Abstract
Accurate determination of the permeability of crushed coal medium is the basis for the study of their permeability characteristics. To investigate the permeability characteristics of this special porous medium composed of crushed coal particles, the permeability parameters of crushed coal specimens of different initial porosities were measured by designing a lateral-limit compression seepage test system. Parameters were determined separately for specimens of different initial porosities. (1) the Reynolds number distribution region characterising the seepage state was determined and obtained. Specimens with initial porosity distribution between 0.02 and 0.08, and seepage Reynolds number distribution in the low-permeability zone, under Darcy flow; (2) the intrinsic permeability of the crushed coal medium was obtained by using the Ergun equation. The complex inverse proportional relationship between the drag coefficient and Reynolds number was derived; (3) Through the determination of the permeability of the crushed coal medium, the mean value of βK value was obtained to be about 45.7, and the analysis of the permeability of porous medium can determine its critical permeability. The relationship between the Forchheimer number Fo and critical Reynolds number was measured. The results indicate that it conforms to a linear distribution. In-depth analysis of these two parameters can be used to explore the flow transition process between laminar, transition, and turbulent flow. This study provides insight into the permeability characteristics of the media in fractured coal bodies.
Highlights
Accurate determination of the permeability of crushed coal medium is the basis for the study of their permeability characteristics
Accurate determination of the permeability of porous media consisting of crushed coal grains is seen as a difficult t ask[7,8,9], which is important for studying the analysis of the permeability characteristics of crushed coal grains and porous coal media in mines
The traditional Forchheimer equation or Ergun equation mainly includes the effects of viscosity and inertia, the composition and structure of arbitrary porous media cannot be characterized by porosity variations alone[12,13,14]
Summary
Accurate determination of the permeability of crushed coal medium is the basis for the study of their permeability characteristics. To investigate the permeability characteristics of this special porous medium composed of crushed coal particles, the permeability parameters of crushed coal specimens of different initial porosities were measured by designing a lateral-limit compression seepage test system. Specimens with initial porosity distribution between 0.02 and 0.08, and seepage Reynolds number distribution in the low-permeability zone, under Darcy flow; (2) the intrinsic permeability of the crushed coal medium was obtained by using the Ergun equation. Percolation in crushed coal grains has been a matter of interest and has a very long history of research[1,2] This porous medium composed of crushed coal grains demonstrates more complex permeability characteristics. It is worth noting that the modified Ergun equation predicts the experimental results w ell[22,23], this limits to some extent the form of fixed expressions it uses and introduces the question of whether its parameters can be calculated accurately in all cases
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