Structure optimization and coal breaking effect of air jet nozzle for post-mixed abrasive

Authors

YANG Heng, Henan Energy Group Limited, Zhengzhou 450046, ChinaFollow
WEI Jianping, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, China
CAI Yubo, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, China
ZHANG Lulu, School of Municipal and Environmental Engineering, Henan University of Urban Construction, Pingdingshan 467041, China
LIU Yong, State Key Laboratory Cultivation Base for Gas Geology and Gas Control, Henan Polytechnic University, Jiaozuo 454003, China; State Collaborative Innovation Center of Coal Work Safety and Clean-efficiency Utilization, Henan Polytechnic University, Jiaozuo 454003, ChinaFollow

Abstract

Hydraulic pressure relief and penetration enhancement technology plays an important role in coal seam gas hozard control, but it is easy to lead to dynamic phenomena such as hole collapse, drill holding and hole spraying during its application in the soft coal seams. Non-hydraulic pressure relief and penetration enhancement is one of the feasible technologies to break through the bottleneck of efficient gas extraction technology in soft coal seams. To this end, the post-mixed abrasive air jet coal breaking and pressure relief technology was proposed with the efficient coal breaking capability of abrasive air jet. Specifically, the abrasive and air are conveyed to the bottomhole by two separate channels, and the post-mixed nozzle structure coupled with jet pump-Laval nozzle is adopted to eject, mix and accelerate the abrasive at the bottomhole, so that the abrasive has high impact kinetic energy to achieve efficient coal breaking. Based on ANSYS-FLUENT gas-solid two-phase flow model, the rule of abrasive ejection, mixing and acceleration in the post-mixing nozzle was analyzed, the force of abrasive particles in the acceleration process was studied, to obtain the optimal post-mixing nozzle structure for efficient coal breaking by mixed abrasive air jet. Besides, post-mixing abrasive gas jet coal breaking experiments were carried out to verify the coal breaking performance. The research results show that the impact kinetic energy of the abrasive is determined by the ejection and acceleration capacity of the post-mixing nozzle. The ejection capacity of the post-mixing nozzle is related to the outlet diameter of the ejecting nozzle and the length of its expansion section. A reasonable outlet diameter of ejection nozzle can help reduce the airflow fluctuation at nozzle outlet, while the length of the expansion section will affect the airflow velocity there. Herein, the two-stage nozzle is adopted, with the contraction section in 2 mm length, the throat in 2 mm diameter, the expansion section in 5 mm length, and the nozzle outlet in a 3 mm diameter. The acceleration effect of the acceleration structure on the abrasive mainly depends on the expansion ratio of the acceleration nozzle. Generally, the internal airflow of the nozzle at an expansion ratio of 1 makes the abrasive particles subjected to a larger resultant force, and the external abrasive of the acceleration nozzle subjected to the traction force, pressure gradient force and virtual mass force with less fluctuation, with obvious abrasive acceleration effect. Conclusively, the acceleration nozzle is designed with a contraction tube with 4 mm length and 7.73 mm outlet diameter, a 40 mm long throat, and a 15 mm long expansion tube at the expansion ratio of 1. On this basis, a coal breaking capacity experiment was conducted with the optimized nozzle structure. Meanwhile, the erosion experiment was carried out at the ejection pressure of 4 MPa, target distance of 60 cm, and abrasive mass flow of 50 g/s. After 30 s of erosion, an erosion pits of about 10 cm in diameter and 5 cm in depth was produced by the optimized post-mixing nozzle structure on the coal blocks. Thus, it is proved that the system has good coal breaking effect with the designed parameters of the optimal post-mixing nozzle structure and has the capability of engineering application.

Keywords

pneumatization penetration enhancement, abrasive gas jet, jet pump, nozzle structure optimization, crushed soft coal seam

DOI

10.12363/issn.1001-1986.22.11.0889

Recommended Citation

YANG Heng, WEI Jianping, CAI Yubo, et al. (2023) "Structure optimization and coal breaking effect of air jet nozzle for post-mixed abrasive," Coal Geology & Exploration: Vol. 51: Iss. 2, Article 8.
DOI: 10.12363/issn.1001-1986.22.11.0889
Available at: https://cge.researchcommons.org/journal/vol51/iss2/8

Reference

[1] 徐凤银,闫霞,林振盘,等. 我国煤层气高效开发关键技术研究进展与发展方向[J]. 煤田地质与勘探,2022,50(3):1−14.

XU Fengyin,YAN Xia,LIN Zhenpan,et al. Research progress and development direction of key technologies for efficient coalbed methane development in China[J]. Coal Geology & Exploration,2022,50(3):1−14.

[2] 孙四清,郑凯歌. 井下高压水射流切割煤层增透效果数值模拟[J]. 煤田地质与勘探,2017,45(2):45−49.

SUN Siqing,ZHENG Kaige. Numerical simulation study on permeability enhancement effect of high pressure water cutting coal seam[J]. Coal Geology & Exploration,2017,45(2):45−49.

[3] 卢义玉,黄杉,葛兆龙,等. 我国煤矿水射流卸压增透技术进展与战略思考[J]. 煤炭学报,2022,47(9):3189−3211.

LU Yiyu,HUANG Shan,GE Zhaolong,et al. Research progress and strategic thinking of coal mine water jet technology to enhance coal permeability in China[J]. Journal of China Coal Society,2022,47(9):3189−3211.

[4] 王建伟. 松软低透气性煤层水力压裂增透瓦斯抽采技术研究[J]. 矿业安全与环保,2021,48(6):47−52.

WANG Jianwei. Research on gas drainage hydraulic fracturing improvement technology for soft and low permeability coal seam[J]. Mining Safety & Environmental Protection,2021,48(6):47−52.

[5] HUANG Fei,MI Jianyu,LI Dan,et al. Comparative investigation of the damage of coal subjected to pure water jets,ice abrasive water jets and conventional abrasive water jets[J]. Powder Technology,2021,394:909−925.

[6] 邱德才,武贵生,陈冬冬,等. 复合水力化增透技术在低渗突出煤层瓦斯抽采中的应用[J]. 煤田地质与勘探,2015,43(1):13−16.

QIU Decai,WU Guisheng,CHEN Dongdong,et al. Compound–hydraulic technology enhancing permeability in lowly permeable and outburst–prone seam[J]. Coal Geology & Exploration,2015,43(1):13−16.

[7] 王耀锋,何学秋,王恩元,等. 水力化煤层增透技术研究进展及发展趋势[J]. 煤炭学报,2014,39(10):1945−1955.

WANG Yaofeng,HE Xueqiu,WANG Enyuan,et al. Research progress and development tendency of the hydraulic technology for increasing the permeability of coal seams[J]. Journal of China Coal Society,2014,39(10):1945−1955.

[8] 虎维岳,李静,王寿全. 瓦斯在煤基多孔介质中运移及煤与瓦斯突出机理[J]. 煤田地质与勘探,2009,37(4):6−8.

HU Weiyue,LI Jing,WANG Shouquan. The flowing and outburst mechanism of gas in coal–based pore and fractured medium[J]. Coal Geology & Exploration,2009,37(4):6−8.

[9] 刘勇,崔家玮,魏建平,等. 自激振荡脉冲超临界二氧化碳射流发生机制[J]. 煤炭学报,2022,47(7):2643−2655.

LIU Yong,CUI Jiawei,WEI Jianping,et al. Generating mechanism of self–excited oscillation pulsed super–critical carbon dioxide jet[J]. Journal of China Coal Society,2022,47(7):2643−2655.

[10] LIU Yong,ZHANG Juan,WEI Jianping,et al. Optimum structure of a laval nozzle for an abrasive air jet based on nozzle pressure ratio[J]. Powder Technology,2020,364(3):343−362.

[11] 高杰,王海锋,仇海生. 高压氮气致裂增透实验系统的研发及应用[J]. 煤矿安全,2017,48(8):13−15.

GAO Jie,WANG Haifeng,QIU Haisheng. Development and application of testing system of high pressure nitrogen blasting experiment for increasing permeability[J]. Safety in Coal Mines,2017,48(8):13−15.

[12] 刘勇,何岸,魏建平,等. 高压气体射流破煤应力波效应分析[J]. 煤炭学报,2016,41(7):1694−1700.

LIU Yong,HE An,WEI Jianping,et al. Analysis of stress wave effect during coal breakage process by high pressure gas jet[J]. Journal of China Coal Society,2016,41(7):1694−1700.

[13] 刘勇,代硕,魏建平,等. 低压磨料空气射流破硬岩规律及特征实验研究[J]. 岩石力学与工程学报,2022,41(6):1172−1182.

LIU Yong,DAI Shuo,WEI Jianping,et al. Experimental study on hard rock breaking laws and characteristics by low–pressure abrasive air jet[J]. Chinese Journal of Rock Mechanics and Engineering,2022,41(6):1172−1182.

[14] HUANG Fei,ZHAO Zhiqi,LI Dan,et al. Investigation of the breaking manifestations of bedded shale impacted by a high–pressure abrasive water jet[J]. Powder Technology,2022,397:117021.

[15] 卢义玉,李良伟,汤积仁,等. 前混合磨料水射流连续加料系统设计与实验研究[J]. 重庆大学学报,2018,41(8):111−120.

LU Yiyu,LI Liangwei,TANG Jiren,et al. Design and experimental research of the continuous feeding system of premixed abrasive water jet[J]. Journal of Chongqing University,2018,41(8):111−120.

[16] 左伟芹,卢义玉,夏彬伟,等. 前混合磨料射流新型连续加砂系统设计与实验[J]. 应用基础与工程科学学报,2013,21(2):328−335.

ZUO Weiqin,LU Yiyu,XIA Binwei,et al. System design of continuous feeding abrasive for pre–mixed abrasive jet and its experiment[J]. Journal of Basic Science and Engineering,2013,21(2):328−335.

[17] 张成光,张勇,张飞虎,等. 新型后混合式磨料水射流系统的研制[J]. 机械工程学报,2015,51(5):205−212.

ZHANG Chengguang,ZHANG Yong,ZHANG Feihu,et al. Development of new entrainment abrasive waterjet system[J]. Journal of Mechanical Engineering,2015,51(5):205−212.

[18] 李良元,黄威,王锐,等. 后混合式磨料水射流的磨料供给系统[J]. 采矿技术,2013,13(5):47−48.

LI Liangyuan,HUANG Wei,WANG Rui,et al. Abrasive supply system with post–mixed abrasive water jets[J]. Mining Technology,2013,13(5):47−48.

[19] 郭鑫辉，刘勇，刘笑天，等. 一种用于后混式磨料气体射流输送磨料的双层钻杆装置：202120629218. 9[P]. 2021-11-16.

[20] 张东鑫，刘勇，刘笑天，等. 一种自动精准控制磨料质量流量的磨料供给装置：CN202220208635. 0[P]. 2022-06-14.

[21] 刘勇,李志飞,魏建平,等. 磨料空气射流破煤冲蚀模型研究[J]. 煤炭学报,2020,45(5):1733−1742.

LIU Yong,LI Zhifei,WEI Jianping,et al. Erosion model of abrasive air jet used in coal breaking[J]. Journal of China Coal Society,2020,45(5):1733−1742.

[22] 刘勇,魏建平,王登科,等. 磨料气体射流冲蚀磨损岩石特征分析[J]. 煤炭学报,2018,43(11):3033−3041.

LIU Yong,WEI Jianping,WANG Dengke,et al. Erosive wear characteristic of rock impacted by abrasive gas jet[J]. Journal of China Coal Society,2018,43(11):3033−3041.

[23] 张娟. 膨胀比对高压磨料气体射流破煤影响规律研究[D]. 焦作：河南理工大学，2020.

ZHANG Juan. Study on the influence of nozzle pressure ratio on coal breaking by high pressure abrasive air jet[D]. Jiaozuo：Henan Polytechnic University，2020.