STUDY ON MIST COOLING CHARACTERISTICS OF TURBINE GUIDE VANE WITH DOUBLE-WALL STRUCTURE UNDER OPERATING CONDITIONS

Mist/air cooling is an innovative cooling method designed for protecting turbine blades under elevated temperature conditions. This study presents the first application of this cooling technique to a double-wall structured turbine vane in actual operating conditions, with conjugate heat transfer simulations conducted to evaluate its performance. The investigated double-wall vane features a complete cooling structure, including impingement holes, film holes, and pin-fins. The effects of radiative conditions and mist parameters are analyzed, and comparative simulations are conducted to evaluate the performance of air and steam cooling. Results indicated that thermal radiation causes an overall reduction in the effectiveness of vane surface cooling, with a significant decrease of 14.5&#37; observed in the leading-edge (LE) region. When adding mist with a mist-to-air mass ratio (m*) of 10&#37; and a droplet diameter (<i>d</i>_p) of 30 &mu;m, the average cooling effectiveness on the pressure and suction sides reaches 0.773 and 0.749, respectively. Compared to air-only cooling, adding mist achieves a remarkable improvement of 24.4&#37; in LE cooling performance. The simulation results further reveal that mist cooling is relatively insensitive to variations in <i>d</i>_p but exhibit significant enhancement with increasing m*. However, the application of mist/air cooling results in a less uniform surface temperature distribution compared to both air and steam cooling methods, suggesting the need for vane structural optimization to achieve better coolant matching.