Effect of dimple shape and depth on tribological performance of textured surface

Piston-cylinder contact accounts for 12.5% of the total fuel consumption in an IC engine. The tribological performance of this mechanism can be improved by introducing surface texturing on the piston ring and skirt. The film between the surfaces remains in hydrodynamic region due to surface texturing. The numerical study emphasizes the effect of Reynolds number and geometric shapes on load-bearing capacity, pressure distribution, and friction force of the 3D hydrodynamic model with incompressible lubricant. Furthermore, the effect of dimple depth for the best geometry case is presented. The analysis is performed in ANSYS fluent software, considering steady-state laminar flow with constant density and viscosity for the velocity of 9 m/s, 18 m/s, and 27 m/s. Reynolds-averaged Navier-Stokes equations (RANS) model is used to predict the fluid motion considering laminar flow by utilizing the SIMPLE pressure-velocity coupling algorithm and second-order upwind discretization scheme. Square, ellipse, triangular, and circular dimples are simulated with different geometric parameters, and optimized geometry is obtained. A sliding section of the piston ring is considered with a film thickness of 100 microns. The introduction of texturing on the surface improved the load carrying capacity. The current study compared different dimple shapes and found that change in the shape of dimple also influences load carrying capacity. The comparison is carried out by keeping areas of different dimple shapes constant for consistency, and the square dimple textured model indicated the best performance of a 123% increase in load-carrying capacity at a velocity of 27 m/s when compared with the non-textured model. Furthermore, an increase in depth from 30 µm to 50 µm resulted in a decrease of load-carrying capacity at a maximum of 42.5 % when compared with the non-textured specimen at the high-velocity case.