Experimental and numerical investigation on the conjugate heat transfer characteristics of a double-wall turbine vane with mist injections

This study examined conjugate heat transfer (CHT) characteristics of an air-cooled and mist/steam-cooled double-wall vane using experimental and numerical methods. Thermocouples embedded in the shallow slots on the surface of the air-cooled vane were used to measure wall temperature at the mid-span cross-section under varying operating conditions, including relative mainstream Reynolds numbers ( Re rel = 0.75–1.03), coolant-to-hot gas mass flow ratio (MFR = 5.9%–14.4%), and temperature ratio (TR = 1.75–2.47). The experimental data facilitated the establishment of the overall cooling effectiveness (OCE) correlation, and the numerically predicted method for CHT performance of the vane in a cascade with and without mist was validated and evaluated. The enhanced cooling capacity of the steam coolant prompted a numerical investigation into the effect of mist injections on the steam-cooled double-wall vane's OCE for a hydrogen-fueled gas turbine by varying mist proportion ( m s = 5%–20%) and droplet diameter ( d p = 5 μm–20 μm). The results demonstrated that the numerical method adopted in this study is quite effective and aligns with the experimental data. The MFR substantially influences the OCE of the air-cooled double-wall vane, increasing from 5.9% to 9.5%. The steam-cooled double-wall vane exhibits a synergistic relationship between the m s and d p , enhancing overall cooling effectiveness, especially at the suction side, as m s increases. The optimal averaged OCE of the steam-cooled vane at the mid-span and across the entire surface of the vane was achieved at m s = 20% with a relatively small particle size of 10 μm, resulting in an approximately 11% increase compared to conditions without mist, equating to an 88.6 K reduction in the vane's wall temperature.