The Heat Transfer Characteristics in Stepped Hole of Traditional Metal Materials Induced by Stepped Film Holes

Abstract

With the increase of temperature requirement, the application of metal matrix materials is gradually reduced due to its poor temperature resistance. In order to improve the application of traditional metal based materials, new cooling technology must be developed to meet the application of metal based materials. In this paper, the cooling flow field of cylindrical hole and two kinds of stepped film holes based on metal materials is simulated by large eddy method(LES), the development of vortex structure and flow characteristics in the mixing area of coolant flow and mainstream are analyzed and studied. The distribution is strongly effected by stronger thermal convection compared with the new temperature resistant material. The results show that four kinds of vortices form downstream the film hole, namely, horseshoes vortex, shear layer vortex, hairpin vortex and the counter rotate vortex pair (CVP). The CVRP formed on the stepped plane which strongly influences the flow and heat transfer of downstream, which is more evident in metal based materials, especially resulted by its isotropic features. Compared with the cylindrical film hole, the structure of step plane efficiently decreases the coolant flow velocity which results in a decrease of the CVP intensity so that the cooling film is adherent to the wall. The thermal conductivity of metal base material is strong, which has a great influence on the temperature distribution inside the wall. Velocity pulsation tightly influenced by CVP, in where the CVP intensity is strong, velocity pulsation is also strong so that the coolant flow strongly mixes with the mainstream. The flow velocity and velocity pulsation decrease with the increasing of the area ratio of stepped hole. The influence of geometric parameters on the heat transfer performance is mainly due to the high heat transfer performance of the metal matrix material.