Numerical Simulation and Experimental Study on High-Pressure Water Jet Descaling in Coal Mine Drainage Pipeline
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RESEARCH PAPER
Numerical Simulation and Experimental Study on High‑Pressure Water Jet Descaling in Coal Mine Drainage Pipeline Aiming Wang1 · Pengfei Sun2 · Ziwei Zhang3 · Baomei He1 · Guoying Meng1 · Jie Yang1 · Xiaohan Cheng1 Received: 21 September 2019 / Accepted: 28 October 2020 © Shiraz University 2020
Abstract Traditional chemical and mechanical descaling methods are expensive, inefficient and environmental pollution for removing scales in coal mine main drainage pipeline. In this study, a water jet is proposed to remove pipe scales, which can solve the inadequacies of traditional methods. Parametric optimization for water jet and descaling nozzle are analyzed. Firstly, the mechanical properties of scale materials are obtained for the first time by uniaxial compressive tests and Brazilian disk splitting tests. Secondly, crushing mechanism and crushing effect of pipe scale subjected to water jet are studied by AUTODYN software. Relationship between the nozzle’s key structure parameters and the axial static pressure and velocity of the fluid field inside the nozzle are analyzed by Fluent software. Moreover, the axial dynamic pressure and velocity of fluid field outside the nozzle are also analyzed. The above numerical simulations indicate that the pressure, flow and target distance of water jet should be 20 MPa, 40L/min and 50 mm, respectively; the outlet diameter, contraction angle and length-diameter ratio of the nozzle should be 2 mm, 13°and 2, respectively. Finally, experiments are conducted for the validation of these parameters. The results provide guidance for the development of the water jet descaling technique of the coal mine drainage pipeline. Keywords Coal mine · Pipe of main drainage system · Water jet descaling · Parameter optimization · Simulation and experimental study * Aiming Wang [email protected]; [email protected]
1 Introduction
Pengfei Sun [email protected]
Coal mine’s main drainage system plays a critical role in the production safety of coal mine (Mingjun 2013). Because coal mine water contains suspended substances such as slime and some insoluble salts, the mine drainage pipe is prone to scale. Pipe scales increase the resistance of pipeline, reduce drainage efficiency, increase power consumption and affect production safety of coal mine. Descaling is an important means to prolong the service life of pipelines and ensure the normal operation of pipelines. Currently, replacing drainage pipes, chemical descaling and mechanical descaling are widely used in coal mines (Xuming 2004; Chunling et al. 2014). Replacing the drainage pipes method is replacing scaled pipes manually with new pipes. The chemical descaling method uses a specially configured chemical solutions to soften pipeline scales. The inner wall of pipes needs to be immersed in the chemical solution for a long time and then the chemical solution and the scale is discharged into the environment together. However, the descaling effect of the chemical descaling method is not good when the scale is thick. Hence, the mechanic
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