Design And Research On Combined Cutting System Of Drum Shearer&High Pressure Water Jet

With the decreasing of soft coal seam resource, the state-owned large andmedium-sized coal mines are paying more and more attention to the technology ofmining hard coal-rock seam. It is difficult to mine hard coal-rock seam under existingtechniques, because the cutting ability of common drum shearer is not adequate. Inorder to mine the hard coal-rock seam resource safely and high-effectively, a newcutting system is proposed in this dissertation. In the new cutting system, thecombined cutting device is installed on the drum shearer of full-mechanized miningequipments to form the combined cutting system of drum shearer and high pressurewater jet which can cut hard coal-rock effectively and has a lot of positive effects,such as dust removal, wetness, cutting region cooling, fire danger decreasing and soon. It is the research direction of improving social and economy benefits.In this dissertation，the structure characteristics of drum and high pressure waterjet are researched and analyzed, and the equation of high pressure water jet turbulentflow averaged velocity is deduced. The physical parameters and porosity of hardcoal-rock are described and analyzed, and mixed-mode fracture criterions aresummarized, which is prepared to the research of the combined cutting mechanism.Based on the rock breaking mechanisms of pick and water jet, the process ofcombined cutting hard coal-rock is divided into four phases. In order to show up thestatic loading of combined impact, the variation law of coal-rock stress distributionand the constitutive relationship of coal-rock damage, the classic theory of rockbreaking by water jet, impact dynamics, damage mechanics and fractal theory areapplied. And the equations of surface damage and hard coal-rock stress wavessuperimposition damage are obtained, which provides the theoretical basis to criterionof hard coal-rock internal damage and porosity development.Based on the energy point of catastrophe theory, the discriminant of combinedinstability caving damage is obtained. The mining seepage theory is applied, and thebran-new mathematical-physical analysis models are built to describe the instabilityprocess and conditions of hard coal-rock under combined cutting.The single pick&nozzle combined cutting test-bed is built and the test blocksare prepared to test the parameters of pick impact angle, impact speed, cuttingthickness, target distance, incidence angle, cutting distance between pick-tip andwater jet point, and so on. Through the single pick&nozzle combined cutting tests, the best parameters combination is obtained, the combined cutting laws are foundedand the process and mechanism theory analysis of the combined cutting are verified.The drum&water-jet combined cutting test-bed is built to test the drum shearer&high pressure water jet combined cutting, in which the design and manufacture ofcombined cutting drum is finished, the problem of rotary sealing is solved, the cuttingeffects of different cutting modes are contrasted and the influence laws of motionparameters on combined cutting are found.The theoretical analysis of combined cutting process in this dissertation isvalidated by the physical phenomenon and results of combined cutting experiments.The combined cutting system of drum shearer&high pressure water jet is proved tobe a necessary, feasible and effective technique to realize the hard coal-rock’s cutting.The sufficient technical supports and practical experience for the combined cuttingsystem to be manufactured through industrialization are acquired by the theory andexperimental research of this dissertation.