Conjugate Heat Transfer Analysis of an i-4 Engine including Pistons, Liners, Block, Heads, Water Cooling Jacket, and Oil Cooling Jets

Internal combustion engine (IC engine) vehicles are commonly used for transportation due to their versatility. Due to this, efficiency in design process of IC engines is critical for the industry. To assess performance capabilities of an IC engine, thermal predictions are of utmost consequence. This study describes a computational method based on unsteady Reynolds-averaged Navier–Stokes equations that resolves the gas–liquid interface to examine the unsteady single phase/multiphase flow and heat transfer in a 4-cylinder Inline (i-4) engine. The study considers all important parts of the engine i.e., pistons, cylinder liners, head, block etc. The study highlights the ease of capturing complex and intricate flow paths with a robust mesh generation tool in combination with a robust high-fidelity interface capturing VOF (Volume-of-Fluid) scheme to resolve the gas-liquid interfaces. Results obtained show the dominant processes that determine the oil distribution to be the piston speeds from reciprocating motion of the pistons and the flow rate of oil injected through the squirter jets. A novel heat transfer approach (mixed time-scale coupling) is used to solve for the temperatures in the engine solids. To resolve the heat transfer between the squirter jet flow and piston/cylinder liner, the approach separates the conjugate heat transfer calculation into a fluid heat simulation and a solid heat simulation while setting up a communication method to exchange the thermal boundary conditions between them. The communication method takes into account the changes in heat transfer from piston to cylinder liner due to changes in position of the piston. The study also considers water jacket cooling in the engine block and head to holistically assess the overall heat transfer in the engine solids. Results of thermal simulation show the solid temperatures to be in direct correlation with the oil distribution near those solids as well as the flow rate of water coolant in water jacket cooling system.