超声热效应促进煤层瓦斯解吸扩散数值模拟

A Numerical Simulation of Coalbed Methane Desorption and Diffusion Enhanced by Ultrasound Heating

以声场声能转化为热能,提高煤层系统的温度,改善系统的解吸一扩散为基础,将煤样假设为含有大孔隙和微孔隙基质的双重孔隙结构,引入温度对微孔隙扩散系数的影响,提出了利用温度梯度扩散模型建立超声热效应促进煤层瓦斯解吸—扩散的热平衡方程和物质平衡方程,应用Matlab工具实现了声场促进煤层瓦斯解吸扩散的数值模拟。对有无超声作用下,煤层瓦斯解吸一扩散的数值模拟分析得出:超声热效应可以明显地提高煤样的温度,增大微孔隙扩散系数,提高大孔隙游离气的动态百分数,降低微孔隙中吸附气的动态百分数。为超声波促进煤层瓦斯解吸—扩散,提高煤层瓦斯抽采率提供了分析的理论基础。

We discuss the development of coal bed micro-structure and the mechanism of enhancing the desorption/diffusion of coalbed methane by ultrasound. We present a mathematical model to describe the desorption/diffusion process of coalbed methane due to the ultrasound heating effect. Two cases of gas release with or without ultrasound fields in coal samples were simulated. We found that the temperature and the micropore diffusion coefficient of the system were improved by ultrasound transferred heat energy, while the dynamic fraction of free gas in pores was enhanced and the dynamic fraction of adsorbed gas was weakened.