Critical concentration effects of nanoparticle on combustion involved into secondary atomization and micro-explosion for B/JP-10/SP-80 nanofluid fuel

Abstract

To increase the combustion heat of JP-10-based aviation fuel, boron nanoparticles (B NPs) and corresponding surfactant SP-80 was added into JP-10 to prepare the B/JP-10/SP-80 nanofluid fuel. However, critical concentrations of boron nanoparticle to influence the combustion performance involved into secondary atomization and micro-explosion have not been unveiled. This paper experimentally presented the combustion of B/JP-10/SP-80 nanofluid fuels containing the boron concentration of 0.25 ∼ 10.0 wt%. The combustion characteristics were achieved by investigating the combustion stages, effective burning rate, secondary atomization, micro-explosion, flame temperature, interior temperature of droplet, droplet lifetime, flame emission spectrum, morphology and size of the residues. Results show that at dilute concentrations the nanofluid fuels stably burned, and lastly took once micro-explosion till the depletion. While at dense concentrations, multiple secondary atomization and micro-explosions occurred during combustion. The critical nanoparticle concentration effect on the transition of combustion mode involved into secondary atomization and micro-explosion lies in the range of 2.5 ∼ 5.0 wt%, corresponding surfactant concentration of 1.25 ∼ 2.5 wt%. The addition of boron nanoparticle with high concentrations provides the porous / compact shell formed by boron agglomeration and melt bonding of B2O3 on the boron surface to promote the build-up and increment of pressure during the evaporation combustion of the JP-10, resulting in the occurrence of secondary atomization and micro-explosion. The secondary atomization and micro-explosion bring boron nanoparticles into the gaseous flame zone and to participate in the combustion, and thus much more combustion heat is released. The achieved combustion heat of boron nanoparticles feedbacks on the droplet, which increases the internal temperature of the droplet as well as the flame temperature. Although the effective burning rate of nanofluid fuel droplets decreased with the elevated boron concentration, the secondary atomization and micro-explosions greatly shortened the lifetime of the droplet by producing quantities of secondary droplets. The thermal feedback effect of the combustion flame was analyzed by coupling the flame temperature and the emission spectrum. Finally, the combustion routes involved into secondary atomization and micro-explosion were proposed to understand deeply the combustion behavior of B/JP-10/SP-80 nanofluid fuel.