A Comprehensive CFD-FEA Conjugate Heat Transfer Analysis for Diesel and Gasoline Engines 2019-01-0212

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 research evaluates a method of Conjugate Heat Transfer (CHT) analysis for a diesel as well as a gasoline engine that combines the combustion Computational Fluid Dynamics (CFD), Engine Finite Element Analysis (FEA), and cooling jacket CFD with the aim of getting more accurate temperature distribution and heat loss predictions in the engine compared to standard de-coupled CFD and FEA analysis methods. This conjugate heat transfer technique was successfully applied to the 15.0 L Cummins ISX heavy duty diesel engine operating at 1250 rpm and 2.0 L GM LHU gasoline engine at 2000 rpm. Combustion CFD simulations are performed for the diesel & gasoline engine and results 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 is achieved. A comprehensive CHT methodology is proposed and the model is then validated against experimental data available from thermocouples embedded inside the piston surface, liner and head. The detailed CHT model includes the coolant circuit and oil gallery. The overall predictions from the model match closely with the experimental data. The CHT results from this detailed method are also compared with a traditional experience-based FEA method developed in-house at Southwest Research Institute. The work establishes a validated modeling framework for CHT modeling in diesel and gasoline engines.