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Elevated temperature and pressure laminar flame speed measurements of propane and n-heptane fuel blends were conducted using a Rapid Compression Machine-Flame (RCM-Flame) apparatus. Herein, the lack of experimental flame speed data at simultaneously high temperatures and pressures akin to practical combustion conditions is addressed. The RCM-Flame apparatus is validated against a larger constant volume combustion chamber (CVCC) and simulations using a propane-nitrogen-oxygen mixture at ambient temperature and different pressures, demonstrating high fidelity. Further experiments with an n-heptane-nitrogen-helium-oxygen mixture reveal agreement between experimental and simulated flame speeds at semi-elevated, post-compression conditions. Trials with a propane-helium-oxygen mixture over varied temperatures and pressures demonstrate measured flame speeds falling between two kinetic mechanism simulations, maintaining the general trend. A power-law model correlating laminar flame speeds with elevated temperatures and pressures is developed for propane-helium-oxygen flames at a unity equivalence ratio. Overall, the kinetic mechanisms are shown to be able to predict flame speeds at elevated temperatures and pressures providing validation at conditions not yet explored in literature, optimistically advancing combustion research for practical applications. 

The autoignition characteristics of ammonia (NH3) and dimethyl ether (DME) blends were examined in this research project. The study investigates the autoignition characteristics by measuring ignition delay times across a range of gas temperatures from 621 to 725 K and at pressures of 5, 10, and 20 bar by using a rapid compression machine (RCM). Ignition delays of NH3/DME blends, with DME concentrations in the fuel mixture ranging from 0 to 50%, were measured, simulated, and compared with JP-8 and JP-5 fuel ignition delays. At a pressure of 20 bar, blends containing 30 and 50% DME concentrations exhibited ignition delay times similar to those of JP-8 and JP-5. Furthermore, the fuel blend with a 30% DME concentration showed similar ignition delays at the lower pressures of 5 and 10 bar. Several kinetic models were used to model the autoignition and compared with the measured data. Simulation results fairly matched the measured ignition delays. Through rigorous experimental verification, this comprehensive analysis evaluated the reliability of existing chemical models and paved the way for further studies on customized fuel blends, thereby contributing to the ongoing debate on sustainable energy alternatives.