Experimental investigation of iron combustion in O2-containing mixtures of different diluent inert gases

This study investigated the combustion behavior of micrometric iron particles (45-53 µm) in 21% oxygen containing mixtures with various inert diluent gases, including nitrogen, argon, helium, and carbon dioxide. The iron particles were burned in an electrically-heated laminar flow drop tube furnace under conditions of high heating rates and high temperatures. The combustion process was captured by a high-speed camera and particle temperatures-time histories were measured by both a three-color optical pyrometer and an electronic camera. Combustion products were collected for further analysis using a multi-stage cascade impactor. The results revealed the effects of the inert diluent gases on particle combustion behaviors, such as peak temperature, combustion duration, and nanoparticle formation. Combustion of the iron particles in argon diluent resulted in the highest particle temperatures, followed by those in nitrogen, helium and carbon dioxide diluents. The largest amount of nanoparticles relative to the input iron mass was generated in argon (6%), followed by nitrogen (4.1%), then helium (2.8%) and, finally, carbon dioxide (0.6%). This significant change in nanoparticle formation occurred despite only limited changes in the peak particle temperature.