PSI - Issue 42

6

Ricardo Pires et al. / Procedia Structural Integrity 42 (2022) 639–646 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

644

The values for the parameters of the Morrow equation (Table 3) were obtained from Oh et al. (2018). Table 3. Parameters used in Morrow equation (Eq. 1) obtained from Oh et al. (2018).

In addition, the analyses discussed before were then repeated using the 445M2 ferritic stainless steel, and these allowed establishing a gas temperature drop even higher, allowing exit gas temperatures lower (269 ºC) than those obtained with the EGR made of AISI 304L. Moreover, lower induced stresses at the fin’s entrance were noticed (Fig. 6). This will undoubtedly result in higher fatigue lives for the EGR made of ferritic stainless steel.

Fig. 6. Stress values at critical locations on the hybrid tube and the EGR inner fin for the 445M2 ferritic stainless steel. . Furthermore, the passage of the exhaust gases and the coolant induce very low stresses, typically well below 10 MPa, confirming the temperature as the critical design variable. Finally, the last word for the frequencies and modes of vibration of the EGR to say that a combustion motor with 4 cylinders and 4 stages, running at 6000 rpm, will generate vibrations in the order of 200 Hz. However, looking at Fig.7, it is possible to see that resonance will never occur since the first natural frequency of the EGR is higher than 1190 Hz, well above the 200 Hz caused by the motor. Moreover, as the fin’s length increases, the first natural frequencies will also increase together with its mass value.