NOZZLE FOR A FOG GENERATOR

Abstract

 The invention relates to a nozzle for distributing a heat-vaporsed fog liquid. The nozzle includes multiple outlets, which are designed so that the flow rate from the outlets in the central part is lower than the flow rate from those in the peripheral part.

Description

TECHNICAL FIELD OF THE INVENTION

[0001] The invention relates to an nozzle for distributing heated (gas phase) fog liquid. The nozzle includes multiple outlets, which are designed so that the flow rate from the outlets in the central part is lower than the flow rate in the peripheral part.

BACKGROUND TO THE INVENTION

[0002] Fog generators for security applications are deployed at a crime scene to obstruct the view of the perpetrator and to disorient them. They are used to protect people and valuables, and to deter criminals. For security operations, a fog generator is normally technically based on the principle of ejecting a (gas phase) fog liquid, in practice, this is usually a glycol-containing liquid. By heating it to a sufficiently high temperature (more than 200 °C, and usually over 250 °C) in a heat exchanger or heat accumulator, the liquid becomes converted into its gas phase. The gas phase escapes via the outlet channel of a nozzle into the "indoor space that needs to be protected". Since the gas vapour condenses immediately under the influence of atmospheric pressure and room temperature, it forms, and is dispersed as a obscurating fog. The principle is quite different from, for example, spreading an aerosol through automatic extinguishers and -sprinklers. In those cases, water is driven through a nozzle under great force to form (break-up) small droplets. However, these droplets do not form an opaque fog, and are therefore unsuitable for the security applications mentioned above.

[0003] Obviously, it is important for the fog to fill the space as fully as possible and within the shortest possible time. It is also important to influence the orientation that the fog cloud takes, for example, so that the fog protects the valuable items first, and then disperses into the rest of the indoor space. Recent innovations in fog generators for security applications have been concerned with increasing the speed at which fog is generated (e.g. WO2014102365 and WO2015140762), and with improving the possible orientation of the fog generators (e.g. EP2860486).

[0004] Nozzles for fog generators are already known, and have, for example, been described in DE29720164 and DK200400794. Nevertheless, there remains a need for the fog to be ejected in the form of a wide plume by such fog generators, and in particular, for this plume to be adjustable and made wider. A wider dispersed plume of fog could fill space faster and thus increase the effectiveness of the fog generator. This is particularly important for fog generators with a large and fast capacity to eject gassed fog liquid and condensated fog clouds as a result.

SUMMARY OF THE INVENTION

[0005] The inventors have surprisingly found that an optimal dispersed density and orientated cloud of fog development can be obtained through the use of an improved nozzle. An important principle is the use of multiple ejection channels or outlets, having part of the outlets located centrally, whilst the other outlets are peripherally oriented, and in which the flow rate through the central outlets is lower than the flow rate through the surrounding outlets. Surprisingly, it has been shown that if the flow rate in the central part is equal to or higher than the flow rate in the surrounding part, the mist cloud becomes narrower. Without wishing to be weighed down by theory, it is believed that the condensing fog greatly reduces in volume due to conversion from the gaseous to the liquid phase. By having a higher flow rate in the centre of the fog plume, a strong volume reduction is effected in the central part and the surrounding stream of fog is, as it were pulled / sucked inwards. Secondly, it is not ideal to provide no central fog ejection, as the mist plume may not obtain sufficient density in the centre and the emissions will not be balanced. The ideal balance is achieved by providing a lower rate in the centre than in the surrounding region. In this way, a wider plume of fog is obtained which is opaque and dispersed throughout the entire fog cloud.

[0006] Therefore, the invention provides a nozzle for the distribution of a heat-vaporised fog, the nozzle comprising:

• at least one inlet for the vaporised fog liquid,
• a first set of outlets (channels) located in the central part of the outer surface of the nozzle, and
• a second set of outlets situated in the peripheral part of the outer surface;

in which the flow rate through the first set of outlets is lower than the flow rate through the second set of outlets.

[0007] In one particular embodiment, the central part extends from the centre of the outer surface up to a distance r₁ and runs around the peripheral part from a distance r₁ to a distance r₂.

[0008] Preferably, the flow rate through the first set of outlets should be less than 70% of the flow rate through the second set of outlets.

[0009] In another particular embodiment, the majority of the outlets point in a different direction to those at the inlet. More specifically, the majority of the outlets have an (axis) direction having an angle of at least 5 ° relative to the axis at the inlet.

[0010] The nozzle is by preference, mainly made from a thermosetting or polyimide polymer.

[0011] In addition, the present invention also provides the use of the nozzle in this invention to spread the heated gas phase (vapour) of a fog liquid, so gas condenses in the environment and thus forms an opaque obscurating fog.

[0012] The invention also provides for a fog generator comprising a nozzle according to this invention.

BRIEF DESCRIPTION OF THE FIGURES

[0013] With specific reference now to the figures, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the different embodiments of the present invention only. They are presented in the cause of providing what is believed to be the most useful and readily description of the principles and conceptual aspects of the invention. In this regard no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention. The description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

Fig. 1: Front view of a nozzle according to the invention.

Fig. 2: Front view of a nozzle according to the invention. In this embodiment, the outlets (3) are present only in the upper half of the outer surface (4) of the nozzle (1). A possible choice for r₁ and r₂ is indicated. Line A is the cross-section of the embodiment of the invention as shown in figure 3.

Fig. 3: Rear-view plan of the cross-section of a nozzle according to the invention.

Fig. 4: Side-view of a nozzle according to the invention.

Fig. 5: Cross-section of a nozzle for boring the outlets.

DETAILED DESCRIPTION OF THE INVENTION

[0014] As described above, the present invention provides a nozzle (1) for distributing the gased fog liquid, this nozzle comprising:

• at least one inlet (2) vaporized fog liquid,
• a first set of outlets (3) located in a central part of the outer surface (4) of the nozzle, and
• a second set of outlets (3) located in a peripheral part of the outer surface (4);

in which the flow rate through the first set of outlets is lower than the flow rate through the second set of outlets.

[0015] The first set of outlets comprises at least two (2), preferably at least 3 outlets. The second set of outlets also comprises at least 2 outlets, but preferably at least 4 outlets, in particular at least 5 outlets.

[0016] In one particular embodiment, the nozzle comprises at least 10, in particular at least 15, more in particular at least 20 outlets.

[0017] The majority of the outlets have a preferential direction that differs from the inlets.

[0018] In particular, the majority of the outlets have one (axis) direction, having an angle of at least 5° relative to the axis of the inlet. Alternatively expressed, the majority of the outlets have an (axis) direction at an angle of at least 5° with respect to the axis running from the centre of the inlet to the centre of the outer surface of the nozzle.

[0019] By providing the direction of the outlets into an angle with respect to the central axis of the nozzle, a better distribution of the fog can be obtained, and the fog coming from the various outlets can be prevented from interfering with each other. In one particular embodiment, less than 10%, in particular, almost none, of the outlets are in the same direction as another outlet.

[0020] In one particular embodiment, the central part extends from the centre of the outer surface up to a distance r₁ and the peripheral part extends from a distance r₁ to a distance r₂. In this embodiment, the central part and the peripheral part touch each other at distance r₁. In a particular embodiment, r₂ is the distance from the centre of the outer surface to the outer edge of the farthest outlet. In a further embodiment, r₁ is one-fifth of r₂. In another embodiment, r₁ is less than half of r₂

[0021] In another embodiment, the flow rate through the first set of outlets is less than 70%, specifically less than 60%, to be more precise, less than 50% of the flow rate through the second set of outlets. Referred to herein, the flow rates through a set of outlets is the collective flow rate through these outlets. Naturally, the flow rates can be controlled, both by increasing/decreasing the cross-sections of the outlets, as well as by increasing/decreasing the number of outlets in the central and surrounding parts. Preferably, the length of a channel that forms an outlet is at least 2 times, and in some cases 3 times greater than the diameter of the channel. In this way, this outlet provides directionality to the out-flowing gas stream.

[0022] The nozzle is, by preference, mainly made from a thermosetting or polyimide polymer. By using a poorly heat conductive material, a number of advantages are obtained. Typically, after the fog ejection has ended, the heat exchanger and the nozzle can be flushed with air or with a propellant gas. If a thermally conductive material, such as a metal, is used, it has been shown that a part of the liquid fog which is still present in the heat exchanger and nozzle condenses inside the nozzle.

[0023] Surprisingly it was found that such condensation was significantly decreased if a thermally poorly conductive material like a plastic was used. This should withstand the heat load of the hot vaporised fog liquid. It is now assumed that, in an nozzle made from thermally conductive material, the heat carried by the vaporised liquid fog and purging air is diffused too quickly through the nozzle, so that it cools down too quickly, and, consequently, condenses inside the nozzle. This condensation is especially undesirable because it leads to the 'ejection' of fluid droplets at the end of the fog expulsion cycle. An additional advantage of using polymers is that these are inexpensive and relatively easy materials to shape, which thus lowers the costs of manufacturing the nozzle. The thermosetting polymer is resistant to the temperatures set out herein.

[0024] The present invention also provides the use of a nozzle as described herein to disperse fog. More specifically, to distribute a heat-vaporised fog liquid, such that the vaporised fog liquid condenses in the surrounding area. In this way, an opaque and obscurating fog is formed. The vaporised fog liquid typically has a temperature of more than 200 °C, in particular more than 230 °C, more in particular than 250 °C.

[0025] In one particular embodiment, the fog liquid is an aqueous solution. In a further embodiment, the fog liquid comprises a polyol, such as glycol.

[0026] This invention also provides a fog generator comprising an nozzle (1) as described herein. More specifically, the fog generator comprises a heat accumulator for heating the fog liquid such that it is converted into its gaseous phase, a nozzle as described herein, and a connection to deliver the vaporised fog liquid from the heat exchanger to the inlet of the nozzle. For example, the connector may be a channel that runs from the outlet of the heat exchanger to the inlet of the nozzle. The nozzle can be connected to and disconnected from the fog generator. In one embodiment, the invention provides the combination of a fog generator as described herein, and a nozzle, in which the nozzle and the fog generator are adapted so they can be joined to each other, e.g., by means of a (sealing) screw thread interaction (5). The nozzle for this invention may also be linked to an anchorage, like the metal anchorages (6) shown in Figures 4 and 5. In a further embodiment, the fog generator also comprises a reservoir with fog fluid fluid. Because the effect of the nozzle of the current invention is more significant for fog generators dispersing large volume of fog in short notice, the present invention also provides a fog generator as described herein, wherein the heat exchanger is as described in WO2015140761 (in particular, as described in the claims thereof), and/or in which the reservoir for the fog liquid is as described in EP2860486 (in particular as described in its claims).

[0027] In another embodiment, the outlets are asymmetrically positioned in the outer surface. So, for example, the outlets can only be provided on one half of the outer surface. As a result, the nozzle can be positioned and oriented in a way that a fog cloud can be obtained in a specific direction and shape. For example, if the fog generator is attached to a wall, it is not necessary to eject the fog upwards (towards the ceiling). For this purpose, a nozzle can be fitted which only has nozzle outlets on the lower part of the outer surface, as shown for example in Figure 2.

Claims

1. A nozzle for dispersing fog liquid that has been vaporized by heat, the nozzle comprising:

- at least one inlet for the vaporised fog liquid,

- a first set of outlets located in the central part of the outer surface of the nozzle, and

- a second set of outlets situated in a peripheral part of the outer surface;

wherein the flow rate through the first set of outlets is lower than the flow rate through the second set of outlets.

2. The nozzle of claim 1, wherein the first set of outlets comprises at least 2 outlets.

3. The nozzle according to any one of the preceding claims, wherein the second set of outlets comprises at least 4 outlets.

4. The nozzle according to any one of the preceding claims, wherein the first set of outlets comprises at least 3 outlets and the second set of outlets comprises at least 5 outlets.

5. The nozzle according to any one of the preceding claims, wherein the majority of the outlets have a different direction than the inlet.

6. The nozzle according to any one of the preceding claims, wherein the central part extends from the centre of the outer surface up to a distance r₁ and wherein the peripheral part extends from distance r₁ to distance r₂.

7. The nozzle according to any one of the preceding claims, wherein the flow rate through the first set of outlets is less than 70% of the flow rate through the second set of outlets.

8. The nozzle according to any one of the preceding claims, wherein the nozzle is substantially composed of a thermosetting polymer, preferably a polyimide or polyamide-imide polymer.

9. Use of a nozzle according to any one of the preceding claims to disperse a fog liquid that has been vaporized by heat, such that the vaporised fog liquid condenses in the surrounding environment such that it forms an opaque fog.

10. The use according to claim 9, wherein the vaporised fog liquid has a temperature of 200 °C or more when it flows into the inlet of the nozzle.

11. A fog generator comprising

- a heat accumulator for heating a fog liquid such that it is converted into its gaseous form,

- the nozzle according to any one of claims 1 to 8, and

- a connection to deliver the vaporised fog liquid from the heat accumulator towards the inlet of the nozzle.

Drawing