Abstract:
The invention relates to apparatus and a method for separating solid particles from fluids and particularly gas flows. The apparatus is particularly for use in conjunction with an internal combustion engine or vacuum cleaner. The apparatus includes a cyclone separator which has at least two axial common cyclone separator elements, an inner and outer element, in conjunction with a two-stage electrostatic precipitator. The apparatus allows the filtration of fluid effectively, even if the flow varies over time.

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is a national stage application under 35 USC 371 of International Application No. PCT/GB2007/002081, filed Jun. 7, 2007, which claims the priority of United Kingdom Application Nos. 0611296.5 and 0621935.6, filed Jun. 8, 2006, and Nov. 3, 2006, respectively, the contents of which prior applications are incorporated herein by reference. 
     FIELD OF THE INVENTION 
     The invention to which this application relates is to apparatus and a method for separating solid particles from fluids and particularly gas flows and in particular, although not necessarily exclusively, for use in conjunction with internal combustion engines or vacuum cleaners, to act as a means for filtering the said particles from an incoming air flow. 
     BACKGROUND OF THE INVENTION 
     A problem with apparatus of this type is that if the particles carried in the airflow are not effectively removed without a large energy loss across said apparatus, then the operation of the engine may be adversely affected and/or the operation of the vacuum cleaner is not sufficiently efficient. 
     SUMMARY OF THE INVENTION 
     An aim of the present invention is to provide a means whereby particles can be efficiently removed from a fluid flow thereby allowing the efficient removal of particles from the same and improving the operation of the apparatus with which the cleaning apparatus is used. 
     In a first aspect of the invention, there is provided apparatus to perform a cleaning action by removing particles from a fluid flowing through said apparatus, said apparatus comprising a cyclone separator means positioned substantially in the path of said fluid flow, said means having one or more inlets and fluid flow guide means, and at least one electrostatic precipitator means positioned substantially in said flow and wherein said cyclone separator means includes at least two axial flow cyclone separator elements provided in a concentric configuration along a common axis. 
     In one embodiment each cyclone element in order from the outer separator element has an increased separation efficiency so as to allow successively smaller sizes of particles to be removed from the fluid flow. 
     In one embodiment the inlets are provided tangentially to the fluid flow to guide the fluid in a desired path into the cyclone separator means. 
     In one embodiment, a multistage electrostatic precipitator is provided, typically a two stage precipitator. 
     In one embodiment, the apparatus is provided in conjunction with an internal combustion engine and the fluid flow with which the system is utilised, is an air flow passing towards the internal combustion engine to aid the operation of the engine. 
     In an alternative embodiment the cleaning apparatus is provided in conjunction with a vacuum cleaner. 
     In one embodiment, the apparatus includes a collection means such as a hopper in which particles which are removed from the fluid flow by the apparatus, can be collected and discarded as required. 
     In one embodiment, the apparatus includes an inlet duct, which duct directs the fluid flow and also houses a voltage emitter rail. 
     Typically, a negative voltage is applied to the emitter rail to provide particles in the fluid flow with a negative voltage and at least one plate of the electrostatic precipitator is positively charged so as to attract the negatively charged particles to the same and allow the same to be collected for subsequent disposal. 
     Typically, one or more plates in the precipitator, are provided with a negative charge so as to cause the negatively charged particles, to be accelerated from those relatively charged plates towards the at least one positively charged plate in the precipitator. 
     Typically, a plurality of the negative and positively charged plates are interspersed alternately such that adjacent plates in the precipitator, have opposing charges. 
     Typically, the cyclone separator means is positioned intermediate the emitter rail and in advance of the electrostatic plates with respect to the fluid flow such that the fluid flow passes through the cyclone separator prior to reaching the electrostatic plates. 
     In an alternative embodiment the precipitator is located upstream of the cyclone separator means. 
     Typically, the cyclone separator means induces a circular fluid flow as the fluid passes to the electrostatic plates and, furthermore, the rotational flow which is created by the cyclonic separator, causes particles of a certain size or greater in the fluid to be thrown against the external surfaces of the cyclonic separator, allowing those particles to be removed from the fluid flow. This allows the cyclonic separator to act as a first stage filter to allow larger particles to be removed from the fluid flow prior to the fluid reaching the electrostatic plates. This serves to improve the efficiency of the removal of particles from the fluid flow. 
     Preferably the cyclone separator means is located such that the airflow is relatively high and the precipitator means is located where the airflow is relatively low. 
     In one embodiment the precipitator includes a plurality of plates which are mounted on the outer surface of the outer cyclone separator element. 
     In a further aspect of the invention there is provided a fluid flow to an internal combustion engine, said fluid flow passing through apparatus including a cyclone separator means and an electrostatic precipitator means positioned substantially in the flow of said fluid and wherein the cyclone separator means includes at least two concentrically mounted cyclone separator elements. 
     Typically the cyclone separator elements are mounted on a common axis. 
     In either of the above embodiments of apparatus, the use of the electrostatic precipitator and/or axial cyclone separator, allows the removal of particles from the fluid flow and hence prevents the said particles from reaching the internal combustion engine and it is found that the use of the axial cyclone separator and subsequently the electrostatic precipitator allows improved and efficient filtering of the particles from the fluid. 
     In a yet further aspect of the invention, there is provided apparatus to remove particles from the flow of fluid entering a vacuum cleaner, said apparatus including a cyclone separator means and precipitator unit wherein, said cyclone separator means includes at least two concentric axial flow cyclone separator elements arranged from the outer element in order of increasing efficiency. 
     In one embodiment, the axial cyclone separator is selected so as to allow particles of a larger size to be removed from the fluid flow prior to the fluid reaching the electrostatic precipitator and the control of the precipitator is selected so as to allow particles of a selected size to be removed from the fluid flow. 
     In a yet further aspect of the invention there is provided cleaning apparatus including a cyclone separator and an electrostatic precipitator wherein the precipitator includes a plurality of plates which are mounted on the outer surface of the outer cyclone separator element. 
     This assembly serves to attract particles to the plates, especially those smaller particles which would not be thrown to the wall of the outer cyclone and hence allows these smaller particles to also be removed from the fluid flow. 
     Typically the precipitator plates collect particles through electrostatic attraction and mechanical impaction; and is required as, on occasion, the swirl induced airflow which throws the majority of particles to the outer cyclone wall cannot separate the smallest particles. Thus, in accordance with the invention the particles which circulate the plates and do not follow the same path as particles of a greater mass are efficiently removed from the airflow through impaction on the plates and electrostatic attraction to them. 
     Thus, this assembly can be used to advantage in any form of cyclone separator whether it includes one or a plurality of cyclone separator elements. 
     This particularly advantageous aspect of the design serves to effectively remove small particulates, whereas in prior art devices there is no means possible to separate particles which are not thrown to the outer wall of the cyclone. 
     Typically, in whichever embodiment the cyclone separator means is positioned in a relatively high airflow speed and the precipitator means is positioned in a relatively lower airflow speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Specific embodiments of the invention are now described with respect to the accompanying Figures wherein: 
         FIG. 1   a  shows a detailed view of the apparatus in one embodiment; 
         FIG. 1   b  shows an exploded view of the components of the apparatus in accordance with  FIG. 1   a;    
         FIG. 2  shows a sectional view of the apparatus with an inlet pipe removed; 
         FIG. 3  shows a plan view of an emitter rail of the apparatus; 
         FIG. 4  shows a side view of the emitter rail of  FIG. 3 ; 
         FIG. 5  shows a plan view of the inlet of the apparatus; 
         FIG. 6  shows a plan view of a cyclone guide element in accordance with one embodiment of the invention; 
         FIG. 7  shows a side view of the cyclone guide element of  FIG. 6 ; 
         FIG. 8  shows a plan view of an inner cyclone guide element; 
         FIG. 9  shows a side view of the inner cyclone guide element. 
         FIG. 10  shows a cut through view of the outer casing; of the cyclone separator. 
         FIG. 11  shows a plan view of the casing of  FIG. 10 , 
         FIG. 12  shows a plan view of a particle collecting plate; 
         FIG. 13  shows a plan view of an emitter plate; 
         FIG. 14  shows an arrangement in a schematic manner in accordance with one embodiment of the invention; and 
         FIG. 15  shows an arrangement in a schematic manner in accordance with a further embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in  FIGS. 1   a  and  b , the apparatus in accordance with the invention provides an electro-inertial cleaning apparatus and the apparatus, in this embodiment, comprises an inlet tract  1  which extends from the main body of the system  4  and  9 . The apparatus can be positioned at the front, in this case of a vehicle, so as to receive a cooling air flow which is denser and has a higher oxygen content resulting in more efficient combustion when supplied to the internal combustion engine within the vehicle. Thus airflow does however have to be provided in a relatively “clean” form to the engine to therefore provide the benefits when the airflow reaches the engine (not known) downstream of the cleaning apparatus. 
     The inlet tract&#39;s other purpose is to provide a mount for a high voltage emitter rail  2 . The inlet tract may take any shape or form of that is required to receive the airflow. 
     A removable hopper  10  enables particles which are removed from the airflow by the apparatus to be emptied at relevant service intervals or when full. 
     The construction of the inlet tract  1  and inlet part  4  and main body  9  can be from a polymer with a high deflection temperature to keep the air within the system cool and withstand heat from the engine bay. 
     The inlet  4  connects to  9  via a screw thread connection.  FIG. 10  and feature  25  shows the thread. This eliminates any fasteners required, reducing assemble times and components costs, and allows fast disassemble for any cleaning of the system that may be required. A rubber seal  39  locates between inlet  4  and main body  9  as shown in  FIG. 2  forming an airtight seal. 
     The initial ionisation of the particles occurs in inlet  4  where a negative voltage is applied to the emitter rail  2  through the wire  3 . Particles which are sufficiently charged with a negative voltage collect on positively charged plates  6 , of the multistage electrostatic precipitator. Plates  7  are negatively charged creating an electrostatic field repelling particles towards the positive plates. The spacing of the plates is sufficient so as to avoid arcing and are insulated by a cyclone guide element  5  on which they are mounted. The plates are connected to the respective positive and negative high voltage supplies through the two wires  11  and  12  which run through the centre of guide  5 . 
     As shown in  FIG. 5  holes  17  allow the wires to extend to a high voltage supply. So as to reduce the number of wires, connection rails  35  and  36  provide voltage from the plates below the entrance  20  to those above it as shown in  FIG. 2 . Rubber insulators  37  prevent arcing between the plates. 
     As shown in  FIGS. 12 and 13  features  40  and  41  allow the plates to be assembled on  5 . They lock in place by turning to locate on protrusions  21 .  FIG. 13  shows the spiked shape of negative plate  7 . This is to increase corona discharge from the plates and allows further ionisation of particulates to aid collection efficiency. The plates  6  and  7  are ideally constructed from a non-corrosive metal such as stainless steel. 
     The efficiency of the electrostatic precipitator and the plate&#39;s collection decreases as the airflow increases, therefore more effective collection is expected when the residence time of particulates in the system is sufficient for them to initially gain a negative charge and then collect on the positive plates. The two stage electrostatic precipitator is effective at collecting particles at voltages in order of 10,000 volts D.C. 
     To prevent particulate build up on the plates and potential re-entrant of particles the high voltage supply is integrated into the vehicle engine control unit (ECU). The circuit turns off when the airflow is sufficiently high to allow the particles to be purged through the two axial cyclone separators. As the particles lose their charge due to the circuit turning off, the airflow cleans the plates preventing caking and other undesirable affects. 
     The emitter rail shown in  FIGS. 3 and 4  is composed of a single piece construction and entails many emitter points so as to maximise corona discharge from these points. The material is preferably a non-corrosive metal such as stainless steel. The plastic construction of the inlet tract  2  insulates the emitter rail and the emitter rail cover  15  prevents accidental contact being made. The high voltage wire  3  connects the emitter rail to a negative DC high voltage. 
     The inlet  4  consists, in accordance with one embodiment of the invention, of a tangential protrusion that introduces air to a cyclone separator element  5  as shown in  FIGS. 6 and 7 .  FIGS. 6 and 7  show the shape of the helical guide element  22  that induces a swirl on the gas flow. This is the first stage of separation and larger particulates which are subject to centrifugal forces are thrown to the walls of main body  9  and exit through the large slits  24  as shown in  FIG. 10 . This serves to eject larger particulates prior to entry to the smaller inner cyclone, preventing fouling and adverse operation of the inner cyclone. 
     The particulates collect in the hopper  10  which fits over the main body  9  and is sealed by an interference fit between rubber seal  38  as shown in  FIG. 2 . The cyclone guide element  5  incorporates a location slit  23  that locates on  18  as shown in  FIG. 5  ensuring correct assembly.  FIG. 10  shows a location slot  29  which the end of  5  secures in. 
     The flowing gas has to pass through entrance  20  as shown in  FIG. 2  so as to exit through  13 . This is the entrance to the second axial cyclone separator element and its purpose is to separate small particulates in the order of 10 microns at high airflows when electrostatic collection would be low. The entrance  20  is protected by negatively charged plates  7  which repel any particulates. The entrance is positioned sufficiently far enough from the inlet so particles have time to collect on the plates, thus reducing the amount of particulates that may enter the inner cyclone. 
       FIGS. 8 and 9  show the second cyclone guide element  51  that fits inside  5  and ensures a swirling flow is induced upon the gas due to the curved helical feature  30 . Feature  32  locates within  5  ensuring correct assembly. 
     The protrusion  31  stabilises the vortex generated and ensures that it does not break down before particulates have been purged. Particles which are subject to centrifugal forces and are thrown to the inner wall of  5  and exit through slits  27  as shown in  FIG. 11 .  FIG. 10  shows the protrusion  28  that extends within  9  to extract the clean gas flow. The hopper  10  is tapered to allow particles which are purged to descend without re-entrant occurring. 
     The two axial cyclone separator elements enable small particles to be purged at high airflows and the use of no swirl vanes ensures that clogging of the system never occurs. 
     To further reduce the pressure drop through the system pressure recovery vanes may be incorporated into the exit  13  to convert the swirling flow back into a laminar flow. This is an optional component and depends on the intended application of the system. 
     The size of the system and ratio of cyclone guide separator element  5  to body  9  may change to accommodate different engine requirements. Similarly the inlet  4  and outlet sizes  13  may also vary. 
     It should be appreciated that the use of the electrostatic precipitator and axial flow cyclonic separator means, in combination with the separator elements mounted concentrically along a common axis in order of increasing efficiency means that small particles can be effectively removed from the gas flow with a relatively low energy consumption. These advantages mean that the need for filter media to be used in engine applications is removed, or if filter media is still used in conjunction with the apparatus in accordance with the invention the life of the filter media is greatly extended without excessive energy consumption. 
     Referring now to  FIGS. 14 and 15  there is illustrated the manner in which particles Z and Y in gas flow  54  can be separated from the flow as it passes the electrostatic precipitator plates  53  mounted on the external face  51  of the cyclone separator element  5 . In  FIG. 15  one cyclone separator element  5  is provided whereas in  FIG. 14  two commonly axially mounted separator elements  5 ,  8  are provided. 
     It is illustrated how the larger particles Z are separated from the gas by the flow induced by the cyclone separator element  5 . The smaller particles Y are separated from the gas flow by attraction to the electrostatic plates  53  and impaction onto the same. The apparatus may also be used with suction means to allow an airflow to be created through the cleaning apparatus which could be, for example an engine motor or fan. The apparatus may also include further cleaning media  55  as required. 
     The arrangement of  FIGS. 14 and 15  may in one aspect of the invention be provided with a single or multiple cyclone separator elements. The outer surface  51  of the outer cyclone guide element  5  is used to mount one or more plates of the electrostatic precipitator which are provided with a charge which is such so as to cause particles which are within the fluid flow which passes the plates, to be attracted to the plates. This therefore allows particles, and particularly smaller particles, to be collected on the plates and hence removed from the fluid flow without the use of the cyclone separating means to do so. This is found to be of a particular advantage with regard to small particles, as it has been found that on occasion, the small particles may not be effectively removed by the cyclone separator means. 
     Thus, in combination, the use of both the electrostatic precipitator and the cyclone separating means, allow small and larger particles to be removed from the fluid flow using the respective apparatus. The provision of the plates on the external surface of the outer cyclone guide element is found to be particularly effective in removing the smaller particles from the fluid flow.