Numerical Investigation on the Structure of High-Speed Cavitating Water Jet Issuing From an Orifice Nozzle

2011 ◽  
Author(s):  
Guoyi Peng ◽  
Hideto Ito ◽  
Seiji Shimizu ◽  
Shigeo Fujikawa
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Volume Fraction ◽  
Water Jet ◽  
Cavitation Number ◽  
Mean Flow ◽  
Mixture Flow ◽  
Gas Volume Fraction ◽  
The Mean ◽  
Gas Volume

A practical mixture flow approach to the numerical simulation of turbulent cavitating flows is developed by coupling a simplified estimation of bubble cavitation to a compressible mixture flow computation. The mean flow of two-phase mixture is calculated by neglecting the slip between bubbles and surround liquid. Navier-Stokes equations for compressible fluids are used to describe the unsteady mean flow field and the RNG k-ε model is adopted for modeling of the flow turbulence. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase varying with the mean flow. The flow structure of submerged water jets issuing from an orifice nozzle is investigated numerically. Both non-cavitating and cavitating jets are calculated under different cavitation numbers in order to clarify the cavitation property of submerged water jet. The results demonstrate that the intensity of cavitation denoted by the maximum value of gas volume fraction and the area of strong cavitation indicted by high value of gas volume fraction increase with the decrease of cavitation number. Under the effect of cavitation bubbles the discharge coefficient of orifice nozzle decreases with the cavitation number.

Numerical Simulation of High-Speed Cavitating Water-Jet Issuing From a Submerged Nozzle

2012 ◽  
Author(s):  
Guoyi Peng ◽  
Hideto Ito ◽  
Seiji Shimizu
Keyword(s):  
Numerical Simulation ◽  
High Speed ◽  
Volume Fraction ◽  
Water Jet ◽  
Cavitation Number ◽  
Local Flow ◽  
Bubble Liquid ◽  
Bubble Cavitation ◽  
Gas Volume Fraction ◽  
Gas Volume

A simplified estimation for the compressibility of cavitating flow is proposed based on the bubble cavitation model and a compressible mixture flow method is developed for the numerical simulation of high-speed cavitating jet by coupling the simplified estimation of bubble cavitation to a compressible turbulent flow computation procedure. The intensity of cavitation in a local field is evaluated by the volume fraction of gas phase, which is governed by the compressibility of bubble-liquid mixture at the current status of local flow field. The method is applied to the simulation of high-speed submerged water jets issuing from an orifice nozzle. Both non-cavitating and cavitating jets are calculated under different cavitation numbers in order to clarify the cavitation property of submerged water jet. The results demonstrate that the intensity of cavitation denoted by the maximum value of gas volume fraction and the area of strong cavitation indicted by high value of gas volume fraction increase with the decrease of cavitation number. Under the effect of cavitation bubbles the discharge coefficient of orifice nozzle decreases with the cavitation number.

scholarly journals Thrust Enhancement Through Bubble Injection Into an Expanding-Contracting Nozzle With a Throat

2014 ◽  
Vol 136 (7) ◽  
Author(s):  
Sowmitra Singh ◽  
Tiffany Fourmeau ◽  
Jin-Keun Choi ◽  
Georges L. Chahine
Keyword(s):  
Volume Fraction ◽  
Bubbly Flow ◽  
Design Tool ◽  
Nozzle Geometry ◽  
Mixture Flow ◽  
Subsonic Flows ◽  
Choked Flow ◽  
Optimum Geometry ◽  
Gas Volume Fraction ◽  
Gas Volume

This paper addresses the concept of thrust augmentation through bubble injection into an expanding-contracting nozzle with a throat. The presence of a throat in an expanding-contracting nozzle can result in flow transition from the subsonic regime to the supersonic regime (choked conditions) for a bubbly mixture flow, which may result in a substantial increase in jet thrust. This increase would primarily arise from the fact that the injected gas bubbles expand drastically in the supersonic region of the flow. In the current work, an analytical 1D model is developed to capture choked bubbly flow in an expanding-contracting nozzle with a throat. The study provides analytical and numerical support to analytical observations and serves as a design tool for nozzle geometries that can achieve efficient choked bubbly flows through nozzles. Starting from the 1D mixture continuity and momentum equations, along with an equation of state for the bubbly mixture, expressions for mixture velocity and gas volume fraction were derived. Starting with a fixed geometry and an imposed upstream pressure for a choked flow in the nozzle, the derived expressions were iteratively solved to obtain the exit pressures and velocities for different injected gas volume fractions. The variation of thrust enhancement with the injected gas volume fraction was also studied. Additionally, the geometric parameters were varied (area of the exit, area of the throat) to understand the influence of the nozzle geometry on the thrust enhancement and on the flow conditions at the inlet. This parametric study provides a performance map that can be used to design a bubble augmented waterjet propulsor, which can achieve and exploit supersonic flow. It was found that the optimum geometry for choked flows, unlike the optimum geometry under purely subsonic flows, had a dependence on the injected gas volume fraction. Furthermore, for the same injected gas volume fraction the optimum geometry for choked flows resulted in greater thrust enhancement compared to the optimum geometry for purely subsonic flows.

scholarly journals Thrust Enhancement Through Bubble Injection Into an Expanding-Contracting-Nozzle With a Throat

2012 ◽  
Author(s):  
Sowmitra Singh ◽  
Tiffany Fourmeau ◽  
Jin-Keun Choi ◽  
Georges Chahine
Keyword(s):  
Volume Fraction ◽  
Bubbly Flow ◽  
Design Tool ◽  
Nozzle Geometry ◽  
Mixture Flow ◽  
Subsonic Flows ◽  
Choked Flow ◽  
Optimum Geometry ◽  
Gas Volume Fraction ◽  
Gas Volume

This paper addresses the concept of thrust augmentation through bubble injection into an expanding-contracting nozzle with a throat. The presence of a throat in an expanding-contracting nozzle can result in flow transition from the subsonic regime to the supersonic regime (choked conditions) for a bubbly mixture flow, which may result in a substantial increase in jet thrust. This increase would primarily arise from the fact that the injected gas bubbles expand drastically in the supersonic region of the flow. In the current work, an analytical 1-D model is developed to capture choked bubbly flow in an expanding-contracting nozzle with a throat. The study intends to provide analytical/numerical confirmation to observed phenomena and to serve as a design tool to guide practical experiments aimed at creating and studying choked bubbly flows through nozzles. Starting from the 1-D mixture continuity and momentum equations along with an equation of state for the bubbly mixture, expressions for mixture velocity and gas volume fraction were derived. Starting with a fixed geometry, an imposed upstream pressure and assuming choked flow in the nozzle, the derived expressions were iteratively solved to obtain the exit pressures and velocities for different injected gas volume fractions. The variation of thrust enhancement with the injected gas volume fraction was also studied. Additionally, the geometric parameters were varied (area of the exit, area of the throat) to understand the influence of the nozzle geometry on the thrust enhancement and on the flow conditions at the inlet. This parametric study provides a performance map that can be used to design a bubble augmented waterjet propulsor that can achieve and exploit supersonic flow. It was found that the optimum geometry for choked flows, unlike the optimum geometry under purely subsonic flows, had a dependence on the injected gas volume fraction. Furthermore, for the same injected gas volume fraction the optimum geometry for choked flows resulted in greater thrust enhancement compared to the optimum geometry for purely subsonic flows.

Qualification of a New Multiphase Pump. the Setting of a New Standard

2021 ◽  
Author(s):  
Åge Hofstad ◽  
Tarje Olderheim ◽  
Magnus Almgren ◽  
Marianna Rondon ◽  
Edouard Thibaut ◽  
...  
Keyword(s):  
High Speed ◽  
Oil And Gas ◽  
Volume Fraction ◽  
Two Phase ◽  
Specific Product ◽  
Multiphase Pump ◽  
Gas Volume Fraction ◽  
Gas Market ◽  
Gas Volume ◽  
Winding Insulation

Abstract The recent trend in the oil industry is to save CAPEX and exploit every offshore field to increase production and maximize reserves. Also, deeper water and longer step-out is a challenge for new fields. The most adapted technology to unlock these reserves is the use of subsea boosting like a multiphase pump on the seafloor. Subsea boosting has been used for decades with well proven results, but up to now, some limitations in power and lift pressure exist. This new multiphase pump development has increased the potential pressure generation manyfold from the typical ΔP of 50 bar (725 psi) at the beginning of the project. Developing such a powerful two-phase pump driven by a liquid-filled motor requires a unique combination of expertise in machinery engineering, electrical engineering, fluid mechanics and rotor dynamics. The objective of the co-authors is to share this experience by bringing some insights on what it takes to develop, test, and qualify such specific product. Outlines of the methodology will be described, key results will be detailed, and lessons learnt will be presented. The new design was fully tested first component-wise and then for a full-size prototype. A wide process envelope was mapped during the final qualification program with 3,000 points tested in the range 2,000-6,000 RPM and 0 - 100% GVF (Gas Volume Fraction). Qualification tests concluded with more than 2,000 cumulative hours. The main challenges in this program were the development of an innovative multiphase impeller and the qualification of the first MPP (MultiPhase Pump) with a back-to-back configuration. Concerning the motor, the development includes a high speed 6,000 RPM, 6 MW liquid-filled induction motor and a new stator winding insulation cable. With this new product, the pump market is ready to overcome challenges to produce deeper and further reservoirs in a constant evolutive oil and gas market.

scholarly journals Dynamics and mass transfer of rising bubbles in a homogenous swarm at large gas volume fraction

2014 ◽  
Vol 763 ◽  
pp. 254-285 ◽  
Author(s):  
Damien Colombet ◽  
Dominique Legendre ◽  
Frédéric Risso ◽  
Arnaud Cockx ◽  
Pascal Guiraud
Keyword(s):  
Mass Transfer ◽  
High Speed ◽  
Bubble Dynamics ◽  
Volume Fraction ◽  
Interfacial Area ◽  
Optical Probe ◽  
Bubble Velocity ◽  
Gas Volume Fraction ◽  
Bubble Rising ◽  
Gas Volume

AbstractThe present work focuses on the collective effect on both bubble dynamics and mass transfer in a dense homogeneous bubble swarm for gas volume fractions${\it\alpha}$up to 30 %. The experimental investigation is carried out with air bubbles rising in a square column filled with water. Bubble size and shape are determined by means of a high-speed camera equipped with a telecentric lens. Gas volume fraction and bubble velocity are measured by using a dual-tip optical probe. The combination of these two techniques allows us to determine the interfacial area between the gas and the liquid. The transfer of oxygen from the bubbles to the water is measured from the time evolution of the concentration of oxygen dissolved in water, which is obtained by means of the gassing-out method. Concerning the bubble dynamics, the average vertical velocity is observed to decrease with${\it\alpha}$in agreement with previous experimental and numerical investigations, while the bubble agitation turns out to be weakly dependent on ${\it\alpha}$. Concerning mass transfer, the Sherwood number is found to be very close to that of a single bubble rising at the same Reynolds number, provided the latter is based on the average vertical bubble velocity, which accounts for the effect of the gas volume fraction on the bubble rise velocity. This conclusion is valid for situations where the diffusion coefficient of the gas in the liquid is very low (high Péclet number) and the dissolved gas is well mixed at the scale of the bubble. It is understood by considering that the transfer occurs at the front part of the bubbles through a diffusion layer which is very thin compared with all flow length scales and where the flow remains similar to that of a single rising bubble.

scholarly journals Modeling the Excess Velocity of Low-Viscous Taylor Droplets in Square Microchannels

Fluids ◽  
2019 ◽  
Vol 4 (3) ◽  
pp. 162 ◽  
Author(s):  
Thorben Helmers ◽  
Philip Kemper ◽  
Jorg Thöming ◽  
Ulrich Mießner
Keyword(s):  
High Speed ◽  
Process Intensification ◽  
Continuous Phase ◽  
Channel Cross Section ◽  
Optimization Approach ◽  
Mean Flow ◽  
Bypass Flow ◽  
Wall Film ◽  
Proposed Model ◽  
The Mean

Microscopic multiphase flows have gained broad interest due to their capability to transfer processes into new operational windows and achieving significant process intensification. However, the hydrodynamic behavior of Taylor droplets is not yet entirely understood. In this work, we introduce a model to determine the excess velocity of Taylor droplets in square microchannels. This velocity difference between the droplet and the total superficial velocity of the flow has a direct influence on the droplet residence time and is linked to the pressure drop. Since the droplet does not occupy the entire channel cross-section, it enables the continuous phase to bypass the droplet through the corners. A consideration of the continuity equation generally relates the excess velocity to the mean flow velocity. We base the quantification of the bypass flow on a correlation for the droplet cap deformation from its static shape. The cap deformation reveals the forces of the flowing liquids exerted onto the interface and allows estimating the local driving pressure gradient for the bypass flow. The characterizing parameters are identified as the bypass length, the wall film thickness, the viscosity ratio between both phases and the C a number. The proposed model is adapted with a stochastic, metaheuristic optimization approach based on genetic algorithms. In addition, our model was successfully verified with high-speed camera measurements and published empirical data.

scholarly journals Effect of the Gas Volume Fraction on the Pressure Load of the Multiphase Pump Blade

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 650
Author(s):  
Guangtai Shi ◽  
Dandan Yan ◽  
Xiaobing Liu ◽  
Yexiang Xiao ◽  
Zekui Shu
Keyword(s):  
Flow Rate ◽  
Static Pressure ◽  
Volume Fraction ◽  
Pump Impeller ◽  
Impeller Blade ◽  
Multiphase Pump ◽  
Pressure Load ◽  
Gas Volume Fraction ◽  
Power Capability ◽  
Gas Volume

The gas volume fraction (GVF) often changes from time to time in a multiphase pump, causing the power capability of the pump to be increasingly affected. In the purpose of revealing the pressure load characteristics of the multiphase pump impeller blade with the gas-liquid two-phase case, firstly, a numerical simulation which uses the SST k-ω turbulence model is verified with an experiment. Then, the computational fluid dynamics (CFD) software is employed to investigate the variation characteristics of static pressure and pressure load of the multiphase pump impeller blade under the diverse inlet gas volume fractions (IGVFs) and flow rates. The results show that the effect of IGVF on the head and hydraulic efficiency at a small flow rate is obviously less than that at design and large flow rates. The static pressure on the blade pressure side (PS) is scarcely affected by the IGVF. However, the IGVF has an evident effect on the static pressure on the impeller blade suction side (SS). Moreover, the pump power capability is descended by degrees as the IGVF increases, and it is also descended with the increase of the flow rate at the impeller inlet. Simultaneously, under the same IGVF, with the increase of the flow rate, the peak value of the pressure load begins to gradually move toward the outlet and its value from hub to shroud is increased. The research results have important theoretical significance for improving the power capability of the multiphase pump impeller.

scholarly journals A Review on the Application of Multiphase Twin Screw Pump as a Downhole Wet Gas Compressor to Improve Gas Wells Recovery Factor

2021 ◽  
Vol 15 ◽  
pp. 223-232
Author(s):  
Sharul Sham Dol ◽  
Niraj Baxi ◽  
Mior Azman Meor Said
Keyword(s):  
Volume Fraction ◽  
Energy Industry ◽  
Gas Wells ◽  
Screw Pump ◽  
Research Activities ◽  
Wet Gas ◽  
Gas Compression ◽  
Twin Screw ◽  
Gas Volume Fraction ◽  
Gas Volume

By introducing a multiphase twin screw pump as an artificial lifting device inside the well tubing (downhole) for wet gas compression application; i.e. gas volume fraction (GVF) higher than 95%, the unproductive or commercially unattractive gas wells can be revived and made commercially productive once again. Above strategy provides energy industry with an invaluable option to significantly reduce greenhouse gas emissions by reviving gas production from already existing infrastructure thereby reducing new exploratory and development efforts. At the same time above strategy enables energy industry to meet society’s demand for affordable energy throughout the critical energy transition from predominantly fossil fuels based resources to hybrid energy system of renewables and gas. This paper summarizes the research activities related to the applications involving multiphase twin screw pump for gas volume fraction (GVF) higher than 95% and outlines the opportunity that this new frontier of multiphase fluid research provides. By developing an understanding and quantifying the factors that influence volumetric efficiency of the multiphase twin screw pump, the novel concept of productivity improvement by a downhole wet gas compression using above technology can be made practicable and commercially more attractive than other production improvement strategies available today. Review and evaluation of the results of mathematical and experimental models for multiphase twin screw pump for applications with GVF of more than 95% has provided valuable insights in to multiphase physics in the gap leakage domains of pump and this increases confidence that novel theoretical concept of downhole wet gas compression using multiphase twin screw pump that is described in this paper, is practically achievable through further research and improvements.

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