Abstract:
The invention provides an air purification system in form of tubing, by which particulates of various sizes in the air flow can be collected. The system includes an air inlet, an air outlet and a particulate removing unit located therebetween, the particulate removing unit including a tubing array of material having low dielectric constant, when an air flow passes through the system electrostatic effect is created between the air flow and the tubing material so as to remove the particulates entrained within the air flow. The invention also provides a method for removing particulates from air flow using the electrostatic effect created between the air flow and said material.

Description:
TECHNICAL FIELD 
     The invention relates to an air purification system for removing dust particulates of various sizes contained in the air flowing therethrough. 
     BACKGROUND 
     Various types of air purification system are known in the art. For example, dust filtering screens and/or dust collecting bags are widely used in traditional air purification systems, in which the dust particles are arrested on the dust filtering screens or in the dust collecting bags. This air purification method has an advantage of simplicity; however, it requires cleaning or replacing the dust filtering screens or the dust collecting bags on regular basis, and thus is very inconvenient and also uneconomical. In the meantime, the existence of dust filtering screens or dust collecting bags will also create a relatively high air resistance. This air resistance will block the air flow motion, and therefore lower the efficiency of dust particulate removal. 
     U.S. Pat. No. 7,594,954 discloses an air purification system which can collect dust particulates from air flow by means of electrostatic effect. To this end, this air purification system includes an electrostatic filter, which is provided with several electrodes, including a discharge electrode and a passive electrode being connected to high-potential and low-potential terminals of high voltage power supply respectively. Although achieving a more or less satisfactory dust particulate efficiency, the electrostatic filter requires a high voltage power supply to generate electrostatic effect, which not only increases the operation cost but also complicates the structure of the system. 
     SUMMARY OF THE INVENTION 
     In order to eliminate some or all of the above mentioned problems, the present disclosure aims to provide an air purification system with no extra power supply, which can collect dust particulates with different sizes from the air flowing through the system in an efficient way. 
     This objective is achieved by an air purification system that can create electrostatic effect therein in a spontaneous manner. The system comprises a housing with air inlet and air outlet, and at least one dust particulate removing unit. Surrounding air is introduced into the housing via the air inlet, then flows through the dust particulate removing unit, and is finally discharged out of the housing via the air outlet. According to the present disclosure, the dust particulate removing unit includes a tube array consisting of a plurality of tubes. The material of the tubes is selected so that electrostatic effect will be created when air flows through the tubes. Therefore, dust particulate contained within the introduced air flow can be removed therefrom by the electrostatic effect created, without a need of extra power supply. 
     As known, static electricity can be generated by touching two differing surfaces together and then separating them due to the phenomena of contact electrification and the triboelectric effect. When air flows through a certain surface, the molecules or atoms of air will experience the above mentioned touching-and-separating motion phase, and thus a surface charge imbalance will be generated, which yields static electricity finally. Under this principle, the air purification system according to the present disclosure can remove the dust particulates from air flow by means of electrostatic effect generated spontaneously. Since no extra power supply is needed, the whole system can be operated at a low cost, and the structure of the system can be simplified. In the meantime, the dust particulate removing unit in form of tube array also results in a lightweight structure, Moreover, since no filtration material such as dust filtering screen is necessary, the air flow motion will not be inappropriately blocked. 
     In an embodiment, the system comprises at least two dust particulate removing units, Preferably, the static electricity generated in one dust particulate removing unit has an opposite polarity to that generated in the dust particulate removing unit adjacent to said dust particulate removing unit, Materials that can generate positive or negative static electricity are well known in the art, and can be suitably selected by one skilled in the art. In this way, the dust particulate removing efficiency can be significantly increased by the opposite polarities of static electricity generated in two adjacent dust particulate removing units. 
     In another embodiment, the upstream ends, with respect to the air flow direction, of different tubes in one single dust particulate removing unit are located at different longitudinal positions. Additionally or alternatively, the end faces of the upstream ends of tubes are tilted to the longitudinal direction of tubes. This arrangement can also enhance the static electricity generated, and thus increase the dust particulate removing efficiency. 
     According to a further embodiment, with respect to the air flow direction, tubes of the upstream dust particulate removing unit have a larger diameter than those of the downstream dust particulate removing unit. Additionally or alternatively, the axes of tubes in one dust particulate removing unit deviate from those in the dust particulate removing unit adjacent to said one dust particulate removing unit. Preferably, the deviation is equal approximately to the radius of tube. 
     The tube array in the dust particulate removing unit is mainly provided for removing relatively fine particulates from the air flow. To remove some larger particulates, a dust particulate collector is provided directly under the compartment formed between two adjacent dust particulate removing units. The dust particulate collector advantageously comprises two partial cylinders communicating with each other but with different sizes, and the smaller one is connected to the bottom side of the housing. In this way, larger dust particulates will be effectively trapped inside the side collector. 
     Optionally, an air flow guide is provided in or near the air inlet for introducing the outside air into the housing in a direction non-parallel to the longitudinal direction of tubes. Additionally or alternatively, other air flow guides are provided inside the housing for changing the air flow direction and/or rate. By means of these air flow guide, the electrostatic effect can be enhanced. 
     The air purification system according to the present disclosure can be used in many outdoor or indoor conditions. For example, it can be installed outside a car so that dust will be collected when the car is moving. Moreover, it can be installed at places in a windy environment such as roadside or anywhere inside a building. In addition, it can also be installed on the roof of building so that dust will be collected when normal air stream pass through the system. Obviously, mounting the air purification system on the above mentioned locations is cheap and simple. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The accompanying drawing is provided to facilitate the understanding of the present disclosure. It constitutes a part of the specification but does not restrict the scope of the present disclosure in any aspects. In the drawing: 
         FIG. 1  shows the tubing air purification system according to the invention in a cutaway view; 
         FIG. 2  shows the cross-sectional view of the tubing air purification system along line A-A shown in  FIG. 1 ; 
         FIG. 3  shows the side view of tubes in one dust particulate removing unit; and 
         FIG. 4  shows the stagger arrangement of the tubes in two dust particulate removing units adjacent to each other. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     In the following the present disclosure will be explained in a detailed way with reference to the accompanying drawings. 
     As shown in  FIG. 1 , the air purification system  10  according to the present disclosure is provided with a housing  1 . The housing, in the example as shown in  FIG. 1 , is shaped as a cuboid box. However, one skilled in the art will understand that other shapes of the housing  1 , such as toroid, parallellepipe etc., also fall within the scope of the present disclosure. An air inlet  2  and an air outlet  3  are located on the front side and rear side of the housing  1  respectively. Surrounding air can be introduced, as shown by the arrow, in the housing  1  through the air inlet  2 , and then discharged from the housing  1  through the air outlet  3  after being treated in the air purification system  10 . If necessary, an extraction fan (not shown) can be optionally placed near the air inlet  2  so as to maintain a desirable air flow rate. 
     According to the present disclosure, the air purification system  10  comprises at least one dust particulate removing unit  20 , which is in a form of an array of hollow tubes  25  (which are best shown in  FIG. 2 ). The dust particulate removing unit  20  is structured as a modular unit. Therefore, it can be easily taken out from the housing  1  via an access door (not shown) located in a side of the housing  1  for cleaning or replacement, and then reinserted therein after suitable treatments. As an example, the dust particulate removing unit  20  can be cleaned with ultrasonic means. 
       FIG. 2  is the cross-sectional view of the air purification system  10  along line A-A, which shows, as an example only, the arrangement of the tubes  25  within a dust particulate removing unit  20 . The tube array as shown is a regular array consisting of a total of 20 tubes, in 5 rows and each row 4 tubes. Of course, it is understood that the tube array can be an irregular array so as to be adapted for different shapes of the housing  1 . As shown in  FIG. 2  also, the tubes  25  are held together by means of a holding element  18  so that a modular unit is obtained. In one example, the holding element  18  is an adhesive tape wrapped around the tube array. Of course, the tubes  25  can be also held together through directly applying adhesive to the contact areas  16  of tubes  25 . 
     The tubes  25  in the dust particulate removing unit  20  can be made of materials having low dielectric constant, for example, nylon, silicone rubber, etc. Therefore, when air flows through the tube array electrostatic effect will be created around each of the tubes in a nature way due to the touching-separating interaction between the air flow and the surfaces of tubes  25 . Such spontaneously generated electrostatic effect is capable of capturing fine particulates, e.g. with a size less than 10 μm, from the incoming air flow, and causes the captured dust particulates being adhered to the outer surfaces of the tubes. Therefore, the dust particulates contained in the air introduced in the housing  1  can be removed from the air flow and thus disposed within the spaces  12  formed among the outer surfaces of the tubes  25 . Then, after passing through the tube array, the air with little or no dust particulates will be discharged out of the air purification system  10  into the surroundings through the air outlet  3 . In this manner, the dust particulates can be removed from the introduced air by means of electrostatic effect generated spontaneously; thus there is no need for an extra power supply. Consequently, the whole air purification system  10  can be operated at a low cost. In the meantime, since the extra power supply as in the prior arts is unnecessary, the structure of the air purification system  10  is significantly simplified. Moreover, due to the structure of tube array, the whole dust particulate removing unit and thus the air purification system is light-weighted. Further, in an example the tube  25  can be implemented in form of a drinking straw, leading to a very cost-effective structure. 
     For effectively creating electrostatic effect in the tube array, it is suggested to increase the touching-separating interaction between the air flow passing through the tube array and the surfaces of the tubes. As shown in  FIG. 1 , an optional air flow guide  5  is provided in or near the air inlet  2 . The air flow guide  5  can be implemented as a plurality of vanes which are oriented in a direction non-parallel with the longitudinal direction of the housing  1 , i.e., the longitudinal axes of the tubes  25 . Therefore, when air is introduced into the housing, it flows at a certain angle with respect to the longitudinal axes of the tubes  25 . In this case, the touching-separating interaction between the incoming air flow and the surfaces of the tubes is enhanced, and therefore a high level of electrostatic effect is obtained, which is advantageous for dust particulate removing. Moreover, the housing can be further provided with additional air flow guides for changing the air flow direction and/or rate inside the housing; therefore, the touching-separating interaction can be further enhanced. For example, the additional air flow guide can be implemented as deflection plate, flow restriction structure, and so on, and may be placed in the compartment  50  formed between two adjacent dust particulate removing units. 
     In another example, the electrostatic effect can be also enhanced by selecting a certain geometric parameters of tubes  25 . Tests show that a satisfactory electrostatic effect is obtained if the ratio of the length L of tube  25  to the diameter D thereof is no more than 10, i.e. L≦10D. As a rule, the diameter D of tube  25  generally ranges from 5 to 10 mm; in this case, the length L thereof can be selected as less than 50 to 100 mm correspondingly. According to a particular embodiment, the diameter D of tubes is 5 mm, the length L thereof is 50 mm, the tubes are made of PVC and the flow rate of the incoming air is 1 m/s, then the dust particulate removing efficiency can be as high as 10-35%. 
       FIG. 3  shows an advantageous variant for tube structure according to the present disclosure, In the dust particulate removing unit  20  as shown, although the downstream ends  22  (defined with respect to the air flow direction, which is shown by the arrow indicated in the drawing) of all tubes  25  terminate at one and the same vertical plane, their upstream ends  21  do not locate in one and the same vertical plane; in other words, the upstream end  21  of each tube  25  in one unit does not start from the same longitudinal position. Therefore, a so-called fractal arrangement is obtained. Additionally or alternatively, the upstream ends of some tubes  25  can form an acute angle with respect to the longitudinal direction, as shown at  21   a ,  21   b  in the bottom part of the drawing. Preferably, the upstream end of a tube forms a positive acute angle with respect to the longitudinal direction while that of the adjacent tube forms a negative acute angle with respect to the longitudinal direction. With the fractal arrangement or the tilt end face or the combination thereof, the above mentioned touching-separating interaction can be further enhanced, thus leading to a strong electrostatic effect. 
     Referring back to  FIG. 1 , the air purification system  10  according to the present disclosure comprises two or more dust particulate removing units arranged one behind another along the longitudinal direction of the housing  1 . Thus a compartment  50  is formed between every two dust particulate removing units. In the example shown in  FIG. 1 , three modular dust particulate removing units  20 ,  30 ,  40  are provided in the housing one behind another, and consequently two compartments  50  are formed between the three units  20 ,  30 ,  40 . Optionally, an additional compartment  50  can be provided just before the air outlet  3 . Obviously, the air purification system according to the present disclosure can include more dust particulate removing units and compartments, and the quantities of dust particulate removing units and compartments can be selected by one skilled in the art as needed. 
     As mentioned above, the air purification system  10  according to the present disclosure operates under the electrostatic effect created in the tube array due to the touching-separating interaction between the air flow and the tube surface. In a preferred embodiment, materials of tubes in different dust particulate removing units are different, such that in one unit a positive or negative static electricity is created while in the unit adjacent to said one unit a negative or positive static electricity is created. In other words, the polarities of the static electricity generated in two adjacent dust particulate removing units are opposite to each other. Materials that can generate positive or negative static electricity are well known; for example, rubber fur, glass, nylon and wool etc. can generate positive static electricity, while silicone rubber, Teflon, polypropylene and celluloid etc. can generate negative static electricity. In a preferable embodiment, tubes in a dust particulate removing unit are made of nylon while tubes in the unit therebehind are made of silicone rubber. In this manner, positive static electricity and negative static electricity are alternatively generated in the adjacent dust particulate removing units of the air purification system, and thus the dust removing efficiency can be significantly increased. 
     In the case of several modular dust particulate removing units being provided, the removing efficiency can be further enhanced by means of selecting diameter of tubes in different dust particulate removing units. For example, tubes in one unit are generally made with equal diameter for the sake of convenience; however, the tube diameter can be gradually reduced in different units along the direction of air flow. In the example as shown in  FIG. 1 , the diameter of tubes in the dust particulate removing unit  20  is larger than that of the dust particulate removing unit  30 , which is in turn larger than that of the dust particulate removing unit  40 . 
     As a variant, all the tubes in all the units are of equal diameter; however, the longitudinal axes of tubes in one unit do not align with those in the unit adjacent thereto. As shown in  FIG. 4 , the longitudinal axis  28   a  of tube  25   a  in the dust particulate removing unit  20  deviates from the longitudinal axis  28   b  of corresponding tube  25   b  in the dust particulate removing unit  30  by a distance Δ. With this stagger arrangement the electrostatic effect will be further enhanced, and thus the dust particulate removing efficiency can be maximized. As a preferable example, the distance Δ equals to the radius of the tubes. 
     With electrostatic effect created therein, the dust particulate removing unit is capable of mainly removing relatively fine particulates, say with a diameter less than 10 μm, from the incoming air. However, sometimes there are larger particulates entrapped within the incoming air, which should be desirably removed also. To this end, the compartment  50  between two dust particulate removing units can act as a structure for removing larger particulates. This is achieved by the turbulence phenomenon naturally generated in the compartment when the incoming air flow leaves one unit and is going to enter into another one. Due to the turbulence phenomenon generated in the compartment  50 , larger particulates will be trapped into a bottom collector  70  located directly under the compartment  50 . To collect larger particulates more effectively, according to an example of the present disclosure, the length L′ of the compartment  50  is preferably selected as shorter than the length L of the dust particulate removing unit  20 . In a particular embodiment, the length L′ of the compartment  50  is less than about half of the length L of the unit  20 , i.e., L′≦L/2. Tests show that a favorable result can be obtained when L′≦L/2. 
     Moreover, in an advantageous embodiment the bottom collector  70  is comprised of two cylinders with different diameters but communicating with each other. In other words, the cross section of the bottom collector  70  is shaped as calabash. The portion of the smaller cylinder is connected to the housing  1 . In this way, the larger dust particulates separated from the air flow will be effectively trapped in the larger cylinder of the bottom collector  70  with little possibility of escaping therefrom, and thus the dust removing efficiency can be significantly increased. To facilitate cleaning the dust particulates accumulated therein, the bottom collector  70  is provided with a sealing plug (not shown), which, for example, is located at the bottom of the larger cylinder. The sealing plug can be pulled out so that one can clean the dust particulates accumulated in the bottom collector  70  by suitable tools. 
     It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present invention extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.