scholarly journals CFD-Based Study of Nozzle Section Geometry Effects on the Performance of an Annular Multi-Nozzle Jet Pump

Processes ◽  
2020 ◽  
Vol 8 (2) ◽  
pp. 133 ◽  
Author(s):  
Kai Xu ◽  
Gang Wang ◽  
Liquan Wang ◽  
Feihong Yun ◽  
Wenhao Sun ◽  
...  
Keyword(s):  
Cfd Simulation ◽  
Internal Flow ◽  
Streamwise Vortex ◽  
Working Fluid ◽  
Streamwise Vorticity ◽  
Jet Pump ◽  
Circular Nozzle ◽  
Spanwise Vortex ◽  
Volume Method ◽  
Peak Value

CFD simulation and analysis of the internal flow field of the annular multi-nozzle jet pump are carried out to study the effects of nozzle section geometries on performance of the pump based on the finite volume method and realizable k-ε model. The results show that the square nozzle peak efficiency is 3% higher than that of the circular nozzle and 4.1% higher than that of the triangular nozzle. According to the simulation results, the mixing mechanism of the working fluid and second fluid is analyzed on the basis of the vortex dynamics. The results show the following: the recirculation area and the friction loss of the non-circular nozzle are reduced, and the mixing effect is improved; the streamwise vortex plays a major role in the mixing process and decays to an extremely small value at the end of the throat after attenuating rapidly in the suction chamber; compared with the streamwise vortex, the strength of the spanwise vortex is relatively stronger; the spanwise vortex still fluctuates after developing to a certain extent in the throat; the maximum streamwise vorticity peak value of the square nozzle is 31% more than that of the circular nozzle and 39% more than that of the triangular nozzle; the maximum spanwise vorticity peak value of the square nozzle is 19% less than that of the circular nozzle and 12% less than that of the triangular nozzle.

scholarly journals Analysis of the Design of a Poppet Valve by Transitory Simulation

Energies ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 889 ◽  
Author(s):  
Ivan Gomez ◽  
Andrés Gonzalez-Mancera ◽  
Brittany Newell ◽  
Jose Garcia-Bravo
Keyword(s):  
Computational Model ◽  
Dynamic Behavior ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Published Data ◽  
Minimal Effect ◽  
High Frequencies ◽  
Poppet Valve ◽  
Dimensional Parameters ◽  
Volume Method

This article contains the results and analysis of the dynamic behavior of a poppet valve through CFD simulation. A computational model based on the finite volume method was developed to characterize the flow at the interior of the valve while it is moving. The model was validated using published data from the valve manufacturer. This data was in accordance with the experimental model. The model was used to predict the behavior of the device as it is operated at high frequencies. Non-dimensional parameters for generalizing and analyzing the effects of the properties of the fluid were used. It was found that it is possible to enhance the dynamic behavior of the valve by altering the viscosity of the working fluid. Finally, using the generated model, the influence of the angle of the poppet was analyzed. It was found that angle has a minimal effect on pressure. However, flow forces increase as angle decreases. Therefore, reducing poppet angle is undesirable because it increases power requirements for valve actuation.

Numerical Study on Streamwise Vorticity and Entrainment Enhancement of a Round Jet

2018 ◽  
Author(s):  
Bangming Li ◽  
Qi Xiao ◽  
Yong Li ◽  
Xu Hu ◽  
Wei Wang
Keyword(s):  
Natural Frequency ◽  
Flow Rate ◽  
Numerical Study ◽  
High Reliability ◽  
Mixing Layer ◽  
Streamwise Vortex ◽  
Nuclear Industry ◽  
Streamwise Vorticity ◽  
Jet Pump ◽  
Round Jet

The jet pump has many outstanding advantages such as simple structure, high reliability, and low operation and maintenance costs and so on. Therefore, it has been widely used in nuclear industry fields. The entrainment ability of the jet pump is the core performance. It is generally recognized that, although the vorticity value of streamwise vortex is smaller than that of spanwise, it plays an important role in the entrainment process. Thus, a numerical simulation of streamwise vortex influence on the entrainment ability of a round jet is carried out. To enhance the entrainment of the round jet, tabs (streamwise vortex generator) and vibrator (perturbation) are set at the exit of nozzle. Tabs are set of number as 0, 2, 4 and 6, and the frequency of vibrator is set as natural frequency and its half. Based on the above configuration, numerical simulations of different nozzle types were carried out. Based on above results, firstly the influence of tabs on the entrainment ability was analyzed. The vortex intensity of the jet flow is obviously enhanced under introducing tabs. Similarly, the intensity of streamwise vortex downstream also increase significantly, thus enhance the entrainment ability. From the figure of local entrainment flow rate, the jet of nozzle with 6 tabs has the strongest entrainment ability; its local entrainment flow rate is 1.5 times of the round jet. Then, the influence of perturbation on the entrainment ability is analyzed. After introducing velocity perturbation, the evolution of the mixing layer evidently accelerated. Under natural frequency perturbation, mixing layer evolution is the most rapid. The mixing layer roll into a vortex ring in less than one diameter distance downstream allowing to 1.75 times the amount of fluid entrained in comparison with the round jet. Finally, integrating the influence of tabs and perturbation, the variation of the jet entrainment ability is analyzed. Due to the combined effect of tabs enhancing vortex intensity and natural frequency accelerating the evolution process, local entrainment ability of the jet is further improved which is more than three times that of the round jet. Taking the nozzle with 6 tabs and perturbation of natural frequency as an example, the streamwise vorticity increases rapidly to a maximum. Local entrainment flow rate also has a corresponding maximum value, which is one-to-one correspondence with the intensity distribution of streamwise vortex, indicating that streamwise vortex plays a predominant role in the entrainment ability of the jet.

Experimental and Numerical Simulation for Thermal Investigation of Oscillating Heat Pipe Using VOF Model

2020 ◽  
Vol 38 (1A) ◽  
pp. 88-104
Author(s):  
Anwar S. Barrak ◽  
Ahmed A. M. Saleh ◽  
Zainab H. Naji
Keyword(s):  
Thermal Resistance ◽  
Heat Pipe ◽  
Heat Input ◽  
Cfd Simulation ◽  
Working Fluid ◽  
Maximum Deviation ◽  
Inlet Temperature ◽  
Maximum Heat ◽  
Oscillating Heat Pipe ◽  
Vof Model

This study is investigated the thermal performance of seven turns of the oscillating heat pipe (OHP) by an experimental investigation and CFD simulation. The OHP is designed and made from a copper tube with an inner diameter 3.5 mm and thickness 0.6 mm and the condenser, evaporator, and adiabatic lengths are 300, 300, and 210 mm respectively.  Water is used as a working fluid with a filling ratio of 50% of the total volume. The evaporator part is heated by hot air (35, 40, 45, and 50) oC with various face velocity (0.5, 1, and 1.5) m/s. The condenser section is cold by air at temperature 15 oC. The CFD simulation is done by using the volume of fluid (VOF) method to model two-phase flow by conjugating a user-defined function code (UDF) to the FLUENT code. Results showed that the maximum heat input is 107.75 W while the minimum heat is 13.75 W at air inlet temperature 35 oC with air velocity 0.5m/s. The thermal resistance decreased with increasing of heat input. The results were recorded minimum thermal resistance 0.2312 oC/W at 107.75 W and maximum thermal resistance 1.036 oC/W at 13.75W. In addition, the effective thermal conductivity increased due to increasing heat input.  The numerical results showed a good agreement with experimental results with a maximum deviation of 15%.

scholarly journals Numerical Investigation of the Effect of Air Leaking into the Working Fluid on the Performance of a Steam Ejector

2021 ◽  
Vol 11 (13) ◽  
pp. 6111
Author(s):  
He Li ◽  
Xiaodong Wang ◽  
Jiuxin Ning ◽  
Pengfei Zhang ◽  
Hailong Huang
Keyword(s):  
Flow Structure ◽  
Mass Fraction ◽  
Internal Flow ◽  
Working Fluid ◽  
Physical Parameters ◽  
Entrainment Ratio ◽  
Air Mass ◽  
Steam Ejector ◽  
Primary Fluid ◽  
Mass Fractions

This paper investigated the effect of air leaking into the working fluid on the performance of a steam ejector. A simulation of the mixing of air into the primary and secondary fluids was performed using CFD. The effects of air with a 0, 0.1, 0.3 and 0.5 mass fraction on the entrainment ratio and internal flow structure of the steam ejector were studied, and the coefficient distortion rates for the entrainment ratios under these air mass fractions were calculated. The results demonstrated that the air modified the physical parameters of the working fluid, which is the main reason for changes in the entrainment ratio and internal flow structure. The calculation of the coefficient distortion rate of the entrainment ratio illustrated that the air in the primary fluid has a more significant impact on the change in the entrainment ratio than that in the secondary fluid under the same air mass fraction. Therefore, the air mass fraction in the working fluid must be minimized to acquire a precise entrainment ratio. Furthermore, this paper provided a method of inspecting air leakage in the experimental steam ejector refrigeration system.

CFD Simulation of Internal Flow and Mixing within Droplets in a T-Junction Microchannel

2021 ◽  
Author(s):  
Xu Chao ◽  
Feishi Xu ◽  
Chaoqun Yao ◽  
Tingting Liu ◽  
Guangwen Chen
Keyword(s):  
Cfd Simulation ◽  
Internal Flow

Optimization of Structure and Calculation of Flow-Force on Poppet Valve under Converging Flow

2011 ◽  
Vol 339 ◽  
pp. 148-151 ◽  
Author(s):  
Shu Juan Zheng ◽  
Long Quan
Keyword(s):  
Cfd Simulation ◽  
Internal Flow ◽  
Poppet Valve ◽  
Converging Flow ◽  
Simulation Results

This paper optimizes the structure of the poppet valve based on the internal flow. The flow-force on poppet valve in the case of the converging flow is simulated and studied by CFD. Simulation results represent that the traditional formula for computing the flow-force can be used only in the certain range, so the formula is modified based on the simulation result.

Research on CFD Simulation of the Cement Slurry Mixer

2012 ◽  
Vol 621 ◽  
pp. 196-199
Author(s):  
Shui Ping LI ◽  
Ya Li Yuan ◽  
Lu Gang Shi
Keyword(s):  
Flow Field ◽  
High Performance ◽  
Cfd Simulation ◽  
Structural Parameters ◽  
Internal Flow ◽  
Simulation Method ◽  
Cement Slurry ◽  
Fluid Machinery ◽  
Computational Fluid Dynamics Cfd ◽  
Machinery Design

Numerical simulation method of the internal flow field of fluid machinery has become an important technology in the study of fluid machinery design. In order to obtain a high-performance cement slurry mixer, computational fluid dynamics (CFD) techniques are used to simulate the flow field in the mixer, and the simulation results are studied. According to the analysis results, the structural parameters of the mixer are modified. The results show the mixer under the revised parameters meet the design requirements well. So CFD analysis method can shorten design period and provide valuable theoretical guidance for the design of fluid machinery.

scholarly journals CFD Simulation of the Dispersion of Exhaust Gases in a Traffic Loaded Street of Astana, Kazakhstan

2016 ◽  
Vol 9 (2) ◽  
pp. 158-166
Author(s):  
Ardak Akhatova ◽  
Assylan Kassymov ◽  
Meruyert Kazmaganbetova ◽  
Luis Ramon Rojas-Solórzano
Keyword(s):  
Cfd Simulation ◽  
Maximum Level ◽  
Weather Conditions ◽  
Control Measures ◽  
Convergence Criterion ◽  
Emission Rates ◽  
Wall Functions ◽  
Mesh Density ◽  
Volume Method ◽  
Future Work

The aim of this paper is to consider one of the most traffic-loaded regions of Astana city (Kazakhstan) and to determine the concentration of carbon-monoxide (CO) in the air during the peak hours. CFD analysis based on the SolidWorks-EFD platform was used to simulate the dispersion of contaminants given the estimated emission rates and weather conditions at the crossroad of Bogenbay Batyr and Zhenis Avenues in Astana. Turbulence prediction was based on k-ε model with wall functions. The governing equations were discretized using the finite volume method and a 2nd order spatial scheme. The mesh verification was based on 1% convergence criterion for a 50% of mesh density increment; air pressure near the wall of a selected building was chosen as the parameter to control the convergence. Numerical results are presented for prevailing conditions during all 4 seasons of the year, demonstrating that the highest levels of CO are recorded in summer and reach the values up to 11.2 ppm which are still lower than the maximum level admitted for humans. Nevertheless, obtained results show that Astana is gradually becoming a city that is likely to reach the critical levels of pollutants in the nearest future if control measures are not taken with enough anticipation. As for a future work, it is proposed to perform in-situ validation of specific scenarios to check and support the results obtained with CFD and to develop then specific policies for tackling the problem before it becomes evident.

Experimental Analysis of Velocity Fields in Hot Extrusion of Aluminium Alloy 6351

2011 ◽  
Vol 491 ◽  
pp. 145-150 ◽  
Author(s):  
Marcelo Martins ◽  
Sérgio Tonini Button ◽  
José Divo Bressan
Keyword(s):  
Metal Forming ◽  
Internal Flow ◽  
Hot Extrusion ◽  
Experimental Tests ◽  
Velocity Fields ◽  
The Finite Element Method ◽  
Forming Process ◽  
Complex Shapes ◽  
Metal Forming Process ◽  
Volume Method

Hot extrusion is a metal forming process with a huge importance in the manufacturing of long metallic bars with complex shapes, and because of this, academics and industries are especially interested in better understanding how metal flows during the process. In order to have a reliable computational tool that can help to solve and to obtain material internal flow, experimental tests and numerical simulation with the finite element method were carried out to obtain results of the velocity fields generated in hot direct extrusion of aluminum billets (aluminum alloy 6351). The experimental results of the velocity field will be used to validate a computational code based on the finite volume method.

CFD SIMULATION OF SHEAR STRESS AND SECONDARY FLOWS IN URETHRA

2007 ◽  
Vol 19 (02) ◽  
pp. 117-127 ◽  
Author(s):  
Yang-Yao Niu ◽  
Ding-Yu Chang
Keyword(s):  
Shear Stress ◽  
Cfd Simulation ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Normal Female ◽  
Urinary System ◽  
Stress Distributions ◽  
Computational Fluid Dynamics Cfd ◽  
Peak Value ◽  
Lower Urinary

In this work, a preliminary numerical simulation of the lower urinary system using Computational Fluid Dynamics (CFD) is performed. Very few studies have been done on the simulation of three-dimensional urine through the lower urinary system. In this study, a simplified lower urinary model with rigid body assumption is proposed. The distributions of urine flow velocity, wall pressure and shear stress along the urethra are simulated based on MRI scanned uroflowmetry of a normal female. Numerical results show that violent secondary flows appear on the cross surface near the end of the urethra when the inflow rate is increased. The oscillative variation of pressure and shear stress distributions are found around the beginning section of the urethra when flow rate is at the peak value.

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