Numerical Simulation and Experimental Study of Multi-Phase Flow Coupling of Oxygen-Rich Molten Pool Top Lance Swirl Nozzle and Variable Angle Side Lance Study Notes

Literature Overview and Core Focus

This study addresses the complex multi-phase flow phenomena occurring in oxygen-rich molten steel refining, specifically examining the interaction between a top lance equipped with a swirl nozzle and variable-angle side lances. While this topic falls within the domain of steelmaking metallurgy rather than cladding or pressure vessel fabrication per se, the underlying fluid dynamics principles — multiphase flow, momentum transfer, and turbulence modeling — have direct relevance to understanding molten pool behavior in electroslag welding and submerged arc welding processes, where similar oxygen-injection and gas-liquid interactions govern slag pool stability and penetration characteristics.

Multi-Phase Flow Modeling Approach

Computational Framework

The study employs a coupled Eulerian-Eulerian multi-phase flow model to simulate the interaction between molten steel, slag, and injected oxygen gas. The computational domain includes the full vessel geometry with the top lance swirl nozzle and multiple side lances positioned at variable angles. The governing equations include the Navier-Stokes equations for each phase, with inter-phase coupling through drag, lift, and turbulent dispersion forces.

Modeling Parameter	Value / Setting	Justification
Turbulence model	RNG k-ε with realizable extension	Better prediction of swirling flows
Phase coupling	Two-way coupling (steel-gas, steel-slag)	Accounts for momentum exchange
Time step	0.001–0.01 s	Resolves gas bubble dynamics
Mesh size	2–5 mm near lances, 10–20 mm bulk	Captures near-field flow features
Gas injection rate	0.5–3.0 Nm³/min	Representative of industrial conditions
Top lance swirl number	0.3–1.2	Range of industrial nozzle designs
Side lance angle	15°–60° from horizontal	Variable geometry study

Key Flow Phenomena Identified

The simulation reveals several important flow phenomena: (1) the swirl nozzle generates a toroidal vortex in the molten pool that enhances mixing and homogenization; (2) side lances inject oxygen bubbles that rise and interact with the top lance-induced flow field; (3) the coupling between top and side lance flows creates complex recirculation patterns that significantly affect oxygen absorption efficiency and slag chemistry evolution.

Experimental Validation

The study validates the numerical model against experimental measurements obtained from a scaled-down model vessel using water as the working fluid and air as the gas phase. Key validation parameters include:

Validation Parameter	Numerical Result	Experimental Result	Deviation
Oxygen absorption rate	85–92%	82–88%	±3%
Flow field velocity	±5% agreement	—	Within acceptable range
Slag layer thickness	±10% agreement	—	Acceptable for process design
Mixing time	45–55 s	40–50 s	Within 10%

The good agreement between simulation and experiment validates the computational approach and provides confidence for using the model to optimize industrial lance configurations.

Relevance to Cladding and Weld Overlay Processes

Although this study focuses on steelmaking, the multiphase flow principles have direct analogies in weld overlay processes. In electroslag welding overlay, the slag pool behavior is governed by similar multiphase flow dynamics — the interaction between molten metal, slag, and arc plasma creates complex flow patterns that determine penetration depth, dilution rate, and microstructure. Understanding how swirl and gas injection affect molten pool dynamics in steelmaking provides valuable insights for optimizing ESW slag pool geometry and electromagnetic stirring in wide-band overlay applications.

Specifically, the concept of using controlled gas injection to modify flow patterns in the molten pool can be adapted to ESW overlay processes where argon or nitrogen shielding gas flow can be manipulated to influence slag pool stability and penetration characteristics. The variable-angle lance concept also parallels the use of multiple electrode configurations in wide-band ESW overlay, where electrode positioning affects the combined heat input distribution.

Key Questions and Reflections

A significant question for process engineers is how to translate the multiphase flow insights from steelmaking to weld overlay applications. The scale difference is considerable — steelmaking vessels operate at meter scales with heat inputs of megawatts, while ESW overlay operates at centimeter scales with heat inputs of kilowatts. However, the dimensionless flow parameters (Reynolds number, Froude number, swirl number) can be used to establish similarity between the two systems, enabling the transfer of design principles.

Another reflection concerns the practical implementation of variable-angle lance configurations. In steelmaking, the side lance angle is a key process variable that can be adjusted to optimize oxygen absorption and mixing. In ESW overlay, the electrode angle is similarly critical for controlling penetration profile and slag pool shape. The study provides a systematic framework for optimizing lance angle that could be adapted to ESW electrode positioning strategies.

Study Insights and Implications

The fundamental insight from this study is that multiphase flow coupling is a critical determinant of process performance in oxygen-rich molten metal systems. For engineers working in weld overlay, this translates to the recognition that slag pool dynamics in ESW and SAW processes are governed by similar multiphase flow principles, and that systematic optimization of gas flow and electrode positioning can significantly improve overlay quality. The study provides a rigorous computational framework that can be adapted to model and optimize slag pool behavior in wide-band overlay processes, ultimately contributing to more reliable and efficient bimetal fabrication.