PSI - Issue 57

Giovanni M. Teixeira et al. / Procedia Structural Integrity 57 (2024) 670–691 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

684

15

heating up to the moment it cools back down to room temperature. Fluctuations in the stress and strain values are expected when the engine operating condition changes. However, for the purpose of durability, just the most severe of the operating conditions needs to be simulated. The present case study considers the rated power operating condition. The temperatures generated at this engine condition are the thermal boundary conditions used as input for the thermo mechanical analysis. These temperatures are obtained by simulation. Heat transfer convective coefficients (or simply HTC) and mean temperatures (Tbulk) are applied at the external surfaces (of a finite element model) in contact with the exhaust gases. They are obtained by CFD (computational fluid dynamics) or by empirically based in-house codes. Contact conductance needs to be defined for those surfaces in contact with the bolts and cylinder head. When symmetry is present (see figure 16) no boundary conditions need to be defined for the nodes lying on the symmetry plane (adiabatic surface). The heat transfer analysis only requires that thermal conductivity be defined as material property (see figure 12).

Fig. 12. SiMo 4.06 thermal conductivity as a function of temperature

3.1. The Heat Transfer Analysis Figures 13 and 14 show the temperature distribution obtained at the end of a heat transfer analysis. The maximum temperature of about 1000K is obtained at the region A indicated below.

Fig. 13. Temperature distribution results from the Heat Transfer Analysis

The maximum temperature observed through the process of heating up and cooling down (thermal shock) of an