One of the major problems for the safe operation of gas turbines is particle ingestion. Indeed, turbogas are often set to work in the most disparate situations in terms of air pollutant concentration and composition, so that solid particle ingestion must be expected and accounted for. For example, in the case of an aircraft, contamination of the air ingested by reactors can threat flight safety. By observing that the particle deposition pattern is strongly influenced by the flow field in the nearby of the walls, the central idea of this work is to employ Active Flow Control (AFC) to mitigate fouling when emergency or anomalous conditions are met by the aircraft. The proposal is to insert a crossflow jet at the machine hub, injecting air bled from compressor discharge in front of the critical locations where fouling is supposed to occur. The present work aspires to lay the foundations for the development of such an AFC device. Thus, the potential of this device is evaluated quantitavely with the aid of CFD simulations. An energy based sticking model, coupled with a mesh-morphing solver, is used to track the airfoil deposition thickness evolution in time. As a solver, the open source CFD suite OpenFOAM is used. Three different design concepts are investigated on the 3D test case geometry of a NGV turbine cascade (VKI LS-89) with fillets at the endwall/blade junction. The counter rotating vortex pair (CVP) arising from crossflow is detected as the main responsible of issuing jet interaction with the mainstream, allowing considerations on the flow field to be developed with an analytical footprint. Effects of endwall fillets on deposition and secondary flows, as well as transverse jet impact on aerodynamic performance and film cooling effectiveness, are also investigated.
|Title of host publication||Proceedings of ASME Turbo Expo 2020: Turbomachinery Technical Conference and Exposition GT2020-15367|
|Publication status||Acceptance date - 9 Apr 2020|