Study on Erosion by Built-In Pulse Impactor Based on Simulation

The built-in pulse impactor used in oil and gas drilling often suffers from erosion issues, which reduce mechanical drilling speed and significantly shorten the drill bit lifespan. To address this, this study employs computational fluid dynamics (CFD) with the discrete phase model (DPM) and DPM erosion model, combined with erosion theory, to simulate the erosion process. The computational domain includes the rotating body, housing, and internal flow channels of the impactor, with key structural parameters: external diameter 120 mm, internal flow height 23 mm, and flow channel angle 30°. Boundary conditions are set as follows: inlet velocity of drilling fluid ranges from 27.558 to 32 m/s, solid particle diameter varies from 0.074 to 0.11 mm, and particle mass flow rate (concentration) is 0.2-0.6 kg/s. The study analyzes erosion lifespan of different materials and identifies influencing factors. Results show that under high-pressure drilling fluid conditions, solid-phase particles cause significantly greater erosion than the liquid phase. Particle distribution is uneven, leading to accumulation in the rotating body, erosion damage intensifies over time, concentrating primarily at the flow channel outlet. CFD simulations indicate that 40CrMo has the longest erosion lifespan (525.47 h), outperforming 45 steel and Q235A. Regarding influencing factors: increasing fluid velocity (especially 30-32 m/s) and particle concentration (0.2-0.5 kg/s) significantly raises the erosion rate; larger particle diameters reduce the erosion rate, with the decreasing trend slowing when diameter exceeds 0.09 mm. The erosion rate is maximum at impact angle 30 °C. This study provides insights for reducing erosion and extending the service life of built-in pulse impactors.