Enhancement of Exit Flow Uniformity by Modifying the Shape of a Gas Torch to Obtain a Uniform Temperature Distribution on a Steel Plate during Preheating

The objective of this study is to improve the exit flow uniformity of a gas torch with multiple exit holes for effective heating of a steel plate. The torch was simulated, and combustion experiments were performed for validation. Based on a basic model, three different revised models were designed and analyzed with the software ANSYS FLUENT 18.2. The flow uniformity (γ) of the velocity distribution at the multiple exit holes was investigated with the pressure drop ranging from 100 to 500 Pa. The basic model had flow uniformity ranging from 0.849 to 0.852, but the three new models had γ1 = 0.901–0.912, γ2 = 0.902–0.911, and γ3 = 0.901–0.914, respectively. The maximum percentage difference of the flow uniformity index between the three new models and the basic model was 7.3%. The basic model with nonuniform flow distribution made a temperature difference of the back side of the steel plate from the center to the edge of around 229 °C, while the modified model with uniform flow distribution had a smaller temperature difference of 90 °C. The simulation results showed good agreement with our experimental results for both the basic model and the modified model. The modified gas torch made a wider and more uniform temperature distribution on a preheated steel plate than the basic one. The results revealed that a trade-off between cost and flow uniformity, as well as the new gas torch, could be applied to a steel-plate preheating process before welding.