Thermal conductivity of colloidal suspensions of jet fuel and carbon-based nanoparticles and its effect on evaporation rate

Recent studies have shown that addition of nano-sized particles to liquid fuels could significantly enhance major combustion characteristics such as burning rate and ignition delay. Colloidal suspensions are known to have enhanced optical properties and thermal conductivity compared to neat liquids; however, in the case of colloidal fuels, the main mechanism responsible for such enhanced properties is not well understood. To better understand these phenomena, colloidal suspensions of jet fuel and different types of carbon-based nanomaterials (carbon nanoparticles, multi-walled carbon nanotubes, and graphene nanoplatelets) prepared at different particle loadings were experimentally tested for their thermal conductivities. Colloidal suspensions of nanotubes showed higher conductivity compared to that of graphene and nanoparticle. This could justify higher burning rate of these fuels. Furthermore, and to differentiate between the effects of thermal conduction and radiation, droplet evaporations tests were carried out on colloidal suspensions of carbon nanoparticle under forced convection and in the absence of any radiation source. It was found that the presence of nanoparticle in jet fuel initially increases evaporation rate. However, a reduction in evaporation rate was observed at higher concentration as a result of particles agglomeration.