ノズルの形状による熔鉄ジェットの安定性

出鋼造塊時の熔鋼の流体力学的研究-III

抄録

In the previous research (ib., Tetsu-to-Hagané vol. 44, 1958, p. 122.), the characteristics of jets of some water solutions and mercury through the nozzles of various diameters and shapes were studied, and the flowing property of a nozzle tapered at entrance and with a short parallel straight part at outlet was better than that of normal one.
In this research, the flowing conditions of the molten iron through 20mm ∅; and 40mm ∅; practical nozzles were observed, and for both sizes of nozzles, specially tapered and nor mally designed types were examined. The results obtained were as follows:
(i) 20mm ∅; nozzle:
The condition of jets through both types of nozzles (specially tapered and normally designed) were almost the same and seemed not to be turbulent at a high head (about 900mm). The flowing properties of both type nozzles were different at a low head. Though the jets through tapered nozzles were dripping under 200mm head, the jets through normal ones dripping under 340mm head.
(ii) 40mm ∅; nozzle:
The jets through tapered nozzles did not show turbulence even at the 900mm head, but the jets through normal nozzles were thought to be turbulent above 700-750mm head. The dripping condition of jets through both tapered and normal nozzles were almost same at a low head. The dripping range of each type nozzle was very small and could not be measured clearly.
(iii) Bubble enfolded by molten iron jet:
If the molten iron jet was assumed to begin enfolding bubbles at the same Reynolds number ×ν (kinematic viscosity) where the mercury jet began to enfold bubbles, the molten iron jets through 20mm ∅; and 40mm ∅; nozzles began to enfold bubbles at 640mm and 580mm heads respectively by calculation.
Though the experiments for higher heads of a ladle and errosion of nozzle material have not been completed yet, some considerations for design of nozzles and ladles were described in conclusion based on the results of the previous and this investigations.