Combustion of Granulated Ti–C Blends: Influence of Granule Size

Effect of the Content of Polyvinyl Butyral on the Synthesis and Phase Composition of Products of Combustion of Ti–Cr–C Granular Mixtures

“…Another mechanism of combustion in granular systems with a flow of filtered gas is convective, as was first observed during the combustion of Ti + C in a cocurrent flow of nitrogen [20] and then detected without an external gas flow [21]. It was shown that in the convection mode, a hot flow of active gas (in our case, products of the decomposition of PVB) not only heats the surfaces of granules but ignites them as well, ensuring a higher combustion front velocity than indicated by calculations based on TFC and observed in an inert gas flow.…”

“…Since the heat of hot DP of PVB (T g − T ig )Uρ b c g is spent on heating the surface layer of granules from the initial temperature to that of ignition (T ig − T 0 )Uρ s c s × 3h*/r, the following balance relation takes place in a stationary combustion wave: (6) where T g is the temperature of the hot gas; T 0 is the initial temperature of the granular mixture; T ig is the temperature of ignition; U is the speed of the combustion front; and h* is the thickness of the surface layer of a granule that the DP of the PVB flow can heat to the temperature of ignition. As in [20,21], the temperature of the α → β transition in titanium T ig = 1155 K was taken as the temperature of ignition when calculating h*. Substituting parameters ρ b /ρ s and c s into expression (6) for mixtures in Tables 2 and 3 at temperatures T g = T ad and T 0 = 293 K, and assuming that c g ≈ 2500 J/(kg K), we obtain an estimate of h*.…”

“…Let us compare the rate of burning of this mixture that of a Ti + C mixture diluted with nickel 80% (Ti + C)/20%Ni (wt.) [21]. Note that in [21], the same titanium and soot powders were used to prepare the initial charge, and granules of the 0.63-1.6 mm fraction formed upon adding a 4% PVB solution in ethanol, as granules in the mixture 3A in this work.…”

“…[21]. Note that in [21], the same titanium and soot powders were used to prepare the initial charge, and granules of the 0.63-1.6 mm fraction formed upon adding a 4% PVB solution in ethanol, as granules in the mixture 3A in this work. We found that these mixtures burn at almost the same speed.…”

Combustion of Powdered and Granulated 5Ti + 3Si Mixtures: Impact of Reagents’ Particle Size

“…The latter circumstance makes the retarding effect of impurity gases less pronounced when the combustion front spreads over the granule. When conditions (1)-( 2) for Ti particles are not met, granulation reduces U because of the delay of combustion transfer between the granules [7]. Indeed (see Table 1), the U values for granules 1, 3, 6, 7, and 8 are smaller than those for respective powders.…”