Study of the state a Francis turbine

2011

Vibration tests of marine gas turbine engines are performed as research of on-line and off-line types. On-line Systems generally monitored one or two vibration symptoms, which asses the limited and/or the critical values of parameters and they, potentially, can warn and/or shutdown engines. Off-line Systems are usually used for vibration analysis during non-steady state of work. The paper presents comparison of different methods of analysis of vibration symptoms measured under run-up and shut-down processes of marine gas turbine engines. Results of tests were recorded on gas turbine engine DR76 type of the COGAG type propulsion system. Main goal of the research was qualified on helpfulness and unambiguous result, from synchronous measurement, order tracking and auto tracking. All vibration symptoms were chosen from the methodology of the diagnosing gas turbine engines operated in the Polish Navy, called Base Diagnosing System. Second purpose of the paper was the estimation of the po...

This paper borders around analysis of rotary engine blade. The blade could be a rotating half that converts mechanical energy into energy. rotary engine blade is important a part of turbocharger that has shown increasing growth of failure damaging rotary engine disk. It deals with Static and thermal analysis of rotary engine blade that is created from metal 718 to estimate its performance. The causes of failure for rotary engine blade have additionally been distinguished. The investigation has been done exploitation SoildWorks 2012 and ANSYS ten.0 software. SolidWorks 2012 is employed for modeling of rotary engine blade and analysis has been done by ANSYS ten.0 software. an effort has been created to analyze the impact of iatrogenic stresses, pressure and temperature on the rotary engine blade. A structural analysis has been meted out to analyze the stresses and displacements of the rotary engine blade. A thermal analysis has been meted out to analyze the thermal gradient and therma...

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 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.

2015

Vibration analysis is the main technique in diagnosing dynamic behavior of industrial machinery and equipment. This technique is applied for the vibration diagnosis 40MW turbo generator which is driven by a gas turbine. Due to high vibration amplitudes of bearings a numerical analysis of the generator rotor is used to highlight the dynamic phenomena and determination of critical speeds. So to validate the numerical model and identify critical speed a complex experimental protocol was conducted to measure both the coupling vibration monitoring system in real time and local measurement by fixing the sensor on the bearing housing. The use of advanced digital signal processing led to highlighting the main faults and obtains the final solution to reduce the amplitude of vibration.

IOP Conference Series: Earth and Environmental Science, 2014

The frequency of the Nordic power grid has become more volatile during recent years. This gives rise to two effects in synchronous machines. Firstly, as grid frequency changes the rotational speed of synchronous machines must change likewise. Secondly, the Nordic grid uses speed droop operation extensively as the primary governing; hence the power produced is a function of the grid frequency. These two coupled effects will lead to the runner and axle on synchronous machines having to cope with a varying level of torque. Even if the unit is supposedly operating at steady state via a fixed set point for the production, the influence of the varying grid frequency is that the torque in not steady at all. Recent years' new high head Francis runners in Norway have shown a tendency towards experiencing fatigue to a greater extent than what seem to be the case for new runners decades ago. Leading to this paper, measurements have been made of the rotational speed; generator power; main servo motor position and grid frequency at a Francis turbine unit. Based on these measurements simulations that include the hydraulic domain have then been performed. From these simulation results a property is constructed which is intended as a qualitative measure of the material stresses induced in the rotating masses of the unit, and is representative of the dynamical loads on the material of the rotating masses. The work is a part of a longer term goal, namely identifying the stress oscillations in a Francis turbine runner operating at speed of rotation oscillating because of grid frequency variations.

Journal of Physics: Conference Series

The ability to predict a francis runners dynamic response to the exciting forces is paramount to avoid unwanted disintegration of the turbines components. In this article, each of the principal factors contributing to the dynamic response of the runner; eigenfrequency, mode shape, damping and pressure force, is individually examined and compared to the measured values from the Francis-99 runner. Even though the runner is made with a bolted connection between the blades and crown/band, and thus severely increasing the complexity, quite accurate predictions are possible using methods previously validated for massive and symmetric runners. All calculations are conducted on the best efficiency point and with eigenmodes corresponding to Nodal Diameter 4 as excited by the second harmonic of the guide vane passing frequency. The calculated natural frequency for the first two ND4 eigenmodes are within ±5% of the measured values. Further are the calculated eigenmodes, forcing pressure field ...

International journal of turbo & jet-engines, 2003

Understanding rotor-stator interaction is essential for the design of turbomachines with increased performance and improved reliability. The sources of unsteadiness currently modeled in the rotor-stator interaction studies include potential flow interaction, wake interaction, hot streak interaction, vortex shedding and shock/boundary layer interaction. The objective of this paper is to investigate the effects of vibrating blades on the rotor-stator interaction in turbomachinery. An existing parallelized solver of the Euler/Navier-Stokes equations for multi-stage compressors and turbines has been extended to model vibrating rotor blades. This numerical implementation can model rotor blades that vibrate with a plunging and/or pitching motion. The rotor blade vibration is superimposed on the blade rotation. The numerical algorithm has been used to simulate the flow in a two-stage turbine. Assuming that the first-stage rotor blades were plunging with an amplitude equal to 10% of the chord and the second-stage rotor blades were pitching with an amplitude of 5 deg, both rows vibrating with a frequency of 1230 Hz, the total-to-total efficiency decreased by approximately 1.8 points compared to the rigid blade turbine. Consequently, vibrating blades can significantly affect the rotor-stator interaction in turbomachinery.

IOP Conference Series: Earth and Environmental Science, 2019

The Norwegian power system today includes a relatively large percentage of Francis turbines with a head of above 300m, in the world. This leads to a need to maintain and develop the national competence regarding the challenges connected to this type of turbine. The importance of this competence is increased by the fact that these turbines have a high installed capacity and are therefore crucial to the production stability. In the later years the old runners in Norwegian high head power plants have begun to show signs of fatigue. Taking the average age of these runners, which is approaching 45 years, into account, this may not be surprising. The surprising fact is that the same signs of fatigue, and in some cases total breakdown due to cracks, also occur in new and modern Francis runners. This leads to a hypothesis that the problem stems from sources other than the turbine runners themselves. The suspected cause of this reduction in the expected lifetime is the change the pattern of turbine operation to accommodate new intermittent energy in the power system and progress in the manufacturing technology enabling thinner blades. As an example the Horizon2020 project HydroFLEX initialised by the European Union aim to produce technology that allows for 30 start-stops per day for Francis runner. A research project funded by the Norwegian Research Council and the Norwegian Hydro Power Industry, aim to increase the available knowledge regarding these high head Francis turbines. The research is done both on a basic and applied level where the focus is to increase the knowledge of the phenomena and to produce validation data for numerical simulations of said phenomena. The fundamental research focus on the hydrodynamic dampening applied on a hydrofoil within a high velocity water flow. The applied research is focused on the Francis-99 runner, a model runner of a High Head Francis turbine, which has been instrumented in order to study the Rotor-Stator-Interaction(RSI) and the structural response of the runner. The research areas both consist experimental and numerical studies, where the experimental results are used to validate the numerical. This paper presents the background of the project, the different activities and some preliminary results from selected activities. The aim of the paper is to introduce the project, participants and the participants view on the future of High Head Francis runners that do not crack due to RSI.

International Journal of Fluid Machinery and Systems, 2020

Over the last years, several breakdowns in hydropower plants with low specific speed Francis runners have been reported. One of the main excitation forces in such runners is the pressure fluctuations originating from the rotor stator interaction. In this paper, the rotor-stator interaction has been analyzed utilizing pressure sensors onboard the runner. The pressure sensors were flush mounted in the hub of the runner and the signals were transmitted through a slip-ring system. The measurements have been analyzed relative to the runner angular position by utilizing an angular position sensor mounted to the shaft end. Measurements with different guide vane angle have been compared in order to study the potential flow interaction and the viscous wake effects for the pressure inside the runner. The results from the onboard pressure measurements found that the phase of the guide vane passing pressure seen by the onboard pressure sensors was independent of the guide vane opening. Hence, the potential flow interaction was found to be the dominant effect and no evidence from the viscous wake effect was found on the onboard pressure.