Experimental Investigation of Heat Transfer in Cavities of Steam Turbine Casings Under Generic Test Rig Conditions

Abstract

This paper presents the first experimental results of the systematic investigation of forced convection heat transfer in scaled generic models of steam turbine casing side spaces with varied geometric dimensions under fully turbulent air flow. Data were obtained by two redundant low-heat measuring methods. The results from the steady-state inverse method are in good agreement with the data from the local overtemperature method, which was applied via a novel miniaturized heat transfer coefficient (HTC) sensor concept. All experiments were conducted at the new side space test rig “SiSTeR” at TU Dresden. The dependencies of the HTC distributions on the axial widths of the cavity and its inlet and on the eccentricity between them were investigated for Reynolds numbers from Re=40,000 to 115,000 in the annular main flow passage. The measured HTC distributions showed a maximum at the stagnation point where the induced jet impinges on the wall surface, and decreasing values toward the cavity corners. Local values scaled roughly with the main flow Reynolds number. The HTC distributions thereby differed considerably depending on the dimensions and the form of the cavity, ranging from symmetric T-shape to asymmetric L-shape, with upstream or downstream shifted sidewalls.