The Flow Characteristics And Its Application Of Three-phase Foam For Fire Fighting In Mine Goaf

Technology of Three-phase foam for mine fire fighting has the merits of grouting, nitrogen injection and inhibitor spraying, so it has been widely used in mine fire fighting. However, because that it is lacking of research on the characteristic of three-phase foam's flow behaviors in mine goaf, the application process design has always been lacking of theoretical support, the role of three-phase foam for fire fighting hasn't been absolutely recognized, In order to change this situation, foam flow behaviors in mine goaf has been studied systematically in the paper. Research results is very useful for improving process design level and the efficiency of fire fighting.In the paper, in order to obtain the viscidity characteristic, the rheological property of three-phase foam was studied. For the three-phase foam, the relationship between shear stress and shear rate was tested, the optimal rheological model was selected by the grey correlation analysis, and the constitutive equation was constructed which point out that the three-phase foam belong to the kind of yield pseudoplastic fluid. And then the result of the starting pressure gradient computed showed that the leaking air force couldn't drive the three-phase foam. Finally author put forward that the three-phase foam could interdict the leaking air and reduce the emission of hazardous gas in goaf.In order to provide experimental fundamentals for theoretical study on seepage characteristics of three-phase foam, the osmosis device and the experimental measurement system were designed and constructed, and the experiment about the seepage characteristics of three-phase foam was completed. The pressure drop and flow during the seepage of three-phase foam was measured to analyze the resistance seepage characteristics of three-phase foam. The results showed that the three-phase foam is characterized by shear thinning in low speed seepage; the main factors to the seepage resistance of three-phase foam are concentration of slurry and permeability of porous media, while the foaming multiple has little influence. The consistence between the results of the experiment and the numerical computation on the seepage experiment of three-phase foam based on the apparent viscosity from constitutional equation is found, and so it is testified that the apparent viscosity of three-phase foam which is derived from constitutional equation could be applied in the seepage calculation. On the basis of the experimental study and theoretical analysis,seepage manner of three-phase foam in the gob is established, and three dimensional unsteady mathematical model of three-phase foam which seeps in the gob is established by the use of theory of multiphase flow and seepage flow. In order to verify the mathematical model, experimental and numerical simulation study on the flow characteristics of three-phase foam are carried out in the control of large area gob fire of small coal pits in surface mine, and characteristics of three-phase foam such as stack height and diffusion distance, etc are inspected on the spot, and the simulation results is coincident with the conclusions which is obtained by field observations.Taken into account of the difficulty to observe the flow characteristics of three-phase foam in the gob hidden space, CFD simulation technology is drawn into the study on the flow characteristics of three-phase foam in the gob and numerical simulation method is raised to study the flow characteristics of three-phase foam. The flow characteristics of three-phase foam in fully mechanized caving face are studied when it poured by embedded pipe in upper crossheading. which shows that stacking height and diffusion width of three-phase foam can each reach to 3.62m and 36.9m, and stacking height and diffusion width are notably affected by the face's dip angle and perfusion flow. Stacking height and diffusion width of three-phase foam are increased with the increase of perfusion flow, while the diffusion width of three-phase foam is greatly decreased with the increase of face angle. Relation curves of stacking height and diffusion width along with flow rate and face angle are drawn through a great deal of simulation study.Under the guidance of the results of experimental and theoretical research, design method of application process for three-phase foam is established, and perfusion technology of three-phase foam in coal mine has been optimal designed and applied, which solve the fire prevention in large-scale fully mechanized caving face gob, large scale coal spontaneous combustion fire in surface gob and concealed fire at the near gob eare in fully mechanized caving face, and preferable fire prevention effect has been achieved as well as the full play of three-phase foam in fire extinguishing efficiency.