EXPERIMENTAL and NUMERICAL STUDY on IMPINGEMENT HEAT TRANSFER and FLOW CHARACTERISTICS on A SEMICIRCULAR RIBBED TARGET SURFACE

Impact cooling is an effective way to enhance heat transfer, especially in the gas turbine blades. In the leading edge of the blade where has the high heat load, jet impingement cooling is widely used due to its high heat transfer characteristic in stagnation region.The focus is on finding a cooling structure that can improve the heat transfer effect of the internal impact structure at the leading edge without increasing the internal flow resistance. In this paper, using transient liquid crystal experiments researches for the flow and heat transfer characteristics of a semi-circular structure, which is simplified from the real blade leading edge 's inside surface and have different rib structures.This paper studies five cases:no rib, round-shaped raised structure,oblique rib,round-shaped raised structure and oblique rib and span-wise rib and arc rib to find their heat transfer and flow characteristics.Some rib-shaped protrusion has three heights, which are 30%, 50%, 70% of the impact distance H.Experimental conditions of Reynolds number are Re = 10000, 15000, 20000, 25000, 30000. The experimental verification results show that the internally strengthened heat transfer structures studied in this paper can improve the heat transfer effect of the leading edge array of the turbine blade impact target surface without increasing the flow resistance.The structure with both oblique ribs and roundshaped raised structures has the highest surface average Nusselt number of the target plate and the lowest discharge coefficient of the channel .The structure with both span-wise ribs and arc ribs has a staggered high heat transfer area distribution ,which can maybe use in some special cases.