Francisco Botero - Academia.edu (original) (raw)

Papers by Francisco Botero

IOP Conference Series: Earth and Environmental Science, 2019

The purpose of this paper is to validate in prototype, the results related to the description of ... more The purpose of this paper is to validate in prototype, the results related to the description of dynamic behaviour obtained in a Kaplan turbine model. A comparative analysis between model and prototype measurement at homologous operation conditions is presented. The phenomena of interest are tip vortex cavitation development and rotor stator interaction (rsi), associated to operation at high power outputs. The selection of suitable signal processing tools allows a clear identification of the role played by the modulation of the main rsi frequencies on cavitation phenomena. The comparison between pressure acceleration measurements on model and prototype at draft tube wall are consistent, both in time and frequency domain analysis. The acceleration measurement at the draft tube wall (manhole) is suggested as a trustworthy dynamic indicator for prediction (model) and monitoring (prototype) purposes.

Advances in Turbomachinery [Working Title]

The hydrodynamic instabilities in a turbomachine can be divided into two main groups: periodic (o... more The hydrodynamic instabilities in a turbomachine can be divided into two main groups: periodic (or quasi-periodic) and nonperiodic. And the total instability, calculated from a statistical parameter with linear characteristics, such as variance, can be defined as the sum of periodic and nonperiodic instabilities. Based on the above, the main objective of the study was to estimate the periodic instabilities in a pump operating as a turbine. For this purpose, pressure fluctuation signals from sensors installed on the turbomachine volute and spaced 135° apart were used. The signals were analyzed in the time and frequency domain to identify, initially, the periodic instabilities and their relationship with the spectral components and, subsequently, to estimate the magnitude of these instabilities as the variance of the filtered series in the spectral band related to the periodic instability. In addition, the study aims to establish the contribution of periodic instabilities to total ins...

In the present study, the fluid-structure coupling is inves-tigated in the guide vanes cascade of... more In the present study, the fluid-structure coupling is inves-tigated in the guide vanes cascade of a pump-turbine scale model placed in the EPFL PF3 test rig. The paper focuses on the advanced instrumentation used to get reliable and complete fluid-structure coupling results. Semi-conductor strain gages are installed on three guide vanes which are especially weakened to account for stronger fluid-structure coupling phenomena. These are statically calibrated in terms of torsion torque and bending force. A laser vibrometer is used to measure the vibrating guide vane velocity. Piezo-resistive pressure sensors are placed around the weakened guide vanes to monitor the influence of the structural vibrations on the surrounding flow. An underwater non-intrusive system is used to get an impulse excitation. The instrument set enables a reliable fluid-structure

Revista Facultad de Ingeniería Universidad de Antioquia, 2021

This article presents the investigation, analysis, and results of the intake gate closure of two ... more This article presents the investigation, analysis, and results of the intake gate closure of two vertical fixed-wheel gates at the hydroelectric project Ituango in Colombia (2400 MW) under free- flow conditions. This atypical operation was considered successful notwithstanding adverse conditions, and therefore, it can be classified as a unique operation in the field of hydraulic gates. In this article, some relevant parameters, such as the hydraulic force of the servomotor during the operation of the gate, were measured before and after the operation and analyzed, and the results were presented. A new chart is proposed for the downpull coefficient based on the collected data, which could be implemented in the closure of gates against the free flow. Considering the abovementioned factors, the authors propose some recommendations and present drawn conclusions contributing to state of the art on design, manufacturing, and operation of this type of hydraulic gates and structures for lar...

IOP Conference Series: Earth and Environmental Science, 2021

In order to prevent a turbine to reach its runaway speed when load rejection occurs, an emergency... more In order to prevent a turbine to reach its runaway speed when load rejection occurs, an emergency closing system must be devised in case the regulation system fails. For Kaplan turbines, fixed wheel gates located in the turbine intake or in the draft tube outlet are usually employed. Gates of this type are move by gravity and the closing velocity is controlled by gantry cranes. The closing maneuver is complex due to the high flow rates inherent to runaway conditions and the rotational deceleration during the gate’s closing time. Research on this topic is scarce and limited, and numerical studies are usually clouded by uncertainties concerning the setting of proper boundary conditions. In this work, the closing maneuver of the emergency fixed wheel gates at the intake of a Kaplan turbine was studied with CFD two-phase transient simulation. The software used was ANSYS CFX, that solves unsteady Navier-Stokes equations (URANS) by means of the finite volume method. The simulated domain i...

International Journal of Aerospace Engineering, 2021

This article includes the phases of conceptualization and validation of a picosatellite prototype... more This article includes the phases of conceptualization and validation of a picosatellite prototype named Simple-2 for remote sensing activities using COTS (Commercial-Off-The-Shelf) components and the modular design methodology. To evaluate its performance and ensure the precision and accuracy of the measurements made by the satellite prototype, a methodology was designed and implemented for the characterization and qualification of CanSats (soda can satellites) through statistical tests and techniques of DoE (Design of Experiments) based on CubeSat aerospace standards and regulations, in the absence of official test procedures for these kinds of satellite form factor. For the above, two experimental units were used, and all the performance variables of the different satellite subsystems were discriminated. For the above, two experimental units were used, and all the performance variables of the different satellite subsystems were discriminated against. These were grouped according t...

Ingenieria y Universidad, 2021

Objective: Identify and characterize subsynchronous hydrodynamics phenomena in a low specific spe... more Objective: Identify and characterize subsynchronous hydrodynamics phenomena in a low specific speed centrifugal pump based on its four-quadrant characteristic curve. Materials: A 1.5 HP ITT Goulds pump instrumented with pressure transductors, an accelerometer, a torque sensor and a tachometer. Flow rate measurement was done with an ultrasonic transit time clamp-on flow meter. Methods: Time and frequency domain analysis with phase analysis were used to identify spectral components linked to hydrodynamic phenomena such as rotating stall and surge. Results and discussion: This work approaches an alternative method to calculate the phase angle using pressure signals without filtering. Related with hydrodynamic phenomena, the evidence collected suggests the presence of rotating stall in some operation points of the four-quadrant characteristic curve. Furthermore, in the third quadrant, rotating stall coexist with surge. Conclusions: The instrumentation and methods regarded in this work a...

A new universal test rig has been installed at the HES-SO VS Sion - Switzerland to assess the hyd... more A new universal test rig has been installed at the HES-SO VS Sion - Switzerland to assess the hydraulic performances of different types of small-power turbomachines (up to 10 kW) and other hydraulic components with complex geometry, following the IEC 60193 standard recommendations. The closed-loop circuit allows simulating different implantation levels of the model and therefore recovering the cavitation performances as well. The present work introduces a state-of-the-art approach of an automatic regulation for hydraulic test rigs. An autonomous regulation system based on real-time measurements is developed using the capabilities of a National Instruments compact Reconfigurable Input Output device. Indeed, during operation, the system can keep constant the value of the desired parameters (e.g. testing head, discharge, pumps speed, Thoma number, etc.). Then, the implemented wireless communication architecture between the hydraulic test rig and further measurements/monitoring systems ...

American Journal of Hydropower, Water and Environment Sytems

REVISTA COLOMBIANA DE TECNOLOGIAS DE AVANZADA (RCTA)

Turbinas Kaplan o Francis trabajando en condiciones fuera de diseño pueden exhibir fenómenos hidr... more Turbinas Kaplan o Francis trabajando en condiciones fuera de diseño pueden exhibir fenómenos hidrodinámicos como la torcha, que representan riesgos para la instalación y operación de turbinas. En el presente estudio se reprodujo este tipo de fenómeno en una bomba centrífuga trabajando como turbina. Para caracterizar el fenómeno, los movimientos periódicos de la torcha fueron estimados por dos métodos comparables entre sí. El primero, procesamiento de imágenes de una secuencia de fotos tomada con una cámara de alta velocidad, y el segundo, señales de sensores de presión consideradas como fluctuaciones de presión. Análisis en el dominio del tiempo y la frecuencia permitieron encontrar la relación entre espectros de la torcha y las áreas proyectadas en la secuencia de imágenes del fenómeno.

Ingenieria y Universidad

Objective: This paper introduces a methodology for the non-intrusive detection of von Kármán vort... more Objective: This paper introduces a methodology for the non-intrusive detection of von Kármán vortex street cavitation. It is based on the cyclostationary analysis of the airborne noise radiated by the collapsing bubbles. Materials and methods: A hydrodynamic profile is mounted in the test section of a high-speed cavitation tunnel, and the phenomenon is reproduced under controlled conditions of flow and pressure. The angle of incidence is kept constant. Flow velocity is varied to regulate the vortex generation frequency, and the pressure is adjusted to control the cavitation onset. High-speed photography is used to confirm the occurrence of cavitation in the core of the vortices. A laser vibrometer pointing to the upper surface of the profile validates the fluid-structure interaction due to the vortex shedding. A microphone is used to sense the sound produced by the phenomenon and transmitted to the environment. Results and discussion: The cyclic coherence showed uncoupled evidence of the periodic detachment of vortices and the presence or absence of cavitation in their cores, reaching values close to 0.7 for specific frequencies. Conclusion: A non-intrusive monitoring approach and a statistical indicator were implemented to allow the diagnosis of such phenomena.

ASME 2010 7th International Symposium on Fluid-Structure Interactions, Flow-Sound Interactions, and Flow-Induced Vibration and Noise: Volume 3, Parts A and B, 2010

In the present study, the fluid-structure coupling is investigated in the guide vanes cascade of ... more In the present study, the fluid-structure coupling is investigated in the guide vanes cascade of a pump-turbine scale model placed in the EPFL PF3 test rig. The paper focuses on the advanced instrumentation used to get reliable and complete fluid-structure coupling results. Semiconductor strain gages are installed on three guide vanes which are especially weakened to account for stronger fluid-structure coupling phenomena. These are statically calibrated in terms of torsion torque and bending force. A laser vibrometer is used to measure the vibrating guide vane velocity. Piezo-resistive pressure sensors are placed around the weakened guide vanes to monitor the influence of the structural vibrations on the surrounding flow. An underwater non-intrusive system is used to get an impulse excitation. The instrument set enables a reliable fluid-structure coupling investigation in hydraulic pump-turbine scale model. Finally, the results show a strong coupling between the vibrating guide vanes and the surrounding unsteady flow.

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D, 2011

ABSTRACT Flow numerical simulations in a low specific speed radial pump-turbine scale model are p... more ABSTRACT Flow numerical simulations in a low specific speed radial pump-turbine scale model are performed to investigate off-design operating conditions in generating mode. The Best Efficiency Point (BEP) and the runaway operating conditions at 10° guide vanes opening are addressed. The computational domain includes the full reduced scale model water passage from the spiral casing inlet to the draft tube outlet. The numerical simulation is performed using the Ansys CFX code, solving the incompressible unsteady Reynolds-Averaged Navier-Stokes equations. Wall pressure measurements in the stator are used to validate the numerical results. Then, detailed analysis is focused on the onset of the flow instabilities when the machine is brought from BEP to runaway. In these severe operating conditions, one single stall cell is found to rotate with the impeller at subsynchronous speed in the vaneless gap between the impeller and the guide vanes. It is found to be the effect of flow separation developed at the inlet of several consecutive impeller channels which lead to their blockage.

Le travail actuel a été rendu possible uniquement par l'engagement et l'implication, de près ou d... more Le travail actuel a été rendu possible uniquement par l'engagement et l'implication, de près ou de loin, d'un grand nombre de personnes auxquelles je tiens à adresser les plus sincères remerciements. Je tiens, tout d'abord, à remercier mes directeurs de thèse, le Professeur François Avellan pour m'avoir accordé sa confiance et m'avoir donc permis d'effectuer ce travail de recherche, et le Dr. Mohamed Farhat pour m'avoir guidé particulièrement dans la recherche expérimentale. Ce travail a été réalisé dans le cadre du projet de recherche Hydrodyna 2 (Eureka No. 4150), en partenariat avec ALSTOM Hydro, ANDRITZ Hydro et VOITH Hydro, ainsi que l'UPC-CDIF. Je voudrais remercier la Commission pour la Technologie et l'Innovation de la Confédération (CTI), Swisselectric Research et le CCEM pour leurs supports financiers, ainsi qu'aux partenaires d'Hydrodyna pour leur engagement et leur support. Je remercie également les membres du jury, Professeur Marc Parlange, Dr. Jean-Bernard Houdeline, Professeur Chisachi Kato et Dr. Peter Ott pour le temps consacré à la lecture de ce manuscrit, ainsi que pour leurs critiques enrichissantes au moment de la défense privée. Je souhaite remercier en particulier Steven et Francisco, avec qui j'ai vécu de nombreuses nuits blanches pendant les trois campagnes de mesures expérimentales, accomplies avec beaucoup de succès. Ces campagnes ont été rendues possibles également par la brave équipe des mécaniciens du LMH, Maxime, Victor, Mattias, Jean-Daniel, Christian, Raymond sous la direction de Louis Bezençon. Ce travail s'appuie aussi sur le soutien du bureau d'étude coordonné par Philippe Cerutti, qui assure également le fonctionnement des moyens informatiques, ainsi que sur toute l'équipe des plateformes sous la direction de Henri-Pascal Mombelli. Je remercie Isabelle Stoudmann pour son efficacité dans les travaux administratifs et pour tous ses précieux conseils. En tant que membre du groupe numérique, Ali, Olivier, Cécile, Steven et évidemment Pierre, j'ai profité d'une bonne ambiance de travail et de précieux conseils. Pour cela, je tiens à les remercier chaleureusement. Je voudrais également remercier tous mes collègues qui se sont déjà envolés du laboratoire, Ali, Olivier, Stefan, Philippe, Nicolas, Sébastien, Amir et Francisco, qui m'ont encouragé à poursuivre dans cette voie et qui m'ont, chacun à leur manière, aidé ou motivé. Au même temps, un très grand merci à tous ceux qui sont arrivé plus tard, et avec qui j'ai eu des échanges particulièrement fertiles. Je pense à Steven, Marc, Martino, Mathieu, Andres, Ebrahim, et les deux Christian. Un très grand merci à Danail pour tous ses conseils et pour m'avoir fourni un modèle dans la vie académique.