TY - JOUR

T1 - Unsteady flow phenomena in turbine shroud cavities

AU - Kluge, Tim

AU - Lettmann, Iris S.

AU - Oettinger, Marcel

AU - Wein, Lars

AU - Seume, Joerg R.

N1 - Funding Information: The investigations were conducted as part of the joint research programme AG Turbo and supported by the German Federal Ministry for Economic Affairs and Energy and MTU Aero Engines AG. German Federal Ministry for Economic Affairs and Energy, 03ET7021O; MTU Aero Engines AG.

PY - 2021/10/19

Y1 - 2021/10/19

N2 - This paper presents those flow parameters at which coherent structures appear in the blade tip cavities of shrouded turbine blades. To the authors’ knowledge, this is reported for the first time in the open literature. The unsteady flow in a shroud cavity is analysed based on experimental data recorded in a labyrinth seal test rig. The unsteady static wall pressure in the shroud cavity inlet and outlet is measured using time-resolving pressure sensors. Sensors are located at staggered circumferential positions to allow cross-correlation between signals. The unsteady pressure signals are reduced using Fourier analysis and cross-correlation in combination with digital filters. Based on the data, a theory is formulated explaining the phenomena reflected in the measurements. The results suggest that pressure fluctuations with distinct numbers of nodes are rotating in the shroud cavity outlet. Moreover, modes with different node numbers appear to be super-imposed, rotating at a common speed in circumferential direction. The pressure fluctuations are not found at all operating points. Further analysis indicates that the pressure fluctuations are present at operating points matching distinct parameters correlating with the cavity flow coefficient. Unsteady RANS simulations predict similar flow structures for the design operating point of the test rig.

AB - This paper presents those flow parameters at which coherent structures appear in the blade tip cavities of shrouded turbine blades. To the authors’ knowledge, this is reported for the first time in the open literature. The unsteady flow in a shroud cavity is analysed based on experimental data recorded in a labyrinth seal test rig. The unsteady static wall pressure in the shroud cavity inlet and outlet is measured using time-resolving pressure sensors. Sensors are located at staggered circumferential positions to allow cross-correlation between signals. The unsteady pressure signals are reduced using Fourier analysis and cross-correlation in combination with digital filters. Based on the data, a theory is formulated explaining the phenomena reflected in the measurements. The results suggest that pressure fluctuations with distinct numbers of nodes are rotating in the shroud cavity outlet. Moreover, modes with different node numbers appear to be super-imposed, rotating at a common speed in circumferential direction. The pressure fluctuations are not found at all operating points. Further analysis indicates that the pressure fluctuations are present at operating points matching distinct parameters correlating with the cavity flow coefficient. Unsteady RANS simulations predict similar flow structures for the design operating point of the test rig.

KW - Cavities

KW - Flow instabilities

KW - Labyrinth seals

KW - Turbines

KW - Unsteady flow

UR - http://www.scopus.com/inward/record.url?scp=85124327525&partnerID=8YFLogxK

U2 - 10.33737/jgpps/141211

DO - 10.33737/jgpps/141211

M3 - Article

AN - SCOPUS:85124327525

VL - 5

SP - 177

EP - 190

JO - Journal of the Global Power and Propulsion Society

JF - Journal of the Global Power and Propulsion Society

ER -