松软煤层用泡沫发生器结构优化及发泡效果模拟

Structure optimization of foam generator for soft coal seam and foaming effect simulation

【目的】空气螺杆钻进技术用于松软煤层瓦斯抽采孔钻进,存在粉尘污染严重、钻头寿命低、钻孔净化困难等问题。采用空气螺杆泡沫钻进技术是解决问题的有效途径,拥有良好发泡性能的泡沫发生器是实现泡沫钻进技术的关键之一,但目前大多泡沫发生器无法满足要求。【方法】针对此问题,基于螺旋式泡沫发生器,增设空气动能转化装置,设计了一款小尺寸泡沫发生器。采用数值仿真分析方法,对空气动能转化装置结构设计的合理性和涡轮搅拌段搅拌叶片的安装角度进行了评价和优化。【结果和结论】结果表明:(1)空气动能转化装置能有效驱动泡沫发生器的主轴转动,在0.8 MPa空气压力条件下,叶片平均转速可达621.61 r/min。(2)完成动能转化后,气体可以继续进入泡沫发生器内部,与泡沫基液进行气液混合,达到设计目的。(3)通过混合相的迹线分布、流体域湍流分布、气相分布以及气泡粒径分布等情况对比分析,安装角度为30°的搅拌叶片,其搅拌效率和气液混合效果好。研究成果为空气螺杆泡沫钻进工艺在松软煤层瓦斯抽采孔的成功应用奠定了基础。

[Objective]The application of air screw drilling technology in gas drainage borehole within soft coal seam presents challenges,including severe dust pollution,low drill bit lifespan,and great difficulty in borehole purification.The use of air screw foam drilling technology is an effective way to solve the problem.A foam generator with good foaming performance is one of the keys to implementing the foam drilling technology.However,most current foam generators could not meet the requirements.[Methods]In response to this issue,a small-sized foam generator was designed based on the spiral foam generator,with an air kinetic energy conversion device increased.Besides,the rationality of the structural design of the air kinetic energy conversion device and the installation angle of the stirring blades in the turbine stirring section were evaluated and optimized using the numerical simulation analysis methods.[Results and Conclusions]The results show that:(1)The air kinetic energy conversion device could effectively drive the main shaft of the foam generator to rotate,achieving an average rotational speed 621.61 r/min under 0.8 MPa air pressure.(2)After the kinetic energy conversion,the gas can enter the foam generator continuously and mix with the foam base liquid to achieve the design purpose.(3)By comparing and analyzing the trace distribution of the mixed phase,turbulence distribution in the fluid domain,gas phase distribution and bubble size distribution,it is found that a stirring blade with an installation angle of 30°has good stirring efficiency and gas-liquid mixing effect.The research results have established a foundation for the successful application of air screw foam drilling technology in gas drainage boreholes within soft coal seams.