59312 - Effect of Spanwise Hole to Hole Spacing on Overall Cooling Effectiveness of Effusion Cooled Combustor Liners for a Swirl Stabilized Can Combustor 

In modern low NOX combustion chambers, due to the premixing of air and fuel, there is a lack of sufficient air available for cooling the combustion liner. Hence, it is very crucial to optimize liner cooling designs to reduce coolant consumption and maximize the life cycle of the combustion liner.  One of the most effective ways to cool the combustion liner is through effusion cooling, also known as full coverage film cooling. Effusion cooling involves small uniformly spaced holes distributed throughout the liner. Effusion cooled configurations are preferred due to being lightweight, efficient and easy to manufacture. Due to its advantages, in recent years, there has been a large increase in application of effusion cooling in turbine blades and combustor liners.  Extensive literature exists on the performance of different effusion cooling geometries under flat plate and heated flow conditions but literature on the coolant flame interaction under realistic engine conditions is sparse.  The present work involves the experimental study of overall cooling effectiveness of an effusion cooled metal liner for a can combustor under realistic reacting (flame) and non-reacting (heated flow) conditions. The can combustor was equipped with an industrial swirler, which subjected the liner walls to realistic flow and turbulence fields.  For this study, effusion liners with three different Non-dimensionalzed circumferential hole spacing (r/d) of 6, 8 and 10 and its associated effect on heat transfer was studied.  The experiments were carried out a constant Reynolds number of 12000 based on the combustor diameter. The combustor liners were made out of 3mm thick stainless steel SS316L with an inner diameter and length of 203mm and 228mm. Infrared imaging (IR) was used to map the temperature of the outer surface of the metal liner. The walls of the combustor liner were painted black to aid with the IR measurement and the experiments were carried out at steady state conditions. The non-reacting experiments were carried out by heating the mainstream air at inlet of test section to 445K the reacting experiments were carried out with a methane flame at three different equivalence ratios. For both the experiments, the coolant inlet temperature was maintained 295K.  A detailed study on the variation of cooling effectiveness for different blowing ratios and equivalence ratios have been presented in the paper.