Evaluation sur modèle réduit et prédiction de la stabilité de fonctionnement des turbines Francis
Graph Chatbot
Chat with Graph Search
Ask any question about EPFL courses, lectures, exercises, research, news, etc. or try the example questions below.
DISCLAIMER: The Graph Chatbot is not programmed to provide explicit or categorical answers to your questions. Rather, it transforms your questions into API requests that are distributed across the various IT services officially administered by EPFL. Its purpose is solely to collect and recommend relevant references to content that you can explore to help you answer your questions.
Stability of operation of Francis turbines Hydraulic disturbances often come with the operation of Francis turbines outside of design head and flow. In some cases, the excessive amplitude of the dynamic system response to these disturbances leads to restriction in the normal operation of the plant. Disturbances largely depend upon operating conditions and the particular turbine design. The response amplitude is under a strong influence from the feed pipe dynamics. Technical and economic consequences of a faulty stability of operation are such that the prediction of stability from model tests is one of the major challenges in present research on hydraulic machinery. Acceptance tests performed on a scale model in a hydraulic laboratory may provide the necessary elements for a full description of characteristics significant for the stability of operation of the full-size turbine in its piping system. This thesis is discussed in the report. 2. Dynamic characterization on the scale model The diagnosis for the dynamic behaviour associated with a machine design and given operating conditions is based on the observation of pressure fluctuations in various positions on the model and test circuit. Auxiliary measurements and surveys of cavitation, noise and vibrations support this data. This study presents a set of evaluation criteria for the elaboration of a diagnosis. The method is illustrated using practical examples from published works and from the numerous experiments performed by the author. A discussion of similitude shows that a diagnosis set using this method provides a good characterisation of the dynamic behaviour associated with the particular turbine design. Adapting acoustic power methods to Francis turbine tests provides a quantitative evaluation of disturbance sources. This tool makes it possible to look forward to an actual prediction of oscillation amplitudes associated with the full-size turbine operation. 3. Elements for the prediction The test laboratory provides a description of the dynamic behaviour associated with a particular turbine design in a guaranteed range of operation. This description is based on three elements of evaluation: discussion of the various dynamic phenomena according to operating conditions: relative frequency and amplitude of the part load precession, of 80 % load oscillation, relative frequency of draft tube column free oscillations, vortex-free region, organisation of the full load pulsation; survey of the draft tube cavitation compliance, lumped at the runner outlet, according to operating conditions; relative emission of the acoustic power toward the piping system, according to operating conditions. These three elements allow an adequate representation of the Francis turbine for a computation of stability of operation involving the piping system dynamics. However, this is the limit of what the test laboratory can say; the prototype piping system layout is liable to change after the turbine model acceptance tests. Once the turbine is adequately described the prediction of stability is performed using known methods and is done under responsibility of the technical consultant. 4. Conclusions The proposed method complies with technical and economic requirements of a laboratory acceptance test on a scale model. Following a simple experimental procedure, if yields a good description of the dynamic behaviour associated with a particular Francis turbine design and its guaranteed range of operation. It provides the elements for computations of stability of operation. Systematic use of the method and comparisons with field observations are the logical sequel to this research. This necessary phase of development will make the stability computations finer, for instance in handling damping in the connecting pipes. It will also provide the basis for a definition of scale effects to be used for the correction of similitudes.
This page is automatically generated and may contain information that is not correct, complete, up-to-date, or relevant to your search query. The same applies to every other page on this website. Please make sure to verify the information with EPFL's official sources.
A water turbine is a rotary machine that converts kinetic energy and potential energy of water into mechanical work. Water turbines were developed in the 19th century and were widely used for industrial power prior to electrical grids. Now, they are mostly used for electric power generation. Water turbines are mostly found in dams to generate electric power from water potential energy. Water wheels have been used for hundreds of years for industrial power. Their main shortcoming is size, which limits the flow rate and head that can be harnessed.
The Francis turbine is a type of water turbine. It is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency. The process of arriving at the modern Francis runner design took from 1848 to approximately 1920. It became known as the Francis turbine around 1920, being named after British-American engineer James B. Francis who in 1848 created a new turbine design.
A turbine ('tɜːrbaɪn or 'tɜːrbɪn) (from the Greek τύρβη, tyrbē, or Latin turbo, meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical power when combined with a generator. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor.
This paper proposes a novel approach to predict the machining time of small-scale radial-inflow turbine impellers for organic Rankine cycle power systems based on preliminary design parameters. The time prediction method uses machining databases of differe ...
For the design optimization of the Pelton turbine, it is highly demanded to investigate the flow inside the turbine casing, which includes the water jet from the nozzles, the interaction between the jet and rotating runner, and the flow ejected from the bu ...
This paper presents preliminary results of an experimental study on the occurrence and development of the upper part-load instability in a reduced-scale Francis turbine. The study includes draft tube pressure measurements, high-speed flow visualization, an ...
