scholarly journals Numerical Study of the Winter–Kennedy Flow Measurement Method in Transient Flows

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1310
Author(s):  
Binaya Baidar ◽  
Jonathan Nicolle ◽  
Bhupendra K. Gandhi ◽  
Michel J. Cervantes
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Cross Sectional ◽  
Transient Flows ◽  
Sectional Plane ◽  
The Stability ◽  
Opening And Closing ◽  
Spiral Casing

This paper explores the possibility of using the Winter–Kennedy (WK) method for transient flow rate measurement in hydraulic turbines. Computational fluid dynamic (CFD) analysis of a numerical model of an axial turbine was carried out for accelerating and decelerating flows. Those were obtained by linearly opening and closing of the guide vanes, respectively, while retaining the inlet pressure constant during the simulations. The behavior of several WK configurations on a cross-sectional plane and along the azimuthal direction of the spiral casing was studied during the transients. The study showed that there are certain WK configurations that are more stable than others. The physical mechanism behind the stability (or instability) of the WK method during transients is presented. Using the steady WK coefficient obtained at the best efficiency point (BEP), the WK method could estimate the transient flow rate with a deviation of about 7.5% and 3.5%, for accelerating and decelerating flow, respectively.

scholarly journals A Numerical Study of Sub-Millisecond Integrated Mix-and-Inject Microfluidic Devices for Sample Delivery at Synchrotron and XFELs

2021 ◽  
Vol 11 (8) ◽  
pp. 3404
Author(s):  
Majid Hejazian ◽  
Eugeniu Balaur ◽  
Brian Abbey
Keyword(s):  
Molecular Dynamics ◽  
Flow Rate ◽  
Numerical Study ◽  
Three Dimensional ◽  
Microfluidic Devices ◽  
Liquid Jets ◽  
Mixing Efficiency ◽  
X Ray Diffraction ◽  
Cross Sectional ◽  
Time Required

Microfluidic devices which integrate both rapid mixing and liquid jetting for sample delivery are an emerging solution for studying molecular dynamics via X-ray diffraction. Here we use finite element modelling to investigate the efficiency and time-resolution achievable using microfluidic mixers within the parameter range required for producing stable liquid jets. Three-dimensional simulations, validated by experimental data, are used to determine the velocity and concentration distribution within these devices. The results show that by adopting a serpentine geometry, it is possible to induce chaotic mixing, which effectively reduces the time required to achieve a homogeneous mixture for sample delivery. Further, we investigate the effect of flow rate and the mixer microchannel size on the mixing efficiency and minimum time required for complete mixing of the two solutions whilst maintaining a stable jet. In general, we find that the smaller the cross-sectional area of the mixer microchannel, the shorter the time needed to achieve homogeneous mixing for a given flow rate. The results of these simulations will form the basis for optimised designs enabling the study of molecular dynamics occurring on millisecond timescales using integrated mix-and-inject microfluidic devices.

Numerical Study of Transient Flow and the Influence of Height and Viscosity in a Cyclonic Chamber in a Distribution System

2017 ◽  
Author(s):  
Carolina C. Rodrigues ◽  
Henrique K. Eidt ◽  
Rafael Dunaiski ◽  
César Y. Ofuchi ◽  
Flávio Neves ◽  
...  
Keyword(s):  
Distribution System ◽  
Transient Flow ◽  
Separation Efficiency ◽  
Numerical Study ◽  
Petroleum Industry ◽  
Wire Mesh ◽  
Intermittent Flow ◽  
Transient Effects ◽  
Centrifugal Pumps ◽  
The Stability

In the petroleum industry, during the production and transportation of oil, multiphase flow occurs, due to the usual mixture of the crude oil, water and gas. This type of flow can be simplified, for study purposes, as a two-phase one, in which the gas is one phase, and a mixture of oil and water is the other. Separation of gaseous and liquid phases at the wellhead level is done by a separator and has innumerous advantages, including avoiding or at least reducing typical problems of multiphase flows such as intermittent flow, severe slugging and hydrates deposition. Another advantage is to increase the efficiency of the submersible centrifugal pumps or other artificial lift process used. A recurrent problem found in exploration and production of oil and gas is the range of the fluid viscosities encountered during exploration and extraction of petroleum, which can greatly vary with the temperature or the composition of the oil being extracted. Thus, it is necessary to understand how this parameter affects the performance of the equipment used. In addition, installation and maintenance of separators are hampered by the large size of this type of equipment. Therefore, a prior distribution system is here proposed, aiming to distribute the flow in more than one branch, in order to decrease the general size of the separation equipment needed, while maintaining the flow rate and separation efficiency. This distribution system has a cyclonic chamber, in which the flow enters through two nozzles tangentially oriented with the wall of the chamber, which performs a pre-separation due to the centrifugal field, and divides the flow into four outlets. This work presents a numerical study on the height influence of the cyclonic chamber in a distribution system. The transient beginning of the flow is analyzed, with the stability of the film being study. This work is focused on the behavior of the liquid phase in this proposed distribution system, so that only single-phase liquid flow at the inlet of the distribution system is considered. A validation was done through comparison with experimental data obtained in a test rig, in which was used one wire mesh sensor with 12 wires in order to evaluate the thickness of the liquid film over time. In addition, different heights and viscosities are studied in order to evaluate their influence on the flow. The parameters investigated are the film thickness, velocity and turbulence kinetic energy fields and flow rates at the outlets, focusing on the stability of the film and the transient effects associated with the beginning of the flow. In order to perform this study, the commercial software ANSYS-CFX 15.0 was used, with a hybrid mesh, for four different heights and two inlet velocities.

New Design Method for Spiral Casings Considering the Properties of the Impeller and Spiral Casing at Design and Off-Design Conditions and Numerical Verification With CFD

2018 ◽  
Author(s):  
Philipp Epple ◽  
Manuel Fritsche ◽  
Michael Steppert ◽  
Michael Steber
Keyword(s):  
Design Process ◽  
Flow Rate ◽  
Velocity Component ◽  
Tangential Velocity ◽  
Sectional Area ◽  
Cross Sectional ◽  
Flow Rates ◽  
Tangential Velocity Component ◽  
Design Point ◽  
Spiral Casing

Radial fans for industrial applications are very commonly operated with a spiral casing, also called volute. The function of the volute is to collect the air from the impellers outlet and to transport it to the fans outlet. In the volute the tangential velocity component of the impeller is transformed in a straight velocity component at the volute’s outlet. In the volute the static pressure is increased according to the cross sectional area of the volute. When the flow exits the impeller the flow rate is given basically by the radial velocity component times the outlet area of the impeller. In the volute, however, the flow rate is basically given by the tangential velocity component at the impeller exit and in the volute considering the conservation of angular momentum. Hence, there is only one operating point, i.e. the design point of the volute, where the flow rate in the impeller matches the flow rate in the volute. In the literature the design of the volute is performed at the design point only and the cross sectional area of the volute is usually computed distributing the flow rate linearly from the tongue to the exit of the volute. In this work an extended theoretical approach was developed considering the design point flow rate and off design flow rates. At the design point, the properties of the specific impeller, i.e. it’s radial and its tangential velocity components at the impeller’s exit are considered to design the volute. Furthermore, also the off-design characteristics of the impeller, i.e. its radial and tangential velocity components are considered in the design process of the volute. The flow rates in the impeller and in the volute match only at the design point, at off-design points the flow rates in the impeller and in the volute are different. This has an important impact on the design process of impeller – volute units. Each volute has also to be matched to the specific impeller. In the numerical part a usual volute was designed considering the properties of a particular impeller. The performance of the volute and of complete fan was investigated with the commercial Navier–Stokes Solver ANSYS CFX. A detailed analysis of the results and the flow conditions in volute as well as in the impeller-volute unit and a comparison with the results predicted by the new volute theory is given.

scholarly journals Computational Fluid Dynamic Analysis of Flow Rate Performance of a Small Piezoelectric-Hydraulic Pump

2021 ◽  
Vol 11 (11) ◽  
pp. 4888
Author(s):  
Phuc Nguyen Anh ◽  
Jae-Sung Bae ◽  
Jai-Hyuk Hwang
Keyword(s):  
Flow Field ◽  
Flow Rate ◽  
Transient Flow ◽  
Fluid Dynamic ◽  
Check Valve ◽  
Internal Flow ◽  
Pump Efficiency ◽  
Rate Performance ◽  
Hydraulic Pump ◽  
Computational Fluid Dynamic Analysis

This paper investigates the transient flow rate performance of small piezoelectric-hydraulic pumps. In a previous study, a small piezoelectric hydraulic pump was designed and developed to be applicable to the braking systems of small- and medium-sized UAVs (unmanned aerial vehicles). To this end, a thin plate spring check valve was designed in order to effectively discharge the flow in a single direction. The flow rate of the piezoelectric-hydraulic pump is an important criterion for evaluating pump efficiency. Therefore, a study on the parameters affecting such a flow rate is necessary to enhance the efficiency of piezoelectric hydraulic pumps used in brake systems. This study on small piezoelectric-hydraulic pumps is performed to accurately predict the flow rate using a CFD (Computational Fluid Dynamics) tool. In other words, an unsteady CFD method is applied to model the transient flow rate characteristics and the internal flow field of the fluid. The visualization of the internal flow field is evaluated for a better understanding of the flow fields inside the pump. Moreover, this work also illustrates the detailed motion of both the inlet and outlet check valves during the pump operation that fully reflects the phase shift between the check valves and the piston motion, all of which affect the flow rate performance of the pump. An experiment of flow rate characteristics was conducted on a designed piezoelectric-hydraulic pump, which verifies the validity of the CFD results.

scholarly journals Numerical study on the transient behavior of a radial pump during starting time

2021 ◽  
Author(s):  
Faouzi Omri ◽  
Lamjed Hadj Taieb ◽  
Sami Elaoud
Keyword(s):  
Flow Rate ◽  
Transient Flow ◽  
Numerical Study ◽  
Transient Behavior ◽  
Motor Speed ◽  
Pump System ◽  
Starting Time ◽  
Pumping System ◽  
Radial Pump ◽  
Impeller Geometry

Abstract This paper presents a fast simulation model for predicting the dynamic response of a motor-pump system to startup event. The purpose is to analyze the effect of the impeller acceleration time, the final flow rate and the impeller geometry on the pump transient flow during starting operations. The motor speed and torque variations were predicted by simulating the transient law of the three-phase induction motor by adopting the d-q axes theory. The pump model was built by solving the unsteady flow governing equations with the method of characteristics (MOC). The whole model was validated with available tests from literature. Accordingly, the computation of impeller acceleration, the motor torque, the unsteady pressure and flow rate was made for various starting conditions. The results have revealed that during its starting time, the pump hydraulic transients are well influenced by the motor speed acceleration, the flow inertia and the impeller geometry. Through the analysis of the simulation results, the conclusion was that the accuracy of the present method is reasonable, and it can be used for assisting pumping system design.

An Experimental and Numerical Study on Coaxial Extrusion of a Non-Newtonian Hydrogel Material

2021 ◽  
pp. 1-34
Author(s):  
Ilhan Yu ◽  
Roland K. Chen
Keyword(s):  
Newtonian Fluid ◽  
Flow Rate ◽  
Numerical Study ◽  
Flow Behavior ◽  
Extrusion Process ◽  
Pluronic F127 ◽  
Flow Rate Ratio ◽  
Guiding Principle ◽  
Fluid Behavior ◽  
The Stability

Abstract Coaxial extrusion is a commonly used process to manufacture tubular structures to mimic vascular systems in 3D bioprinting. In this study, the stability of coaxial extrusion of a non-Newtonian material, Pluronic F127, is investigated. The extrusion process is considered stable when the extrudate form a core-annular structure. When it is unstable, dripping or jetting of the inner fluid is observed. In this study, the effects of the viscosity ratio, flow rate ratio, and the non-Newtonian behaviors on the stability of the coaxial extrusion process are investigated experimentally and numerically. The results show that all three factors can affect the stability of the process. When the ratio of viscosities increases, the process becomes unstable. The extrusion process tends to be stable when the flow rate of the outer fluid is much higher than that of the inner fluid. When the overall flow rate decreases, due to the non-Newtonian fluid behavior, the extrusion process can become unstable. This study shows the interconnected relationship between viscosity, flow rate, and non-Newtonian fluid behaviors and their effects on the stability of the coaxial extrusion process. The non-Newtonian flow behavior needs to be considered when studying or using coaxial extrusion. This study also provides a guiding principle on how to alter extrusion parameters in order to achieve the desired flow pattern.

Numerical study of fluid dynamic flow within an internal combustion engine cylinder

2017 ◽  
Author(s):  
Ana Marta Souza ◽  
Antônio César Valadares de Oliveira ◽  
Enrico Temporim Ribeiro ◽  
Francisco Souza ◽  
Marcelo Colombo Chiari
Keyword(s):  
Internal Combustion Engine ◽  
Combustion Engine ◽  
Numerical Study ◽  
Fluid Dynamic ◽  
Internal Combustion ◽  
Dynamic Flow ◽  
Engine Cylinder

scholarly journals Research on a Piezoelectric Pump with Flexible Valves

2021 ◽  
Vol 11 (7) ◽  
pp. 2909
Author(s):  
Weiqing Huang ◽  
Liyi Lai ◽  
Zhenlin Chen ◽  
Xiaosheng Chen ◽  
Zhi Huang ◽  
...  
Keyword(s):  
Flow Rate ◽  
Fluid Transport ◽  
Smooth Transition ◽  
Driving Voltage ◽  
Piezoelectric Pump ◽  
Venous Valve ◽  
Output Pressure ◽  
Small Flow ◽  
Working Principle ◽  
Opening And Closing

Imitating the structure of the venous valve and its characteristics of passive opening and closing with changes in heart pressure, a piezoelectric pump with flexible valves (PPFV) was designed. Firstly, the structure and the working principle of the PPFV were introduced. Then, the flexible valve, the main functional component of the pump, was analyzed theoretically. Finally, an experimental prototype was manufactured and its performance was tested. The research proves that the PPFV can achieve a smooth transition between valved and valveless by only changing the driving signal of the piezoelectric (PZT) vibrator. The results demonstrate that when the driving voltage is 100 V and the frequency is 25 Hz, the experimental flow rate of the PPFV is about 119.61 mL/min, and the output pressure is about 6.16 kPa. This kind of pump can realize the reciprocal conversion of a large flow rate, high output pressure, and a small flow rate, low output pressure under the electronic control signal. Therefore, it can be utilized for fluid transport and pressure transmission at both the macro-level and the micro-level, which belongs to the macro–micro combined component.

Sign in / Sign up

Export Citation Format

Share Document