Advances Toward the Goal of a Genuinely Conjugate Engine Heat Transfer Analysis

As the design of engines advances and continues to push the capabilities of current hardware closer to their durability limits, more accurate and reliable analysis is necessary to ensure that designs are robust. This research evaluates a method of conjugate heat transfer analysis for a diesel engine that combines the combustion CFD, Engine FEA, and cooling jacket CFD with the aim of getting more accurate heat loss predictions and a more accurate temperature distribution in the engine than with current analysis methods. A 15.0 L Cummins ISX heavy duty engine operating at 1250 RPM and 15 bar BMEP load is selected for this work. Spray combustion computational fluid dynamics (CFD) simulations are performed for the diesel engine and the results are validated with experimental data. Finite Element Analysis (FEA) simulations were performed in a separate software platform. Data interchanges between CFD and FEA software codes were performed at specified sub-cycle engine intervals and the simulations ran for multiple engine cycles. A comprehensive CFD-FEA conjugate heat transfer (CHT) methodology is proposed and the accuracy of this method is measured against the existing diesel engine analysis procedures. The detailed CHT model includes the coolant circuit and oil gallery. The CHT results from this detailed method are compared with a traditional thermal FEA method developed in-house at Southwest Research Institute that uses experience based heat transfer coefficients (HTCs) that have been validated to testing. Finally, point-wise measurements of temperature at various locations on the cylinder head are compared with simulation results and are found to correlate reasonably well.