Boron particle ignition in high-speed flow

Boron Particle Ignition in Secondary Chamber of Ducted Rocket

“…Increase of the total pressure intensified oxygen diffusion through the oxide layer but reduced the oxide vaporizing rate. It also leads to increased gas density, with the attendance opposite influence on tangential friction stress [15]. Similar effects on the ignition time at a fixed gas temperature and velocity as functions of total pressure and oxygen mole fraction are shown in Figure 6.…”

“…According to literature [15], the constant C 1 = 2.0 and the coefficient of surface tension σ = 0.01. We and Re can be expressed by where u r = U ∞ − W represents the relative velocity between gas flow and boron particles.…”

“…The change in the liquid oxide layer of boron particles due to aerodynamic shattering can be reduced: In the analysis below we resort to King's model, based on the assumption that the exothermic reaction between boron and oxygen takes place at the boron-boron oxide interface as a result of oxygen diffusion across the melting oxide layer [4,15]. As the oxygen converts the boron into boric oxide, thickens the oxide layer, and releases heat, the oxide simultaneously vaporizes at the outer surface, this second process is endothermic and reduces the heating rate.…”

“…Heat is added to or removed from the particle by convection and radiation, while inside the particle it is transferred by conduction from the surface to the center. Ignition occurs when the liquid oxide layer at the leading point of the particle is completely removed by the tangential friction stress effects [4,15].…”

“…Preheating of the boron particles in gas generator makes it possible to utilize the velocity difference between gas and particles in secondary chamber for removal of the liquid oxide layer with the aid of Stokes' forces. Povitsky and Goldman demonstrated there is indication of regime of fast ignition enhanced by Stokes' forces by experimentally and numerical simulation [15].…”