Abstract

Pressure and flowrate measurements were conducted for an air-cooled salient pole hydro model generator in order to validate a computational fluid dynamics (CFD) simulation approach. The ventilation system of the model generator was driven by adjustable external fans, which allows detailed pressure measurements for a range of operating conditions. The CFD model to be validated consists of full generator geometry which is modelled in high geometrical detail. The steady-state multiple reference frame approach was chosen for the simulations, and the influence of different rotor-stator interfaces and turbulence models was investigated. The comparison of measurement and simulations includes the static pressure along the flow path through the machine, the performance map of the external fans, and an analytical approach to describe the dimensionless machine parameters of the model generator. Good overall agreement was found between measurement and CFD, which justifies the application of the presented simulation approach in the design of ventilation and cooling systems for hydro power generators. Qualitatively the CFD simulations reproduced all measured flow effects. Also quantitatively a good prediction of measured values was identified for a broad range of operating conditions. However, it was found that the simulation accuracy does not only depend on the numerical models in use but also on the specific operating conditions and their affiliated airflow characteristics.

Highlights

  • 2.3 Operating conditions As only the aerodynamic behavior of the investigated machine was of interest, all measurements were carried out without rotor winding excitation and in stator winding phase-to-phase short circuit

  • The cooler was modelled as porous media, where the pressure loss was taken into account by an additional momentum sink term in the equations being solved during the computational fluid dynamics (CFD) simulation

  • Due to the need of detailed measurement data to validate simulation tools, Voith Hydro designed and built a model generator which allows the investigation of new generator design features or different configurations, e.g., different ventilation concepts

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Summary

Introduction

The remaining electromagnetic losses in the range of 1% of the generator’s rated power produce a considerable amount of heat To remove this heat from the machine, a safe and reliable ventilation and cooling system is designed during the layout process individually for each hydro power generator. Voith Hydro operates a fully functional salient pole model generator which allows detailed measurement campaigns for different machine configurations without the limiting boundary conditions that are found in operational hydro power plants This includes but is not limited to the investigation of the ventilation and cooling system of the model machine. The measurement data is evaluated, interpreted, and compared to the simulations This includes the discussion of the static pressure along the flow path through the machine and the performance map of the fans. The focus is on the comparison between CFD and measurement results

Model generator configuration
Operating conditions
Measurement setup
Static pressure
Thermodynamic state
Volumetric flowrate
Simulation setup
Model overview
Meshing
Result evaluation
Flow path diagram
Fan performance
Dimensionless machine parameters
Findings
Summary and conclusions
Full Text
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