TY - JOUR

T1 - Experimental investigation of the mass flow gain factor in a draft tube with cavitation vortex rope

AU - Landry, C.

AU - Favrel, A.

AU - Müller, A.

AU - Yamamoto, K.

AU - Alligné, S.

AU - Avellan, F.

N1 - Funding Information:
The research leading to the results published in this paper is part of the HYPERBOLE research project, granted by the European Commission (ERC/FP7- ENERGY-2013-1-Grant 608532).
Publisher Copyright:
© Published under licence by IOP Publishing Ltd.

PY - 2017/4/4

Y1 - 2017/4/4

N2 - At off-design operating operations, cavitating flow is often observed in hydraulic machines. The presence of a cavitation vortex rope may induce draft tube surge and electrical power swings at part load and full load operations. The stability analysis of these operating conditions requires a numerical pipe model taking into account the complexity of the two-phase flow. Among the hydroacoustic parameters describing the cavitating draft tube flow in the numerical model, the mass flow gain factor, representing the mass excitation source expressed as the rate of change of the cavitation volume as a function of the discharge, remains difficult to model. This paper presents a quasi-static method to estimate the mass flow gain factor in the draft tube for a given cavitation vortex rope volume in the case of a reduced scale physical model of a ν = 0.27 Francis turbine. The methodology is based on an experimental identification of the natural frequency of the test rig hydraulic system for different Thoma numbers. With the identification of the natural frequency, it is possible to model the wave speed, the cavitation compliance and the volume of the cavitation vortex rope. By applying this new methodology for different discharge values, it becomes possible to identify the mass flow gain factor and improve the accuracy of the system stability analysis.

AB - At off-design operating operations, cavitating flow is often observed in hydraulic machines. The presence of a cavitation vortex rope may induce draft tube surge and electrical power swings at part load and full load operations. The stability analysis of these operating conditions requires a numerical pipe model taking into account the complexity of the two-phase flow. Among the hydroacoustic parameters describing the cavitating draft tube flow in the numerical model, the mass flow gain factor, representing the mass excitation source expressed as the rate of change of the cavitation volume as a function of the discharge, remains difficult to model. This paper presents a quasi-static method to estimate the mass flow gain factor in the draft tube for a given cavitation vortex rope volume in the case of a reduced scale physical model of a ν = 0.27 Francis turbine. The methodology is based on an experimental identification of the natural frequency of the test rig hydraulic system for different Thoma numbers. With the identification of the natural frequency, it is possible to model the wave speed, the cavitation compliance and the volume of the cavitation vortex rope. By applying this new methodology for different discharge values, it becomes possible to identify the mass flow gain factor and improve the accuracy of the system stability analysis.

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U2 - 10.1088/1742-6596/813/1/012022

DO - 10.1088/1742-6596/813/1/012022

M3 - Conference article

AN - SCOPUS:85017437201

SN - 1742-6588

VL - 813

JO - Journal of Physics: Conference Series

JF - Journal of Physics: Conference Series

IS - 1

M1 - 012022

T2 - HYdropower Plants PERformance and FlexiBle Operation Towards Lean Integration of New Renewable Energies Symposium, HYPERBOLE 2017

Y2 - 2 February 2017 through 3 February 2017

ER -