Issue34

J. He et alii, Frattura ed Integrità Strutturale, 34 (2015) 564-573; DOI: 10.3221/IGF-ESIS.34.62 570 R ESULTS AND DISCUSSIONS he erosion property of drilling muds on a fluidic amplifier has been numerically modeled by CFD simulation. Especially the particle size, jet velocity and the solid content of drilling muds have been separately analyzed. The discrete phase model of Fluent has been utilized to all numerical simulations, thereby the jet velocity and erosion contour of a fluidic amplifier can be expressed by the particle distribution according to simulation results, which indicates the easy-to-wear position of a fluidic amplifier. In addition, the erosion of drilling muds on a fluidic amplifier can be discussed with various materials of the amplifier. The erosion rate of a fluidic amplifier in hydraulic hammers is obtained according to the simulation results. As shown in Fig. 3, while the input flow rate of drilling muds is 30 L/s, the velocity contours of a fluidic amplifier in hydraulic hammers are obtained, and the distribution of solid particles in drilling muds are also presented. It can be concluded that the wall attachment effect of drilling muds in a fluidic amplifier is steady, which means the hydraulic hammer can normally work. The maximum velocity of drilling muds is 72.4 m/s, and the velocity of slagging nozzle is near to 0, it may be caused by the output pressure boundary condition, which is accessed to natural environment. The distribution of solid particles in a fluidic amplifier is also presented in Fig. 3. It can be implied that the solid particles are accumulated in the flow domain, and a small quantity of solid particles assemble in slagging nozzle. The inner wall of the fluidic amplifier is severely abraded due to the uneven distribution of solid particles with high velocity and pressure. The simulation results show highly agreements with actual cases, as shown in Fig. 1. The erosion rate of drilling muds on a fluidic amplifier is shown as Fig. 4. Totally 7 groups of drilling muds with different performance parameters are deployed in the numerical simulations, and the anti-erosion property of a fluidic amplifier can vary with the drilling muds. It can be inferred that the erosion of a fluidic amplifier is mainly accumulated near the jet nozzle, the maximum erosion rate is ranging from 5 8.9 10   to 4 1.12 10   . While the jet velocity of drilling muds is excessing 68.9 m/s, the erosion of drilling muds on a fluidic amplifier is dramatically changing to some extent. Moreover, the effect of particle size in drilling muds on erosion rate of a fluidic amplifier can be discussed by 1 # , 2 # and 3 # samples. Simultaneously, the effect of solid content in drilling muds on erosion rate can be implied by sample2 # , sample 6 # and sample 7 # . In end, the effects of drilling muds with various performance parameters on erosion rate of a fluidic amplifier has been discussed and concluded. Figure 5 : Erosion rate of drilling muds on a fluidic amplifier almost linearly varies with particle size. Effects of Particle Size on Anti-erosion Property The particle size of drilling muds has a great influence on the anti-erosion property of a fluidic amplifier. As shown in Fig. 5, the erosion rate is nearly linearly varying with the particle size of drilling muds. The minimum erosion rate of a fluidic amplifier is 5 4.25 10   while the particle size of drilling muds is 20  m. Nevertheless the maximum erosion rate is T