Abstract: A foam production method includes mixing liquid nitrogen with a foaming material to produce foam. A gas is produced in situ from liquid nitrogen. As the ratio of the volume of the gas produced by gasification of liquid nitrogen to the volume of the liquid nitrogen is relatively high, when a large gas supply flow is needed to generate a large foam flow, a liquid nitrogen storage device of a small volume can be used instead of bulky air supply devices such as high-pressure gas cylinders, air compressors, air compressor sets and the like, reducing the volume of the air supply device. In addition, the liquid nitrogen used in foaming will release nitrogen gas after the foam blast, such that the nitrogen is also able to inhibit combustion on the surface of burning materials, accelerating the extinguishing of the fire.

Abstract: An aerated swirling vertical shaft with double volute chambers comprises an upper volute chamber (2) and a first shrinking section (3) beneath the upper volute chamber (2), a venting passage (4) outside the upper volute chamber (2), a vertical shaft section (7) beneath the first shrinking section (3), as well as an aerated lower volute chamber (5) and a second shrinking section (6) communicated with the aerated lower volute chamber (5) between the first shrinking section (3) and the vertical shaft section (7), wherein the upper end of the aerated lower volute chamber (5) is connected with the first shrinking section (3), the lower end of the second shrinking section (6) is connected with the vertical shaft section (7); the upper end of the venting passage (4) is communicated with the atmosphere and the lower end is communicated with the aerated lower volute chamber (5).

Abstract: An aerated swirling vertical shaft with double volute chambers comprises an upper volute chamber (2) and a first shrinking section (3) beneath the upper volute chamber (2), a venting passage (4) outside the upper volute chamber (2), a vertical shaft section (7) beneath the first shrinking section (3), as well as an aerated lower volute chamber (5) and a second shrinking section (6) communicated with the aerated lower volute chamber (5) between the first shrinking section (3) and the vertical shaft section (7), wherein the upper end of the aerated lower volute chamber (5) is connected with the first shrinking section (3), the lower end of the second shrinking section (6) is connected with the vertical shaft section (7); the upper end of the venting passage (4) is communicated with the atmosphere and the lower end is communicated with the aerated lower volute chamber (5).

Abstract: An aerated swirling vertical shaft with double volute chambers comprises an upper volute chamber (2) and a first shrinking section (3) beneath the upper volute chamber (2), a venting passage (4) outside the upper volute chamber (2), a vertical shaft section (7) beneath the first shrinking section (3), as well as an aerated lower volute chamber (5) and a second shrinking section (6) communicated with the aerated lower volute chamber (5) between the first shrinking section (3) and the vertical shaft section (7), wherein the upper end of the aerated lower volute chamber (5) is connected with the first shrinking section (3), the lower end of the second shrinking section (6) is connected with the vertical shaft section (7); the upper end of the venting passage (4) is communicated with the atmosphere and the lower end is communicated with the aerated lower volute chamber (5).