| Swirling abrasive water jet is a kind of jet in which the mixed flow of abrasive and water is transformed into a rotating flow state.The jet fully combines the advantages of swirling jet and abrasive jet in industrial applications,overcomes inherent defects.It could reduce energy consumption in rock fragmentation,high hardness and kinetic energy of abrasive is used when abrasives are added in water,and can achieve better rock breaking effect in a short period of time.With the continuous improvement and development of the technology of swir-ling abrasive jet,the jet is widely used in many fields of industry.The flow law and rock breaking characteristics of rotating abrasive jet are studied based on the theory of fluid rotating flow and multiphase flow dynamics in this paper.It is aimed at problems in engineering application for using guide elements to generate swirl.A new type of mixed abrasive jet nozzle is proposed according to the principle of tangential injection swirl,The nozzle structure is mainly composed of an inner cavity,an outer cavity,a tangential direction,a vertical flow passage and a contraction cavity.The flow through the external cavity smoothly into the tangential channel and the rotation of the rotating cavity,vertical inflow can enhance the axial impact.The internal and external flow field of the nozzle was simulated based on computational fluid dynamics software FLUENT.Firstly,the jet characteristics of swirling and ordinary abrasive jet in submerged and non-submerged state are analyzed,the results show that the abrasive velocity reaches the maximum at 3 mm from the nozzle outlet,and the diffusion angle is 25%higher than that of the submerged jet,and the diffusion angle of the swirling abrasive jet is 20%higher than that of the straight jet.Secondly,the flow characteristics of swirling jet nozzle flow field has been studied,the results show that the development of swirling abrasive jet is divided into six stages,increasing the inlet pressure,increasing the velocity of water and abrasive particles and decreasing the velocity difference between particles and water.Then,the law of abrasive velocity distribution and attenuation law are obtained,the abrasive volume fraction of the flow field along the radial direction is "V",The volume fraction of the abrasive volume in the external flow field is related to the spray distance.As the volume fraction of the inlet abrasive increases,the volume fraction of the abrasive is increased.As the abrasive grain size increases,the volume fraction of the abrasive outlet increases first and then decreases slowly,the biggest increase is 65.5%.Finally,the effects of different impact angles on the bottom hole pressure characteristics and distribution are analyzed,the results show that the peak value at 0° is the maximum,the peak value of pressure deviates from the center of the jet at 20?50°.The orthogonal experimental design method was used to optimize the nozzle structure of the swirling abrasive jet.The diameter of the inner and outer cavities,the length of the cavity,the angle of contraction cavity,the length of vertical flow passage and the length of the straight column respectively are 12mm,5mm,30mm,60°,4mm and 6mm,and the three tangential inlet channel is best.The influence of the length of vertical flow passage,the angle of contraction cavity and the length of the straight column on the impact pressure of the bottom hole is analyzed by the experimental research,and the experimental and simulation data are compared,the results show that the simulation results are consistent with the experimental results,and there is a certain size parameter to make the impact pressure reach the maximum.The influence of nozzle erosion time,angle and different rock types and structure parameters on rock erosion is studied by erosion experiment,the basic characteristics of rock erosion hole and the influence of erosion time on erosion efficiency,the best size parameters corresponding to the numerical simulation make the best erosion effect are obtained,the rock erosion volume increases by about 34.6%when the dip angle is 10°,argillaceous sandstone is volume,hole diameter and depth of erosion than quartz sandstone increased in 12.2%?26%,5%?12.4%and 6.96%?11.4%. |
PDF Full Text Request