Effect of Diluents on the Autoignition of Propane Mixtures Using a Rapid Compression Machine

Abstract

The autoignition process of different propane mixtures was studied to determine how the diluent choice (helium and argon/nitrogen) affects the ignition delay, the production of excited radicals, and the overall combustion process. An optically accessible rapid compression machine, high-speed camera, flame spectrometer, and numerical model were used to investigate the combustion process. The ignition delay times were measured at a wide range of compressed gas temperatures from 860 to 950 K, a compressed gas pressure of approximately 34 bar, and two equivalence ratios of 1.0 and 1.5. Chemiluminescence at wavelengths of 309, 555, 590, and 623 nm from the decay of excited radicals was detected during the autoignition process, and their respective intensities were measured and compared at various test conditions. A new kinetic model was built by combining reaction rates of excited radicals and species from the literature. The new model was validated against the measured ignition delay data of this work. The ig...