A Comprehensive CFD-FEA Conjugate Heat Transfer Analysis for Diesel and Gasoline Engines

As the efforts to push capabilities of current engine hardware to their durability limits increases, more accurate and reliable analysis is necessary to ensure that designs are robust. This paper evaluates a method of Conjugate Heat Transfer (CHT) analysis for a gasoline and a diesel engine that combines combustion Computational Fluid Dynamics (CFD), engine Finite Element Analysis (FEA), and cooling jacket CFD with the goal of obtaining more accurate temperature distribution and heat loss predictions in an engine compared to standard de-coupled CFD and FEA analysis methods. This novel CHT technique was successfully applied to a 2.5 liter GM LHU gasoline engine at 3000 rpm and a 15.0 liter Cummins ISX heavy duty diesel engine operating at 1250 rpm. Combustion CFD simulations results for the gasoline and diesel engines are validated with the experimental data for cylinder pressure and heat release rate. Radiation models were implemented to estimate heat transfer more accurately for diesel engine. FEA simulations are performed in a separate software platform. Data exchanges between CFD and FEA software codes are performed at specified sub-cycle engine intervals and the simulations are continued for multiple engine cycles until cycle-to-cycle convergence of wall temperatures is achieved. The model predictions are validated against experimental data available from thermocouples embedded inside the cylinder head. The detailed CHT model includes the coolant circuit and oil gallery. The overall predictions from the model match closely with the experimental observations. The work establishes a validated modeling framework for CHT modeling in gasoline and diesel engines.