Optimization and Dynamic Modeling of Friction Losses in Reciprocating Diesel Engines With Emphasis on Rod-Crank Geometry and Ring–Cylinder Contact

Abstract

Abstract. This technical report presents a physics-based model to quantify frictional power losses in a reciprocating diesel engine, focusing on the effects of the connecting-rod-to-crank-radius ratio (L/r) and piston-ring contact area. Simulations were performed for three L/r ratios (2.43, 3.2, and 3.59) and three ring configurations: a single 1.25 mm ring; two rings of 1.25 mm and 1.5 mm; and three rings of 1.25 mm, 1.5 mm, and 1.5 mm. Results indicate that frictional power increases with contact area, from 102 W (single ring, L/r=3.59) to 326 W (three rings, L/r=2.43). Shorter rods amplify lateral forces and friction, whereas longer rods reduce losses with diminishing returns. Normalization against the baseline two-ring case (187 W) highlights these trends. The model identifies an optimal configuration at a moderate L/r ratio with two rings of balanced thickness, minimizing energy loss while maintaining ring durability and sealing performance.