Multiscale analysis of thermomechanical stresses in double wall transpiration cooling systems for gas turbine blades

Ratchetting and Creep Failure in Twin-Wall Turbine Blades Experiencing Severe Thermal and Centrifugal Loading

“…We define SCF here as the maximum hole stress (calculated by elastic 3D FE simulations in Fig 9a ) normalised by the theoretical nominal stress in the 𝜃𝜃 −direction (given by Eq 4ii for 𝑦𝑦 = −𝑡𝑡 ℎ /2 and 𝑝𝑝 = 0). In agreement with [3], the SCF at the film hole is practically independent of wall thickness ratio, 𝑡𝑡 𝑐𝑐 /𝑡𝑡 ℎ , and reduces linearly with the 𝑝𝑝/𝜎𝜎 𝑇𝑇 ratio according to SCF = 3.6 −11 𝑝𝑝/𝜎𝜎 𝑇𝑇 , whereas the SCF at the impingement hole increases with 𝑝𝑝/𝜎𝜎 𝑇𝑇 ; here SCF = 1.85 −9 𝑝𝑝/𝜎𝜎 𝑇𝑇 . These explain the slopes of the SPf and SPi boundaries in Figs 10a-b; the boundaries are obtained by simply scaling the elastic stresses by SCF in the expressions of Section 3.2 (by using 𝑝𝑝 = 0 as SCF is defined here based on the 𝜃𝜃 −nominal stress for convenience).…”

“…These benefits are realised by increasing the gas turbine inlet temperature beyond current levels. The implementation of DWTC in high pressure turbine blade components (see Fig 1a), however, results in them experiencing extreme thermomechanical (TM) loading [2][3][4], which can be a barrier to the widespread adoption of this technology in practice.…”

“…Studies on aerothermal and mechanical aspects of DWTC currently consist of a short list of recent reports [1][2][3][5][6][7][8][9][10][11][12][13][14]. On the aerothermal side, cooling arises from a combination of processes: (a) impingement cooling internally via flow through impingement holes in the internal cool wall; (b) film cooling due to directed flow through angled film holes in the external hot wall; and (c) conductive cooling along pedestals connecting the walls (see Fig 1b).…”

Designing against severe stresses at compound cooling holes of double wall transpiration cooled engine components

“…This implies that the stress state in the vicinity of effusion holes is dictated by the global features of the temperature field, rather than the temperature perturbations near the holes. A concurrent study [61] further supports this argument based on results for the system of Fig 1b, obtained through a series of CFD-heat transfer-FE stress analyses. These studies allow us to assume that the stress state in the vicinity of holes is not influenced by the different temperature perturbations that would in practise occur when the hole shape-size characteristics are modified.…”

Coupled Aerothermal-Mechanical Analysis in Single Crystal Double Wall Transpiration Cooled Gas Turbine Blades with a Large Film Hole Density

“…The relationship between the film hole density and the structural integrity of DWTCs has received even less attention. Relevant work has only been presented by the authors in terms of elastic theoretical and Finite Element (FE) analysis [2] τ crss critical resolved shear stress (MPa) Δτ crss sum of τ crss at peak temperature and τ crss at room temperature at a particular location in the system (MPa)…”