Patent Publication Number: US-2019176171-A1

Title: Misting apparatus and method of use

Description:
The invention relates to a misting apparatus for producing mist from a pressurized liquid, such as water. 
     Dust is a potential hazard to personnel, for example at construction sites and industrial facilities. It is known to provide dust suppression units which eject a plume of water droplets, or mist, in order to take dust out of suspension in the air. The physical mechanism is related to the relative size between the droplets in the mist and the dust particles. Similar technology is used, typically with smaller droplets, for odour control (for example, at sewage treatment works and other facilities that suffer from odours). 
     Known dust or odour suppression units have an electrically-powered fan and a ring of water-injecting nozzles to emit a spray. Such units are typically powered by relatively high voltage AC electrical power, for example 415 volt 3-phase power. 
     Known dust or odour suppression units are typically used on large sites where there may be a regulatory requirement to do so. As such, they are typically bulky, may require professional installation and safety monitoring, and may therefore be expensive to operate. 
     According to a first aspect there is provided a misting apparatus for producing a mist from a pressurized liquid, comprising: a fan shaft having a rotational axis; a rotary jet assembly configured to drive the fan shaft and comprising a radially extending arm configured to convey the pressurized liquid to a jet nozzle, wherein the jet nozzle is configured to eject the pressurized liquid in a jet to generate a jet reaction force having a tangential component; a fan coupled to the fan shaft for driving an airflow; and a spray nozzle configured to eject the pressurized liquid into the airflow to produce a mist. 
     There may be a plurality of radial arms, for example two diametrically opposed arms. The fan shaft may be integral with the rotary jet assembly. The fan shaft or hub of the rotary jet assembly may comprise a fluid pathway for providing the liquid to the rotary jet assembly. The fan shaft may comprise a fluid pathway for providing the liquid to the spray nozzle. 
     The jet assembly may comprise a manifold configured to receive the pressurized liquid. The manifold may comprise: a first outlet configured to provide the liquid to a conduit extending along the radial arm to the jet nozzle; and a second outlet comprising the spray nozzle or configured to provide liquid to the spray nozzle. Accordingly, the manifold rotates in use. A hub and/or shaft of the jet assembly may comprise the manifold. 
     The fan shaft may be coupled to a mount by a rotary seal. The mount may provide pressurized liquid to the fan shaft through the rotary seal. The fan shaft may be coupled indirectly, for example via a hub of the rotary jet assembly. 
     The misting apparatus may be for receiving a pressurized liquid of variable pressure. The jet nozzle and the spray nozzle may be fluidically coupled so that the flow rate of liquid through the jet nozzle is approximately proportional to the flow rate of liquid through the spray nozzle over a pressure range. For example, the flow rates may be substantially proportional over a range of approximately 50-200 bar. 
     The spray nozzle may be mounted to rotate together with the fan shaft in use. For example, the spray nozzle may be directly mounted on the fan shaft, or on a component fixed to rotate with the fan shaft, or may be integral with the fan shaft. The spray nozzle may be detachably attached to the fan shaft. 
     The fan may comprise a plurality of blades each having a radially outer tip. The jet nozzle may be disposed radially outward of the tips of the blades. 
     The misting apparatus may further comprise a housing. The housing may comprise a jet containment disposed around the rotary jet assembly for capturing liquid ejected from the jet nozzle. The misting apparatus may comprise a collector for collecting liquid captured by the jet containment for recirculation to a pump or reservoir. The jet containment may be configured so that liquid captured therein flows under the action of gravity to the collector. 
     The misting apparatus may further comprise a drive unit coupled to the fan shaft so as to be driven to rotate by rotation of the fan shaft. The drive unit may be for driving a liquid return pump for pumping collected liquid from the collector. The misting apparatus may comprise an attachment point for detachably attaching a liquid return pump so that in use a liquid return pump attached to the attachment point is driven by the drive unit. For example, the attachment point may be configured to engage with the liquid return pump by a quick release or snap-fit mechanism. The attachment point may be formed in the collector or another part of the housing. The attachment point may comprise an opening for insertion of a shaft of the liquid return pump to engage with the drive unit. A shaft of the drive unit may protrude through or adjacent to the attachment point for engaging with the liquid return pump. The misting apparatus may further comprise a liquid return pump coupled with the drive unit and arranged to pump liquid from the collector. 
     The jet containment may have a radially inner opening through which the radial arm of the rotary jet assembly extends. The jet containment may have an axial extent which is greater than the axial extent of the opening so that liquid captured in the jet containment can flow along a radially inner wall of the jet containment axially adjacent the opening. The jet containment may comprise a radially outer wall to contain liquid ejected from the jet nozzle and a radially inner wall to inhibit ejected liquid from entraining in the airflow driven by the fan. 
     The radial arm may extend past the radially inner wall of the jet containment so that the jet nozzle is radially outward of the radially inner wall. The lip of the radially inner wall axially adjacent the radial arm may be provided with a flange to inhibit ejected liquid from entraining in the airflow driven by the fan. The jet containment may comprise a forward portion forward of the radially inner opening and bounded by a forward radially inner wall and/or an aft portion aft of the radially inner opening and bounded by an aft radially inner wall. 
     The housing may comprise an airflow nozzle downstream of the jet containment, and the jet containment may define a channel radially outward of the airflow nozzle for capturing liquid ejected from the jet nozzle. The jet nozzle may be radially outward of the airflow nozzle. 
     The housing may comprise an airflow intake upstream of the jet containment, and the jet containment may define a channel radially outward of a junction between the airflow intake and the jet containment. The junction may be defined where an axially extending portion of the airflow intake and a radially extending portion of the jet containment meet. The jet nozzle may be radially outward of the junction between the airflow intake and the jet containment. 
     The jet containment may define a substantially annular channel. 
     The jet nozzle may be configured to eject the pressurized liquid along a direction having an axial component. Accordingly, when the misting apparatus comprises a jet containment, the jet may be directed axially away from a radially inner opening in the jet containment that is provided for the radial arm. This may prevent ejected liquid from being entrained in the airflow. 
     The apparatus may comprise a housing including an airflow nozzle, and the apparatus may further comprise a drip collector coupled to a downstream end of the airflow nozzle, the drip collector having a radially inner wall defining an outlet of the apparatus radially within the downstream end of the airflow nozzle, a radially outer wall disposed around the downstream end of the airflow nozzle, and a channel therebetween for collecting drips conveyed along the wall of the airflow nozzle. The drip collector may have a plurality of holes in the radially inner wall. Such holes may prevent buffeting. 
     The misting apparatus may further comprise a composite line for delivery of pressurized liquid from a source of pressurized liquid and for return of liquid captured from the jet nozzle to the source of pressurized liquid. The composite line may be flexible. 
     According to a second aspect there is provided an apparatus, comprising: a portable device for pressurizing liquid; a misting apparatus in accordance with the first aspect fluidically coupled to the portable device to receive pressurized liquid. The misting apparatus may be mounted above the portable device on a support. The support may be a post, such as a telescopic post. 
     There may be a plurality of misting apparatus in accordance the first aspect each fluidically coupled to the portable device to receive pressurized liquid. The portable device may be configured to pressurize liquid to between 30 bar-200 bar. The portable device may be configured to provide pressurized liquid at a flow rate of between 5-60 litres per minute. 
     The liquid may be water. 
     According to a third aspect there is provided a method of suppressing dust in a hazardous environment or controlling odour, the method comprising: providing an apparatus in accordance with the first aspect with pressurized liquid between 30 bar-200 bar at a flow rate of between 5-60 litres per minute to eject a mist to suppress dust or control odour. 
     The invention may comprise any combination of the features and/or limitations referred to herein, except combinations of such features as are mutually exclusive. 
    
    
     
       The invention will now be described, by way of example only, with respect to the accompanying drawings, in which: 
         FIG. 1  schematically shows a side view of a portable device for pressurizing a liquid with a misting device mounted on a post; 
         FIG. 2  schematically shows in perspective view an exterior of the misting device of  FIG. 1 ; 
         FIG. 3  schematically shows a perspective view of inner components of the misting device of  FIG. 1 ; 
         FIG. 4  schematically shows a side view of the inner components of  FIG. 3 ; 
         FIG. 5  schematically shows a cross-sectional side view of the rotary jet assembly and housing of the misting device of  FIG. 1 ; 
         FIG. 6  schematically shows a perspective exploded view of the misting device of  FIG. 1 ; 
         FIG. 7  schematically shows a perspective view of a return pump arrangement for the misting apparatus of  FIG. 1 ; and 
         FIG. 8  schematically shows a portable device for pressurizing a liquid with a plurality of misting devices coupled by flexible conduits. 
     
    
    
       FIG. 1  shows a portable device  10  for pressurizing a liquid, in particular water, and a misting apparatus  100 . The device  10  is a portable pressure unit typically used for pressure washing, and in this particular example comprises a wheeled trailer  12  supporting a generator  14 , water reservoir  16  and pump  18 . 
     A misting apparatus  100  is provided mounted on a support post  200  to eject a mist of water droplets from an elevated position. In this example, there is a supply line  206  for supplying pressurized water from the portable device  10  to the misting apparatus  100 , and a support post  200  acts as a return line for recirculating water, as will be described below. 
       FIG. 2  shows exterior components of the misting apparatus  100  in further detail. The misting apparatus  100  includes a housing  102  extending along a central axis  104  of the apparatus  100  and comprising an air intake  106 , a jet containment  108  and an airflow nozzle  110  provided with a drip collector  112 . The air intake  106  is for receiving air from the surrounding environment. It comprises an aft opening  114  fitted with a safety grate  116 , and a substantially conical body tapering forwardly to accelerate the airflow therethrough. 
     The jet containment  108  is disposed downstream of the air intake  106  and extends radially outward from a circular junction between the air intake  106  and the jet containment  108  to define an annular channel disposed radially outwardly of an air flowpath through the misting apparatus  100 , as will be described in detail below. 
     The airflow nozzle  104  is downstream of the jet containment  108  and comprises a frustoconical tapering body at a taper angle of approximately 15° downstream. In this example apparatus, the air intake  106 , jet containment  108  and airflow nozzle  104  are generally axisymmetric and coaxial with one another. 
     Below the jet containment  108  there is a collector  118  for collecting water captured within the jet containment  108 . The collector is generally cuboidal with curved upper edges to couple to a lower portion of the jet containment  108  having openings for water to flow through. In this example the collector  118  is a separate component from the jet containment  108 , which aids in servicing and maintenance, but in other examples may be integrally formed with the jet containment. 
       FIGS. 3 and 4  show internal components of the misting apparatus  100  located within the housing  102 . A circular mounting ring  120  comprising a central hub, radially outer rim and supporting spokes is configured to be installed within the housing against an aft radially-extending annular wall of the jet containment, for example by bolts extending through the jet containment  108  and through the mounting ring  120 . When assembled in the housing  102 , the mounting ring  120  has a central opening which is coaxial with the axis  104  of the misting apparatus, which is therefore defined as an axis of rotation for rotational components of the misting apparatus, as will be described in detail below. 
     A rotary seal  122  having an aft stationary part and a forward rotating part is mounted to the mounting ring  120  upstream of the mounting ring, for example by a series of bolts or rivets that extend through a flange of the rotary seal  122  and the hub of the mounting ring  120 . The rotary seal  122  is configured to receive a high pressure liquid in an axial inlet  124  of the stationary part, for example water at up to  300 bar, and to discharge the high pressure liquid through a rotating outlet of the rotating part. In this example, the rotary seal  122  is configured so that the outlet is coaxial with the rotational axis  104  of the mounting assembly. In this example, the rotating part is in the form of a rotatable seal shaft  126  that extends through the central opening of the mounting ring  102 . 
     A rotary jet assembly  130  is mounted on the seal shaft  126  downstream of the mounting ring  120  so as to rotate together with the seal shaft  126  and receive pressurized liquid therefrom. In this example, the jet assembly  130  comprises a hub  132  mounted on the seal shaft  126 , a fan shaft  134  extending from the hub  132 , and two radially extending arms  136  extending from the hub  132 . In this particular example, the hub  132  and fan shaft  134  are integrally formed, but in other examples they may be distinct components coupled to rotate together. 
     In this example the two radial arms  136  are diametrically opposed from one another, such that they extend along the same diametrical and radial line through the hub  132  Each radial arm  136  has a radial extent such that its distal end extends into the annular channel defined by the jet containment  108 . Each radial arm  136  is provided with a jet nozzle  138  configured to eject a jet of pressurized liquid along a direction so as to generate a jet reaction force on the jet assembly  130  having a tangential component. In this particular example, each radial arm defines a fluid pathway for conveying fluid from a manifold within the jet assembly (in particular, within the hub  132  and shaft  134 ) to the respective jet nozzle  138 . As shown in  FIGS. 3 and 4  each jet nozzle  138  extends substantially tangentially with respect to the rotational axis  104 , but in other examples, the or each jet nozzle may extend along a direction inclined with respect to the tangential direction, as will be described in detail below. It will be appreciated that in other examples, there may be a single radial arm  136 , or more than two radial arms  136 . 
     The fan shaft  134  extends along the rotational axis  104  forwardly of the hub  132 . A fan  140  is mounted on the fan shaft  134  so as to rotate together with the fan shaft  134 . In this example, the fan  140  comprises a fan hub  142  having a central opening for locating over the fan shaft  134 , for example by bolts extending through axial holes in the hub and arranged to be received in a flange of the fan shaft  134 . The fan  140  further comprises a plurality of fan blades  144  radially extending from the hub  142  and configured to rotate to propel airflow through the misting apparatus in a direction from the air intake  106  to the airflow nozzle  110 . 
     The fan  140  has an axial location downstream of the hub  132  of the rotary jet assembly  130 , and also downstream of the jet containment  108  and within the airflow nozzle  110 . In this example the fan blades  144  have a radial extent which is less than the radial extent of the radial arms  136  and the radial position of the jet nozzles  138  of the jet assembly  130 . For example, the radius of the tips of the fan blades  144  may be approximately 15 cms, whereas the radial position of the jet nozzles  138  may be approximately 20 cms. 
     The fan shaft  134  extends through and axially forward of the fan  140  and in this example terminates at a nozzle connection  150  at the extreme axial end of the fan shaft, coaxial with the rotational axis. The nozzle connection  150  is configured to receive a spray nozzle  152 , which in this example is detachably attachable to the nozzle connection  150 , for example by a screw thread or other fastener. The spray nozzle  152  therefore rotates together with the fan shaft. In this particular example, the spray nozzle  152  has a plurality of angularly spaced holes configured to eject respective jets of liquid substantially axially towards a radially outwardly extending conical surface of the nozzle  152 , such that the jets impinge on the conical surface and are dispersed radially outwardly into an airflow through the fan  140  to form droplets of a mist, as will be described in detail below. The fan shaft  134  defines an internal fluid pathway which fluidically couples the nozzle connection  150 , and thereby the spray nozzle  152  received therein, with the manifold within the jet assembly  130 . 
     The manifold may be considered to comprise the fluid pathways through the or each rotary arm to the jet nozzles and the fluid pathway through the fan shaft  134  to the nozzle connection and nozzle. The manifold is defined within the rotary jet assembly and is thereby configured to rotate together with the radial arms  136 , jet nozzles  138  and the fan  140 . In particular, the manifold comprises an inlet to receive pressurized liquid (in this example water from the outlet of the seal shaft  126 ), and outlets for the or each jet nozzle  138  and the spray nozzle  152 . Each outlet may be considered the outlet to the individual fluid pathways extending through the radial arm, or the outlet of such fluid pathways at the respective nozzles  138 ,  152 . 
     In this example, the manifold has no control valves or other valves between the jet nozzles  138  and the spray nozzle  152 , such that the amount of flow through each nozzle (and fluid pathway thereto) depends on the pressure drop through the respective nozzle and supply route, as will be described in detail below with respect to a method of use. 
     In other examples, there may be a spray nozzle formed in the fan shaft (rather than a detachably attachable spray nozzle), for example one or more holes formed in the fan shaft  134 . Such holes may be radially extending in a side (e.g. a cylindrical side) of the fan shaft  134 , and/or may be formed in an axial end face of the fan shaft  134 . 
       FIG. 5  shows a partial cross-sectional view of a radial arm  136  and jet nozzle  138  extending into the jet containment  108 . As described above, the jet containment  108  defines an annular channel  160  that in this example extends radially outwardly of a junction  162  between the aft air intake  106  and the jet containment  108 , and also radially outwardly of the proximal end (i.e. the end towards the middle of the apparatus as a whole) of the airflow nozzle  110 .  FIG. 5  shows further features of this arrangement. In particular, the jet containment has aft and forward radially extending walls  164  coupled by a radially outer wall  166 , and also two radially inner walls: an aft radially inner wall  168  and a forward radially inner wall  170 . The radially inner walls define therebetween an opening  172  through which the radial arm  136  extends. The radially inner walls are provided with flanges adjacent the opening to retain captured water on the radially inner wall. In other examples, there may only be one radially inner wall, and the opening may be axially adjacent the respective wall. 
     The jet containment  108  is configured to capture liquid ejected by the jet nozzles  108 . In particular, the radially outer wall  166  is configured to retain the liquid by limiting the radial extent to which it can be ejected, and the or each radially inner wall  168 ,  170  is configured to prevent such liquid from falling or rebounding radially inwardly towards the central airflow extending through the misting apparatus (i.e. towards the rotational axis  104 ). It will be appreciated that in use liquid that is ejected axially forward and/or aft of the opening  172  will either fall directly to the lower side of the annular channel under gravity, or shall fall onto a radially inner wall  168 ,  170  and flow thereabout towards the lower side of the annular channel  160 . In some examples, the jet nozzles  138  may be configured to eject liquid along a direction inclined slightly out of a plane normal to the rotational axis so as to have an axial extent, so as to cause more of the liquid to be ejected over a radially inner wall  168 ,  170  rather than the opening  172 . In one such example, such jets of a jet nozzle  138  may oppose one another with respect to such a normal plane, such that there is substantially equal flow forward and aft, and any axial reaction force from the jets is thereby substantially equalised. 
       FIG. 6  shows an exploded view of components of the misting apparatus  100 . Components not previously described in detail include the drip collector  112  and a return pump  180 . 
     The drip collector  112  is in the form of an annular C-shaped channel having a radially outer wall, a radially inner wall, and a downstream curved end connecting the two. The radially outer wall is configured to fit over the distal (i.e. farthest) end of the airflow nozzle  110 , whereas the radially inner wall is configured to fit within the distal opening of the airflow nozzle  110  and be slightly separated therefrom such that drips collecting on and flowing axially down the inner wall of the airflow nozzle  110  flow directly into the C-shaped channel. Under gravity and in the absence of a throughflow of air, such drips shall flow circumferentially around the C-shaped channel to a lower point of the channel (i.e. a point closest to the ground level when positioned above ground). A drip collection hose  113  is provided to collect such drips and, under gravity, deliver them to the collector  118  (via an opening in the collector  118 ). The collection hose  113  may be configured to be inclined so that such drips are reliably returned to the collector, for example the hose may be flexible but appropriately sized to avoid bunching, or may be substantially rigid or relatively stiff to prevent it becoming bent out of the desired inclined configuration. 
     The drip collector may have a plurality of holes in the radially inner wall. Such holes may prevent buffeting. In other examples, there may be no such holes. 
       FIGS. 6 and 7  show the collector  118  and a return pump  180  of the misting apparatus, with the misting apparatus coupled to a supporting return conduit  200 . 
     In this example, the return conduit  200  functions as a support post for the misting apparatus, as shown in  FIG. 1 . In other examples, the return conduit  200  may be flexible. 
     In this example, the misting apparatus  100  is coupled to the supporting return conduit  200  by a flexible joint (not shown). For example the flexible joint may include an adjustable hinge so that an operator can set the rotational axis of the misting apparatus within a range of attitudes (pitches). In other examples, the flexible joint may include an oscillating mechanism for rotating the misting apparatus around a vertical axis. 
     In this example, the return conduit  200  serves as a return line for returning liquid captured by the jet containment  108  and collector  118  to the source of pressurized liquid, such as the portable device  10  described above with respect to  FIG. 1 . Further, a liquid return pump  180  and associated return lines are provided for recirculating the collected water under power, as will be described in detail below. 
     As shown in  FIG. 7 , the collector  118  is provided with a main outlet  202  which can be inserted into a support post or the return conduit  200  (which may be a supporting return conduit, as described above), or a flexible joint arrangement arranged therebetween. The collector  118  is also provided with a secondary outlet  204  adjacent the main outlet  202 . The secondary outlet  204  may be provided with a quick-release attachment for attaching a further or alternative return line. 
     The return pump  180  is coupled to the collector at an attachment point  188  (shown in  FIG. 2 ), and has an inlet  190  coupled to a primary return line  184  extending between the collector  118  and the return pump  180 , and an outlet  192  coupled to a secondary return line  194  extending between the return pump  180  to the portable device  12 . 
     As shown in  FIG. 7 , a drive unit  186  for the return pump is provided within the housing  102 . In this example, the drive unit  186  is sealed within a partitioned portion of the collector  118  to protect the drive unit  186  from water collected in the collector  118 . The drive unit  186  comprises a wheel (or gear) mounted on a drive shaft  196  within the housing and substantially parallel with (and offset from) the rotational axis  104 . The drive unit  186  is coupled to the seal shaft by a drive belt  198 , such that the drive unit  186  is driven to rotate as the seal shaft is driven to rotate (by virtue of being coupled to the rotary jet assembly  130 ). 
     The return pump  180  comprises a stub shaft (not shown) receivable (and in this example, received) in the attachment point  188  so as to be driven by rotation of the drive unit  186  (e.g. a keyed shaft). The return pump  180  further comprises an impeller for driving liquid received through the inlet  190  from the primary return line  184  and out through the outlet  192  to the secondary return line  194 . 
     In some examples, the return pump  180  and attachment point  188  may be configured to cooperate with each other, for example by a quick release or snap-fit mechanism. For example, the return pump  180  could be coupled to the attachment point  188  by a push-fit mechanism, and secured by a removable pin engaging through walls slots in both the return pump  180  and the attachment point  188 . Accordingly, the return pump  180  can be quickly connected to the misting apparatus  100 , and the return line routed through the return pump  180 , in order to drive the collected liquid through the return line under power (rather than relying on gravity alone). 
     Accordingly, the operator may connect the misting apparatus for liquid return in a variety of different ways. In a first example, as described above, the main outlet  202  may be received on a supporting return line  200  and may be open to return collected water through the supporting return line  200  by gravity. This arrangement may be supplemented by additionally connecting the liquid pump  180  and corresponding return lines  184 ,  194  to return the collected water under power. In other examples, the main outlet  202  may be blocked off, for example with a plug, and liquid return may be solely via the secondary outlet  204 . In such examples, the main outlet  202  may still be used to provide a supporting attachment for the misting apparatus  100 . The secondary outlet  204  may be provided with a quick release valve which opens when a return line is coupled thereto, and closes when the return line is removed. 
     In yet a further example, the misting apparatus may be provided with a mobile reservoir, for example a relatively small reservoir remote from the source of pressurized water. The misting apparatus may be supported on the mobile reservoir by the main outlet  202  forming a spigot connection with an inlet of the mobile reservoir, and the main outlet  202  may be open so that collected water drains into the mobile reservoir. The return pump  180  may be attached to the drive unit  186 , and a return line  184  may extend between the mobile reservoir and the return pump  180 , to direct collected water from the reservoir back to the source of pressurized water. The outlet of the reservoir may be configured so that a buffer supply of water is maintained in the reservoir, which may be useful to provide a base weight for the misting apparatus (i.e. to prevent movement or toppling of the misting apparatus). The buffer supply may also improve operation of the pump, since it may not be subject to intermittent lack of collected water. 
     An example of using the misting apparatus  100  will now be described, by way of example only. 
     In this particular example, the misting apparatus  100  is provided to suppress dust. An operator selects an appropriate spray nozzle  152  for dust suppression, for example based on the size of holes in the nozzles, and a supply pressure for the pressurized liquid (which in this example is water). In this example, pressurized water is supplied from the portable device  10  at a pressure of approximately 50 bar. The spray nozzle  152  is selected so that, at a flow rate of approximately 30 litres per minute (through the misting apparatus  100  as a whole), approximately 10 litres per minute flows through the spray nozzle  152  to produce a mist in an airflow through the nozzle having a droplet size in the order of 50 μm to 200 μm, for example approximately 100 μm. 
     It will be appreciated that a spray nozzle  152  may provide a mist suitable for dust suppression (or odour control) over a range of pressures and flow rates, for example from 50 bar to 200 bar and flow rates of between 10 litres per minute to 40 litres per minute (through the misting apparatus as a whole). The applicant has found that the flow rate through the spray nozzle  152  as a proportion of the total flow rate of liquid through the spray nozzle  152  is typically between 25% and 40%. 
     Further, in certain configurations where a spray nozzle having particularly large or particularly small jet holes are required (for example, to achieve a desired droplet size), the jet nozzles may be replaced in order to achieve a desired flow rate through the spray nozzle and jet nozzles respectively. 
     In this example the misting apparatus  100  is coupled on the supporting return conduit  200  coupled to the portable device, such that the misting apparatus  100  is disposed above the portable device, for example at a height of approximately 2 m above ground level. 
     The pressurized water is delivered through a supply line  206  extending between the reservoir  16  of the portable device and a port in the housing of the misting apparatus, with an internal supply line extending from the port on the interior of the housing to the rotary seal  122 , from where it is transferred into the hub  132  of the rotary jet assembly. Within the manifold of the rotary jet assembly, the flow of pressurized water divides so that a first portion of the flow is conveyed along the radial arms  136  to the jet nozzles  138 , and a second portion of the flow is conveyed through the fan shaft  134  to the nozzle attachment  150  and spray nozzle  152 . The relative proportions of the first and second portions are determined according to the pressure drop through each flow path, and in this particular example approximately two thirds of the flow is conveyed along the radial arms  136  to the jet nozzles  138 , whereas the remaining third is conveyed along the fan shaft  134  to the spray nozzle  152 . 
     The jet nozzles  138  eject the pressurized water along a substantially tangential direction relative the rotational axis  104  into the annular channel  160  of the jet containment, thereby imparting a jet reaction force having an opposing tangential component on the radial arms  136 . This jet reaction force causes the rotary jet assembly to rotate. In this particular example, the jet assembly  130  is caused to rotate at a velocity of approximately 2000 rpm, but in other examples the jet assembly may rotate faster or slower, for example between 1000 and 3000 rpm. 
     Rotation of the jet assembly  130 , including the integral fan shaft  134 , causes corresponding rotation of the fan  140  mounted thereto. The fan blades  144  of the fan  140  therefore rotate to propel an airflow through the mounting assembly. In particular, the fan blades  144  drive an airflow through the mounting assembly  140  in a direction substantially along the rotational axis  104  from upstream (outside of) the air intake  106 , through the jet containment  108  radially within (i.e. inward of) the annular channel  160 , through the airflow nozzle  110  and drip collector  112  to be discharged in a plume. For example, with the fan rotating at approximately 3000 rpm the airflow may be discharged from the airflow nozzle  110  at a velocity of approximately 10 m/s. In other examples, this exit velocity may be higher or lower, for example between 5 m/s and 20 m/s. 
     The remaining second portion of the pressurised water from the manifold within the rotary jet assembly  130  is conveyed along the fan shaft to be discharged from the spray nozzle  152 . As described above, in this example the spray nozzle  152  is configured to discharge jets of pressurized water radially into the airflow through the airflow nozzle  110  to result in a mist having droplets of approximately 100 μm. 
     The mist is discharged into the surrounding environment to suppress dust or odour. For example, dust or odour particles having a size of the same order of magnitude as the size of the droplets within the mist may be entrained together with the droplets and taken out of suspension in the air of the environment. 
     In order to adjust the speed of the airflow through the misting apparatus, and correspondingly adjust the quantity of water ejected through the spray nozzle, the operator may adjust the supply pressure and/or flow rate on the portable device  10  (or other source of pressurized liquid). For example, the operator may adjust a valve, such as a needle valve, on the pump  18  of the portable device  10 . 
     As described above, the jet containment  108  is configured to capture and convey water discharged from the jet nozzles. In this particular example, approximately 80% of the water ejected through the jet nozzles  138  is captured by the jet containment  108  and collected in the collector  118  (i.e. through openings in a lower portion of the jet containment  108  adjacent the collector  118 ). The remaining 20% is considered to return through the radial opening  172  of the annular channel  160  of the jet containment  108 , and is therefore entrained into the airflow through the misting apparatus  100 . 
     Whilst in some examples the water collected in the collector may flow from the collector  118  back to a reservoir of the portable device  10  under gravity alone, in this example a return pump  180  is additionally provided between the collector  118  and portable device  10  in order to return the water under power, as described above. 
     The portable device and misting apparatus therefore conveniently provide the ability to generate a mist, for example for dust suppression or odour control. In particular, since the misting apparatus is powered by the pressurized liquid alone, there are no electronic components, or electricity supply to the misting apparatus. This may avoid the potential hazard of electrical equipment being exposed to water. 
     Further, the rotary jet assembly provides a particularly simple and inexpensive means for providing a rotational drive for the fan. The rotary jet assembly enables easy re-capture of the ejected liquid. The manifold of the rotary jet assembly provides a particularly simple and inexpensive means for directing the pressurized liquid to the jet nozzles (for rotary drive) and to the spray nozzle, and enables the relative proportions of these flows to be adjusted by switching nozzles, thereby providing simple and inexpensive control of the amount of liquid in a mist, and the rotary speed and therefore the velocity of the airflow through the mist. Further, providing the manifold and fluid pathways within the rotary jet assembly may result in an arrangement requiring few parts, and mounting the spray nozzle on the rotary shaft enables an even distribution of droplets in the airflow, without providing multiple misting nozzles. 
     The particular arrangement of the misting apparatus, as claimed, may result in a relatively inexpensive construction which may be suitable for use with relatively inexpensive and/or portable sources of pressurized liquid. For example, the misting apparatus may be coupled to sources of pressurized liquid typically used for pressure washers, and may therefore be particularly convenient for use in environments where there is a demand for dust suppression or odour control over a relatively limited area, or where there is demand for a low-cost, temporary, portable or adaptable system. 
       FIG. 8  shows an alternative implementation of the misting apparatus  100 . In this particular example, a portable device  10  is provided to power multiple misting apparatus  100 . As shown in  FIG. 8 , three misting apparatus  100  are individually coupled via flexible supply conduits  200  to the same portable device  10 , which has three separate outlets for pressurized liquid. In this example, the flexible supply conduits  200  house a supply line and a separate return line, and the misting apparatus are each provided with a return pump  180  to return re-captured liquid along the return line under pressure (not shown). 
     It will be appreciated that the generator of the portable device may be powered by any suitable power source, for example a diesel generator or electrical generator. Further, it will be appreciated that the misting apparatus may be coupled to other equipment configured to provide pressurized liquid, for example a non-portable source. 
     Whilst a particular example has been described in which radial arms of a rotary jet assembly have a radial extent such that jet nozzles are located within an annular channel of the jet containment, it will be appreciated that in other examples there may be alternative configurations. For example, no jet containment or annular channel of such may be provided. Further, in other examples, the jet nozzles may be positioned radially outward of the tips of the fan, or radially outward of other features of the misting apparatus which define the radial extent of the airflow therethrough, for example features of the housing such as the airflow nozzle or a neck of the air intake. In still further embodiments, the radial arms may be configured so that the jet nozzles are disposed within the radial extent of the airflow, for example behind the disc of the fan, though such arrangements may encourage jets from the jet nozzles to become entrained in the airflow. 
     Whilst examples have been described in which the airflow nozzle tapers inwardly along the airflow direction, it will be appreciated that in other examples, the nozzle may be un-tapered or may taper outwardly. Un-tapered or outwardly tapering nozzles may promote a wide dispersion of a mist, and may be suitable for a wide range of applications, for example odour control. In at least some such examples, the jet containment may extend radially outwardly of the junction between the air nozzle and the jet containment (i.e. radially outwardly of the proximal end of the airflow nozzle), which may inhibit liquid ejected in the jet containment from entraining in the airflow flowing through the apparatus and being discharged through the airflow nozzle. 
     The features of any dependent claim may be combined with the features of any of the independent claims or other dependent claims.