scholarly journals Numerical Research on Performance of High-Speed Partial Emission Pump

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Qingjiao Shui ◽  
Ting Jiang ◽  
Binghui Pan ◽  
Tianxing Yang ◽  
Wei Pan
Keyword(s):  
Liquid Phase ◽  
High Speed ◽  
Phase Particle ◽  
Characteristic Curve ◽  
Particle Diameter ◽  
Two Phase ◽  
Factors Affecting ◽  
External Characteristic ◽  
Numerical Simulation Methods ◽  
Small Flow

The high-speed partial emission pump is a small flow and high-head pump, which has been widely used. To study the main factors affecting the performance of high-speed partial emission pumps, numerical simulation methods were used to calculate the performance parameters of high-speed partial emission pumps with and without inducers, and the external characteristic parameters were verified through comparison test values. The results show that the head of the high-speed partial emission pump with inducer is nearly 15 m higher than that of the high-speed partial emission pump without inducer. Considering the influence of air in the high-speed partial emission pump on the working performance, the two-phase flow with different flow rates, different particle sizes, and different concentrations was calculated, and the different liquid phase distributions, liquid phase velocity vector diagrams, and external characteristic curve were compared. The results show that under the same flow condition, the gas-phase particle diameter has the most severe influence on the external characteristic.

Characterization of Superheated Liquid Jet Atomisation With Phase Doppler Anemometer (PDA) and High-Speed Imaging

2006 ◽  
Author(s):  
Dilek Yildiz ◽  
Patrick Rambaud ◽  
Jeroen van Beeck ◽  
Jean-Marie Buchlin
Keyword(s):  
Droplet Size ◽  
High Speed ◽  
Initial Conditions ◽  
Particle Diameter ◽  
Superheated Liquid ◽  
High Speed Imaging ◽  
Two Phase ◽  
Phase Doppler Anemometer ◽  
Geometrical Effects ◽  
Initial Storage

A flashing phenomenon is often met in liquid propulsion of safety fields in industrial environments. This violent evaporation occurs when a liquid finds itself suddenly in a thermodynamic non-equilibrium and becomes superheated. To investigate theoretically the source processes and validate models for design and safety assessments, knowledge of accurate and reliable data such as distribution of droplet size, velocity and temperature in the closest field of flashing occurrence is mandatory. In this present work, an experimental study is undertaken in order to characterize the two-phase jet after a sudden accidental release and aims to quantify the effects of initial conditions such as initial storage pressure, temperature, geometrical effects of the release points etc on the spray characteristics. To fulfil this goal, a laser-based optical technique like Phase Doppler Anemometry (PDA) is used to obtain information for particle diameter and velocity evolution in this harsh environment. Cases for different initial pressures, temperatures and orifice diameters are studied and the droplet size and velocity evolution are presented in function of initial parameters.

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.

Visualization of Two-Phase Refrigerant Flow Through an Ice-Maker Evaporator

2010 ◽  
Author(s):  
Brandon S. Field
Keyword(s):  
Liquid Phase ◽  
Flow Pattern ◽  
High Speed ◽  
Phase Distribution ◽  
Phase Flow ◽  
Refrigeration System ◽  
Two Phase ◽  
Optimal Flow ◽  
Transient Period ◽  
Flow Through

A transparent evaporator plate has been affixed to a commercial ice-maker refrigeration system and high-speed visualization of the two-phase boiling of the R134a has been made as water is frozen on the top of the plate. The startup transient period of the freeze cycle, characterized by superheated vapor throughout the evaporator, can last up to 10 minutes as the water is pre-cooled, and the freeze cycle follows. The two-phase flow patterns have been observed as distance along the evaporator plate during the freeze cycle, and observations about the liquid phase distribution are made. The refrigerant path is a series of spiral turns, which sets up a flow pattern of the liquid phase gathering along the inner wall of the channel and being dragged by the high speed vapor. This is not an optimal flow pattern for heat transfer because the liquid is not distributed to the top of the channel.

Visualization Study on Gas Bubble Break-Up and Transport Phenomena in Microchannels

2011 ◽  
Author(s):  
Dongwook Yim ◽  
Jaeyong Sung ◽  
Jung Yul Yoo
Keyword(s):  
Liquid Phase ◽  
Bubble Size ◽  
High Speed ◽  
Silicone Oil ◽  
Flow Patterns ◽  
Flow Rate Ratio ◽  
Gas Bubble ◽  
Two Phase ◽  
Flow Rates ◽  
Break Up

In the present research, a visualization study is carried out to understand the flow patterns and break-up formation in flow-focusing microfludic device, which usually involve gas-liquid two-phase flow patterns such as bubbly flow, slug flow, and annular flow. High-speed camera and fluorescence microscopy are used to the characterize microscale gas-liquid two-phase flows in 191.64 μm × 200 μm rectangular PDMS microchannel which are fabricated by using soft lithography technique. N2 and Silicone oil serve as the gas and liquid phases, respectively. The influence of gas and liquid flow rates and the viscosity of the liquid phase on the bubble size, flow patterns, and generating frequency are experimental studied. This study is focused on viscosity of liquid phase. In order to influence of viscosity of liquid phase, various viscosity silicone oils are used in this study. The breakup mechanism, bubble generating rate, and gas bubble making time are investigated at the cross junction. The gas bubble size and space of between bubbles are dependent on the flow rates of the liquid and gas, and viscosity of liquids. The slug length L is also dependent on the flow rates of the liquid and gas in such a manner that the ratio of slug length to the channel width is a function of the flow rate ratio of gas to liquid.

SYNTHESIS OF HYDROGEN IN ACOUSTOPLASMA DISCHARGE IN A LIQUID-PHASE STREAM

2019 ◽  
pp. 42-48 ◽  
Author(s):  
N. A. Bulychev
Keyword(s):  
Liquid Phase ◽  
Organic Compounds ◽  
Electrode Materials ◽  
Solid Phase ◽  
Plasma Discharge ◽  
Raw Material ◽  
Two Phase ◽  
Reduced Pressure ◽  
External Power Source ◽  
Phase Medium

In this paper, the plasma discharge in a high-pressure fluid stream in order to produce gaseous hydrogen was studied. Methods and equipment have been developed for the excitation of a plasma discharge in a stream of liquid medium. The fluid flow under excessive pressure is directed to a hydrodynamic emitter located at the reactor inlet where a supersonic two-phase vapor-liquid flow under reduced pressure is formed in the liquid due to the pressure drop and decrease in the flow enthalpy. Electrodes are located in the reactor where an electric field is created using an external power source (the strength of the field exceeds the breakdown threshold of this two-phase medium) leading to theinitiation of a low-temperature glow quasi-stationary plasma discharge.A theoretical estimation of the parameters of this type of discharge has been carried out. It is shown that the lowtemperature plasma initiated under the flow conditions of a liquid-phase medium in the discharge gap between the electrodes can effectively decompose the hydrogen-containing molecules of organic compounds in a liquid with the formation of gaseous products where the content of hydrogen is more than 90%. In the process simulation, theoretical calculations of the voltage and discharge current were also made which are in good agreement with the experimental data. The reaction unit used in the experiments was of a volume of 50 ml and reaction capacity appeared to be about 1.5 liters of hydrogen per minute when using a mixture of oxygen-containing organic compounds as a raw material. During their decomposition in plasma, solid-phase products are also formed in insignificant amounts: carbon nanoparticles and oxide nanoparticles of discharge electrode materials.

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.

Axial dispersion in the liquid phase in a horizontal two-phase tube reactor

1991 ◽  
Vol 56 (6) ◽  
pp. 1249-1252
Author(s):  
Marie Fialová ◽  
Ctirad Verner ◽  
Lothar Ebner
Keyword(s):  
Liquid Phase ◽  
Flow Regimes ◽  
Basic Flow ◽  
Axial Dispersion ◽  
Two Phase ◽  
Tube Reactor

The characteristics of axial dispersion in the liquid phase were measured for two basic flow regimes in a horizontal two-phase tube reactor. The data obtained indicate that in some flow regions, axial dispersion can be quite significant.

scholarly journals Utility of the Mini-Cog for Detection of Cognitive Impairment in Primary Care: Data from Two Spanish Studies

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Cristóbal Carnero-Pardo ◽  
Isabel Cruz-Orduña ◽  
Beatriz Espejo-Martínez ◽  
Carolina Martos-Aparicio ◽  
Samuel López-Alcalde ◽  
...  
Keyword(s):  
Primary Care ◽  
Cognitive Impairment ◽  
Characteristic Curve ◽  
Total Sample ◽  
Phase Iii ◽  
Kappa Index ◽  
Two Phase ◽  
Clock Drawing Test ◽  
Pooled Data ◽  
Post Hoc

Objectives. To study the utility of the Mini-Cog test for detection of patients with cognitive impairment (CI) in primary care (PC).Methods. We pooled data from two phase III studies conducted in Spain. Patients with complaints or suspicion of CI were consecutively recruited by PC physicians. The cognitive diagnosis was performed by an expert neurologist, after formal neuropsychological evaluation. The Mini-Cog score was calculatedpost hoc, and its diagnostic utility was evaluated and compared with the utility of the Mini-Mental State (MMS), the Clock Drawing Test (CDT), and the sum of the MMS and the CDT (MMS+CDT) using the area under the receiver operating characteristic curve (AUC). The best cut points were obtained on the basis of diagnostic accuracy (DA) and kappa index.Results. A total sample of 307 subjects (176 CI) was analyzed. The Mini-Cog displayed an AUC (±SE) of0.78±0.02, which was significantly inferior to the AUC of the CDT (0.84±0.02), the MMS (0.84±0.02), and theMMS+CDT(0.86±0.02). The best cut point of the Mini-Cog was 1/2 (sensitivity 0.60, specificity 0.90, DA 0.73, and kappa index0.48±0.05).Conclusions. The utility of the Mini-Cog for detection of CI in PC was very modest, clearly inferior to the MMS or the CDT. These results do not permit recommendation of the Mini-Cog in PC.

Reynolds-averaged Navier–Stokes simulation of hydrofoil effects on hydrodynamic coefficients of a catamaran in forced oscillation

2016 ◽  
Vol 231 (2) ◽  
pp. 364-383
Author(s):  
Amin Najafi ◽  
Mohammad Saeed Seif
Keyword(s):  
High Speed ◽  
Experimental Approach ◽  
Navier Stokes ◽  
Hydrodynamic Coefficients ◽  
Laboratory Equipment ◽  
Factors Affecting ◽  
High Frequencies ◽  
Frequency Independent ◽  
Reynolds Averaged Navier Stokes

Determination of high-speed crafts’ hydrodynamic coefficients will help to analyze the dynamics of these kinds of vessels and the factors affecting their dynamic stabilities. Also, it can be useful and effective in controlling the vessel instabilities. The main purpose of this study is to determine the coefficients of longitudinal motions of a planing catamaran with and without a hydrofoil using Reynolds-averaged Navier–Stokes method to evaluate the foil effects on them. Determination of hydrodynamic coefficients by experimental approach is costly and requires meticulous laboratory equipment; therefore, utilizing the numerical methods and developing a virtual laboratory seem highly efficient. In this study, the numerical results for hydrodynamic coefficients of a high-speed craft are verified against Troesch’s experimental results. In the following, after determination of hydrodynamic coefficients of a planing catamaran with and without foil, the foil effects on its hydrodynamic coefficients are evaluated. The results indicate that most of the coefficients are frequency-independent especially at high frequencies.

Development and Validation of a Three-Dimensional Multiphase Flow CFD Analysis for Journal Bearings in Steam and Heavy Duty Gas Turbines

2012 ◽  
Author(s):  
Stephan Uhkoetter ◽  
Stefan aus der Wiesche ◽  
Michael Kursch ◽  
Christian Beck
Keyword(s):  
Experimental Data ◽  
Multiphase Flow ◽  
Gas Turbines ◽  
High Speed ◽  
Three Dimensional ◽  
Air Entrainment ◽  
Journal Bearings ◽  
Heavy Duty ◽  
Present Contribution ◽  
Two Phase

The traditional method for hydrodynamic journal bearing analysis usually applies the lubrication theory based on the Reynolds equation and suitable empirical modifications to cover turbulence, heat transfer, and cavitation. In cases of complex bearing geometries for steam and heavy-duty gas turbines this approach has its obvious restrictions in regard to detail flow recirculation, mixing, mass balance, and filling level phenomena. These limitations could be circumvented by applying a computational fluid dynamics (CFD) approach resting closer to the fundamental physical laws. The present contribution reports about the state of the art of such a fully three-dimensional multiphase-flow CFD approach including cavitation and air entrainment for high-speed turbo-machinery journal bearings. It has been developed and validated using experimental data. Due to the high ambient shear rates in bearings, the multiphase-flow model for journal bearings requires substantial modifications in comparison to common two-phase flow simulations. Based on experimental data, it is found, that particular cavitation phenomena are essential for the understanding of steam and heavy-duty type gas turbine journal bearings.

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