Impact of Swirl Flow on the Cooling Performance of an Effusion Cooled Combustor Liner

Abstract

An experimental study on combustor liner cooling of modern direct lean injection combustion chambers using coolant ejection from both effusion cooling holes and a starter film has been conducted. The experimental setup consists of a generic scaled three sector planar rig in an open loop hot gas wind tunnel, which has been described earlier in Wurm et al. (2009, “A New Test Facility for Investigating the Interactions Between Swirl Flow and Wall Cooling Films in Combustors, Investigating the Interactions Between Swirl Flow and Wall Cooling Films in Combustors,” ASME Paper No. GT2009-59961). Experiments are performed without combustion. Realistic engine conditions are achieved by applying engine-realistic Reynolds numbers, Mach numbers, and density ratios. A particle image velocimetry (PIV) measurement technique is employed, which has been adjusted to allow for high resolution near wall velocity measurements with and without coolant ejection. As the main focus of the present study is a deeper understanding of the interaction of swirl flows and near wall cooling flows, wall pressure measurements are performed for the definition of local blowing ratios and to identify the impact on the local cooling performance. For thermal investigations an infrared thermography measurement technique is employed that allows high resolution thermal studies on the effusion cooled liner surface. The effects of different heat shield geometry on the flow field and performance of the cooling films are investigated in terms of near wall velocity distributions and film cooling effectiveness. Two different heat shield configurations are investigated which differ in shape and inclination angle of the so called heat shield lip. Operating conditions for the hot gas main flow are kept constant. The pressure drop across the effusion cooled liner is varied between 1% and 3% of the total pressure. Results show the impact of the swirled main flow on the stability of the starter film and on the effusion cooling performance. Stagnation areas which could be identified by wall pressure measurements are confirmed by PIV measurements. Thermal investigations reveal reduced cooling performance in the respective stagnation areas.

Investigation on the Effect of a Realistic Flow Field on the Adiabatic Effectiveness of an Effusion-Cooled Combustor

“…To authors' knowledge, the only studies taking into account swirled flows are the recent investigations at Karlsruhe Institute of Technology [5,10]. Both papers report the experimental investigations performed on a test rig composed by three nozzles assembled in planar configuration and embedded in a heat shield which is also equipped with a starter film device.…”

“…Thus, a reliable estimate of liner thermal protection achieved by means of effusion cooling cannot leave out of consideration the presence of a complex 3D flow field interacting with the coolant jets [5].…”

“…In Ref. [5], the focus was on the impact of the swirled flow on film cooling effectiveness as well as of the heat shield geometry on the starter film penetration. The analysis showed a variation of local blowing ratio which closely follows the adiabatic effectiveness distribution.…”

A New Test Facility for Investigating Thermal Behaviour of Effusion Cooling Test Plates for RQL Combustors

“…Thus imply a severe impact on the performance of the liner cooling system and attest the importance of investigations under realistic swirling conditions. This aspect was fully remarked by the thorough experimental analysis conducted by Wurm et al [4,5] and by Andreini et al [6,7,8]. Both research groups carried out several measurement campaigns on atmospheric enlarged-scale rigs, replicating three sectors of a combustion chamber in a planar arrangement.…”

Unsteady Flow Field Characterization of Effusion Cooling Systems with Swirling Main Flow: Comparison Between Cylindrical and Shaped Holes

“…Fundamental experimental studies on cylindrical and shaped holes were proposed by several authors [2][3][4][5] with the final aim of measuring flow field with non intrusive laser diagnostics, typically developing test rigs with axial and uniform main flow. More recently, with the aim of reproducing similar conditions to those present in the combustion chambers, several authors proposed the introduction of a swirling mainstream, to focus their studies on the mutual interactions between the swirling and coolant flows [6,7] on liner time-averaged thermal characteristics.…”