1. Longitudinal spacing between a group of fans
If there is sufficient spacing between a group of fans in the tunnel, the gushing cyclone will have sufficient slow down. If the gushing cyclone slow down is not complete, it will affect the working characteristics of the next level of fans. In general, the longitudinal interval between a group of fans is named 10 times or about 10 times of the equivalent diameter of the hydraulic power generation of the tunnel cross section, and the longitudinal interval (m) of the wind turbine can also be taken as one tenth of the dynamic pressure of the fan (Pa). The distance between the management center in the middle of the same group of fans is named at least 2 times of the diameter of the fan. The layout of jet fans in the tunnel does not necessarily have the same interval. If there is sufficient longitudinal interval between the fans, the fans can be arranged near the side of the tunnel as far as possible. If the radial installation part of the fan allows a certain skew, the longitudinal spacing between the fan can be reduced, and the installation index can be improved.
Influence factors and selection of jet fan thrust
2. The air velocity in the tunnel, the closeness between the environmental protection fan and the boundary layer and the vault
The thrust of the fan is measured according to the angular momentum of the fan under the standard of stationary gas. If the gas at the entrance of the fan is in fitness motion, the transition value of the angular momentum of the gas in the fan must be reduced. If the installation site of the jet fan is close to the tunnel boundary layer or the vault, additional friction damage will be caused between the gas water jet and the boundary layer or the vault.
3. Fan specifications
The ratio of power consumption and thrust of jet fan is related to the wind at the fan outlet. According to the given thrust regulation, the higher the wind at the outlet, the greater the power consumption. Therefore, in order to reduce operation costs, fans with large diameter, low speed ratio or small leaf Angle of view should be selected as far as possible. In view of the given fan specifications, if the thrust is reduced, the total number of fans will be increased, and then the project investment of the fan itself will be increased, but at this time the wind outlet of the fan will also be reduced, prompting the silencer to cancel or reduce its length.
4. Run the fan reversibly
Compared with single-side fan, reversible fan has lower efficiency and higher noise, but this kind of fan can make tunnel operation with great selectivity. When very necessary, the single tunnel can act as a dual operation, in the event of a fire, the fan can flip the smoke exhaust system.