In this paper, the variations in coalbed gas content, initial gas desorption property and coal strength after drilling-slotting integration technique and gas drainage were investigated by testing seven coal samples obtained from the coal seam #10 of Yangliu Coal Mine. The MICP and N 2 GA were combined to characterise the pore-size distribution. It is revealed that the residual coalbed gas content decreases substantially with the decrease in boreholes distances. Nevertheless, the variations in initial gas desorption velocity and coal hardiness coefficient represent an opposite tendency. In the microscopic aspect, the variation in pore-size distribution is notable. With the decrease in the boreholes distances, the adsorption pore proportion decreases and the seepage pore proportion increases. The drilling-slotting integration technique and gas drainage affect the aforementioned three macroscopic indices by changing the pore characteristics and moisture content. Besides, the guiding significance for field application of this technique is elaborated.
This paper points out that the coal-bed methane can not only cause gas outburst and explosion, but is also the greenhouse gas. At the same time, methane is un-renewable clean energy. In order to exploit methane effectively, the numerical simulation method was used to investigate the stress distribution and evolution during the process of mining the upper protective coal seam. The results match well with the filed experiment. The result revealed that the stress drops significantly and the cracks are much more developed in the “core stress relieved area” within 10 m in front of the coal face and -30 m behind the coal face, where the methane extraction concentration is usually more than 60%. The results have important significance on methane exploitation.
To investigate the process of droplet impact on an orifice plate, a two-dimensional SPH model is established. An improved linked-list search algorithm with improvement of computational domain changing with fluid is described. By analyzing the numerical results with the experimental data, influences of viscosity, gravity, and internal pressure on the spreading of droplet over the orifice are studied. It is demonstrated that spreading will change to jet flow after the droplet reaches the orifice, and then the jet will pass it rapidly and in this rather short time the effect of gravity contributes very litte to the motion. However, viscosity can induce the jet to move in a curve into the orifice. Besides, with the internal pressure and inertial effect, the lower part of the jet will fluctuate regularly. The fluctuations make the jet repeat inflation and absorption to absorb the fluid from higher pressure area, resulting in Hole Suction phenomenon. Through analyzing the pressure of the vertical section of orifice edge, we find that internal pressure plays a significant role to the droplet which is absorbed into the orifice and finally leads to splashing. Numerical results are in good agreement with the experimental data.
In this paper, the variations in coalbed gas content, initial gas desorption property and coal strength after drilling-slotting integration technique and gas drainage were investigated by testing seven coal samples obtained from the coal seam #10 of Yangliu Coal Mine. The MICP and N 2 GA were combined to characterise the pore-size distribution. It is revealed that the residual coalbed gas content decreases substantially with the decrease in boreholes distances. Nevertheless, the variations in initial gas desorption velocity and coal hardiness coefficient represent an opposite tendency. In the microscopic aspect, the variation in pore-size distribution is notable. With the decrease in the boreholes distances, the adsorption pore proportion decreases and the seepage pore proportion increases. The drilling-slotting integration technique and gas drainage affect the aforementioned three macroscopic indices by changing the pore characteristics and moisture content. Besides, the guiding significance for field application of this technique is elaborated.
In order to study the explosion characteristics of nanometer aluminum, comparative experimental studies on explosion characteristics of nanometer aluminum powder and common aluminum powder with different grain diameters have been carried out by using the horizontal pipeline explosive test device. After analyzing both the explosion process and the data of explosion characteristics of two aluminum powder during the experiment, some explosion characteristics of nanometer aluminum powder different from common aluminum powder can be concluded. Research result expressed: The maximal duration of explosion pressure of nanometer aluminum powder in its explosion process is much longer, which is about 3 to 4 times longer than non-nanometer aluminum; In the nanometer range, the scope of explosion pressure is much wider (between the 40~750kPa) than others, and as a whole, explosion pressure of the nanometer aluminum powder is much higher than the micron aluminum powder; In the process of explosion propagation of aluminum powder, flame combustion wave and explosion pressure wave show the positive feedback mechanism, which is interacting with each other and accelerating each other.
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