Abstract

Application of effusion cooling or effusion based compound cooling in the state of art gas turbine combustor is more and more common, especially in aero-engines. A linearly arranged planar optically accessible three-nozzle lab scale combustor equipped with perforated testing plate for cooling is designed. Overall cooling effectiveness is experimentally examined as the key indicator of cooling performance at non-reacting flow conditions. Main air is electrically heated to about 573K. Temperature of perforated liner is recorded by the short-wave infra camera with careful calibration. Effect of effusion hole inclination angle is investigated by comparing at forward (30°), normal (90°) and backward (150°) cases. Pressure drop across the nozzle is set to be 3%, 4% and 5% respectively and that is 0–2.5% for the effusion plate. The main purpose of this work is to characterize combustor liner effusion cooling capacity at conjugate heat trasnfer conditions, and backward cooling configuration is firstly investigated.

Results clearly show that effusion cooling behavior is strongly influenced by main swirling flow regime near the combustor liner wall. To be specific, three zones as Corner Recirculation Zone (CRZ), Impinging Zone (IZ) and Developing Zone (DZ) can be divided. IZ is the region which we should treat carefully for liner cooling design because it sustains the highest heat load. Generally, inclined holes perform better cooling characteristics than normal ones. The important observation is that backward injections reveal “anti-impinging” ability, which can enhance the cooling effectiveness in upstream CRZ and IZ greatly with high coolant consumption. The potential drawback is that reverse cooling jets may induce intense interactions with main flow. But it is still a good choice for optimizing combustor effusion cooling, especially in swirling impinging regions.

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