Numerical modelling of the tribological and gas-dynamic interaction between piston rings and liner in internal combustion engines

This research investigates the complex behavior of the piston‐ring‐liner system in internal combustion engines, emphasizing lubrication regimes, frictional losses, blow‐by effects, and overall mechanical performance under varying conditions. Both hydrodynamic and mixed lubrication states are analyzed, along with solid–solid contact phenomena under high loads, which pose significant thermal and mechanical challenges at elevated speeds and power demands. A primary focus is the lubrication mechanism within the piston–ring–liner interaction. We employ a mixed lubrication model that integrates fluid film lubrication with asperity contacts, using the Greenwood–Tripp model and the Patir–Cheng flow factor formulation. This method elucidates the interplay between the oil film and surface roughness under differing temperature and pressure conditions that affect lubricant viscosity. The full Reynolds equation is solved, accounting for cavitation and non-linear fluid. Frictional heating—which reduces lubricant viscosity and impacts both hydrodynamic friction and asperity contact—is also examined. Thermal effects are incorporated by solving the energy equation to capture local temperature distributions across the lubricated contacts. For engine sealing, the blow-by phenomenon is studied using a 1D CFD model to assess pressures around the piston rings and predict gas leakage from the combustion chamber to the crankcase. This analysis is vital for understanding how the rings conform to the cylinder liner under operational stresses, with phenomena like ring flutter potentially causing increased blow-by at high speeds. The study evaluates a high-performance engine at speeds ranging from 3000 rpm to 10,000 rpm, including a scenario with a non-linear fluid at 10,000 rpm, to capture both low- and high-speed behaviors and the influence of non-Newtonian fluid properties. This integrated approach, combining mixed lubrication with advanced numerical models, provides valuable insights for enhancing engine efficiency and understanding the dynamic thermal interactions within the piston–ring–liner system.