Numerical simulations on effect of cooling hole diameter on the outlet temperature distribution for a gas turbine combustor

Abstract

The outlet temperature distribution characteristics of a gas turbine combustor are critical to the durability and lifetime of the turbine. Regarding to an advanced high-temperature-rise combustor, the air flow rate for swirling increases while the volume of air used to cool the wall and control the outlet temperature field decreases, causing severe challenges in effectively regulating the outlet temperature field, consequently. In the present work, with a focus on regulating the outlet temperature field under conditions of low cooling and mixed gas volume, numerical simulations of a single-sector centrally-staged combustor are carried out. The effusion cooling structure of multi-inclined cooling holes with 30° inlet angle are used on the liner wall. The impact of liner wall cooling holes with different diameters on the outlet temperature distribution characteristics is analyzed, while the variation in relative areas and distribution shapes of low-temperature regions near the outlet wall and hot streaks are obtained. The results suggest that under a constant inlet mass flow rate, both pattern factor (PF) and radial pattern factor (RPF) of the combustor increase with the increment of cooling hole diameter. Compared to the 0.5 mm hole diameter, when the diameter of each single cooling hole is doubled to 1.0 mm, the PF and RPF increase respectively by 1.14 times and 1.83 times, meanwhile, the combustion efficiency decreases from 99.97% to 97.74%, and the pressure drop reduces from 4.3% to 2.4%. Increasing the diameter of cooling holes enhances the cooling film thickness on the liner wall, resulting in the expansion of low-temperature regions near the outlet wall. Furthermore, in comparison with the smaller diameter, the larger diameter forces the combustion reaction zone to shift toward the outlet, leading to the expansion of hot streaks and a deterioration in the uniformity of the outlet temperature field. The combustor corresponding to the design scheme of multi-inclined cooling holes with 0.5 mm diameter has the most uniform outlet temperature field and the highest combustion efficiency, showing the optimum performance.