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

Abstract

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.

Thermal and physical characterization of glass fiber phenolic for aircraft interiors

“…It can be seen that the relative discrepancies of about 8.83% and 7.53% are obtained between the experimental and the theoretical permeability values for SS3 and SS5 which are quite low in terms of this kind of study. 20 These results confirm the reliability of the bench; hence, it can be used for the permeability study.…”

“…More details regarding test methodology and permeability determination can be found in the previous work. 20,27…”

“…These vapors try to escape from the material by permeating through the fiber pores. 8,9 While the phenomena of the permeation depends upon the pressure drop, gases and number of open pores available, 8,19,20 these parameters can vary due to formation of char and thermal load at different heat fluxes (i.e., temperatures). Hence, the permeation can vary which will affect the decomposition of the composite.…”

Thermal decomposition of multilayer honeycomb core laminate sandwich composite panels in cone calorimeter apparatus – Effect of the top decomposed layer

“…31 In this method, a revised form of Brinkman's equation is used to determine Darcian (K D ) permeability. 31,37 Darcian term is for low velocity regime filtration (Darcian flows) and the Forchheimer term is related to the Stokes's law (non-Darcian flows) which takes into account the inertial effects related with flow resistance. 31,38…”

In-situ X-ray tomography on permeability evolution of C/SiC porous ceramic for hypersonic vehicles

“…Furthermore, during the ight process at super high speed, the porous medium is necessarily subjected to complex loads including the external aerodynamic load, seepage pressure of coolant, heat stress caused by aerodynamic heating, and structural load of the vehicles [8][9][10][11][12] . Thus, it is a signi cant issue whether the ow of coolant can be precisely calibrated and the uniformity of coolant in the porous medium can still remain unchanged or not while the porous medium undergoes heavy loads [13][14][15] . It is urgent to elucidate the permeability evolution subjected to external loads.…”