Numerical investigation of a novel multistage swirl cooling conception in blade leading edge of gas turbine

Swirl cooling is one of the latest and promising internal cooling strategies, which has been widely reported in the designs of the turbine blade leading edges. Based on the traditional single-stage swirl cooling configuration, this paper introduces a novel conception of multistage swirl cooling configuration (two and three stage), aiming to improve the cooling performances of the leading edges without increasing the cooling air consumption. In the new multistage configurations, the vortex chamber is divided into several stages, so that the tangential velocity of cooling air is significantly increased. To reveal the heat transfer and flow characteristics of cooling air in the multistage swirl cooling configuration, a series of numerical simulations are conducted by conjugate heat transfer algorithm under the realistic conditions of gas turbine operations and the real leading edge model of a VKI turbine blade. The numerical results indicate that: under the same coolant mass flow rate, the averaged Nusselt number in the three-stage swirl cooling structure is at least over 75% higher than that in the single-stage structure, and the Nusselt number distribution is also more uniform. At ReD = 40,000, the surface temperature averaged over the entire leading edge wall of the three-stage swirl cooling structure can be nearly 100 K lower than that in the single-stage one. The significant heat transfer enhancement of multistage swirl cooling is at the cost of a higher total pressure loss. However, if the bends connecting the adjacent stages are modified into round-shaped, the pressure loss can be significantly decreased, therefore the thermal performances of the multistage swirl cooling models are higher than that of the single-stage model.