Federico Torriano

CFD Analysis of Ventilation Flow for a Scale Model Hydro-Generator

In 2006, the first Computational Fluid Dynamics (CFD) simulations of the ventilation of specific hydro-generator components were performed at the Hydro-Quebec Research Institute (IREQ) and lately the entire ventilation circuit is being investigated. Due to the complexity of flow calculations, a validation process is necessary and for this reason a 1:4 scale model of a hydro-generator has been built at IREQ to get experimental data by means of particle image velocimetry (PIV). This paper presents 2D and 3D simulation results for the scale model obtained with a commercial CFD code and addresses the challenges associated with the application of CFD to hydro-generators. In particular, the effect of rotor-stator interface (RSI) types and configuration is analyzed to determine the approach that best suits this application. Two-dimensional calculations show that the steady state multiple frames of reference (MFR) solution is highly sensitive to the type (frozen rotor (FR) vs. mixing plane (MP)) and location of the RSI. A parametric study is performed where each interface configuration is compared to the transient case results. The MFR-FR interface model produces results that may vary significantly depending on the relative rotor position and the radial location of the RSI in the air gap. The MFR-MP interface model appears to be more coherent with reference values obtained from a transient case, since the radial velocity profiles in the stator are similar. Furthermore with an appropriate radial positioning of the interface, the windage losses are within 20%. Simulations of the complete 3D ventilation circuit revealed a maximum variation of 10% in both total ventilation flow rate and total windage losses, between the RSI configurations studied. However, the relative flow distributions, normalized with respect to the total flow rate, are unaffected by changes in RSI configuration. This paper focuses mainly on sensitivity studies to numerical settings, but this comparison still requires experimental validation before any final conclusions can be made.Copyright

Study of a Taylor-Couette-Poiseuille flow in an annular channel with a slotted rotor

This paper investigates a Taylor-Couette-Poiseuille flow in an annular channel of a slotted rotating inner cylinder, corresponding to a salient pole hydrogenerator. The purpose of this study is to improve the understanding of flow and thermal phenomena in electrical machines using a simplified scale model. Some numerical tests are first shown to investigate the influence of certain numerical parameters. Finally, CFD and CHT studies of the flow regimes are presented in the slotted rotor geometry and compared to experimental and literature data.

Numerical thermofluid analysis of a power transformer disc-type winding

This contribution describes the early results of a long term R&D collaboration established between IREQ and EFACEC. This partnership focuses on disc-type windings, which are the most common geometry used in real core-type transformers. One of the main objectives so far has been the comparison of two different in-house thermal models (THNM1 and THNM2) with the most accurate numerical approach, namely a tridimensional CFD model. Both codes proved to be robust and able to predict the thermal behavior, particularly for ON conditions. From this comparison, it is currently observed that THNM1 predictions tend to be closer to CFD flow patterns and disc temperatures, seemingly due to its CFD calibrated friction and convection heat transfer coefficients expressions. Further analysis will be performed in the future to compare such in-house models and CFD with measurements obtained under a tightly controlled experimental environment.

Experimental and numerical thermofluid study of a disc-type transformer winding scale model

In this study, measurements are carried out on an ON disc-type winding scale model that includes all main components usually found on a real transformer. Moreover, 3D CHT simulations of the entire cooling circuit are performed and the computed oil flow rate and winding temperatures are compared with the experimental data for uniform and nonuniform heat loss distributions. The results show that the CFD model can predict with an accuracy of about 10% the oil flow rate circulating in the winding and it can compute with quite good accuracy the discs temperatures. Numerical simulations with a reduced computational domain (i.e., winding region only) are also performed with the CFD model and two in-house THNM codes. The comparison between the predicted and measured disc temperatures shows that the CFD model is the most accurate and that the THNMs can predict quite well the global thermal behavior of the winding, even though discrepancies are locally observed.

PIV Characterization of the Air Flow in a Scale Model of a Hydrogenerator

In hydroelectric power plants, generators are essential components and, like all machines, generate heat due to losses. The most common way to evacuate this heat is by circulating a cooling fluid (generally air) through the generator’s components. Due to the geometrical complexity, it is quite challenging to simulate the flow to predict the cooling in a generator, and in-situ measurements are costly and difficult to perform due to the limited access. For this reason, a 1:4 scale model of a hydroelectric generator was built at the research institute of Hydro-Quebec (IREQ). In this paper, particle image velocimetry (PIV) measurements of the flow in the opening of the generator scale model pit, in the space between the enclosure wall and the cooler exit, at the cooler exit, in the covers, in the air gap and in the interpole region are presented. Experimental aspects pertaining to the seeding of the flow, calibration targets, and experimental method are also discussed. Furthermore, a comparison of the experimental data with CFD (Computational Fluid Dynamics) simulation results using ANSYS-CFX is given.Copyright