### Abstract

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.

Original language | English |
---|---|

Article number | 012022 |

Journal | Journal of Physics: Conference Series |

Volume | 813 |

Issue number | 1 |

DOIs | |

Publication status | Published - 2017 Apr 4 |

Externally published | Yes |

Event | HYdropower Plants PERformance and FlexiBle Operation Towards Lean Integration of New Renewable Energies Symposium, HYPERBOLE 2017 - Porto, Portugal Duration: 2017 Feb 2 → 2017 Feb 3 |

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### ASJC Scopus subject areas

- Physics and Astronomy(all)

### Cite this

*Journal of Physics: Conference Series*,

*813*(1), [012022]. https://doi.org/10.1088/1742-6596/813/1/012022

**Experimental investigation of the mass flow gain factor in a draft tube with cavitation vortex rope.** / Landry, C.; Favrel, Arthur Tristan; Müller, A.; Yamamoto, K.; Alligné, S.; Avellan, F.

Research output: Contribution to journal › Conference article

*Journal of Physics: Conference Series*, vol. 813, no. 1, 012022. https://doi.org/10.1088/1742-6596/813/1/012022

}

TY - JOUR

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

AU - Landry, C.

AU - Favrel, Arthur Tristan

AU - Müller, A.

AU - Yamamoto, K.

AU - Alligné, S.

AU - Avellan, F.

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.

UR - http://www.scopus.com/inward/record.url?scp=85017437201&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85017437201&partnerID=8YFLogxK

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

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

M3 - Conference article

VL - 813

JO - Journal of Physics: Conference Series

JF - Journal of Physics: Conference Series

SN - 1742-6588

IS - 1

M1 - 012022

ER -