Ignition and combustion characteristics and agglomerate evolution mechanism of aluminum in nAl/JP-10 nanofluid fuel

Abstract

The ignition and combustion processes of concentrated nAl/JP-10 nanofluid fuel were studied by using a CO2 laser ignition system with online diagnosis, intermediate sampling, and offline analysis. The energy release properties of aluminum (Al) nanoparticles in droplets and the influence of oxygen content on agglomerate evolution were studied. The phase separation of liquid fuel and Al nanoparticles occurs during the combustion process of concentrated nAl/JP-10 nanofluid. The burning forms of Al nanoparticles within the droplet include local, splash out, and agglomerate burning. Among them, agglomerate burning is the primary form of energy release. During the combustion process, Al particles gradually form an Al agglomerate, and the oxidation reaction of Al nanoparticles mainly occurs after the diffusion flame disappears. Oxygen content has a significant effect on the agglomerate burning of Al nanoparticles. When oxygen content is > 10%, the Al particles are successfully ignited. When oxygen content reaches 50%, a deflagration of the agglomerate occurs, and the Al particles rapidly oxidize to completely release heat and form a dense alumina sphere.