There is a general desire to decrease the specific fuel consumption and to increase the thrust/weight ratio of gas turbines, which calls for higher turbine inlet temperatures. Thus, there is a need for efficient cooling methods that will ensure low and uniform wall liner temperatures. Other parts needing protection are the turbine end walls, turbine blades and the flame-holders.
The most effective cooling method is transpiration cooling, where the coolant flows through a porous wall. A large area is available for heat transfer and the air that emerges from the wall forms a protective film. The major disadvantage with transpiration cooling is that particles or oxides clog the pores. A much more practical cooling method therefore is effusion cooling. A large number of small injection holes are drilled through the wall. These holes are big enough to ensure that no particles become stuck and impede the airflow.
A scaled experiment was designed and measurements were performed on a flat plate with many rows of injection holes inclined 30º to the main flow direction. Measurements were made on one of these slanted jets in the third row using three-component Laser Doppler Anemometry (LDA).
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