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

^{*}

## Abstract

**:**

## 1. Introduction

Ref. | Model Type | Software | Gas Flow | Powder Stream |
---|---|---|---|---|

Lin (2000) [2] | 2D | Fluent | k-ε model | Discrete Phase Model (DPM) |

Pinkerton and Li (2004) [3] | mathematical model | |||

Pan et al. (2005) [4] | 2D | Not mentioned | No gas | Stochastic model |

Pan et al. (2006) [5] | 2D | Fluent | k-ε model | DPM |

Zekovic et al. (2007) [6] | 3D | Fluent | k-ε model | DPM |

Wen et al. (2009) [7] | 2D | Fluent | k-ε model | DPM |

Tabernero et al. (2010) [8] | 3D | Fluent | k-ε model | DPM |

Zhu et al. (2011) [9] | 2D | Fluent | k-ε model | DPM |

Smurov et al. (2012) [10] | 2D | Not mentioned | ||

Kovaleva et al. (2013) [11] | 2D | Not mentioned | self-created | |

Nie et al. (2014) [12] | 2D | Fluent | k-ε model | DPM |

Arrizubiteta et al. (2014) [13] | 3D | Fluent | k-ε model | DPM |

Liu et al. (2016) [14] | 3D | Fluent | k-ε model | DPM |

Zhang el al. (2016) [15] | 3D | Fluent | k-ε model | DPM |

Koruba et al. (2018) [16] | 2D | Fluent | k-ε model | DPM |

Ju et al. (2019) [17] | 3D | Fluent | Eulerian two-fluid models | DPM |

Guo et al. (2020) [18] | 3D | Fluent | k-ε model | DPM |

## 2. Research Method

^{−4}s. Through binarization and colors of the five photos, they are combined into one image. By measuring the distance between the positions of the particles at different times in the composite image, the velocity of the particles can be measured. In this method, the measured particle velocities under different parameters are compared with the simulated results in Figure 5. It also shows that the simulation results are in good agreement with the experimental results. Furthermore, since the image can only obtain two-dimensional information, the comparison of velocity is only conducted by two-dimensional vectors, which is less than the maximum particle velocity of the numerical simulation results.

## 3. Result and Discussion

#### 3.1. Collision between Powders and Passage Inner Wall

#### 3.2. The Influence of Nozzle Structure Parameters

#### 3.2.1. Passage Length

#### 3.2.2. Passage Diameter

#### 3.2.3. Passage Shrinkage

#### 3.3. The Influence of Process Parameters

#### 3.3.1. Particle Size Distribution

#### 3.3.2. Inner Laser Shielding Gas

#### 3.4. The Principle of Powder Spot Size Control

_{p}and passage diameter d have a quadratic effect on $\frac{\mathrm{d}{\overrightarrow{u}}_{p}}{\mathrm{dt}}$, and the density of powder ${\rho}_{p}$ has a proportional effect on it. This indicates that smaller powder spot diameters can be obtained by selecting a powder with a smaller particle size and density and the nozzle with finer diameter passages.

## 4. Conclusions

## 5. Outlook

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Conflicts of Interest

## References

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**Figure 6.**Schematic of powder incident direction and concentration distribution of powder stream for coaxial discrete nozzle. (

**a**) The powder is parallel to the passage; (

**b**) the powder is tilt to the passage.

**Figure 8.**The influence of different passage diameters on powder focus spot size. (

**a**) 2.0 mm; (

**b**) 1.5 mm; (

**c**) 1.0 mm.

**Figure 9.**Powder focus spot diameters with and without passage shrinkage. (

**a**) no shrinkage; (

**b**) 2° shrinkage.

**Figure 10.**Particle sizes distribution in powder stream for coaxial-discrete nozzle. (

**a**) 65–85 μm; (

**b**) 25–125 μm.

**Figure 11.**Influence of inner shielding gas on carrier gas. (

**a**) 20 L/min; (

**b**) 10 L/min; (

**c**) 0 L/min.

**Figure 12.**Influence of inner shielding gas on powder stream. (

**a**) 20 L/min; (

**b**) 10 L/min; (

**c**) 0 L/min.

Powder Material | Ti6Al4V |

Powder Size | 75 μm, Spherical |

Powder Flow Rate | 5 g/min |

Particle Carrier Gas Flow Rate | 8 L/min |

Inner Shielding Gas Flow Rate | 10 L/min |

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**MDPI and ACS Style**

Li, L.; Huang, Y.; Zou, C.; Tao, W.
Numerical Study on Powder Stream Characteristics of Coaxial Laser Metal Deposition Nozzle. *Crystals* **2021**, *11*, 282.
https://doi.org/10.3390/cryst11030282

**AMA Style**

Li L, Huang Y, Zou C, Tao W.
Numerical Study on Powder Stream Characteristics of Coaxial Laser Metal Deposition Nozzle. *Crystals*. 2021; 11(3):282.
https://doi.org/10.3390/cryst11030282

**Chicago/Turabian Style**

Li, Liqun, Yichen Huang, Chunyu Zou, and Wang Tao.
2021. "Numerical Study on Powder Stream Characteristics of Coaxial Laser Metal Deposition Nozzle" *Crystals* 11, no. 3: 282.
https://doi.org/10.3390/cryst11030282