TS-51 Impingement/Effusion Cooling : Influence of the Number of Holes on the Cooling Effectiveness for an Impingement X/D of 10.5 and Effusion X/D of 7.0(Session C-2 Heat Transfer 2)

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Impingement/efusion cooling offers one of the most effective ways of cooling gas turbine combustor walls and turbine blades. The optimum effusion cooling occurs with the maximum number of effusion holes that can be manufactured in a given surface area. It is shown in the present work that a much lower number of impingement holes than effusion holes can be used, with no significant reduction in the cooling effectiveness compared with using the same number of impingement and effusion holes. For adequate combustor wall cooling a cooling effectiveness of 0.7 is normally required and this was achieved with a coolant flow rate per unit surface area, G, of 0.4kg/sm^2, at a coolant to mainstream density ratio of 2.5. Conventional film cooling would require approximately a G of 1.0kg/sm^2. The effusion film cooling accounted for 0.3 of the cooling effectiveness and the impingement cooling was responsible for the rest. However, if the number of effusions holes was reduced the effusion cooling effectiveness was reduced and this reduced the overall cooling effectiveness.
公益社団法人日本ガスタービン学会の論文
1999-11-14