. The experimental data were characterized at set point temperature 584 o C and pressure 21.3 bar. For reproducibility purposes, 32 injections have been averaged and presented. A drop in temperature due to fuel spray cooling effects has been recorded by TCs at the chamber centerline whereas TCs near the chamber walls did not show a significant drop in temperature. Thus, there was no evidence that the fuel spray reached the chamber walls. The measurements showed that the combustion occurs in the main part of the chamber and the region near the fuel injector nozzle did not show a significant rise in temperature.

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