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research-article

POD and extended-POD analysis of pressure fluctuations and vortex structures inside a steam turbine control valve

[+] Author and Article Information
Peng Wang

Key Lab of Education Ministry for Power Machinery and Engineering, School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Gas Turbine Research Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
5080209340@sjtu.edu.cn

Hongyu Ma

Key Lab of Education Ministry for Power Machinery and Engineering, School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Gas Turbine Research Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
hongyuma@sjtu.edu.cn

YingZheng Liu

Key Lab of Education Ministry for Power Machinery and Engineering, School of Mechanical Engineering, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China; Gas Turbine Research Institute, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China
yzliu@sjtu.edu.cn

1Corresponding author.

ASME doi:10.1115/1.4040903 History: Received July 06, 2018; Revised July 08, 2018

Abstract

In steam turbine control valves, pressure fluctuations coupled with vortex structures in highly unsteady three-dimensional flows make essential contributions to aerodynamic forcing on the valve components, and give rise to flow-induced vibration and acoustic effects. Present study used state-of-the-art data-driven analysis, namely proper orthogonal decomposition (POD) and extended-POD, to extract the energetic pressure fluctuations and dominant vortex structures of the control valve. To this end, typical annular attachment flow inside a control valve was investigated from a detached eddy simulation (DES). Subsequently, the energetic pressure fluctuation modes were extracted from the pressure field's POD analysis. The vortex structures contributing to these energetic pressure fluctuations were extracted by the extended-POD analysis on pressure-velocity coupling field. Finally, dominant vortex structures were revealed directly by POD analysis on valve's velocity field. The results demonstrated that flow instabilities inside the control valve were mainly induced by the wall-attached jet oscillations and the derivative flow separations and reattachments. In pressure field's POD analysis, the axial, antisymmetric and asymmetric pressure modes occupied most of the pressure fluctuation intensity. By further conducting extended-POD analysis, the vortex structures' incorporation with the energetic pressure modes was identified as mainly attributed to the synchronous, alternating and single-sided oscillation behaviors of the annular attachment flow. However for velocity field's POD analysis, the vortex structures, buried in the dominant modes at St=0.017, were primarily resulted from alternating oscillations of the annular wall-attached-jet.

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