II. Axial Flow Fans

II. Axial Flow Fans

Axial flow fans can be classified by structural type into cylindrical, simplified cylindrical, and fan-type axial flow fans. Based on the matching direction of the shaft. Currently, axial flow fans in China are categorized by pressure into low-pressure and high-pressure types. Low-pressure axial flow fans have a total pressure ≤490 Pa, while high-pressure axial flow fans have a total pressure >490 Pa but <4900 Pa. Fundamental Application of High-Pressure Centrifugal Fans High-pressure centrifugal fans serve as critical equipment for strong convection full-hydrogen hood furnaces, representing both the core technology and starting point of strong convection systems. The impeller of a high-pressure centrifugal fan is secured to the motor's output shaft end. The shaft and impeller are fixed via a tapered body equipped with standard flat nuts and locking components. A dedicated flange atop the motor connects via bolts to the lower flange at the furnace center. The motor is encased in a specialized sealed water jacket, which forms a tight seal with another large central flange on the furnace. Hydrogen enters the furnace through the gap around the fan shaft near the motor's upper end cover. The motor cavity is filled with the same hydrogen protective gas as the furnace. A guide vane installed at the motor's top forms a small fan with centrifugal action. This pumps hydrogen from the lower end through the inner side of the special enclosed water jacket and between the motor stator and rotor. This creates a cooling circulation system both inside and outside the motor, effectively cooling the motor and purifying its internal gases. This provides a critical guarantee for steel plate surface quality and safe production. Heat dissipation fins welded inside the cooling water jacket increase the cooling surface area. These fins surround the motor, enabling thorough cooling of both the motor and its bearings. Higher furnace temperatures result in lower hydrogen protective gas density, reducing fan power consumption. Therefore, the fan power consumption is relatively low. A 22 kW power rating was selected to accommodate full hydrogen protective gas. This high-pressure centrifugal fan represents a currently advanced structural design with the following prominent advantages: (1) Bearings connecting the fan and furnace chamber require no sealing. The motor is encased in a sealed water jacket and bolted to the furnace chamber with a sealed connection. This replaces dynamic seals prone to hydrogen leakage or external air ingress with static seals. This innovation fundamentally resolves critical shaft leakage issues in furnace platform circulation fans, significantly enhancing the feasibility of using hydrogen as the sole protective gas. (2) The entire high-pressure centrifugal fan operates in a high-temperature environment. Its closed cooling water jacket features a rational design and delivers excellent performance. (3) The high-pressure centrifugal fan utilizes a variable-frequency motor, enabling seamless speed adjustment. (4) The high-pressure centrifugal fan boasts a simple structure, reduced maintenance requirements, and extended service life.