Rock Breaking Performance Of Self-excited Oscillating Pulsed Waterjet

Rock breaking theory,elastic wave dynamics theory and fluid structure coupling theory are synthetically used to solve the problems of low rock breaking efficiency and serious wear of conical pick in the heading face of hard rock roadway.Rock breaking performance of self-excited oscillating pulsed waterjet(SOPW)is carried out combined with numerical simulation and experimental research,aiming to reveal the rock failure under the impact of SOPW.In addition,the aim is to explore the influence of structural parameters of self-excited oscillation nozzle and operating parameters on cutting load and cutting tool temperature,which can provide scientific basis for improving the rock breaking efficiency of driving equipment for hard rock.Based on hydrodynamics,the frequency domain similar network model of SOPW is established firstly,to investigate the oscillation mechanism,amplitude frequency characteristics and generating conditions of SOPW.In addition,the influence rules of structural parameters and fluid parameters of self-excited oscillation device on the oscillation characteristics of jet are qualitatively analyzed.Secondly,based on the shock wave theory,the wave equation of water jet rock breaking is established,and the crack propagation mechanism during rock breaking by SOPW is analyzed.Furthermore,the mathematical model of rock breaking by conical pick assisted with SOPW is established by using fracture mechanics,to explore the load distribution characteristics of conical pick with and without the assistace of waterjet.Moreover,the theoretical formula of conical pick temperature assisted with waterjet during the rock breaking process is established to explore the cooling effect of waterjet on mechanical conical pick.In order to explore the micro mechanism of SOPW and the influence rule of structural parameters on the oscillation performance of pulsed jet,a numerical model of physical flow field of self-excited oscillation nozzle with different structural dimensions was established.And the flow test at the outlet of self-excited oscillation pulsed jet nozzle was carried out under the same working condition to verify the reliability of numerical simulation on the prediction of self-excited oscillation performance.Combined with numerical simulation,the evolution process of vortex ring and its influence on the velocity of SOPW are explored,and the formation process as well as the micro mechanism of SOPW is further revealed.Finally,the influence of structural parameters and system pressure on the oscillation performance of pulsed waterjet is analyzed,which provides the basis for the design of self-excited oscillation pulsed jet nozzle.Numerical model of rock breaking by continuous water jet and SOPW is established based on finite element method(FEM)combined with smoothed particle hydrodynamics(SPH),and the validity and accuracy of the numerical model are verified by the rock breaking test under the same working condition.Microscopic analysis of rock breaking process by SOPW,including the formation of the crushing zone,the crack initiation and propagation of cracks,are observed.And the mechanism of rock crack growth,damage evolution,stress propagation and attenuation under the impact of SOPW are also revealed.Furthermore,the mechanism and rock breaking performance with different pulse amplitudes,pulse frequencies and confining pressures are investigated,which provides guidance for the study of rock breaking performance of conical pick assisted with SOPW.In order to obtain the effects of different structural parameters,system pressures,standoff distances of SOPW and rock sample characteristics on rock rock breaking morphology,rock breaking volume and specific energy consumption,experimental study on rock breaking performance of SOPW is conducted based on high pressure water jet test system.With the aim to explore the evolution process of jet flow pattern during the of rock breaking process,and to master the relationship of initial crushing pressure,fracture pressure varies with the rock compressive strength.In addition,the change trend between rock breaking morphology and standoff distance is pointed out,and the best parameter combination of rock breaking performance is obtained through orthogonal test,which provides technical guidance for the research of rock breaking performance of conical pick assisted with SOPW.Using high-pressure water jet rock breaking system and single pick rock cutting test system,the influence of system pressure of waterjet,cavity length,section cone angle and traverse speed on the characteristics of load and friction reduction of conical pick is studied.And the aim is to analyze the changing trend of cutting load and temperature of conical pick during the rock breaking process assisted with SOPW.The results of test show that SOPW can reduce the cutting load and the temperature as well as the wear of conical pick.The dissertation has 125 figures,10 tables and 178 references.