Ventilation system for covered traffic ways

Abstract

 The invention relates to a ventilation system for a covered roadway section (1), said system comprising means (6a,6b) to produce an air flow in the covered roadway section (1). The means (6a,6b) are arranged so that they can produce an air flow (L) counter to the traffic direction (R), such that the air flow realized in this way in combination with the air flow generated by the traffic on balance results in there being a reduced outflow of air from the traffic exit of the roadway section (1).

Description

[0001] The invention relates to a ventilation system and method for ventilating a covered traffic way, for example a tunnel.

[0002] The quality of air is generally so poor around tunnel mouths and covered or enclosed traffic ways on national highways, that it does not comply with the requirements set by government relating to air quality, such as the national air quality decree (Besluit Luchtkwaliteit) in the Netherlands. One of the reasons for this is the generally high concentration of polluted air that leaves such a tunnel mouth. This is a result of the concentrated release of pollution conveyed toward the tunnel mouth inter alia by exhaust gases and the production of dust due to contact between vehicle tires and the roadway. Such pollution can be carried along for example with the air flow generated by the traffic.

[0003] Known ventilation systems attempt to resolve this problem of air pollution at the level of tunnel mouths etcetera, by suctioning out the air at the level of the traffic exit and expelling it toward the environment via an air purification installation. Such a ventilation system, however, is not particularly efficient, among other reasons because the traffic intensity can obviously fluctuate greatly and the ventilation system is not adjusted thereto or has to be provided with an expensive and complex regulating system that measures traffic intensity and adjusts the ventilation system accordingly.

[0004] The object of this invention is to provide a ventilation system for ventilating covered roadway sections that does not have the disadvantages referred to above inter alia.

[0005] The ventilation system according to the invention is thereto characterized as described in claim 1. More particularly, the ventilation system according to the invention comprises means to produce an air flow in the covered roadway section, whereby the means are arranged so that they can produce an air flow counter to the traffic direction, such that the air flow realized in this way in combination with the air flow generated by the traffic on balance results in there being a reduced outflow of air from the traffic exit of the covered roadway section. By developing as it were a counterflow of air in front of the tunnel mouth counter to the direction in which the traffic is traveling, it is possible to achieve an at least partial blocking of the polluted air flow leaving with the traffic. At the other end of the tunnel, the air in the tunnel will also be at least partially drawn into the tunnel, for example by the air flow generated at that point by the incoming traffic, and/or by injecting means mounted there if required. Not only is it possible to achieve with the invention almost no or a reduced volume of polluted air accumulating in the environment close to tunnel mouths, but the efficiency of the ventilation system can also be greatly increased at the same time. According to the invention, a quantity of air will indeed gradually be confined in the tunnel, which will become increasingly polluted due to for example exhaust gases and/or dust particles. The air trapped in the tunnel or other covered roadway section will therefore comprise an on average high concentration of pollution. The invention is furthermore inter alia based on the knowledge that such a high concentration of pollution does not present any problems for people who are in the tunnel because the average duration for which they are in the tunnel is short. Although the ventilation system is suitable for any type of covered roadway section, the advantages thereof are particularly apparent in route sections that are not covered for too long a distance, for example up to 2.5 km, more preferably up to 1 km and most preferably up to 500 m.

[0006] When reference is made in this application to tunnel or covered roadway section, this is understood to mean any covered section of a traffic route. The invention is thus suitable for application in roadways, railways, metro, tramways, shipping and furthermore anywhere where a problem of pollution occurs under a covering. The ventilation system can therefore for example be excellently applied in tunnels that are interrupted in length, such as those prescribed for example for conveying hazardous substances.

[0007] By regulating the flow rate of the air flow produced, it is possible to adjust the flow rate of the outflow of air from the traffic exit of the roadway section in a simple fashion. In a preferred embodiment of the ventilation system according to the invention, the means are arranged such that the air flow realized in this way in combination with the air flow generated by the traffic on balance results in there being almost no outflow of air from the traffic exit of the roadway section. To determine the outflow of air from the tunnel mouth, the average outflow of air per unit of time is used, whereby the average is taken over the surface of the relevant traffic exit. Therefore, where reference is made in this application to "almost no outflow of air", it is understood to mean that the flow rate of the air flow from the tunnel calculated over the surface of the relevant exit is almost equal to zero. In this preferred embodiment, the air flow produced is such that the net air rate in the tunnel mouth is reduced to approximately zero. The vehicles leave the tunnel and the air that flows around the vehicles more or less remains suspended due to the counter air flow. To avoid having to stop too much energy in the counter air flow, it is possible to reduce the permissible maximum speed of the vehicles in the tunnel to 80 km/hr for example. In this preferred variant, the outflow of air will be "almost" zero, because the traffic obviously fluctuates and so too the quantity of air conveyed along with the traffic.

[0008] In a preferred embodiment of the ventilation system according to the invention, the means of producing an air flow in the tunnel comprise at least one ventilating fan and preferably more than one ventilating fan. It is thus possible to provide the tunnel for example with a series of ventilating fans arranged in the longitudinal direction thereto spaced at a specific distance from each other, said fans being able to maintain the produced air flow against the traffic. In this way, any slowdown in the produced air flow due to the traffic air flow in the counter direction is reduced or prevented.

[0009] In a further preferred embodiment of the ventilation system according to the invention, the covered roadway section comprises a first and a second traffic direction and the means are arranged such that they can produce an air flow counter to each traffic direction and that the air thus required for the first or second direction of traffic is substantially extracted from the second or first traffic direction respectively. In this variant, the air for a direction of travel - for example a tunnel tube - is therefore taken in from the other tunnel tube, where the same air flow counter to the direction of travel is generated. At the extremities of the tunnel, the air is as it were turned around from one tunnel tube with respect to its direction of flow and injected into the other tunnel tube. In this preferred variant, this takes place at both ends of the double tunnel tube, thus creating an air flow in the tunnel that is almost permanent when in use, that flows counter to the direction of travel and that is reversed at the extremities. This air flow forms a "closed" packet of air as it were, that is circulated in the double tunnel tube counter to the direction of travel, and is confined as it were in the tunnel. The traffic moves through this "closed" volume of air, whereby the exhaust gasses emitted by the traffic and dust particles are trapped in the tunnel, more particularly in this "closed" packet of air.

[0010] It is hereby advantageous to characterize the ventilation system in that it comprises at least two means for producing an air flow and in that these means are arranged at the level of each extremity of the covered roadway section. Such means preferably comprise at least two ventilating fans.

[0011] In a further preferred embodiment, the ventilation system according to the invention comprises means for producing an air flow that can be regulated separately. In this way it is possible to allow for a difference in traffic intensity and/or average traffic speed between the first and second traffic direction. Because the flow rate of the air flow produced by each ventilating fan can be separately regulated, it is possible to adjust the flow rate of the outflow of air from the tunnel at each end of the tunnel to an averagely low value and preferably to zero. In a traffic direction having a large amount of fast-moving traffic, the ventilating fan arranged at the relevant extremity will, in such a case, supply a higher flow rate than the ventilating fan arranged at the extremity of a traffic direction having slower-moving traffic.

[0012] The ventilation system according to the invention preferably also comprises an air ducting device at the level of the extremities of the covered roadway section. Such a ducting device ensures that air can be conveyed from the roadway section in line with the first traffic direction toward the roadway section in line with the second traffic direction. In a further preferred embodiment, the air ducting device comprises intake and injection apertures arranged around the traffic entrance and/or exit, if required said apertures being provided with blades for guiding the air flow and/or heat exchangers for cooling or warming the air flow. By arranging the apertures around the mouths of the tunnel, the traffic is not impeded on the intake side or on the injection side and yet a reasonably homogeneous flow of air is achieved which can be effectively directed. To further improve this embodiment, the air ducting device preferably comprises connecting ducts provided with ventilating fans between the intake and injection apertures.

[0013] In another preferred embodiment of the invention, the ventilation system is characterized in that it also comprises at least one air outlet situated between the traffic entrance and traffic exit. When in use, the inventive ventilation system, as already described above, will result in a substantially "closed" volume of air in the tunnel, in which the quantity of pollution continually increases. The air outlet ensures that at least a part of this air can escape from the tunnel. The advantage of the air outlet is that the position thereof can be selected and therefore so can the point at which polluted air enters the environment.
If required, the covered road section can be provided with more than one air outlet to spread the quantity of polluted air entering the environment. Although this is possible according to the invention, the air outlets are in principle not intended to spread the quantity of polluted air over the environment. The ventilation system preferably comprises at least two air outlets that can extract a quantity of air from the ventilation system independently of each other, so that the system can thus be kept in equilibrium. Furthermore by doing so, it is possible to achieve different flow rates in the two roadway sections, all depending on the traffic intensity that can vary per roadway section.

[0014] It is furthermore advantageous if the ventilation system comprises means to guide the air present in the covered roadway section toward the air outlet. Such means can for example be additional ventilating fans. In another preferred variant, the ventilation system comprises an air outlet provided with an air treatment device, preferably an air cleaning device. Such devices are known per se and can for example comprise wet gas washers, electrostatic filters, cloth filters, etcetera. By extracting a small sub-flow of the total air packet when the system is in operation and then cleaning it in a cleaning installation, it is possible to prevent the quantity of pollution in the tunnel building up without restriction. A further advantage of the ventilation system according to the invention is that the concentration of pollution in the sub-flow can be really high, thus making the cleaning process highly efficient. The cleaning installation is preferably positioned in the tunnel where there is a high concentration of pollution. This can for example be in the vicinity of the ventilating fans mounted in the tunnel. If required, the air cleaning device comprises a piping system leading to a central filter unit, whereby polluted air can be conveyed to the unit.

[0015] A particularly suitable air cleaning device comprises the combination of a plasma reactor and a wet washer or scrubber that is preferably connected in series. This combination is effective for removing dust and nitrogen oxides (NO_x) in particular. A relatively high volume of nitrogen oxides and relatively low volume of hydrocarbons are generally present in the ventilation air. When the system is in operation, the nitrogen oxides in the plasma reactor are at least partially converted into NO₂ which is at least partially transformed into NO₃^2- by the OH radicals present in the plasma reactor. The nitric acid formed in this way can then be washed out in the scrubber connected in series, possibly together with the dust present in the polluted air. As the volumes of NO_x and dust in the form of suspended solids are relatively low, it is possible to drain the washing water from the scrubber directly into the sewer system if required, which is a considerable advantage.

[0016] In a further preferred embodiment, the wet gas washer is arranged as an NO_x scrubber. The washing medium applied herein is preferably a mixture of hydrogen peroxide (H₂O₂) and nitric acid (HNO₃). Such a process can quickly be implemented at temperatures of between approximately 30°C and 80°C.

[0017] If required, the ventilation system is also provided with an alarm unit and/or a cut-out unit, which operates in the event of an emergency, for example if traffic is at a standstill and/or if there is a fire.

[0018] The invention also relates to a method for ventilating a covered roadway section, the advantages of which have already been described above when describing the ventilation system. The inventive method comprises the production of an air flow in the covered roadway section, such that this air flow in combination with the air flow generated by the traffic on balance results in there being a reduced outflow of air from the traffic exit of the covered roadway section. Further preferred embodiments of the method are described in claims 14 to 18.

[0019] Further features of the invention will emerge from the non-restrictive preferred embodiment of a device according to the invention shown in the following figures. The following are shown:

• Figure 1 schematically shows a top view of an embodiment of the ventilation system according to the invention;
• Figure 2 schematically shows a front view of an embodiment of the ventilation system.

[0020] With reference to the figures, a covered section 1 of a roadway 2 is shown. The roadway comprises a first traffic direction 2a and a second traffic direction 2b, whereby R indicates the direction of travel. The ventilation system comprises means (6a, 6b), preferably ventilating fans, at the level of each tunnel mouth, which are able to produce an air flow L counter to each traffic direction (2a, 2b). The air volume required for the first direction of travel 2a is extracted from the second direction of travel 2b on the left-hand side of the covering 1 in the preferred embodiment shown. The air volume required for the second direction of travel 2b is extracted from the first direction of travel 2a on the right-hand side of the covering 1 in the preferred embodiment shown. The ventilation system further comprises an air ducting device (3a, 3b) which, as shown in Figure 2, in turn comprises intake and injection apertures 5 arranged around the traffic entrance and/or traffic exit. The air ducting device (3a, 3b) further comprises connecting ducts (7a, 7b) provided with ventilating fans (6a, 6b) between the intake and injection apertures. The embodiment shown in Figure 1 comprises roadway sections (2a, 2b) that are situated adjacent to each other. It is also possible according to the invention for roadway sections (2a, 2b) to be situated at a slight distance from each other. In this case, the connecting ducts (7a, 7b) are of a length that exceeds the total width of both roadway sections (2a, 2b). It is advantageous in this case to provide the connecting ducts (7a, 7b) with auxiliary ventilating fans (not shown) to facilitate the air flow through them. With reference to the left-hand side of Figure 1, it is possible in practice according to the invention for air to be taken in from direction of travel 2b by ventilating fan 6a via intake apertures 5. The air is moved through the duct 7a toward the lane having direction of travel 2a, where it is injected in the indicated direction L via injection apertures 5. On the right-hand side of Figure 1, air is taken in from direction of travel 2a by ventilating fan 6b, and then re-injected into the lane having direction of travel 2b via duct 7b and injection apertures 5. In this way, a substantially continuously circulating air flow is created, as schematically shown in Figure 1 via arrows L. Ventilating fans (6a, 6b) are adjusted, such that the air flow L produced by these fans in combination with the air flow generated by the traffic on balance results in there being almost no air flow from tunnel 1 via the traffic exits.

[0021] By way of example, the air in a tunnel flows on average at a rate of 4-5 m/s in the direction of travel, these figures obviously depending on the speed of the vehicles. The counter air flow L produced by the ventilating fans (6a, 6b) also flows at an average rate of 4-5 m/s according to the invention, thus counteracting the rate of the air carried toward the outside by the traffic 10 resulting in an average rate of approximately zero. For a tunnel mouth that is 10 m wide and 6 m high, the ventilating fans (6a, 6b) therefore have to produce approximately 10x6x5 = 300 m³ of air per second. If desired, the requisite flow rate can be further realized by the auxiliary ventilating fans 8 arranged along the length of tunnel 1.
The ventilation system further comprises at least one air outlet 11 situated between both traffic extremities, and if required more than one. Some of the ventilating fans 8 can be used to guide at least a part of the polluted air present in the covered roadway section 1 toward the air outlet 11. This is preferably provided with an air cleaning device (not shown), such as a filter unit for example.
By way of example, the air is injected around at an average flow rate of 300 m³/s through both tunnel tubes (12a, 12b) against the flow of traffic R. If the pollution in the tunnel tube is increased by a factor of approximately 20, a sub-flow to be guided toward the air outlet 11 at a flow rate of 15 m³/s is sufficient to achieve an equilibrium in the concentration of pollution. Because the average concentration of pollution in such a case is approximately twenty times the average concentration that can be expected in tunnel 1 in the prior art due to emissions from vehicles 11 in the tunnel tube 12, the efficiency of the air cleaning process also increases by a factor of 20 compared to what is usual in the prior art, by means of the air cleaning device.

[0022] The ventilation system according to the invention can be applied to all enclosed roads, sunken tunnels and tunnels incorporating closed structures. In practice, a continuous and substantially "closed" air flow is also obtained through both tunnel tubes, whereby the air is as it were condensed, thus causing an increase in the concentration of pollution. This is at odds with the usual ventilation systems in the prior art, which are precisely aimed at rarefying the air in the tunnel tube in order to reduce the concentration of pollution. By maintaining the concentration of pollution in the tunnel tubes at an almost constant level according to the invention, it is possible to clean the air in a cost-effective fashion.

Claims

1. Ventilation system for a covered roadway section, said system comprising means to produce an air flow in the covered roadway section, characterized in that the means are arranged such that they can produce an air flow counter to the traffic direction, such that the air flow realized in this way in combination with the air flow generated by the traffic on balance results in there being a reduced outflow of air from the traffic exit of the covered roadway section.

2. Ventilation system according to claim 1, characterized in that the means are arranged such that the air flow realized in this way in combination with the air flow generated by the traffic on balance results in there being almost no outflow of air from the traffic exit of the roadway section.

3. Ventilation system according to any one of the preceding claims, characterized in that the means comprise at least one ventilating fan to produce an air flow in the covered roadway section.

4. Ventilation system according to any one of the preceding claims, characterized in that the roadway section comprises a first and a second traffic direction, in that the means are arranged such that they can produce an air flow counter to each traffic direction and in that the air thus required for the first or second traffic direction is substantially extracted from the second or first traffic direction respectively.

5. Ventilation system according to claim 4, characterized in that it comprises at least two means for producing an air flow and in that these means are arranged at the level of each extremity of the covered roadway section.

6. Ventilation system according to claim 5, characterized in that the means for producing an air flow can be regulated separately.

7. The ventilation system according to any one of the preceding claims, characterized in that the system also comprises an air ducting device at the level of the extremities of the covered roadway section.

8. Ventilation system according to claim 7, characterized in that the air ducting device comprises intake and injection apertures arranged around the traffic entrance and/or traffic exit.

9. Ventilation system according to claim 8, characterized in that the air ducting device comprises connecting ducts provided with ventilating fans between the intake and injection apertures.

10. Ventilation system according to any one of the preceding claims, characterized in that the system further comprises at least one air outlet situated between traffic entrance and traffic exit.

11. Ventilation system according to claim 10, characterized in that the ventilation system comprises at least two air outlets that can extract a quantity of air from the ventilation system independently of each other.

12. Ventilation system according to claim 11, characterized in that the system also comprises means to guide at least a part of the air present in the covered roadway section toward the air outlet.

13. Ventilation system according to claim 12, characterized in that the air outlet is provided with an air treatment device.

14. Ventilation system according to claim 13, characterized in that the air treatment device comprises an air cleaning device.

15. Ventilation system according to any one of the preceding claims, characterized in that the roadway sections are situated at a slight distance from each other, and in that the air ducting device of the ventilation system comprises connecting ducts between both roadway sections, whereby the connecting ducts are provided with auxiliary ventilating fans.

16. Method for ventilating a covered roadway section, comprising the production of an air flow in the covered roadway section such that this air flow in combination with the air flow generated by the traffic on balance results in there being a reduced outflow of air from the traffic exit of the covered roadway section.

17. Method according to claim 16, characterized in that the produced air flow in combination with the air flow generated by the traffic on balance results in there being almost no outflow of air from the traffic exit of the roadway section.

18. Method according to claim 16 or 17, characterized in that the produced air flow is counter to the traffic direction.

19. Method according to any one of claims 16 to 18, characterized in that the roadway section comprises a first and a second traffic direction, each having a traffic entrance and a traffic exit, in that an air flow is produced counter to each traffic direction and in that the air thus required for the first or second traffic direction is substantially extracted from the second or first traffic direction respectively.

20. The use of an air flow produced counter to the traffic direction for ventilating a covered roadway section.

21. Covered roadway section, provided with a ventilation system according to any one of the preceding claims.

Drawing