刘彦伟,龙丽群,左伟芹,等. 环空流体强化自激脉冲淹没水射流调制与破煤特性[J]. 煤炭学报,2023,48(9):3393−3404. doi: 10.13225/j.cnki.jccs.2022.1120
引用本文: 刘彦伟,龙丽群,左伟芹,等. 环空流体强化自激脉冲淹没水射流调制与破煤特性[J]. 煤炭学报,2023,48(9):3393−3404. doi: 10.13225/j.cnki.jccs.2022.1120
LIU Yanwei,LONG Liqun,ZUO Weiqin,et al. Modulation of annular fluid enhanced self-excited pulsed water jet and its coal breaking characteristics[J]. Journal of China Coal Society,2023,48(9):3393−3404. doi: 10.13225/j.cnki.jccs.2022.1120
Citation: LIU Yanwei,LONG Liqun,ZUO Weiqin,et al. Modulation of annular fluid enhanced self-excited pulsed water jet and its coal breaking characteristics[J]. Journal of China Coal Society,2023,48(9):3393−3404. doi: 10.13225/j.cnki.jccs.2022.1120

环空流体强化自激脉冲淹没水射流调制与破煤特性

Modulation of annular fluid enhanced self-excited pulsed water jet and its coal breaking characteristics

  • 摘要: 针对下向孔淹没水射流卸压增透技术的瓶颈问题,即冲击力弱、破煤效率低、冲割煤量少、适应性差等,提出了环空流体强化自激脉冲水射流下向孔破煤增透思想和原理,以破除孔底压持效应和水垫增阻效应,提高淹没状态水射流的冲击力和破煤效率。采用大涡模拟、打击力测试和冲击釜破煤实验等研究方法,研究了淹没条件下环空流体强化自激脉冲水射流的高效调制和破煤特性。首先建立了适用于煤矿下向孔增透的环空流体强化自激脉冲喷嘴物理模型,优化了喷嘴结构参数;然后研制了淹没脉冲射流高频打击力测试系统和环空流体强化自激脉冲水射流喷嘴,量化分析了环空流体强化自激脉冲喷嘴在淹没环境中的打击力和流场特性;最后研发了淹没水射流破煤实验系统,开展了淹没水射流破煤实验,揭示了环空流体强化自激脉冲水射流的破煤特性。研究结果表明:在煤矿下向孔工程条件下,由两侧带有自吸口的亥姆赫兹型自激脉冲喷嘴能够有效产生环空流体强化自激脉冲水射流,最优喷嘴结构参数为上喷嘴直径d1=3 mm、壁面碰撞角α=120°、下喷嘴直径d2=3.6 mm、振荡腔腔长L=10.5 mm、振荡腔腔径D=27 mm、引入口直径d3=4.2 mm,泵压为10 MPa时卷吸环空水量最大值为0.28 L/s,平均0.19 L/s;泵压相同时环空流体强化自激脉冲水射流与自激脉冲水射流主频相近,环空流体强化自激脉冲水射流的主频为253~285 Hz,而自激脉冲水射流的主频为251~282 Hz;环空流体强化自激脉冲水射流的峰值打击力分别为自激脉冲水射流、连续射流峰值打击力的1.05~1.08倍和1.63~1.89倍,平均打击力是自激脉冲水射流的1.09~1.16倍,反映了环空流体强化自激脉冲水射流在淹没状态下能够持续产生较大的打击力,具有良好的脉冲射流特性;相同泵压和靶距条件下,环空流体强化自激脉冲水射流比自激脉冲水射流、连续水射流对煤样的破坏效果更强;环空流体强化自激脉冲水射流具备良好的冲蚀煤体破坏效果,约88.65%的煤渣粒度在8 mm以下,当泵压为10 MPa,靶距为10d1时,冲蚀时间为10 s,射流对煤样的冲蚀作用最佳,冲蚀深度47.32 mm,冲蚀体积15.7 cm3。研究成果不仅可破解煤矿下向孔水射流增透的瓶颈问题,同时具有少掘岩巷、节省成本的优势,有望替代和超越上向孔水射流卸压增透,在煤矿瓦斯灾害防治和煤层气开发领域,具有广阔的应用前景。

     

    Abstract: There are some bottleneck problems in the pressure relief and antireflection technology of submerged water jet in a downward hole, such as weak impact force, low coal breaking efficiency, less coal cutting and poor adaptability. In this study, the idea and principle of coal breaking and antireflection of self-excited pulsed water jet in downward hole strengthened by the annular fluid were put forward in order to break the pressure holding effect at the bottom of the hole and the drag increase effect of water cushion, and improve the impact force and coal breaking efficiency of the submerged water jet. The high-efficiency modulation and coal-breaking characteristics of self-excited pulsed water jet enhanced by annular fluid were studied by using large eddy simulation, impact force test and impact kettle coal breaking experiment. Firstly, the physical model of an annular fluid-enhanced self-excited pulse nozzle suitable for the anti-reflection of downward holes in coal mines was established, and the nozzle structure parameters were optimized. Then a high-frequency impact force test system of a submerged pulsed jet and annular fluid-enhanced self-excited pulsed water jet nozzle was developed, and the impact force and flow field characteristics of the annular fluid-enhanced self-excited pulsed nozzle in the submerged environment were quantitatively analyzed. Finally, the coal breaking experiment system of submerged water jet was developed, and the coal breaking experiment of submerged water jet was carried out, which revealed the coal breaking characteristics of the annular fluid-enhanced self-excited pulsed water jet. The results show that under the engineering condition of a down-hole in the coal mines, the self-excited pulse water jet enhanced by annulus fluid can be effectively generated by the self-excited pulse nozzle with self-priming Helmholtz resonance cavity structure on both sides. The optimal nozzle structure parameters are as follows: the diameter of the upper nozzle d1=3 mm, the angle of collapse wall α=120°, the diameter of the lower nozzle d2=3.6 mm, the length of the oscillation cavity L=10.5 mm, the diameter of the oscillation cavity D=27 mm, the diameter of the inlet port d3 =4.2 mm. When the pump pressure is 10 MPa, the maximum amount of entrainment annulus water is 0.28 L/s, with an average of 0.19 L/s. When the pump pressure is the same, the dominant frequency of the annular fluid-enhanced self-excited pulsed water jet is close to that of the self-excited pulsed water jet. The dominant frequency range of the annular fluid-enhanced self-excited pulsed water jet is 253−285 Hz, while that of the self-excited pulsed water jet is 251−282 Hz. The peak impact force of the annular fluid-enhanced self-excited pulsed water jet is 1.05−1.08 times and 1.63−1.89 times higher than that of the self-excited pulsed water jet and the continuous jet, respectively. The average impact force is 1.09−1.16 times higher than that of the self-excited pulsed water jet, which reflects that the annular fluid-enhanced self-excited pulsed water jet can continuously generate a large impact force in the submerged state and has good pulsed jet characteristics. Under the condition of the same pump pressure and target distance, the damaging effect of annular fluid enhanced self-excited pulsed water jet is stronger than that of self-excited pulsed water jet and continuous water jet on coal samples. The annular fluid enhanced self-excited pulsed water jet has a good erosion effect on coal body, and about 88.65% of the coal slag particle size is below 8 mm. When the pump pressure is 10 MPa, the target distance is 10d1, and the erosion time is 10 s, the jet has the best erosion effect on coal samples, with an erosion depth of 47.32 mm and the erosion volume of 15.7 cm3. The research results can not only solve the bottleneck problem of a downward hole water jet in the coal mines, but also have the advantages of less excavation and cost saving. It is expected to replace and exceed the pressure relief and permeability enhancement of the upward hole water jet. It has broad application prospects in the gas disaster prevention and coalbed methane development of coal mines.

     

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