Issue34

J. He et alii, Frattura ed Integrità Strutturale, 34 (2015) 564-573; DOI: 10.3221/IGF-ESIS.34.62 567 promotes the structure design of hydraulic hammers with a fluidic amplifier. Thus appropriate theory about anti-erosion property simulation of a fluidic amplifier should be selected and applied. Allowing for the material property of a fluidic amplifier, the elasto-plastic deformation theory and micro-cutting theory are employed in the simulation of anti-erosion property of a fluidic amplifier. CFD SIMULATION otally 7 groups of drilling muds with different performance parameters are utilized into CFD simulation, as shown in Tab. 1. There are 3 variables in the whole simulation, which are particle size, velocity and solid content, respectively. In order to obtain more accurate results, the numerical modelling, meshing and solving process are successfully completed. Numerical Modelling and Meshing As shown in Fig. 2, the numerical model of a fluidic amplifier was established by software Inventor according to the parameter of a 203 mm hydraulic hammer. The material models of a fluidic amplifier were defined as 35CrMo and cemented carbide. Figure 2 : Numerical model and meshes of a fluidic amplifier in hydraulic hammers. The parameter of the jet nozzle in a fluidic amplifier is 8.7 mm X 50 mm, and the length of fluidic amplifier is 250 mm. In total, four computed domains are defined in the numerical model of fluidic amplifier, including the domain of jet nozzle, the domain of slagging nozzle, the domain of control nozzle and the domain of output nozzle. The main jet flows through the nozzle with high speed and pressure. In order to improve the strength of a fluidic amplifier, the contact area with drilling muds has been enhanced by cemented carbide, which is partly brazed into the fluidic amplifier. The meshing process will be accomplished by Workbench once the numerical model of a fluidic amplifier is established. There are totally 168190 grids in each of numerical model of a fluidic amplifier, and the meshed grids are hexahedrons, which are obtained by free meshing of Workbench. All of the meshed grids are volume grids with a maximum diameter of 3mm, and the grid coordination is excellent. The contact domains of a fluidic amplifier with drilling muds are remeshed within a refinement of 2 mm. The meshed grids of a fluidic amplifier are shown as Fig. 2. Boundary Conditions In order to gain much more steady wall-attachment effect of a fluidic amplifier while the hydraulic hammer is in performance, the out-put pressure boundary condition of 1 atm. is defined, and the inlet pressure boundary condition is T