The increase usage of naval gas turbines in ships propulsion is expectable in the near future and the existing information on literature about those exhaust systems is not available. In addition, a robust design of these systems should consider, for instance, an in-depth knowledge of the thermomechanical stresses induced due by the aerodynamic pressure of the combustion product’s flow and by the heat flux. Engineering design tools were used to optimise the existing exhaust system’s design and experimental tests were carried out, in order to avoid the occurrence of crack propagation and to ensure structural integrity.
Partners: FFCT/UNL, UNIDEMI, ICEMS-IST, LNEC
Funding organization: Science and Technology Foundation (PT)
Main achievements: - An in-service strain spectrum was collected with a high-temperature spot-welded strain gauge and temperature distribution was monitored with eight thermocouples spot-welded on the critical region of the exhaust system. A pressure distribution was also acquired at its outlet section; - The possibility of usage of a new, cheaper and high-strength austenitic stainless steel (Cr-Mn) in some critical locations of a naval gas turbine exhaust system was assessed; - Axial tensile tests, creep tests, FCGR tests and fatigue strength tests were carried out, at different temperatures, on standard test specimens fabricated with two base materials, namely the austenitic stainless steel AISI 316L and the new Cr-Mn stainless steel. The weld bead profiles of the welded specimens were characterised and the residual stresses existing near the weld toe were determined by the hole-drilling strain-gage method. Corrosion tests were also carried out; - A redesigned geometry of the exhaust system was analysed by finite element method and its fatigue life assessed.