THERMAL ANALYSIS OF STEAM TURBINE BLADES

Abstract

Steam turbine blade temperatures govern creep life, fatigue strength, efficiency, and maintenance cost. This paper presents a rigorous thermal analysis workflow for stationary and rotating blades in highpressure (HP) and intermediate-pressure (IP) sections of a steam turbine operating at inlet conditions of 15–24 MPa and 773–813 K. We formulate a conjugate heat-transfer (CHT) problem coupling internal conduction within the airfoil/roots with external convection and phase-change effects of wet steam, include thermal radiation in casings above 700 K, and evaluate the impact of surface roughness, scale deposition, and film-cooling slots where used. The numerical model is solved using a finite-volume CFD solver for the flow and a finite-element (FE) solver for the solid with tight twoway coupling. We perform mesh-independence and time-step sensitivity studies and estimate heattransfer coefficients using wall-resolved turbulence models validated against correlations. A parametric study (material, coating, and cooling configuration) shows that a 300 μm ceramic thermalbarrier coating (TBC) with conductivity 1.2 W·m⁻¹·K⁻¹ and emissivity 0.85 reduces metal peak temperature by ~55–85 K, while modest film cooling (MFR = 0.8–1.2%) cuts the leading-edge temperature another ~20–40 K. Predicted temperature gradients inform a thermoelastic stress analysis; the maximum von Mises thermal stress falls from 265 MPa (bare blade) to 198 MPa (TBC + film), improving estimated creep life by ~2× under Langer-type cumulative damage rules. The workflow and findings provide a traceable basis for blade thermal design, lifing, and maintenance scheduling.