scholarly journals Numerical Investigation Into the Influence on Hydrofoil Vibrations of Water Tunnel Test Section Acoustic Modes

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Wei Wang ◽  
Lingjiu Zhou ◽  
Zhengwei Wang ◽  
Xavier Escaler ◽  
Oscar De La Torre
Keyword(s):  
Speed Of Sound ◽  
Test Section ◽  
High Speed ◽  
Acoustic Mode ◽  
Acoustic Properties ◽  
Mode Shapes ◽  
Two Phase ◽  
Acoustic Frequency ◽  
Fluid Medium ◽  
Fluid Structure

High-speed water tunnels are typically used to investigate the single-phase and two-phase flows around hydrofoils for hydraulic machinery applications but their dynamic behavior is not usually evaluated. The modal analysis of an NACA0009 hydrofoil inside the test section was calculated with a coupled acoustic fluid–structure model, which shows a good agreement with the experimental results. This numerical model has been used to study the influence on the hydrofoil modes of vibration of the acoustic properties of the surrounding fluid and of the tunnel test section dimensions. It has been found that the natural frequencies of the acoustic domain are inversely proportional to the test section dimensions. Moreover, these acoustic frequencies decrease linearly with the reduction of the speed of sound in the fluid medium. However, the hydrofoil frequencies are not affected by the change of the speed of sound except when they match an acoustic frequency. If both mode shapes are similar, a strong coupling occurs and the hydrofoil vibration follows the linear reduction of natural frequency induced by the acoustic mode. If both mode shapes are dissimilar, a new mode appears whose frequency decreases linearly with speed of sound while keeping the acoustic mode of vibration. This new fluid–structure mode of vibration appears in between two hydrofoil structure modes and its evolution with sound speed reduction has been called “mode transition.” Overall, these findings reinforce the idea that fluid–structure interaction effects must be taken into account when studying the induced vibrations on hydrofoils inside water tunnels.

Combined Acoustic Damping-Cooling System for Operational Flexibility of GT26/GT24 Reheat Combustors

2015 ◽  
Author(s):  
Bruno Schuermans ◽  
Mirko Bothien ◽  
Michael Maurer ◽  
Birute Bunkute
Keyword(s):  
Gas Turbines ◽  
Cooling System ◽  
Acoustic Mode ◽  
Acoustic Properties ◽  
Front Panel ◽  
Mode Shapes ◽  
Front Face ◽  
Operational Flexibility ◽  
Fuel Gas ◽  
Near Wall

In the development process of gas turbine combustion chambers, finding countermeasures for thermoacoustically induced pressure pulsations is a major focus. This paper presents a novel system consisting of a multi-layered and multi-functional high frequency damping and cooling structure that is implemented on the sequential burner front panel of the GT26/GT24 gas turbines. The device features multiple single Helmholtz dampers and an advanced convective near wall cooling system to improve the cooling capability and to reduce the cooling mass flow and thereby reducing NOx emissions. The acoustic properties of the dampers and their placement have been defined as function of the identified acoustic mode shapes. The latter is very important since the dampers are designed to counteract screech tones that have acoustic wave lengths of the order of one burner front face width. In order to identify the acoustic mode shapes, multiple dynamics pressure measurements are applied in the full scale engine. The near-wall cooled damping front panel design represents a new technology which has been developed and successfully validated at engine level in fuel gas and oil operation. The restrictions of the stable operating range due to pulsations are completely eliminated resulting in an increase of operational flexibility and lifetime. In addition to a thorough treatment of the damper’s acoustic performance, information on the improved near wall cooling scheme is given in the paper, too.

Development of Prediction Technology of Two-Phase Flow Dynamics Under Earthquake Acceleration — (5) Measurement of Bubble Deformation Near Wall Under Structure Vibration

2012 ◽  
Author(s):  
Kousuke Mizuno ◽  
Akiko Kaneko ◽  
Hideaki Monji ◽  
Yutaka Abe ◽  
Hiroyuki Yoshida ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Flow Structure ◽  
Test Section ◽  
High Speed ◽  
Bubbly Flow ◽  
Oscillation Amplitude ◽  
Reactor Core ◽  
Two Phase ◽  
Piv Measurement ◽  
Structure Vibration

In a nuclear power plant, one of the important issues is evaluation of the safety of reactor core and its pipes when an earthquake occurs. Many researchers have conducted studies on constructions of plants. Consequently, there is some knowledge about earthquake-resisting designs. However the influence of an earthquake vibration on thermal fluid inside a nuclear reactor plant is not fully understood. Especially, there are little knowledge how coolant in a core response when large earthquake acceleration is added. Some studies about the response of fluid to the vibration were carried out. And it is supposed that the void fraction or the power of core is fluctuated with the oscillation by the experiments and numerical analysis. However detailed mechanism about a kinetic response of gas and liquid phases is not enough investigated, therefore the aim of this study is to clarify the influence of vibration of construction on bubbly flow structure. In order to investigate it, we visualize changing of bubbly flow structure in pipeline on which sine wave is applied. Bubbly flow is produced with injecting gas into liquid flow through a horizontally circular pipe. In order to vibrate the test section, the oscillating table is used. The frequency of vibration added from the table is from 1.0 Hz to 10 Hz and acceleration is from 0.4 G to 1 G (1 G = 9.8 m/s2). The test section and a high speed video camera are fixed on the table. Thus the relative velocity between the camera and the test section is ignored. In the visualization experiment, the PIV measurement is conducted. Then the motion of bubbles, for example the shape, the positions and the velocity are measured with observation. In addition, by varying added oscillation amplitude, frequency and flow rate of the fluids, the correlation between these parameters and bubble motion was evaluated. It was clarified that the behavior of liquid phase and bubble through horizontal circular pipes was affected by an oscillation. When structure vibration affects the flow, two main mechanisms are supposed. One is the addition of body force of the oscillation acceleration to liquid phase and bubble, and the other is the velocity oscillation of the test section and the effect of the boundary layer of the pipe wall. It was also found that when the added oscillation frequency and amplitude was changed, the degree of the fluctuation of liquid phase and bubble motions were changed.

Characteristics of Gas-Liquid Two-Phase Flow Patterns in Miniature Channel Having a Gas Permeable Sidewall

2002 ◽  
Author(s):  
H. Yang ◽  
T. S. Zhao ◽  
P. Cheng
Keyword(s):  
Test Section ◽  
High Speed ◽  
Annular Flow ◽  
Two Phase Flow ◽  
Porous Plate ◽  
Flow Patterns ◽  
Phase Flow ◽  
Two Phase ◽  
Flow Configuration ◽  
Blowing Up

Characteristics of gas-liquid two-phase flow patterns in a miniature square cross-section channel having a gas permeable sidewall have been investigated visually using a high-speed motion analyzer. The problem under consideration is encountered in the design of Direct Feed Methanol Fuel Cells (DMFC). The test section was a horizontally oriented rectangular transparent (Lucite material) channel with its lower wall consisting of a porous plate. Liquid was fed into the test section from its entrance, while gas was injected uniformly into the test section along the lower porous sidewall. The visual study shows the typical flow patterns found in the test section include bubbly flow, plug flow, slug flow, and annular flow. However, unlike the conventional co-current two-phase flow in a channel with gas and liquid uniformly entering from one of its ends, for the flow configuration considered in this work, it was found that two or three of the above mentioned flow patterns appeared simultaneously at different locations of the channel. The length of each flow pattern varied with the flow rates of liquid and gas. A distinct feature of annular flow for the present flow configuration is that small bubbles were continuously generated from the porous plate, which grew by blowing up the liquid film, formed a semi-sphere shape, and then ruptured and released gas into the core flow.

Experimental and Numerical Investigation of Single Bubble Dynamics in a Two-Phase Bubbly Medium

2011 ◽  
Vol 133 (12) ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
Compressible Fluid ◽  
High Speed ◽  
Bubble Dynamics ◽  
Ambient Pressure ◽  
Bubble Radius ◽  
Homogeneous Medium ◽  
Two Phase ◽  
Fluid Medium ◽  
Bubbly Medium

The dynamics of a bubble in a dilute bubbly water-air mixture is investigated experimentally and the results compared with a simple homogeneous compressible fluid model in order to elucidate the requirements from a better advanced numerical solution. The experiments are conducted in view of providing input and validation for an advanced bubbly flow numerical model we are developing. Corrections for classical approaches where in the two-phase flow modeling the dynamics of individual bubble is based on spherical isolated bubble dynamics in the liquid or an equivalent homogeneous medium are sought. The main/primary bubble is produced by an underwater spark discharge from charged capacitors, while the bubbly medium is generated using electrolysis. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the ambient pressure in the container. The size and concentration of the fine bubbles is controlled by the electrolysis voltage, the length, diameter, arrangement, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the primary bubble characteristic quantities such as achieved maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and of the mixture is observed using high speed video photography. The void fraction of the bubbly mixture in the fluid domain is deduced from image analysis of the high speed movies and obtained as a function of time and space. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to a simple compressible fluid medium model which accounts for the change in the medium properties in space and time. This helps illustrate where such simple models are valid and where they need improvements. This information is valuable for the parallel development of an Eulerian-Lagrangian code, which accounts for the dynamics of bubbles in the field and their interaction.

scholarly journals Experimental Investigation of Acoustic Atomization in Liquid Loading Horizontal Gas Wells

2021 ◽  
Author(s):  
Eiman Al Munif ◽  
Jennifer Miskimins
Keyword(s):  
Experimental Data ◽  
Liquid Film ◽  
Test Section ◽  
Positive Impact ◽  
Water Injection ◽  
Acoustic Properties ◽  
Flow Loop ◽  
Gas Wells ◽  
Two Phase ◽  
Artificial Lift

Abstract Enhancing the production in liquid-loaded horizontal natural gas wells using an acoustic liquid atomizer tool is proposed as a possible artificial lift method. The more liquid that is converted to droplets, the more available gas is able to carry the liquid to the surface, resulting in an increase in production. The acoustic atomizer was selected to be the atomization device as it can create very small droplets at certain frequencies leading to a mist flow. The contribution of this research includes obtaining experimental data using different laboratory procedures for horizontal and slightly inclined tubulars. Two-phase (gas and water) injection stream lines are joined to the test section to introduce gas and water at desired rates. An ultrasonic atomizer inside the test section is used to better understand the atomization mechanism as an artificial lift technique. Several experiments with varying factors influencing the acoustic properties are tested including varying liquid and gas rates, four different frequencies, two different flow pipe inclination angles, and two different acoustic device orientations. The results show that when using frequencies of 62 and 62.5 kHz, the outcomes were almost identical for horizontal and slightly inclined pipe. Both frequencies reduced liquid film accumulation by 1% at lower (0.001 m/s) and higher (0.0168 m/s) liquid velocities while gas velocity was kept at 14 m/s. The performance of the acoustic tool was highly dependent on the orientation of the tool inside the flow loop due to its atomizer geometry, shape and size. Sprayers facing up (0°, original case) helped the droplets to be carried by the gas since the gas occupies the top portion of the pipe and did not block the atomizer. The sprayers failed to work while facing the bottom of the pipe (180°) due to water accumulating around the sprayers, plugging the atomizer and hindering it from working. Using an orientation of 90° (sprayers facing sideways) provided better results and positive impact in reducing the liquid film level. The efficiency of the tool decreases in slightly inclined wells. As more liquid quantity accumulated in the well, the atomization technique seems to be slow in reducing the liquid film height. This research presents a set of diverse experimental data to suggest acoustic atomization might be used as a possible artificial lift technique in horizontal wells. The technique shows a 1-4% improvement which might be experimental error or in experimental control. Thus, the device used in the lab needs improvement to work as efficiently as other artificial lift techniques to possibly enhance production.

scholarly journals Investigation of Flow Pattern and Void Fraction of Air and Low Surface Tension Liquid in A 30° Inclined Small Pipe

2021 ◽  
Vol 83 (2) ◽  
pp. 73-83
Author(s):  
Sudarja ◽  
Sukamta ◽  
Fauzan Saputra
Keyword(s):  
Surface Tension ◽  
Flow Pattern ◽  
Test Section ◽  
High Speed ◽  
Liquid Surface ◽  
Phase Flow ◽  
Distilled Water ◽  
Two Phase ◽  
Liquid Surface Tension ◽  
Churn Flow

Two-phase flow in the mini pipe is applied in wide fields. The most common of two-phase flow is a couple of gas and liquid. The essential properties of the liquid are density, viscosity, and surface tension. There are many variations of the flow direction, horizontal, incline, and vertical, in terms of orientation. The two-phase investigation of flow pattern and void fraction of air and low surface tension liquid in a 30° inclined small pipe has been carried out. Dry air was used as a gas phase, while the liquid was the mixture solution of distilled water and 3% (by volume) of butanol. Butanol addition aimed to decrease the surface tension, which became 42.9 millinewton/meter, instead of 71 mN/m when using distilled water. The test section was a 130 mm length, 1.6 mm inner diameter circular glass pipe. The rig used was equipped with the air compressor, pressure tank, high-speed camera, liquid flow meter, and gas flow meter. The liquid was fed to the test section by the pressurized tank, instead of directly pumped, to avoid pulsation. Ranges of gas and liquid superficial velocities were 0.025 – 66.3 m/s and 0.033 – 4,935 m/s, respectively. Flow patterns were obtained from the captured high-speed video. Meanwhile, the void fractions were acquired by image processing of the video. As a result, five distinctive flow patterns were observed: plug, slug-annular, churn, bubbly, and annular. The separated flow was absent. The change of the liquid surface tension affected the shifting of some transition boundary lines in the flow pattern map. The transition line between slug-annular and annular against churn flow was shifted to the lower side or toward lower JL when the liquid surface tension decreased. In short, the churn flow was easier to be formed when the liquid surface tension was lower.

Dynamic Seismic Response Analysis of Nuclear Storage Tank Based on Fluid-Structure Coupling Method

2017 ◽  
Author(s):  
Yu Weng ◽  
Lang Liu ◽  
Yang Jiang ◽  
Hongfang Gu ◽  
Haijun Wang
Keyword(s):  
Liquid Medium ◽  
Storage Tank ◽  
Time History ◽  
Coupling Method ◽  
Response Analysis ◽  
Deformation Method ◽  
Two Phase ◽  
Fluid Medium ◽  
Fluid Structure ◽  
Coupling System

The storage tanks in nuclear facilities has a significant impact on the safety of the reactor and the radiation shielding, so its mechanical property analysis has been widely concerned in the field of engineering and scientific research. Meanwhile, the storage tank is usually filled with gas and liquid medium. In the presence of external disturbances (such as external force, displacement, earthquake etc.), the position and structure of the vessel changes, that lead to changing of the gas-liquid interface. This characteristic can make the storage tank system as a tightly fluid-structure coupling system. In this paper, a storage tank which stored radioactive gas liquid medium is choosing to study such fluid-structure coupling system phenomenon, and a typical dynamic seismic condition is assumed. A two-way fluid-structure coupling method is used with CFD (Computational Fluid Dynamics) and FEM (Finite Element Method) numerical method. The study considered interaction between structure and two phase turbulent fluid. In FEM calculation, the time history seismic acceleration load is applied to the support of tank, and the flow loading coming from fluid medium is applied to the wall of tank which is send from CFD code. Then, the structure displacement which is calculate by FEM is transferred to CFD code. In CFD calculation, multiphase fluid numerical model is applied to simulate the flow characteristics of gas-water two phase fluid, and the turbulent properties are also considered in the calculation. Mesh deformation method is used to simulate the displacement of flow passage boundary which is send by FEM code. After CFD calculation, flow loading is transferred to the tank wall of FEM code again. Such loop of FEM and CFD calculation continues to go on with the seismic time history, the response characteristics of the tank will be solved. In order to evaluate the difference between the above method and the traditional analysis method. An independent calculation used added mass approach is carrying out, in which the effect of steady state water is applied to the wall of the vessel, and this load will not change with the earthquake. All others load and constraint mode are same with the above method. According to the two-way fluid-structure coupling analysis, the detailed characteristics of liquid free surface distribution and structural response of the vessel are obtained. The results show that the response vibration amplitude of the tank structure increases with the earthquake, and the response is mainly affected by the liquid sloshing. According to comparative analysis, the advantages of coupling method are proved. The method from this study can be used for the same type of analysis.

Two-Phase Short Circuit in the Power Grid Powered by a Transformer with a Y/Δ-11 Winding Connection

2020 ◽  
pp. 25-30
Author(s):  
Aleksandr S. Serebryakov ◽  
Vladimir L. Osokin ◽  
Sergey A. Kapustkin
Keyword(s):  
High Speed ◽  
Short Circuit ◽  
Relay Protection ◽  
Electric Circuit ◽  
Operational Reliability ◽  
Research Purpose ◽  
Industrial Complex ◽  
Two Phase ◽  
Short Circuit Currents ◽  
Secondary Winding

The article describes main provisions and relations for calculating short-circuit currents and phase currents in a three-phase traction transformer with a star-triangle-11 connection of windings, which feeds two single-phase loads in AC traction networks with a nominal voltage of 25 kilovolts. These transformers provide power to the enterprises of the agro-industrial complex located along the railway line. (Research purpose) The research purpose is in substantiating theoretical equations for digital intelligent relay protection in two-phase short circuits. (Materials and methods) It was found that since the sum of instantaneous currents in each phase is zero, each phase of the transformer works independently. We found that this significantly simplifies the task of analyzing processes with a two-phase short circuit. In this case, the problem of calculating short-circuit currents in the traction network can be simplified by reducing it to the calculation of an ordinary electric circuit with three unknown currents. (Results and discussion) The article describes equations for calculating short-circuit resistances for one phase of the transformer when connecting the secondary winding as a star or a triangle. The currents in the phases of the transformer winding at short circuit for the star-triangle-11 and star-star-with-ground schemes are compared. It was found that when calculating short-circuit currents, there is no need to convert the secondary winding of the traction transformer from a triangle to a star. (Conclusions) It was found that the results of the research can be used in the transition of relay protection systems from electromagnetic relays to modern high-speed digital devices, which will increase the operational reliability of power supply systems for traction and non-traction power consumers.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

scholarly journals Spatially Resolved Experimental Modal Analysis on High-Speed Composite Rotors Using a Non-Contact, Non-Rotating Sensor

Sensors ◽  
2021 ◽  
Vol 21 (14) ◽  
pp. 4705
Author(s):  
Julian Lich ◽  
Tino Wollmann ◽  
Angelos Filippatos ◽  
Maik Gude ◽  
Juergen Czarske ◽  
...  
Keyword(s):  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Fiber Reinforced ◽  
Structural Dynamic ◽  
Spatially Resolved ◽  
Glass Fiber Reinforced ◽  
Vibration Responses ◽  
And Performance

Due to their lightweight properties, fiber-reinforced composites are well suited for large and fast rotating structures, such as fan blades in turbomachines. To investigate rotor safety and performance, in situ measurements of the structural dynamic behaviour must be performed during rotating conditions. An approach to measuring spatially resolved vibration responses of a rotating structure with a non-contact, non-rotating sensor is investigated here. The resulting spectra can be assigned to specific locations on the structure and have similar properties to the spectra measured with co-rotating sensors, such as strain gauges. The sampling frequency is increased by performing consecutive measurements with a constant excitation function and varying time delays. The method allows for a paradigm shift to unambiguous identification of natural frequencies and mode shapes with arbitrary rotor shapes and excitation functions without the need for co-rotating sensors. Deflection measurements on a glass fiber-reinforced polymer disk were performed with a diffraction grating-based sensor system at 40 measurement points with an uncertainty below 15 μrad and a commercial triangulation sensor at 200 measurement points at surface speeds up to 300 m/s. A rotation-induced increase of two natural frequencies was measured, and their mode shapes were derived at the corresponding rotational speeds. A strain gauge was used for validation.

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