FLOW AND HEAT TRANSFER OF AIR AND STEAM IN INTERNAL COOLING PASSAGES OF TURBINE BLADE

Numerical prediction of three-dimensional flow and heat transfer of air and steam are presented for serpentine cooling channels by using the commercial software CDC. The results show that SSG model is the best turbulence model for the ribbed channels. A study of Grid Generation was performed for flow and heat transfer in serpentine cooling channels, with the same turbulence model. And the results show that the space between the first node and the wall surface (Delta y) is 0.0001 mm and the grid density is 1.3 or Delta y of 0.001 mm and grid density of 1.2 is the appropriate choice for grid generation. Ribbed channels are not sensitive to mesh generation compared with smooth passages. With the same inlet flux, steam heat transfer efficiency is higher than that of air about 15-20%; steam superheat degree is not the key factor for heat transfer, but it had an effect on flow resistance. Compared with smooth channels, ribbed channels reduce the impact of the turn; the best heat transfer regions appear downstream of the turn. V-type ribs have better heat transfer performance than the parallel type ribs; the highest heat transfer occurs in the section between the ribs.