Adhesion Mechanism Of Carbon Particels On Non-catalytic Coke Formation In Pyrolysis Of Hydrocarbon Fuel

As the first choice for hypersonic vehicle coolant fuel, endothermic hydrocarbonfuel has the advantages of high reliability, low cost, perfect cooling effect and high fuelefficiency. Hydrocarbon fuel in high temperature cooling channel is easily cleaved togenerate coke particles. Coke is a kind of mixture of hydrocarbons with a largemolecular weight, and its viscosity and boiling point are very high. The coke easilysticks to the wall and is difficult to be scoured because of its physical properties. Thatnot only reduces the cooling effect, but also brings some great harm to the wall, likecorroding the wall. So we should know the mechanism of pyrolysis coke and the factorsaffecting the accumulation of coke. As the temperature of the cooling channel reaches acertain value, the coke is cracking coke. Because the mechanism of catalytic crackingcoking and its influencing factors are lack of accurate exposition, in this paper,numerical simulations are carried out only about the movement of coke particles whichcome from the thermal cracking reaction of hydrocarbon fuel. The cooling channel issimplified as a two-dimensional rectangular channel. we get the motion characteristicsof the coke particle and also obtain the factors affecting its accumulation. Thisinformation will provide technical supports for the study of hydrocarbon fuel as acoolant.Through literature research, we know that the state of motion of the particle in thecooling pipe is turbulent. Two-dimensional numerical simulation about the cokeparticle’s accumulation is carried out. We use Discrete Particle Method’s soft spheremodel to simulate particle-particle collision. In soft–sphere approach, the force betweentwo colliding particles is solved through a system of spring, damper and skateboard. Wealso consider the influence of adhesive force and drag force on the accumulation of cokeparticle.Without considering heat transfer and chemical reaction，we simulate the flow stateand accumulation characteristics of the coke particle in a vacuum tube. The main resultsare summarized as follows: The adhesion is the main reason for the accumulation of theparticle. The larger the adhesive force is, the more severe the accumulation is. Thefluctuating velocity within the certain rang has no significant effects on theaccumulation of the particle. The accumulation of the particle is also reduced withincrease of the particle’s diameter. Under the liquid-solid coupling, the particle isdifficult to accumulate together. The initial position and velocity of the particle alsoaffect the accumulation to a certain extent.