Effect of Flow Configuration on Darcian and Forchheimer Permeabilities Determination in a Porous Composite Tube

Abstract

Using Fuel Cell on board of aircraft imposes to extract light species (such as Hydrogen and light hydrocarbons) from the liquid fuel which is stored and used, possibly attemperatures where a fuel pyrolysis occurs. Natural porosity of composite material could be used to filtrate the selected species. Hence the permeability of the porous media becomes one of the key parameter to be accurately measured. It is often determined experimentally in laboratory with disc samples (outlet of the flow is achieved through the porous material) and normal flow. However, this configuration is far from the realistic one consisting of tubes (a main flow is found additionally to the one through the material, tangential permeability). Therefore, the effect of a second outlet on the Darcy's and Forchheimer's permeabilities characterization should be studied (despite the permeability is an intrinsic property of the material itself and it should not be dependent on the test apparatus). This paper focuses on a new way of using an existing test bench for the determination of Darcy's and Forchheimer's permeabilities of C/SiC porous composite tube by taking two outlets into account. Operating parameters (temperature, pressure and mass flow rate) are measured for three different configurations: i) secondary outlet (S.O) is 0% open ii) S.O is 50% open and iii) S.O is 100% open. Then Darcy's and Forchheimer's permeabilities are computed by ISO and P 2 methodsusing a direct search algorithm. Obtained results from different methods are compared and discussed. They are in agreement with the literature data which guarantees the reliability of the test bench and of related measures. Nomenclature Acronym CMC = Ceramic Matrix Composite PO/SO ratio = ratio of the flowrate from the Primary Outlet over the one from the Secondary Outlet P.O = Primary outlet 1 2 S.O = Secondary outlet LatinLetters ag = Grain area dg = Grain diameter dp = Pore diameter KD = Darcian's permeability KF = Forccheimer's permeability L = Length Pinlet = Pressure inlet Poutlet = Pressure outlet Re = Reynolds pore number T = Temperature V = Velocity Greek Letters ε = Overall open porosity µ = Dynamic viscosity ρ = Density

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

“…where Re P is the pore Reynolds number and d p is the pore diameter. In all the test cases Re P is found to be ≈1, which means flow is always in a laminar regime 8 and the pressure gradient is linearly proportional to the fluid velocity in the porous material. 8 The Reynold's number represents the ratio of the momentum flux to the viscous stress.…”

“…In all the test cases Re P is found to be ≈1, which means flow is always in a laminar regime 8 and the pressure gradient is linearly proportional to the fluid velocity in the porous material. 8 The Reynold's number represents the ratio of the momentum flux to the viscous stress. This can also be interpreted as the ratio between the inertial forces and the viscous forces.…”

“…Discrepancies of 14% and 2% are observed respectively between the calculated and the supplier's permeability values. The relative error is higher for eq 1 because the flow is less turbulent, 8 while in case of eq 3 there is no Forchheimer's term hence the determination of permeability is more accurate.…”

“…A counter-flow heat exchange between the fuel-coolant and the combustion gases causes the fuel to decompose into several small species such as hydrogen, ethane, and ethylene. 7,8 In addition to these species, carbon particles are also formed; this process is known as coking. 9−13 These solid carbon particles flow through the porous wall and deposit inside the combustion chamber wall pores.…”

Axial Distribution of Permeance and Selectivity of a Porous Cylindrical Tube for Binary Gas Mixtures (CO2/N2)

“…2 The solid oxide fuel cell (SOFC) is among the commonly recognized techniques for power generation in applications such as on board aircraft. 3 To operate the fuel cell efficiently, the availability of high-purity hydrogen is essential. High gravimetric-based energy content and the absence of greenhouse gas emissions make hydrogen a very unique contender in the area of green fuels.…”