Research On Nonlinear Permeability Characteristic Of Porous Media Of Pellets Packing

Porous media materials are widely used today. It includes a variety of natural porous media materials, such as rocks, soil, as well as a variety of man-made porous media materials, such as porous ceramic, porous materials, functional materials,packed bed in the metallurgical and chemical engineering, reactor and heat pipe in the energy projects.Soil, sand shale, ceramics and other materials can be seen as porous media.Under total stress and pore pressure, the deformation of porous media included the gap and solid skeleton deformation. Changes in pore structure will lead to changes in permeability. At this point, the flow is not subject to the Darcy law. Because the total stress and pore pressure are the reasons of changes in pore structure, therefore Penetration can be seen as a function of total stressσand pore pressureρ. That the penetration index is usually dependent on the total stress and pore pressure and that is k=K0eap-bσ.In such a case the permeability of the porous media depends on three parameters:k0, a and b. This article first discussed the characteristics of the seepage field. Pointed out that when the permeability depends on the total stress and pore pressure, even if it is the stability of flow, the pressure gradient in porous media is not constant.When determining the three parameters through the experiment,we must take into account the characteristics of non-uniform of the porous pressure gradient within the sample. In this article I put forward a theoretical model, we get the relations of steady flow of seepage stage, the total stress, pore pressure the three characteristics parameters.And we also get the method of determining permeability parameters of deformable porous media.Secondly when Preparing the porous media, we explored the impact of the ratio, molding methods, molding pressure and molding time on the porous samples whose pore structure, strength and deformation characteristics are uniform.And then the manual porous sample is studied under the conventional three triaxial pressure and we get the curve of fluid volume and time. The curve includes two parts, namely, non-steady-state phase and steady-state phase. And then check that the slope of steady-state phase flow, use the nonlinear least squares method for numerical inversion, we determine the three factors unknown in the mathematical madel Research indicates that deformable porous media penetration is not only changed with the time changes but also with sample length. And comparing with Darcy Law the penetration rate is very different.At last, because the three parameters is known, one-dimensional mathematical model of non-stability percolation is studied and seepage and stability as the limit of non-steady seepage is included in the model. Using the finite volume method,we get the numerical solution of pore pressure and flow. The stability of flow time and flow-time curve those are calculated and very close to the experiment. It Shows that the test method proposed in this paper can be used to determine the non-linear flow characteristics of porous media.