Transient and Spatial Evolution of Clogging of Porous Material by Filtrating Particles

In hypersonic vehicles, regenerative cooling is used to handle the thermal load encountered in the combustion chamber. In this method, the fuel itself flows through a cooling channel and is circulated around the combustion chamber. The channel is made of porous material that enables fuel to also partially flow directly from the channel to the chamber by transpiration, which cools the wall by internal convection. The exposure of the fuel to high temperatures results in fuel pyrolysis producing carbon particles (coke). These particles are transported by the fuel and deposit inside the pores of the material resulting in a decrease of permeability of the medium. This process is very complex since it affects the heat transfers which generate the fuel pyrolysis and the formation of the particles. A test bench is developed in the current work to study the transient effect of the key parameters (i.e., filtrating mass flow rate, a load of particles in the flow) on the particles’ transport and on their spatial distribution inside the material. In the first part of the study, a porous medium with 3 mm thickness is used. It is found that with an increase in operational time, the powder mass accumulated inside the porous medium increases. In the second part of the study, different thicknesses (6, 9, and 12 mm) of porous medium are tried, to study its effect on particle transport. Particle transport is a function of pressure drop; therefore, the thickness of the porous medium is progressively increased at the same inlet mass flow rate which in turn modifies the pressure drop across the porous medium. More interestingly, the particles accumulate in the first 3 mm thickness of the upstream, while in the downstream on the opposite side of the porous material, almost no powder is found. Additionally, the pore Reynold’s number inside the porous media and the Reynold’s number of the fluid inside the permeation cell are determined to explain the transient and spatial evolution of clogging inside the porous media. In all the studied cases, the amount of powder transported through the porous media or collected downstream remains absent.