Numerical Simulation and Optimization of Engine Cooling System Based on One-Dimensional and Three-Dimensional Coupling Analysis Method

<div>The design of motorcycle engine cooling systems is often hampered by a trade-off between computational efficiency and simulation accuracy, making optimized design iterative and costly. A streamlined, coupled 1D–3D methodology, validated across diverse engine configurations, is needed to address this challenge. This study develops and validates an iterative simulation framework to efficiently optimize cooling systems for various motorcycle engines. The 1D system model defines the performance targets, while 3D CFD analysis enables detailed component optimization (water jackets, radiator airflow); an iterative process ensures the target fulfillment. The 1D–3D coupling analysis methodology is applied to single-, two-, and four-cylinder engines. Results show that the coolant flow velocity within the water jackets are sufficient to ensure effective heat removal of engines and confirms the rational layout design of water jackets. The radiator inlet coolant temperature for the original design of those three engines cooling are 109°C, 107°C, 103°C, respectively. Optimizations (fan shroud redesign, impeller width increase, airflow outlet redesign, air guiding device, radiator shield, wind shielding area reduction, cover removal) are made to increase the radiator airflow velocity by 34.92%, 12%, 7.5%, respectively, and successfully reduces the radiator inlet temperatures below the 100°C target (from 109°C to 99°C, 107°C to 100°C, and 103.8°C to 99.2°C, respectively), with results validated experimentally. The deviation between simulation and experiments is below 7%, confirming the overall reliability and accuracy of the simulation model. The study provides a validated, scalable framework for optimizing motorcycle engine cooling systems, balancing accuracy with efficiency. Its applicability to the cases presented suggests potential for broader use in hybrid and electric powertrain thermal management.</div>