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

One of the most effective ways to cool the combustor liner is through effusion cooling. Effusion cooling (also known as full coverage effusion cooling) involves uniformly spaced holes distributed throughout the combustor liner wall. Effusion cooling configurations are preferred for their high effectiveness, low-pressure penalty, and ease of manufacturing. In this paper, experimental results are presented for effusion cooling configurations for a realistic swirl driven can combustor under reacting (flame) conditions. The can-combustor was equipped with an industrial engine swirler and gaseous fuel (methane), subjecting the liner walls to engine representative flow and combustion conditions. In this study, three different effusion cooling liners with spanwise spacings of r/d = 6, 8, and 10 and streamwise spacing of z/d = 10 were tested for four coolant-to-main airflow ratios. The experiments were carried out at a constant main flow Reynolds number (based on combustor diameter) of 12,500 at a total equivalence ratio of 0.65. Infrared Thermography (IRT) was used to measure the liner outer surface temperature, and detailed overall effectiveness values were determined under steady-state conditions. The results indicate that decreasing the spanwise hole-to-hole spacing (r/d) from 10 to 8 increased the overall cooling effectiveness by 2–5%. It was found that reducing the spanwise hole-to-hole spacing further to r/d = 6 does not affect the cooling effectiveness implying the existence of an optimum spanwise hole-to-hole spacing. Also, the minimum liner cooling effectiveness on the liner wall was found to be downstream of the impingement location, which is not observed in existing literature for experiments done under non-reacting conditions.