| High-pressure continuous water jet is widely used in the coal industry because of its advantages of no soot,low noise,no static electricity,no open fire,narrow and uniform slits,easy to control and so on.Application of high-pressure continuous water jet technology in crushing mine（coal）rock operation has decades of practical experience in domestic and foreign engineering fields.However,in practical applications,the use of high-pressure pure water jet to break the hard rock of the roadway excavation face is not effective,and the water resource consumption is large.When high-pressure continuous water jet is combined with the mine mechanical tool to break the rock,it is often difficult to construct in a narrow working face because the coal mining machinery is too large.In view of the above situation,this thesis proposes to use two continuous water jets with the same parameters to break the rock.Based on the rock breaking of single-strand water jet,the mechanism and performance of rock breaking by high-pressure double-strand water jet are analyzed and studied by means of experimental verification,simulation and research analysis.On this basis,the orthogonal experimental design method is used to explore the optimal combination of rock breaking performance parameters.The research conclusions are as follows.The SPH-FEM coupling algorithm is used to create a numerical model of high-pressure double-strand water jet impacting rock.The model is then used to investigate the effects of water jet impact velocity,water jet diameter,impact angle,and impact point spacing on the high-pressure double-strand water jet’s ability to break rock.Rock damage is greatly influenced by the high-pressure water jet’s impact velocity.The amount of damage units done to the rock increases with the water jet’s diameter,while the amount of created backflow water reduces the water jet’s damage capacity.The most obvious damage to the rock model is caused by the double water jet with a 15°impact angle.With the increase of impact point spacing,crushing unit increases first and then decreases.The main damage area of rock model is concentrated between two water jet impact points.It is tested how well a single water jet and a twin water jet shatter rock.The high-pressure double-strand water jet’s ability to break rocks is found to be superior to that of the high-pressure single water jet.In contrast test,the maximum volume of broken rock caused by double water jet is 3.57 times that of single water jet.The performance of the high-pressure double-strand water jet to break rocks increases with the pressure force of the water jet system and increases initially before increasing gradually as the nozzle diameter increases.When the nozzle diameter is 1.2 mm and 1.6 mm,the crushing volume of the rock is similar,but the energy consumption is lower when the nozzle diameter is1.2 mm.In practical work,increasing the nozzle can also be used to improve the rock breaking capacity.With the increase of the angle between impact and impact point,the rock breaking capacity increases first and then decreases,and the best parameters are 15°and 2.0d.The orthogonal test was carried out to analyze the optimal factor parameter combination of high pressure double water jet rock breaking.The results show that the primary and secondary order of the influence of high pressure double water jet rock breaking performance is:jet pressure>impact angle>impact point spacing>nozzle diameter.The optimal factor parameter performance combination of rock breaking is A4B4C2D3,that is,the water jet system pressure is 50 MPa,the nozzle diameter is 1.6 mm,the impact angle is 15°,and the impact point spacing is 2.0 d.The above research conclusions can provide guidance for improving the efficiency and economy of rock breaking by high pressure water jet. |
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