Numerical Simulation of Internal Gas Flow in GTFA-TIG Welding Powder Feeder

Literature Overview

This 2020 study by Li Hui from Ningxia Institute of Technology, Shi Ling and Huang Yong from Lanzhou University of Technology, and Yao Yuhang from Shanghai Chenguang Medical Technology Co., Ltd., presents a computational fluid dynamics (CFD) simulation of the internal gas flow within a GTFA-TIG (Gas Transfer Arc TIG) welding powder feeder. The research was supported by the Ningxia Higher Education Science and Technology Research Project (NGY2017208) and addresses a critical design challenge in advanced welding processes — ensuring uniform powder delivery and stable arc transfer through the powder feeder geometry.

Technical Background

GTFA-TIG welding is an advanced variant of TIG welding in which a fine powder is delivered through the center of the tungsten electrode, creating a plasma arc that melts both the powder and the base metal. This process combines the precision of TIG welding with the dilution control of powder feeding, making it suitable for welding dissimilar materials, repairing worn surfaces, and applying specialized coatings.

The powder feeder is a critical component that must deliver powder at a consistent rate while maintaining a stable gas flow that protects the powder from oxidation and ensures uniform distribution around the tungsten electrode. The internal gas flow pattern directly influences:

• Powder transport velocity and distribution
• Arc stability and transfer characteristics
• Shielding gas coverage of the weld pool
• Powder oxidation rate during transit

CFD Simulation Methodology

The study employed a three-dimensional CFD model with the following specifications:

The boundary conditions included:

Gas Flow Analysis Results

The simulation revealed several key flow characteristics within the powder feeder:

Velocity Distribution

The gas velocity increases significantly as the flow converges toward the tungsten electrode tip. At the feeder inlet, the velocity is uniform at 2–10 m/s, but at the electrode tip, it increases to 15–40 m/s depending on the inlet conditions. This acceleration creates a low-pressure zone that enhances powder entrainment.

Pressure Distribution

The pressure drop across the powder feeder is dominated by the acceleration of the gas flow through the converging section. The maximum pressure drop occurs at the electrode tip, where it reaches 500–2000 Pa below the inlet pressure. This pressure gradient is the primary driving force for powder transport.

Turbulence Intensity

The turbulence intensity increases from 5–10% at the inlet to 20–35% at the electrode tip. This elevated turbulence enhances powder mixing but can also cause powder agglomeration if the intensity is too high.

Flow Separation Zones

At high gas flow rates (>8 m/s), flow separation occurs at the feeder wall near the electrode tip, creating recirculation zones that can trap powder particles and cause delivery inconsistencies. This finding has direct implications for feeder design optimization.

Powder Transport Analysis

The discrete phase model simulation tracked individual powder particles through the feeder:

The results demonstrate that a medium gas flow rate of 5 m/s provides the best balance between powder distribution uniformity and delivery rate consistency. At low flow rates, powder tends to agglomerate and settle on the feeder walls, while at high flow rates, excessive turbulence can cause powder to bounce off the walls and create delivery spikes.

Feeder Geometry Optimization

Based on the simulation results, the following design recommendations were made:

The optimized geometry reduces flow separation, improves powder distribution, and increases delivery rate consistency by 40–50% compared to the original design.

Engineering Practice Integration

For GTFA-TIG welding applications in surface cladding, repair welding, and dissimilar material joining, the powder feeder design is a critical process variable that directly influences weld quality. The CFD simulation results provide a quantitative basis for feeder design optimization, reducing the need for costly experimental trials.

The study also highlights the importance of gas flow rate control. In production welding, the gas flow rate must be maintained within a narrow window (4–6 m/s) to ensure consistent powder delivery. Flow rate fluctuations of more than ±20% can lead to significant variations in weld bead geometry and composition.

Key Reflections

This research demonstrates the value of CFD simulation in welding process development. The ability to visualize and quantify internal flow patterns within the powder feeder provides insights that are difficult to obtain through experimental measurement alone. The simulation results can guide feeder design optimization, reducing development time and cost.

The study also highlights an important consideration for GTFA-TIG welding — the powder feeder is not merely a passive delivery device but an active component that influences the welding process through its effect on gas flow, powder transport, and arc stability. This understanding is essential for developing reliable GTFA-TIG welding procedures.

Summary

The CFD simulation of the GTFA-TIG welding powder feeder reveals that gas flow rate, feeder geometry, and surface finish are the primary design parameters influencing powder delivery quality. An optimized feeder design with a 12 mm inlet diameter, 15° converging angle, 4 mm throat diameter, and 30 mm exit length, operated at a gas flow rate of 5 m/s, provides excellent powder distribution uniformity and delivery rate consistency. These findings provide a solid foundation for the design and optimization of GTFA-TIG welding powder feeders in production applications.