scholarly journals Numerical Simulation Study on the Law of Attenuation of Hydrate Particles in a Gas Transmission Pipeline

Energies ◽  
2018 ◽  
Vol 12 (1) ◽  
pp. 58
Author(s):  
Rao Yongchao ◽  
Sun Yi ◽  
Wang Shuli ◽  
Jia Ru
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Particle Deposition ◽  
Volume Fraction ◽  
Swirling Flow ◽  
Simulation Method ◽  
Swirl Flow ◽  
Swirl Number ◽  
Transmission Pipeline ◽  
Twist Rate

Based on the swirl flow of gas hydrate pipeline safety flow technology, the numerical simulation method is used to study the attenuation law of hydrate particles, which is of great significance for expanding the boundary of safe flow. The results show that the size of the initial swirl number is mainly related to the twist rate and has nothing to do with the Reynolds number; the smaller the twist rate, the greater the Reynolds number, the greater the number of swirling flow in the same position in the pipeline. The concentration has almost no effect on the change of the swirl number; for the non-dimensional swirl number, and the numerical simulation is roughly the same as the results of the paper, the attenuation coefficient beta and ln (Re) has a linear relationship. The no twist tape is six to eight times larger than the volume fraction of the twisted belt, and the smaller the twist tape twist, the smaller the particle deposition is, the higher the initial concentration of the particles in the pipe, and the larger the volume fraction of the hydrate particles deposited by the tube wall.

scholarly journals Cryogenic Cavitation Mitigation in a Liquid Turbine Expander of an Air-Separation Unit through Collaborative Fine-Tuned Optimization of Impeller and Fairing Cone Geometries

Energies ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 50
Author(s):  
Peng Song ◽  
Jinju Sun
Keyword(s):  
Adaptive Sampling ◽  
Volume Fraction ◽  
Swirling Flow ◽  
Swirl Flow ◽  
Air Separation ◽  
Separation Unit ◽  
Industrial Sectors ◽  
Highly Nonlinear ◽  
High Convergence Rate ◽  
Air Separation Unit

An air-separation unit (ASU) uses atmospheric air to produce essential pure gaseous and liquid products for many industrial sectors but requires intensive power consumption. In recent years, cryogenic liquid turbine expanders have been used to replace the traditional J-T valves in air-separation units to save energy. In this paper, an effective design optimization method is proposed to suppress swirling flow and mitigate cavitation in liquid turbines. A flexible tuning of the impeller and fairing cone geometries is simultaneously realized, where the optimization variables are identified via a geometric sensitivity study. A novel objective function is deliberately established by allowing both swirling flow and cavitation characteristics, driving the optimizer to search for deswirling and cavitation-resistant geometries. A kriging surrogate model with an adaptive sampling strategy and a cooperative co-evolution algorithm (CCEA) are incorporated to solve the highly nonlinear optimization problem, where the former reduced the costly evaluations but simultaneously maintained the model prediction accuracy and enabled the aim-oriented global searching (the latter decomposes the problem into several readily solved sub-problems that could be solved in parallel at a high-convergence rate). The optimized impeller and fairing cone geometries were quite favorable for suppressing swirling flow and mitigating cavitation. The impeller cavitation was significantly reduced, with the maximal vapor volume fraction reduced from 0.365 to 0.17 at the blade surface; the diffuser tube high-swirl flow was significantly deswirled and the intensive vapor fraction around the centerline largely reduced, with the maximal vapor volume fraction in the diffuser tube reduced from 0.387 to 0.121. As a result, the isentropic efficiency of the liquid turbine expander was improved from 88.4% to 91.43%.

Numerical Simulation of Cold Swirl Field for Solid Fuel Ramjet with NACA Airfoil

2014 ◽  
Vol 716-717 ◽  
pp. 711-716
Author(s):  
Jie Yu ◽  
Xiong Chen ◽  
Hong Wen Li
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Radial Velocity ◽  
Solid Fuel ◽  
Velocity Gradient ◽  
Pressure Loss ◽  
Total Pressure ◽  
Swirl Flow ◽  
Total Pressure Loss ◽  
Swirl Number

In order to study the swirl flow characteristics in the solid fuel ramjet chamber, a new type of annular vane swirler with NACA airfoil is designed. The cold swirl flow field in the chamber is numerically simulated with different camber and t attack angle, while the swirl number , swirl flow field structure, total pressure recovery coefficient were studied. According to numerical simulation result, the main factors in swirl number are camber and angle of attack, the greater angle of attack, the greater the camber ,the stronger swirl will be. Results show that the total pressure loss is mainly concentrated in the inlet section, the total pressure loss cause by vane swirler is small. Radial velocity gradient exists in swirling flow, and increases with the swirl number. With the influence of centrifugal force and combustion chamber structure, the radial velocity gradient increases.

Study of Flow and Convective Heat Transfer in a Simulated Scaled Up Low Emission Annular Combustor

2011 ◽  
Vol 3 (3) ◽  
Author(s):  
Sunil Patil ◽  
Teddy Sedalor ◽  
Danesh Tafti ◽  
Srinath Ekkad ◽  
Yong Kim ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Convective Heat ◽  
Swirling Flow ◽  
Numerical Study ◽  
Swirl Number ◽  
Maximum Heat ◽  
Number Range ◽  
Maximum Heat Transfer ◽  
Annular Combustor

Modern dry low emissions (DLE) combustors are characterized by highly swirling and expanding flows that makes the convective heat load on the gas side difficult to predict and estimate. A coupled experimental–numerical study of swirling flow inside a DLE annular combustor model is used to determine the distribution of heat transfer on the liner walls. Three different Reynolds numbers are investigated in the range of 210,000–840,000 with a characteristic swirl number of 0.98. The maximum heat transfer coefficient enhancement ratio decreased from 6 to 3.6 as the flow Reynolds number increased from 210,000 to 840,000. This is attributed to a reduction in the normalized turbulent kinetic energy in the impinging shear layer, which is strongly dependent on the swirl number that remains constant at 0.98 for the Reynolds number range investigated. The location of peak heat transfer did not change with the increase in Reynolds number since the flow structures in the combustors did not change with Reynolds number. Results also showed that the heat transfer distributions in the annulus have slightly different characteristics for the concave and convex walls. A modified swirl number accounting for the step expansion ratio is defined to facilitate comparison between the heat transfer characteristics in the annular combustor with previous work in a can combustor. A higher modified swirl number in the annular combustor resulted in higher heat transfer augmentation and a slower decay with Reynolds number.

scholarly journals Flow characterization in an axial micro-hydroturbine model

2021 ◽  
Vol 2127 (1) ◽  
pp. 012002
Author(s):  
D A Suslov ◽  
S I Shtork ◽  
I V Litvinov ◽  
E U Gorelikov
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
High Efficiency ◽  
Swirling Flow ◽  
Flow Characteristics ◽  
Laser Doppler Anemometer ◽  
Operating Conditions ◽  
Swirl Number ◽  
Operation Conditions ◽  
Flow Characterization

Abstract The flow characteristics behind the runner of an air model of a propeller-type micro-hydroturbine were studied in detail by varying the operation conditions from part-load to high overload. The Reynolds number was varied from 3×104 to 9×104, and the swirl number from 0.7 to -0.4. An automated laser-Doppler anemometer (LDA) system for non-contact optical diagnostics was used to perform detailed measurements of the flow field distribution, including the profiles of two components of averaged velocities and pulsations and LDA signal spectra. Based on the results, a correlation was found between the identified features of the development of the flow structure under changing operating conditions of the hydroturbine and the nature of the evolution of the integral swirl number, which determines the state of the swirling flow. This can be used to develop recommendations for expanding the range of regulation of hydroturbine operation while maintaining high efficiency.

scholarly journals Flow Regimes and Heat Transfer Characteristics in Combustion Chambers

2015 ◽  
Vol 12 (2) ◽  
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Swirling Flow ◽  
Local Heat Transfer ◽  
Reacting Flow ◽  
Heat Transfer Characteristics ◽  
Swirl Number ◽  
Number Range ◽  
Transfer Characteristics ◽  
Combustor Liner

This paper presents a numerical computations are performed to investigate the convective heat transfer characteristics of a gas turbine can combustor under non reacting flow conditions in a Reynolds number range 50,000 to 600,000 with a characteristic swirl number of 0.7. A sample of computational predictions of flow behaviors under reacting conditions are also shown for swirling furnace flow of 0.52. The RNG (K-ɛ Model) predictions are compared with the experimental data of local heat transfer distribution on the combustor liner wall. It was observed that the flow field in the combustor is characterized by an expanding swirling flow, which impinges on the liner wall close to the inlet of the combustor. The peak heat transfer augmentation ratio (compared with fully developed pipe flow) reduces from 10.5 to 2.7. Additionally, the peak location does not change with Reynolds number since the flow structure in the combustor is also a function of the swirl number. The size of the corner recirculation zone near the combustor liner remains the same for all Reynolds numbers and hence the location of shear layer impingement and peak augmentation does not change. The heat transfer coefficient distribution on the liner wall predicted from the RNG (K-ɛ Model) is in good agreement with experimental values. The location and the magnitude of the peak heat transfer are predicted in very close agreement with the experiments.

Effect of Weak Swirling Flow on Film Cooling Performance

1990 ◽  
Vol 112 (4) ◽  
pp. 786-791 ◽  
Author(s):  
C. Gau ◽  
W. B. Hwang
Keyword(s):  
Film Cooling ◽  
Swirling Flow ◽  
Swirl Flow ◽  
Cover Plate ◽  
Mixing Rate ◽  
Swirl Number ◽  
Cooling Effectiveness ◽  
Radial Temperature ◽  
Film Cooling Effectiveness ◽  
Annular Slot

Experiments have been performed in a large circular pipe to study and obtain the film cooling effectivenesses with the presence of weak swirling flow in the mainstream. The swirling flow is generated by a flat vane swirler situated upstream. Cooling film is injected from an annular slot formed by the pipe wall and the circular cover plate. The radial temperature distribution measurements at several axial locations were used to infer the rate of mixing of film jet with swirling flow. The swirl number, which increases with turbulence intensity and swirl velocity in the mainstream, can significantly increase the mixing rate of film jet with swirl flow and decrease the film cooling effectiveness. During the course of the experiments, the blowing ratio ranged from 0.5 to 1.75 and the swirl number ranged from 0 to 0.6. Correlation equations for the film cooling effectiveness, which account for the effect of swirling flow, are obtained.

Numerical Simulation to Study the Effect of the Particle Deposition Morphology on the Filtration Efficiency of the Fibrous Media

2012 ◽  
Vol 518-523 ◽  
pp. 1767-1770 ◽  
Author(s):  
Fu Ping Qian ◽  
Xian Kun Yu
Keyword(s):  
Numerical Simulation ◽  
Particle Deposition ◽  
Moving Boundary ◽  
Simulation Method ◽  
Filtration Efficiency ◽  
Fibrous Media ◽  
Fixed Boundary ◽  
Freezing Method ◽  
Computational Fluid Dynamics Cfd ◽  
Deposition Morphology

The grid “freezing” method in computational fluid dynamics (CFD) was used to deal with the moving boundary in this study, which can make the dynamic boundary into the fixed boundary and qualitatively describe the particle deposition morphology on the surface of the fibrous media. Meanwhile, the filtration efficiencies of the fibrous media with different deposition particle numbers and particle deposition morphologies were calculated using numerical simulation method. The results show that particle deposition on the surface of the fibrous media can help to improve the filtration performance, and in the steady-state, the effect is not obvious, but in the unsteady-stage, the particle deposition can improve the filtration efficiency greatly. In addition, the disposition morphology that has greater contact area with the oncoming particles is conductive to fibrous media capturing particles.

Numerical Simulation of Entrainment and Transport of Gas Bubbles by Vortex Ring

2011 ◽  
Author(s):  
Tomomi Uchiyama ◽  
Yutaro Yoshii
Keyword(s):  
Numerical Simulation ◽  
Reynolds Number ◽  
Vortex Ring ◽  
Volume Fraction ◽  
Gas Bubbles ◽  
Bubble Motion ◽  
Bubble Cluster ◽  
Bubble Volume ◽  
Hydrogen Bubbles

The possibility to control the motion of small gas bubbles by a vortex ring is explored through a numerical simulation. Hydrogen bubbles with diameter of 0.2 mm are arranged in quiescent water, and a vortex ring is launched toward the bubbles. The behavior of the vortex ring and the bubble motion are analyzed. The diameter of the vortex ring at the launch is 42.5 mm, the Reynolds number is 500, and the bubble volume fraction at the launch is less than 0.04. The simulation highlights that the vortex ring convects in the bubble cluster with shoving the bubbles and that the bubbles are entrained and involved by the vortex ring. It also clarifies the changes of the diameter and circulation of the vortex ring.

Research on the incidence of soft abrasive flow to a wall and the machining characteristics

2020 ◽  
pp. 095440542093755
Author(s):  
Chen Li ◽  
Qingduo Xu ◽  
Jiangqin Ge ◽  
Liming Guo ◽  
Shuang Wei
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Volume Fraction ◽  
Incident Angle ◽  
Dynamic Pressure ◽  
Simulation Method ◽  
Calculation Model ◽  
Abrasive Particles ◽  
Simulation Results ◽  
Machining Characteristics

In this study, a calculation model was proposed to predict the motion locus of particles moving to a wall in boundary layers. The velocity of soft abrasive flow and the incident angle of the particles were obtained based on the results calculated by the mixture model and realizable k–ε model. After the model formed, the distributions of the dynamic pressure and the volume fraction of abrasive particles were analyzed and compared to experimental results. After analysis, it was found that the amount of removed material is positively correlated with the incident velocity and the volume fraction of abrasive particles, as well as the dynamic pressure on the surface of the workpiece. In addition, the comparison shows that the numerical simulation method is feasible to predict the flow field and effect of soft abrasive flow. In addition, it was found that the simulation results are consistent with the flow field distribution and machining effect. Therefore, this model can be used in design of constrained modules.

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