Ventilation – Vehicular tunnel – With air pump
Patent
1997-02-24
1998-03-03
Joyce, Harold
Ventilation
Vehicular tunnel
With air pump
454342, E21F 100
Patent
active
057228850
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to fans and arrangements of fans particularly for use in tunnels and other enclosed spaces where large volumes of air are required to be moved e.g. for ventilation or smoke control.
It is known that jet fans can be used to ventilate underground tunnels. These fans operate by ejecting a jet of high speed air to entrain and move a larger volume of air. This type of fan known as a jet fan is widely used in underground train and road tunnels although they are widely used in other applications e.g. underground car parks.
In use, the fans are normally attached to the wall or ceiling of the area to be ventilated, however under some circumstances including control of smoke from fires or other airborne dangers, (such as a toxic gas leak etc.) the fans must be reversible so that if there were to be an airborne hazard upstream from the fan, reversing the fan would reduce the spread of the hazard. This is particularly so in the case of fire as reversing the fan can help provide an escape route for people away from the fire.
Previously fans have been conventionally mounted with their principle axis, along which air will initially flow, parallel to the supporting surface. It is usual for the supporting surface to be the ceiling or wall of the tunnel or space to be ventilated, where space is limited the fans can be mounted in niches.
The distance between the fan and the supporting surface should be sufficient to reduce the surface effects such as friction arising from the flow of air along the surfaces. Invariably jet fans will be mounted close to the tunnel wall or ceiling to minimise the tunnel cross-sectional area available for vehicle movement.
In some cases baffles or other flow deflecting means are employed to direct the flow of the air in specific directions away from adjacent surfaces but these are cumbersome and can cause energy losses to the flow from the jet fan.
In circular or rectangular section tunnels the primary jet from the fan needs to be directed away from the walls and the ceiling to minimise losses due to wall friction between the primary jet and the solid surfaces.
In cases where the jet fans are mounted in niches the primary jet needs to be directed clear of solid surfaces.
SUMMARY OF THE INVENTION
We have now invented an improved arrangement for such fans.
According to the invention there is provided an air moving system in which a jet fan is positioned adjacent to a surface or surfaces with the axis of the jet fan at an angle to the said supporting surface or surfaces so as to direct air away from the surface when the fan is working, the jet fan being supported on at least one adjustable mounting so that when the direction of the air being blown by the fan is reversed the fan can be adjusted on its mounting so as to direct the said reversed air flow away from the adjacent surface or surfaces in the opposite direction.
Jet fans are widely known and used for various ventilation applications and are made by Woods of Colchester and many other companies. The size of the fan used depends on the size of the space to be ventilated and the pollutant dilution and movement required.
Jet fan applications cover road vehicle tunnels throughout Europe, America, and the Far East with their cost effectiveness making them first choice ahead of transverse or semi-transverse ventilation.
We have found that by directing the flow of air away from the adjacent surface or surfaces increased efficiency of the ventilation system can be obtained.
The angle of inclination of the axis of the fan to the adjacent surface or surfaces will normally be up to 20 degrees, typically 2 to 15 degrees. The optimum angle depends upon the distance of the fan from the supporting surface or surfaces and the surface characteristics and, if niches are employed, niche geometry.
When it is necessary to reverse the flow of air through such an inclined fan, unless the fan's inclination was altered, air would be blown towards the adjacent surface or surfaces, which would not be desirable. Thi
REFERENCES:
patent: 4412478 (1983-11-01), Osher et al.
Boles Derek S.
Joyce Harold
South Bank University & Enterprises, Limited
Woods of Colchester Limited
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