scholarly journals Numerical Study on Powder Stream Characteristics of Coaxial Laser Metal Deposition Nozzle

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 282
Author(s):  
Liqun Li ◽  
Yichen Huang ◽  
Chunyu Zou ◽  
Wang Tao
Keyword(s):  
High Speed ◽  
Gas Flow ◽  
Numerical Study ◽  
Metal Deposition ◽  
Laser Metal Deposition ◽  
Discrete Phase Model ◽  
Stream Morphology ◽  
Flow Phase ◽  
Discrete Phase ◽  
Stream Characteristics

A 3D model was established to accurately simulate the internal and external powder stream characteristics of the coaxial discrete three-beam nozzle for laser metal deposition. A k-ε turbulence model was applied in the gas flow phase, and powder flow was coupled to the gas flow by a Euler-Lagrange approach as a discrete phase model. The simulated powder stream morphology was in good agreement with the experimental results of CCD and high-speed camera imaging. The simulation results showed that the length, diameter and shrinkage angle of the powder passage in the nozzle have different effects on the velocity and convergence characteristics of the powder stream. The influence of different particle size distribution and the inner laser shielding gas on the powder stream were also discussed in this study. By analyzing the powder stream caused by different incident directions of powder passage, and the collision process between powder and the inner wall, the basic principle of controlling powder stream convergence was obtained.

A numerical study of snow accumulation on the bogies of high-speed trains based on coupling improved delayed detached eddy simulation and discrete phase model

2018 ◽  
Vol 233 (7) ◽  
pp. 715-730 ◽  
Author(s):  
Mingyang Liu ◽  
Jiabin Wang ◽  
Huifen Zhu ◽  
Sinisa Krajnovic ◽  
Guangjun Gao
Keyword(s):  
High Speed ◽  
Numerical Study ◽  
Snow Accumulation ◽  
Phase Model ◽  
Detached Eddy Simulation ◽  
Discrete Phase Model ◽  
Eddy Simulation ◽  
Delayed Detached Eddy Simulation ◽  
Flow Mechanisms ◽  
Discrete Phase

A numerical simulation method based on the improved delayed detached eddy simulation coupled with a discrete phase model is used to study the influence of the snow on the performance of bogies of a high-speed train running in snowy weather. The snow particle trajectories, mass of snow packing on the bogie, and thickness of snow accumulation have been analyzed to investigate the flow mechanisms of snow accumulation on different parts of the bogies. The results show that the snow accumulation on the first bogie of the head vehicle is almost the same as that of the second bogie, but the total accumulated snow on the top side of the second bogie is more than 74% higher than that of the first bogie. Among all the components of the bogies, the motors were found to be strongly influenced by the snow accumulation. The underlying flow mechanisms responsible for the snow accumulations are discussed.

Numerical study on the anti-snow performance of deflectors in the bogie region of a high-speed train using the discrete phase model

2018 ◽  
Vol 233 (2) ◽  
pp. 141-159 ◽  
Author(s):  
Guangjun Gao ◽  
Yan Zhang ◽  
Fei Xie ◽  
Jie Zhang ◽  
Kan He ◽  
...  
Keyword(s):  
High Speed ◽  
Stokes Equations ◽  
Numerical Study ◽  
Three Dimensional ◽  
Snow Accumulation ◽  
Phase Model ◽  
High Speed Train ◽  
Discrete Phase Model ◽  
Discrete Phase ◽  
Deflector Plate

In this paper, the three-dimensional unsteady Reynolds-averaged Navier-Stokes equations with an RNG double-equation turbulence model and a discrete phase model were used for the investigation of snow accumulation on the bogie of a high-speed train. Two kinds of deflector plates, one installed at the front end and the other at the rear end of the bogie, were proposed to reduce snow accumulation. The accuracy of the CFD methodology was validated against wind tunnel tests. The results showed that high-speed air will impact the plates where snow particles get accumulated. The snow covering on the bogie rarely drifts back into the bogie region with air. The amount of accumulating snow in the optimum models is reduced by 50.58% on average as compared to those in the original models. At the rear end of the bogie, the inclined deflector plate reduced snow accumulation by up to 10.91% compared to the vertical deflector plate.

Effect of position of the fiber transport channel on fiber motion in the high-speed rotor

2021 ◽  
pp. 004051752110018
Author(s):  
Rui Hua Yang ◽  
Chuang He ◽  
Bo Pan ◽  
Hongxiu Zhong ◽  
Cundong Xu
Keyword(s):  
High Speed ◽  
Channel Model ◽  
Three Dimensional ◽  
Discrete Phase Model ◽  
Transport Channel ◽  
Rotor Spinning ◽  
Fiber Motion ◽  
Discrete Phase ◽  
Airflow Field ◽  
Fiber Transport

The task of the fiber transport channel (FTC) is to transport the fibers from the carding roller to the rotor. Its geometric position in the spinning machine has a strong influence on the characteristics of the airflow field and the trajectory of the fiber motion in both the rotor and the FTC. In this paper, a three-dimensional pumping rotor spinning channel model was established using ANSYS-ICEM-CFD software with three different positions of the FTC (positions a–c). Further, the simulations of air distribution were performed using Fluent software. In addition, the discrete phase model was used to fit the fiber motion trajectory in the rotor. The simulation results showed that among the three types of FTC, position b is the optimal condition. The gradients of airflow velocity in the channel at position b were greater than those of the other two positions, which is conducive to straightening of the fiber.

Numerical Simulation of Two-Phase Flow inside and outside a Swirl Nozzle for Dispersing Superfine Powder

2012 ◽  
Vol 505 ◽  
pp. 170-174
Author(s):  
Wei Dong Shi ◽  
Liang Zhang ◽  
Hai Yan He ◽  
Jiang Hai Liu ◽  
Liang Chen
Keyword(s):  
Total Pressure ◽  
Concentration Distribution ◽  
Gas Flow ◽  
Reynolds Stress Model ◽  
Phase Flow ◽  
Discrete Phase Model ◽  
Two Phase ◽  
Discrete Phase ◽  
Particle Group ◽  
Nozzle Structure

In this paper, a swirl nozzle is established to disperse superfine powder aerodynamically. And Reynolds stress model (RSM) is adopted to simulate the strongly swirling, compressible and transonic gas flow in the nozzle and its rear. Combined with discrete phase model (DPM), the concentration distribution of particle group in size of 2.5μm is studied. The simulated results show that, the distribution of swirl strength is determined basically by the nozzle structure, while the total pressure has little effect on it; compared with an irrotational nozzle, the swirl nozzle could achieve a better dispersing effect for superfine powder.

scholarly journals Effect of Air Exchange Rate on Particle Decay in a Cleanroom: A Numerical Study

2019 ◽  
Vol 111 ◽  
pp. 01037
Author(s):  
Yunus Emre Cetin ◽  
Mete Avci ◽  
Orhan Aydin
Keyword(s):  
Exchange Rate ◽  
Turbulence Model ◽  
Recovery Time ◽  
Numerical Study ◽  
Particle Dispersion ◽  
Discrete Phase Model ◽  
Governing Equations ◽  
Air Exchange Rate ◽  
Particle Decay ◽  
Discrete Phase

In this study, particle decay in a cleanroom is investigated numerically. A commercial CFD package, FLUENT, is used in the analysis. The governing equations are solved by using the k-å turbulence model. For particle dispersion, the discrete phase model (DPM) is applied. Four different air change rates (3-10-25-43 ACH) with three particle diameters (0,5-5-10 ìm) are considered. It is shown that 10 ACH satisfies the needs in terms of recovery time.

Effect of Powder Flow Rate and Gas Flow Rate on the Evolving Properties of Deposited Ti6Al4V/Cu Composites

2014 ◽  
Vol 1016 ◽  
pp. 177-182 ◽  
Author(s):  
Mutiu F. Erinosho ◽  
Esther Titilayo Akinlabi ◽  
Sisa Pityana
Keyword(s):  
Flow Rate ◽  
Gas Flow ◽  
Pure Copper ◽  
Metal Deposition ◽  
Powder Flow ◽  
Laser Metal Deposition ◽  
Gas Flow Rate ◽  
Flow Rates ◽  
Powder Flow Rate ◽  
Hardness Values

—Pure copper was deposited with Ti6Al4V alloy via laser metal deposition (LMD) process to produce Ti6Al4V/Cu composites. This paper reports the effect of powder flow rate (PFR) and gas flow rate (GFR) of laser metal deposited Ti6Al4V/Cu composites. The deposited samples were characterised through the evolving microstructure and microhardness. It was observed that the PFR and GFR have an influence on the percentage of porosity present in the samples. The higher the flow rates of the powder and the gas, the higher the degree of porosity and vice versa. The widmanstettan structures were observed to be finer as the flow rate reduces which in turn causes a decrease in the hardness values of the deposited composites. The hardness values varied between HV381.3 ± 60 and HV447.3 ± 49.

Numerical Study of the Pusher-Type Billet Reheating Furnace

2005 ◽  
Author(s):  
Linjiang Zou ◽  
Chaoxiang Li ◽  
Yinmei Yuan ◽  
Wei Guo ◽  
Fan Yang ◽  
...  
Keyword(s):  
Software Package ◽  
High Speed ◽  
Gas Flow ◽  
Numerical Study ◽  
Three Dimensional ◽  
Cfd Model ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Iron And Steel ◽  
Reheating Furnace

In the present work, a commercial CFD software package, FLUENT, was used to develop a three-dimensional model of pusher-type billet reheating furnace for the second high speed wire rod plant of XiangTan Iron and steel Co. Ltd. The purpose of the study was to gain a better understanding of the gas flow and velocity and pressure distribution in the furnace. The results show that the numerical results are in agreement with the practice and the characteristics of the furnace configuration. The CFD model can be used to improve the performance and structure by analyzing and studying the behavior of the reheating furnace.

A Numerical Study of Particle Deposition Through Fuel Pebble Bed in HTGR

2018 ◽  
Author(s):  
Qi Sun ◽  
Gang Zhao ◽  
Wei Peng ◽  
Suyuan Yu
Keyword(s):  
Particle Deposition ◽  
Numerical Study ◽  
Three Dimensional ◽  
Intensity Change ◽  
Discrete Phase Model ◽  
Pebble Bed ◽  
Deposition Fraction ◽  
Discrete Phase ◽  
Face Centered ◽  
Fuel Elements

The study on the deposition of graphite dust is significant to the safety of High-Temperature Gas-cooled Reactor (HTGR) due to potential accident such as localized hot-spots and intensity change which is caused by the graphite dust generated by abrasion of fuel elements. Based on the steady flow and three-dimensional face centered structures of fuel pebble bed, the discrete phase model (DPM) were applied to simulate trajectory of graphite dust in conditions of HTGR. To determinate the deposition of particle, the present study introduces a rebound condition with critical velocity by a user defined function. The particle trajectories show most of particle deposition can be summed up as the effect of backflow region, turbulent diffusion and inertial impact. The original trap condition overestimates the deposition fraction especially for large particles compared with involving rebound condition. In addition, the trend of deposition fraction shows as the dimeter of particle increases, deposition fraction decreases first and then increases.

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