Time-Resolved Flow Field Analysis of Effusion Cooling System With Representative Swirling Main Flow

Film cooling jets behaviour in a combustor chamber is deeply affected by swirling flow interactions and unsteadiness; on the other hand, the jets behaviour has a direct impact on different phenomena such as cooling capabilities and ignition. For these reasons, an in-depth characterization of the film-cooling flows in the presence of a swirling mainflow, demands dedicated time-resolved analyses. The experimental setup consists of a non-reactive single-sector linear combustor simulator installed in an open loop wind tunnel. It is equipped with a swirler and a multiperforated plate to simulate the effusion cooling system of the liner. The rig is scaled with respect to the engine configuration, to increase spatial resolution and to reduce the characteristic frequencies of the unsteady phenomena. Time-Resolved Particle Image Velocimetry (TRPIV) was exploited for the investigation testing different values of liner pressure drop. In addition, numerical investigations were carried out to gain a deeper insight of the behaviour highlighted by the experiments and to assess the capability of CFD in predicting the flow physics. In this work, the Stress-Blended Eddy Simulation (SBES) approach implemented in ANSYS Fluent was adopted. Oscillations of the jets and intermittent interactions of the mainstream with the wall of the liner and hence with the film development have been investigated in detail. The results demonstrate how an unsteady analysis of the flow structures that characterize the jets, the turbulent mixing of coolant flows and the interaction between mainstream and cooling jets is strictly necessary to have a complete knowledge of the behaviour of the coolant which in turn affects combustor operability and life-time.