Combustion is a complex physical phenomenon that occurs under various temperature and pressure conditions. Depending on the combustion environment, the reaction pathways of fuels and oxidizers can differ, leading to the formation of different end products. Internal combustion engines and gas turbines typically operate under high temperature and high-pressure conditions. However, in the case of rocket exhaust afterburning, unburned hydrocarbons can undergo combustion in an extreme environment characterized by high temperatures but very low pressures due to the high altitude. Understanding the reaction kinetics in this unique environment is crucial as it can impact the efficiency of supersonic retro propulsion, particularly with regards to flame impingement on spacecraft surfaces. Validating chemical kinetic mechanisms with experimental data is essential for improving their predictive capabilities in both scenarios. This doctoral study aims to validate fuel oxidation mechanisms by providing targets such as ignition delay time, temperature profiles, and temporal evolution of multi-species concentrations under two types of extreme combustion environments: high-temperature/high pressure and high-temperature/low-pressure conditions. The experiments were conducted at the UCF shock tube facility using fixed/scanned wavelength laser absorption spectroscopy. The temperature range varied from 1100 K to 2400 K, and the pressure range from 0.25 atm to 10 atm. The fuels investigated include methane, acetylene, 1,3-butadiene, and three isomers of methyl butene. State-of-the-art reaction mechanisms were employed for chemical kinetics simulations to analyze reaction pathways, species sensitivity, and to compare different models. The findings of this research will assist modelers in refining their reaction mechanisms and improving the overall accuracy.


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Graduation Date





Vasu Sumathi, Subith


Doctor of Philosophy (Ph.D.)


College of Engineering and Computer Science


Mechanical and Aerospace Engineering

Degree Program

Mechanical Engineering


CFE0009689; DP0027796





Release Date

August 2026

Length of Campus-only Access

3 years

Access Status

Doctoral Dissertation (Campus-only Access)

Restricted to the UCF community until August 2026; it will then be open access.