Numerical Investigation on Cooling Air Flow and Resistance Characteristics Inner Laminated Cooling Structures

Abstract

Abstract Today, laminated cooling structures have been widely used in the designs of advanced gas turbines, because the structures with double walls, pins, impingement holes and film holes can provide much higher overall cooling effectiveness than simple film cooling. Of course, this kind of cooling structures also leads to a higher price due to a larger flow resistance to cooling air injection in comparison with the simple film cooling. The previous investigations concerned with the laminated cooling structures mainly focused on heat transfer performances, the flow resistance characteristics within the complex channel of the structures are relatively less. This paper presents a numerical investigation on the characteristics of the cooling air resistance passing through 6 different laminated structures. The influence factors on the fluid flow and resistance performances of cooling air, such as array, density and shape of film hole, as well as impingement-hole area (diameter), are discussed and compared at the same pressure ratios of the inlet to outlet of the 6 laminated structures. The discussions and comparisons reveal the following interesting phenomena: 1) A larger diameter of impingement hole corresponds to a larger mass flow rate of cooling air at the inlet of the laminated structure, but the inlet velocity is mainly dependent on the density of film hole. At the same total area of film holes, a larger density corresponds to a higher inlet velocity. 2) The flow rate through film hole of laminated structures is influenced more and more obvious by the outlet shape and the inflow angle of film hole as the increasing pressure ratio. 3) The resistance coefficients of the entire laminated structures are dependent on the density and shape of film holes. At the same total area of film holes, a higher density corresponds to a lower resistance coefficient. Although fan-shaped film hole can provide a larger cooling air coverage, the price is a higher resistance coefficient. Therefore, the applications of fan-shaped film holes in the laminated structures should be considered only in the regions with low environment pressures.