Session: 40-07 Turbine Secondary Flows and Interactions

Paper Number: 122178

122178 - Noise Source Identification for the Unsteady Low Pressure Turbine Flow Fields 

The paper presents a data processing methodology to identify the noise sources in low pressure turbine stages and their relative importance. Scale adaptive simulation (SAS) has been carried out on a geometry reproducing a LPT stage in the mid span region. The proper orthogonal decomposition (POD) is applied to data matrices constructed with the velocity, the vorticity and the pressure fields in order to distinctly extract the coherent structures responsible for velocity/vorticity fluctuations and pressure waves (i.e. POD modes from the corresponding kernel), their temporal evolution and energy contributions. The cross-correlation matrices of the pressure modes and the velocity modes or the vorticity modes reveal the degree of coupling between pressure and velocity/vorticity oscillations, thus highlighting the modes linked to the same flow phenomena. The results show that the periodic vortex shedding at the stator trailing edge emits strong pressure waves, and the upstream propagating waves reflect against the adjacent stator suction surface. However, the rotor trailing edge vortex shedding is only captured in the FFT spectra downstream the rotor trailing edge but is not captured in the most energetic ensemble of POD modes, hence has little contribution to the overall noise. The POD modes related to the rotor-stator interaction show peak amplitudes at the blade passing frequency and its harmonics and their shapes mimic the potential interaction in the stator domain and the migration of viscous wakes in the rotor domain. The biggest noise sources of the present low pressure turbine stage are identified to be the rotor-stator interaction and the stator trailing edge vortex shedding.

Presenting Author: Lanyi Yan Harbin Engineering University

Presenting Author Biography: Lanyi Yan is currently a joint training PhD student of Harbin Engineering University (China) and University of Genova (Italy). Her research subject is the unsteady flow and multi-physical fields of the low pressure turbine.

Authors:

Lanyi Yan Harbin Engineering University
Daniele Simoni University of Genova
Yigang Luan Harbin Engineering University
Tao Sun Harbin Engineering University
Dario Barsi University of Genova
Pietro Zunino University of Genova