TY - GEN

T1 - Impact of Swirl on the Sensitivity of the Radial Mode Analysis in Turbomachinery

AU - Laguna, Juan D.

AU - Bartelt, Michael

AU - Seume, Joerg R.

PY - 2013/11/14

Y1 - 2013/11/14

N2 - Sound measurements in turbomachinery are a prerequisite for the study and consequent understanding of sound propagation mechanisms. For analyzing these measurements, the Radial Mode Analysis (RMA) is applied. This method decomposes the transmitted sound field in dominant acoustical modes at specific frequencies. Before an experimental campaign is carried out, measurement parameters are selected such that the uncertainty in the results from the application of the RMA is minimized. In order to minimize uncertainties, a sensitivity analysis of the parameters which influence the overall error of the RMA is performed. This analysis focuses mainly on the output of a measurable quantity, namely on the propagating mode amplitudes. Using a numerical simulation, modal structures are generated based upon real turbine operating data with swirling flow and a characteristic operating temperature. The swirling flow is generated by adding an axial vortex to a constant flow-velocity profile. The results show that the sound field varies under consideration of swirling mean flow compared to uniform flow conditions. In the present case, higher-order modes dominate the propagating sound structure. The parameters studied for assessing the sensitivity are the signal-to-noise ratio of the measurement sensors, the number of triggered revolutions, the azimuthal spacing of the sensors, and a triggering delay. The sensitivity analysis gives a detailed insight into the measurement parameters influencing the output of the RMA, e.g. that small triggering delays cause appreciable measurement errors. This knowledge is used to define the requirements for high fidelity measurements.

AB - Sound measurements in turbomachinery are a prerequisite for the study and consequent understanding of sound propagation mechanisms. For analyzing these measurements, the Radial Mode Analysis (RMA) is applied. This method decomposes the transmitted sound field in dominant acoustical modes at specific frequencies. Before an experimental campaign is carried out, measurement parameters are selected such that the uncertainty in the results from the application of the RMA is minimized. In order to minimize uncertainties, a sensitivity analysis of the parameters which influence the overall error of the RMA is performed. This analysis focuses mainly on the output of a measurable quantity, namely on the propagating mode amplitudes. Using a numerical simulation, modal structures are generated based upon real turbine operating data with swirling flow and a characteristic operating temperature. The swirling flow is generated by adding an axial vortex to a constant flow-velocity profile. The results show that the sound field varies under consideration of swirling mean flow compared to uniform flow conditions. In the present case, higher-order modes dominate the propagating sound structure. The parameters studied for assessing the sensitivity are the signal-to-noise ratio of the measurement sensors, the number of triggered revolutions, the azimuthal spacing of the sensors, and a triggering delay. The sensitivity analysis gives a detailed insight into the measurement parameters influencing the output of the RMA, e.g. that small triggering delays cause appreciable measurement errors. This knowledge is used to define the requirements for high fidelity measurements.

UR - http://www.scopus.com/inward/record.url?scp=84890155961&partnerID=8YFLogxK

U2 - 10.1115/GT2013-95460

DO - 10.1115/GT2013-95460

M3 - Conference contribution

AN - SCOPUS:84890155961

SN - 9780791855249

T3 - Proceedings of the ASME Turbo Expo

BT - ASME Turbo Expo 2013

T2 - ASME Turbo Expo 2013: Turbine Technical Conference and Exposition, GT 2013

Y2 - 3 June 2013 through 7 June 2013

ER -