Study On The Influence Of Pores Of Coal With Ultrasonic Wave

The application of ultrasonic excitation cracking technology to coalbed methane production has the advantages of low energy consumption,no pollution and concentration of energy.The ultrasonic excitation cracking technology is a new type of coal cracking technology,which is not mature compared with the traditional cracking technology,but it has the characteristics of environmental protection requirement.In order to further reveal the influence law,efficient utilization and improve it,we have done the laboratory experiment and theory analysis to explore the mechanism of the technology.And we investigated the effect of ultrasonic power,coal moisture content.In addition,we also investigated the adsorption and desorption performance of coal seam gas before and after ultrasonic excitation.Based on the characteristics of ultrasonic wave propagation,this paper analyzes the effect of ultrasonic cavitation,mechanical vibration effect and ultrasonic heat effect on the process of coal body excitation.In addition,in order to explore the effective range of ultrasonic excitation crack technique in coal,the attenuation coefficient of ultrasonic wave in coal is studied by mathematical derivation.In order to better explore the law of ultrasonic fracturing coal,the laboratory system of ultrasonic excitation to crack coal is established.Experiment by means of nuclear magnetic resonance(NMR)technology to study the effect of ultrasonic power to change for crack media the influence law of the experiment of 70 W as the boundary,respectively to study the high power and low power drive crack the effect of coal body,find the different power shift markedly effective crack of coal pore,and ultrasonic crack mechanism of coal is verified by the experiments.The cavitation effect of ultrasound requires effective cavitation bubbles within the coal body,which is related to the water content of coal.In this paper,the internal pore changes of the coal body before and after the ultrasonic excitation induced by ultrasonic excitation are investigated by combining the nuclear magnetic resonance technique and fractal dimension.The changes of internal temperature and the distribution of internal temperature of coal in the process of ultrasonic excitation were studied by thermal imaging technology.The effect of coal water content on the crack effect of ultrasonic excitation was obtained.Moreover combining with numerical simulation and experimental analysis,ultrasonic wave was studied in different porosity the propagation rules of coal and power ultrasonic propagation rules in the coal,for ultrasonic excitation effect of crack technology in the field practice provides theory basis.Finally,the article studied before and after ultrasonic excitation internal adsorption desorption of coalbed methane in coal body,the concepts of adsorption desorption hysteresis resistance coefficient,quantitative of ultrasonic promote coal-bed methane desorption condition have been characterized.