PSI - Issue 71

Anoop Kumar A. et al. / Procedia Structural Integrity 71 (2025) 287–294

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Maximum Von Mises stress in the injector head assembly with modified gas duct for proof pressure is 707 N/mm 2 . It is observed that this maximum stress is seen at the mixer assembly body, made of High Strength Steel, which is lower than its yield strength of 980 N/mm 2 . Though the maximum von Mises stress in the gas duct reduces to 620 N/mm 2 , stresses are still higher than its material (Nickel alloy) yield strength of 549N/mm 2 , developing a peak equivalent plastic strain of 1%, which is safe and acceptable from structural point of view due to its local nature. The maximum permanent plastic deformation in the Gas duct is found to be 1.96mm only which is acceptable as it does not affect the form, fit or functionality of the structure [NASA (2016)]. So, injector head assembly with modified Gas duct is safe and acceptable from the structural point of view for the proof pressure condition. Summary of the effects of increasing thickness of the gas duct is tabulated in Table 2. Fig. 5. (a) von Mises stress in injector head assembly at Proof condition – Modified config..; (b) Equivalent plastic strain in injector head assembly at Proof condition – Modified config.

Table 2: Summary of effects of increasing thickness of the gas duct Hardware Configuration Von Mises stress, N/mm 2

Equivalent plastic strain, % Permanent set, mm Mass, kg

Existing Gas duct

814

9.6

13.5

61.8

620

1.0

1.96

79

Modified Gas duct (Increased thickness)

4.2. Thermo-structural analysis of modified gas duct-diffuser sub-assembly for operating conditions For steady-state operating conditions, the Gas duct-diffuser sub-assembly experiences uniform high temperature and high pressure. Pressure distribution with boundary conditions is given in Fig. 6. (a).

Fig. 6. (a) Pressure load with boundary conditions; (b) von Mises stress in gas duct-diffuser sub-assembly at operating condition