The interaction between upstream and downstream film cooling rows in flow field and heat transfer

Abstract

Towards a higher turbine inlet temperature, full coverage film cooling or effusion cooling is an effective way to cool the hot cascade. The interaction between upstream and downstream film cooling rows becomes more and more important for the evaluation of cooling effectiveness. In this paper, film cooling effectiveness distributions and aero-thermal fields of one film cooling row and two in-line film cooling rows with spacing ratio S/D = 6 are compared and investigated to reveal the row-to-row interaction. The LES model is first validated by a flat plate experiment in which the mainstream velocity equal to 25 m/s, then the LES model is used to analyze the flow field and heat transfer. The results show that the upstream ejection would thickens the downstream boundary layer, making the downstream coolant flow penetrate deeper into the main flow, thus causing poor coolant coverage of the rear film cooling ejection. On the other hand, the lifted kidney vortices of the second row ejection entrain first row ejection to the wall, making the coolant flow from the first row contribute significantly to the coolant coverage on the wall downstream of the second row. The turbulence intensity has great impact on the film cooling effectiveness after the first row, but very small influence on the second row.