Aerosol distributor in filter test system

Abstract

The present application relates to a distributor for filter leak detection in a gas filtration system and an apparatus comprising the same, the aerosol distributor being configured to be positioned in a gas stream upstream of a filter, the aerosol distributor comprising: a hollow housing having at least one aerosol inlet for allowing aerosol to enter a chamber within the housing from an aerosol source and a plurality of aerosol outlet apertures for releasing aerosol from the chamber into the gas stream surrounding the housing, wherein the housing has a plate-like shape having an upstream surface configured to face the incoming gas stream and a downstream surface configured to face the filter, wherein the housing comprises a plurality of channels extending between a channel inlet at the upstream surface of the housing and a channel outlet at the downstream surface of the housing, such that gas from the gas stream is able to pass through the housing.

Description

Field of the Invention

[0001] The present invention generally relates to apparatus for performing filter leak testing in a gas filtration system and, more particularly, to an aerosol distributor for achieving a uniform distribution of a test aerosol in a gas flow upstream of a filter to be tested. Background of the Invention

[0002] In some environments where gases (such as air) are filtered to remove undesirable substances from the gas, it is important to be able to check whether the filter is working and detect any leaks in the filter. One method of checking the filter is to use a filter test system, in which a particulate test substance (usually an aerosol) is injected into the gas stream upstream of the filter and the gas is collected downstream of the filter using a sampling probe. The collected gas is then analyzed for the presence of undesirable substances.

[0003] Filters and filter assemblies can be tested for particle removal from gases using monodisperse or polydisperse aerosols of oils such as dioctyl phthalate (DOP), diisooctyl sebacate (DEHS), or polyalphaolefins (PAO). Other typical aerosols used are aerosols of solid particles such as salt or silica, polystyrene latex aerosols, or aerosols of viable or non-viable cells. For testing molecular filters, gaseous challenge compounds such as toluene or butane in air can also be used. The aerosol is introduced into the gas stream at a point in the pipeline that is sufficiently far upstream from the filter or filter group to ensure that the aerosol is completely dispersed when it reaches the filter or filter group.

[0004] An upstream sampling probe is typically located immediately upstream of the filter to determine the aerosol concentration in the pipeline, and a downstream sampling probe is used to detect filter leaks. During the test, a portion of the gas flow is extracted from the pipeline through the sampling probe and delivered to an external instrument, such as a photometer or particle counter, which determines the aerosol concentration in the upstream and downstream samples.

[0005] The downstream sampling probe can be moved in a plane parallel to the filter surface, allowing the filter surface to be scanned with the sampling probe. This type of scanning sampling probe not only allows the presence of a leak to be detected, but also gives a rough indication of the leak's location relative to the filter surface. A typical sampling probe is made of a tube with several inlet holes distributed through the tube wall along the length of the sampling probe and a central outlet.

[0006] For leak detection to be accurate, it is important that the aerosol particles are evenly distributed in the gas stream when they reach the filter, so that the aerosol particle load is evenly distributed across the entire filter area. If the filter experiences an uneven particle distribution, such as a higher particle concentration towards the middle of the filter and a lower particle concentration towards the edge of the filter, this may result in lower sensitivity to leaks at the edge of the filter compared to leaks closer to the middle of the filter.

[0007] If the test aerosol is injected into the gas stream through a single injection point, the injection point must be located far enough from the filter to allow the aerosol particles to be evenly distributed before reaching the filter surface. This can significantly increase the space requirements of the filter testing system. In setups where multiple filters are used in series, the space requirements for introducing the test substance and extracting the sample are multiplied because the filters must be spaced far enough apart to allow for proper particle distribution.

[0008] In general, in order to completely mix the aerosol with the surrounding air flow, the point where the aerosol is introduced into the air flow should be upstream of such a position where the aerosol needs to be completely mixed by at least 10 pipe cross-sectional dimensions (the pipe through which the air flow passes). However, this size requirement will cause the test section to be much longer than a conventional filter device, and therefore, an undesirable large floor space is required, and material costs are also increased. Alternatively, a baffle or other mixing element can be provided between the aerosol injection point and the filter to provide sufficient mixing over a shorter length. However, the addition of the mixing element significantly limits the air flow through the filter device. Therefore, larger fans, blowers, etc. must be used, which also use more power to achieve the desired air flow compared to the case without these elements. Larger fans increase equipment costs, and the increased air flow resistance consumes more energy, making the system operation more expensive.

[0009] While the aerosol distributor should provide a uniform particle distribution, it is also important that the aerosol distributor's impact on the overall pressure drop of the filter test system be as small as possible.

[0010] A common prior art solution for improving aerosol particle distribution in filter testing systems involves an arrangement of interconnected perforated tubes connected to an aerosol source. Aerosol from the source is fed into the tubes and distributed into the gas stream through the perforations. However, this type of arrangement typically does not produce a satisfactory distribution, as a larger number of particles will pass through the perforations closest to the aerosol source, while a smaller number will pass through the perforations farther away.

[0011] Therefore, an alternative solution for aerosol distribution in filter testing systems would be ideal, which combines the properties of efficient aerosol particle distribution (which allows the aerosol distributor to be placed close to the filter surface) with low pressure drop. SUMMARY OF THE INVENTION

[0012] It is an object of the present disclosure to provide an aerosol dispenser for use in a filter testing system that alleviates at least some of the problems associated with prior art aerosol dispensers.

[0013] Another object of the present disclosure is to provide an aerosol distributor that combines the characteristics of efficient aerosol particle distribution, allows the aerosol distributor to be placed close to the filter surface, and has a low pressure drop.

[0014] The above objectives, as well as other objectives that will become apparent to those skilled in the art from this disclosure, are achieved by the various aspects of the present invention set forth herein.

[0015] According to a first aspect of the present disclosure, there is provided an aerosol distributor for performing filter leak detection in a gas filtration system, the aerosol distributor being configured to be located in a gas flow upstream of a filter, the aerosol distributor comprising:

[0016] A hollow shell having

[0017] at least one aerosol inlet for allowing aerosol from an aerosol source to enter the chamber within the housing, and

[0018] a plurality of aerosol outlet holes for releasing the aerosol from the chamber into the gas flow surrounding the housing, and

[0019] The housing has a plate-like shape having an upstream surface and a downstream surface, the upstream surface being configured to face an incoming gas stream, and the downstream surface being configured to face a filter, wherein the housing includes a plurality of channels extending between a channel inlet on the upstream surface and a channel outlet on the downstream surface of the housing so that gas from the gas stream can pass through the housing.

[0020] An aerosol distributor can be permanently installed in the filter housing upstream of the filter if the integrity of the filter needs to be tested regularly or occasionally. The function of the aerosol distributor is to distribute the aerosol (for example in the form of a carrier stream containing very fine oil particle aerosol) into the gas flow upstream of the filter through many small outlet holes. The aerosol can be, for example, a monodisperse or polydisperse aerosol of an oil, such as dioctyl phthalate (DOP), diisooctyl sebacate (DEHS) or polyalphaolefin (PAO). Other examples of aerosols that can be used include aerosols of solid particles (for example salt or silica), polystyrene latex aerosols, or aerosols of living or non-living cells. For testing of molecular filters, gaseous exciting compounds, such as toluene or butane in air, can also be used. Downstream of the filter, an aerosol sampling probe is often used to detect filter leaks. In order for leak detection to be accurate, it is important that the aerosol particles are evenly distributed in the gas stream when they reach the filter so that the aerosol particle load is evenly distributed over the entire filter area.

[0021] The aerosol distributor of the present invention is intended to be installed in a filter housing or duct upstream of the filter and to be sized so that gas passing through the filter housing or duct towards the filter must also pass through the passage of the aerosol distributor.

[0022] The aerosol distributor of the present invention is configured to inject aerosol into the gas stream in a countercurrent manner. The aerosol injected into the gas stream will then travel and mix with the gas stream as the gas stream passes through a channel extending between the upstream surface and the downstream surface of the housing. The combination of countercurrent injection and mixing of gas and aerosol in the channel provides a very effective aerosol distribution. It has been found that this makes it possible to place the aerosol distributor very close to the filter surface, which in turn allows the construction depth of the filter test device to be reduced and the size to be reduced. Typically, the aerosol distributor of the present invention can be placed at a distance in the range of 50-250 mm from the upstream surface of the filter. This can be compared with corresponding gas distributors in the prior art that require a distance of at least 400 mm.

[0023] It has been found that the aerosol distributor of the present invention reduces the particle distribution deviation over the filter area to less than 15%, which can be compared to a particle distribution deviation of approximately 30% for a corresponding gas distributor of the prior art.

[0024] Surprisingly, it has been found that for the aerosol distributor of the present invention, a particle distribution deviation of less than 15% over the filter area can be achieved at a build depth of as low as 70 mm (including the thickness of the aerosol distributor and the distance between the aerosol distributor and the filter).

[0025] While the aerosol distributor should provide a uniform particle distribution, it is also important that the aerosol distributor has as little impact on the pressure drop in the filter test system as possible. Therefore, the housing should preferably be designed to minimize airflow resistance. It has been found that with the aerosol distributor of the present invention, significant improvements in aerosol distribution can be achieved with minimal impact on the overall pressure drop.

[0026] To achieve acceptable mixing, by providing a suitable size and number of channels through the plate-like housing, the additional pressure drop caused by the aerosol distributor can be significantly reduced compared to conventional aerosol distributor arrangements (comprising interconnected porous tubes and baffles). 3 In a conventional air duct with a square cross-section of 610×610 mm and a flow rate of 1 / h, the pressure drop of the aerosol distributor according to the present invention, which has 784 (28×28) channels, each of which has a circular cross-section with a diameter of approximately 12 mm, is 35 Pa. This can be compared with the pressure drop of 130 Pa of the aerosol distributor in the prior art.

[0027] In some embodiments, the plurality of channels comprises a range of 100-3000 channels per square meter of the overall cross-sectional area of ​​the housing in a plane perpendicular to the general flow direction of the gas flow. In preferred embodiments, the plurality of channels comprises a range of 400-3000 or 500-3000 channels per square meter of the overall cross-sectional area of ​​the housing in a plane perpendicular to the general flow direction of the gas flow.

[0028] The channel inlets and channel outlets are preferably evenly distributed on the upstream and downstream surfaces of the housing, respectively. In some embodiments, the channels extend between the upstream and downstream surfaces of the housing in the general direction of the gas flow (preferably parallel to the general direction of the gas flow). In this way, the aerosol distributor also serves to balance irregularities in the air flow and distribute the air flow more evenly over the surface area of ​​the filter.

[0029] The channels can be provided in different shapes and sizes. In some embodiments, the channels have a circular or square cross-sectional geometry, while in other embodiments, the channels can have a polygonal, such as a hexagonal, cross-sectional geometry.

[0030] In some embodiments, the channel has an overall width or diameter in the range of 5-50 mm, preferably in the range of 8-20 mm, more preferably in the range of 10-15 mm. These ranges have been found to provide a particularly advantageous combination of uniform aerosol distribution, uniform air / gas flow, and low pressure drop.

[0031] The number and size of the channels are preferably combined so that their total cross-sectional area is at least 20%, preferably at least 30%, more preferably at least 40% of the overall cross-sectional area of ​​the housing in a plane perpendicular to the general flow direction of the gas stream.

[0032] As an example, for a square duct with internal dimensions of 610 x 610 mm, the outer dimensions of the housing may be approximately 610 x 610 mm or less, with a depth in the direction of air flow of approximately 10-50 mm, such that the housing fits within and substantially covers the cross-section of the duct. This equates to an overall cross-sectional area of ​​0.37 m2 for the housing in a plane perpendicular to the general direction of gas flow. 2 The housing may, for example, comprise 784 evenly distributed circular channels with an inner diameter of 12 mm. This corresponds to a total channel cross-sectional area of ​​approximately 0.089 m 2 Or about 25% of the overall cross-sectional area of ​​the shell.

[0033] The aerosol distributor is preferably positioned so that the upstream surface faces the incoming gas flow and the downstream surface faces the filter, and the outlet hole is positioned on the upstream surface of the plate-shaped housing, is positioned on the upstream surface, or is positioned within the channel at a position closer to the upstream surface than to the downstream surface. In some embodiments, the outlet hole is positioned on the upstream surface, located between the channels. In some embodiments, the outlet hole is positioned within the channel, located closer to the upstream surface than to the downstream surface.

[0034] In the aerosol dispenser of the present invention, the size of the outlet aperture is preferably chosen such that, during operation, the flow rate of the test aerosol through the outlet aperture is higher than the flow rate of the air in the duct.

[0035] Preferably, the channels and outlet openings are evenly distributed across the cross-sectional area of ​​the aerosol distributor, and thus evenly distributed across the cross-sectional area of ​​the passing gas stream. This allows the aerosol to be evenly distributed throughout the gas stream. To further improve the uniformity of the aerosol distribution, the number of outlet openings and / or the number of channels can be increased.

[0036] The inlet(s) may be positioned anywhere on the housing, but to minimize disruption to the air flow downstream of the aerosol distributor, the inlet is preferably positioned on the upstream surface of the housing, between the channels. The inlets are preferably positioned or distributed symmetrically relative to the outlet openings so that the flow conditions between the inlets and outlet openings remain as similar as possible.

[0037] The aerosol distributor can be designed in a variety of shapes and sizes. The shape of the aerosol distributor is preferably selected to correspond to the pipe or filter housing in which it is to be installed. Since most pipes and housings have a circular or square cross-sectional geometry, the hollow plate-shaped housing is preferably circular or square. The hollow plate-shaped housing can generally have an overall width or diameter in the range of 100-1300 mm, preferably in the range of 250-650 mm. In some embodiments, the hollow plate-shaped housing has a thickness in the range of 5-100 mm, preferably in the range of 10-50 mm.

[0038] The effectiveness of the aerosol distributor of the present invention is believed to be particularly significant because the pressure of the aerosol supplied to the aerosol distributor is typically relatively low. The aerosol pressure from the aerosol source is typically in the range of 0.1-5 bar, preferably in the range of 0.2-3 bar. Therefore, in some embodiments, the aerosol distributor further comprises an aerosol source adapted to supply a test aerosol to the inlet of the housing at a pressure in the range of 0.1-5 bar, preferably in the range of 0.2-3 bar.

[0039] According to a second aspect of the present disclosure, there is provided an apparatus for performing filter leakage detection in a gas filtration system, comprising:

[0040] a filter housing for sealingly mounting the filter within said housing so that a gas flow through the housing passes through the filter, and

[0041] an aerosol distributor located in the gas stream upstream of the filter for releasing a test aerosol from an aerosol source into the gas stream,

[0042] The aerosol distributor includes a hollow shell having

[0043] at least one aerosol inlet for allowing aerosol from an aerosol source to enter the chamber within the housing, and

[0044] a plurality of aerosol outlet holes for releasing the aerosol from the chamber into the gas flow surrounding the housing, and

[0045] The housing has a plate-like shape having an upstream surface and a downstream surface, the upstream surface being configured to face the incoming gas flow and the downstream surface being configured to face the filter, wherein the housing includes a plurality of channels extending between a channel inlet on the upstream surface and a channel outlet on the downstream surface of the housing so that gas from the gas flow can pass through the housing.

[0046] The aerosol distributor of the apparatus of the second aspect may be further defined as an aerosol distributor as described above in relation to the first aspect of the disclosure.

[0047] The aerosol distributor is preferably positioned so that the upstream surface faces the incoming gas flow and the downstream surface faces the filter, and the outlet hole is positioned at the upstream surface of the plate-like shell, which is positioned on the upstream surface or in the channel at a position closer to the upstream surface than the downstream surface.

[0048] The aerosol distributor of the present invention is installed in a filter housing or duct upstream of the filter and is sized so that gas passing through the filter housing or duct towards the filter must also pass through the passage of the aerosol distributor.

[0049] The shape of the aerosol distributor is preferably selected to correspond to the shape of the duct or filter housing in which it is to be installed. Since most ducts and housings have circular or square cross-sectional geometries, the hollow plate-shaped housing is preferably circular or square. The hollow plate-shaped housing can typically have an overall width or diameter in the range of 100-1300 mm, preferably in the range of 250-650 mm. In some embodiments, the hollow plate-shaped housing has a thickness in the range of 5-100 mm, preferably in the range of 10-50 mm.

[0050] The aerosol distributor can be placed at a conventional distance from the filter (typically about 400 mm) to provide improved aerosol distribution than a corresponding single-chamber distributor, or the aerosol distributor can be placed closer to the filter to provide the same or better aerosol distribution than a conventional aerosol distributor, but with a reduced build depth. In some embodiments, the aerosol distributor is installed so that the distance between the aerosol distributor and the filter is in the range of 50-400 mm, preferably in the range of 50-250 mm.

[0051] Downstream of the filter, an aerosol sampling probe is typically used to detect filter leaks. Thus, in some embodiments, a sampling probe is located in the gas flow downstream of the filter for sampling gas from the gas flow to be analyzed to detect the presence of a test aerosol.

[0052] The sampling probe can be provided in many different forms and can be fixed or movable. Since it is desirable that the sampling probe does not significantly interfere with the gas flow, the sampling probe cannot cover the entire area. Different concepts of sampling probes have been proposed, which are moved to scan the filter area. One concept is an elongated sampling probe that extends along the length or width of the filter and moves back and forth perpendicular to its longitudinal extension to scan the area near the filter surface. A typical elongated sampling probe is made of a tube with several inlet holes and a central outlet, and the several inlet holes are distributed along the length of the sampling probe through the tube wall. This type of sampling probe can not only detect the presence of a leak, but can also give a rough indication of the location of the leak on the filter surface. Therefore, in some embodiments, the sampling probe is movable in a plane parallel to the filter surface so that the filter surface can be scanned using the sampling probe.

[0053] In some embodiments, the sampling probe is composed of a series of discrete probes that are evenly distributed across the cross-sectional area of ​​the filter housing, wherein each discrete probe can be analyzed independently. Thus, the series of discrete probes can not only detect the presence of a leak, but also provide a rough indication of the location of the leak on the filter surface.

[0054] In some cases, particularly with a movable sampling probe or a series of discrete probes arranged to scan the filter surface, it is preferred to place the sampling probe close to the filter surface. In some embodiments, the distance between the sampling probe and the filter is in the range of 5-100 mm, preferably in the range of 5-25 mm.

[0055] Since the test aerosol will eventually accumulate in the filter being tested, it is generally desirable to use as little aerosol as possible during the test. In some embodiments, the aerosol distributor may include an assembly having at least two aerosol distributor subunits, each of which can be operated independently of the other aerosol distributor subunits. For example, instead of a single 610×610 mm aerosol distributor, an aerosol distributor consisting of four 305×305 mm aerosol distributor subunits is envisioned, each of which can be operated independently of the other aerosol distributor subunits. An advantage of this configuration is that the total aerosol load to the filter can be reduced when the downstream surface of the filter is scanned using a movable sampling probe arranged to scan the filter surface or a series of discrete fixed probes. During the entire test cycle, only the scanned portion of the filter will be subjected to aerosol, rather than having the entire filter surface subjected to aerosol.

[0056] Alternatively, a second plate-shaped housing as defined above with reference to the first aspect of the present disclosure can be used as a fixed sampling probe. To be used as a sampling probe, the plate-shaped housing is placed downstream of the filter, with the outlet opening facing the downstream surface of the filter. During the test, a portion of the gas flow is extracted from the pipeline through the plate-shaped housing and delivered to an external instrument for determining the aerosol concentration, such as a photometer or particle counter. This configuration may be advantageous because it can be used to simultaneously extract samples from a large number of locations across the cross-sectional area of ​​the passage while maintaining a low overall pressure drop.

[0057] Various embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Reference is now made to the accompanying drawings, which are exemplary embodiments, and in which:

[0059] Figure 1 is a schematic diagram of a gas filtration system having an apparatus for filter leak detection;

[0060] Figure 2a and 2b is a perspective view of an aerosol distributor according to the present invention;

[0061] Figure 3a and 3b is a view of the upstream surface of an aerosol distributor according to the present invention;

[0062] Figure 4a and 4b is a perspective view of an aerosol distributor according to the present invention;

[0063] Figure 5a and 5b is a view of the upstream surface of an aerosol distributor according to the present invention;

[0064] Figure 6a and 6b Shown is a cross-sectional view of an aerosol distributor according to the present invention.

[0065] Detailed Description of the Preferred Embodiments

[0066] Figure 1 A gas filtration system, specifically an air filtration system, is shown, which includes an apparatus for filter leak detection according to various embodiments. The air filtration system 1 includes a filter housing 2 having an upstream test section 3, a filter section 4, and a downstream test section 5 arranged in series. The air filtration system includes an air flow inlet aperture 6 at the upstream end and an air flow outlet aperture 7 at the downstream end.

[0067] The filter housing 2 may include one or more doors (not shown) that can be opened to allow access to the filter 10 contained in the filter housing 2. The filter housing 2 also includes an upstream sampling port 8 and an upstream sampling probe 9, wherein the upstream sampling port 8 is formed through the filter housing 2 and the upstream sampling probe 9 allows a sample of the aerosol concentration in the air flow upstream of the filter to be obtained during filter testing. The filter portion 4 of the filter housing 2 includes a filter mounting mechanism 11, which is substantially aligned with the door. The filter mounting mechanism 11 receives the filter 10 disposed in the filter portion through the door and is capable of being actuated to sealingly hold the filter 10 in position within the filter portion 4 so that air entering the air filtration system 1 through the air flow inlet orifice 6 and discharged from the air flow outlet orifice 7 must pass through and be filtered by the filter 10. The filter mounting mechanism 11 can be any suitable filter clamping mechanism used in commercial gas filtration systems, or other suitable filter clamping system.

[0068] The upstream test section 3 is arranged between the air flow inlet orifice 6 and the filter section 4, and includes a conduit forming a passage that guides the air flow from the air flow inlet orifice to the filter housing. An aerosol distributor 20 is arranged in the passage. The aerosol distributor can be connected to and in fluid communication with the aerosol port 12, and the aerosol port 12 is arranged through the conduit body. One or more aerosol inlets of the aerosol distributor 20 can be connected to the aerosol port 12 via a connecting tube 13. The connecting tube may include a rigid or flexible tube suitable for connecting the aerosol distributor to the aerosol port. Aerosol from an aerosol source 14 can be introduced into the aerosol port 12 and enter the aerosol distributor 20 through the connecting tube 13.

[0069] Figure 2a-2b The basic structural features of an embodiment of an aerosol distributor according to the present invention are shown.

[0070] The aerosol distributor 20 includes a hollow plate-like housing 21 defined by two main surfaces, an upstream surface 22 and a downstream surface 23, connected by an edge surface 24 extending around the periphery of the main surfaces. The housing 21 also includes a plurality of channels 25 extending between a channel inlet on the upstream surface and a channel outlet on the downstream surface of the housing so that gas from the gas stream can pass through the housing 21.

[0071] The major surfaces 22, 23, the edge surface 24 and the plurality of channels 25 together define a chamber within the housing 21. The upstream surface 22 is configured to face the incoming gas flow, while the downstream surface 23 is configured to face the filter.

[0072] The housing 21 is preferably made of plastic or metal. The housing can be assembled from two or more components, for example, a first component comprising a first major surface, an edge surface, and a channel, and a second component comprising a second major surface, wherein the second component can be assembled and secured to the first component, for example, by gluing. Suitable methods for manufacturing the housing or housing components from plastic include 3D printing or molding. The inlet and outlet openings can be prepared, for example, by drilling.

[0073] The shell 21 has at least one aerosol inlet 26 and multiple aerosol outlet holes 27. The at least one aerosol inlet 26 is used to allow aerosol from an aerosol source to enter the chamber inside the shell through the aerosol port and the connecting tube, and the multiple aerosol outlet holes 27 are used to release the aerosol from the chamber into the gas flow around the shell.

[0074] The housing 21 of the aerosol distributor 20 is preferably designed so that when it is installed in a passage, the outlet holes 27 are evenly distributed over the entire cross-sectional area of ​​the passage. In this way, the aerosol is evenly distributed in the air flow.

[0075] As an example, Figures 2a-3b As shown, for a square duct with an internal dimension of 610×610 mm, the external dimension of the housing 21 can be approximately 610×610 mm or less, and the depth in the direction of air flow is approximately 10-50 mm, so that the housing 21 fits in the cross section of the duct and substantially covers the cross section of the duct. The housing 21 can, for example, include 784 (28×28) evenly distributed circular channels 25 with an inner diameter of 12 mm. The housing can also include 196 evenly distributed circular outlet holes 27 with an inner diameter of 1.6 mm, i.e., one outlet hole for every four channels. The housing can also include four circular inlets 26, i.e., one inlet for every 49 outlet holes. When the air flow rate is 3400 m / s, the housing 21 can be configured as follows: 3 At 100 tph, the pressure drop of the aerosol distributor is about 35 Pa. This can be compared with the pressure drop of about 130 Pa of a conventional aerosol distributor in the prior art.

[0076] As another example, Figures 4a-6b As shown, for a square pipe with an internal dimension of 610×610 mm, the external dimension of the housing 21′ of the aerosol distributor 20′ can be approximately 610×610 mm or less, and the depth in the direction of air flow is approximately 10-50 mm, so that the housing fits in the cross section of the pipe and substantially covers the cross section of the pipe. The housing can, for example, include 324 (18×18) evenly distributed circular channels 25′ with an inner diameter of 20 mm. The housing can also include 324 evenly distributed circular outlet holes 27′ ​​with an inner diameter of 1.6 mm, i.e., one outlet hole for each channel. The housing can also include four circular inlets 26, i.e., one inlet for every 81 outlet holes.

[0077] The passages may have the same or different cross-sectional geometries and dimensions. The passages may also have constant cross-sectional geometries and dimensions throughout the length of the passages, or they may have varying cross-sectional geometries and dimensions throughout the length of the passages. For example, the passages may have one diameter at the passage inlet on the upstream surface of the housing and a different diameter at the passage outlet on the downstream surface of the housing.

[0078] exist Figures 2a-3b In the embodiment, the channel 25 has a constant cross-sectional geometry and dimensions throughout the entire channel length. Figures 4a-6b In the embodiment, the passage 25' has a larger diameter at the passage inlet on the upstream surface 22' of the shell 21' and a smaller diameter at the passage outlet on the downstream surface 23' of the shell.

[0079] like Figure 6a and 6b As shown, the major surfaces, edge surfaces, and plurality of channels define a chamber 28 within the interior of the housing. Figure 6a is a cross section taken through the inlet 26 between two rows of channels. Figure 6b is a cross section taken through a row of channels 25' showing the channel walls and the chambers 28 formed between the channels.

[0080] The shape of the aerosol distributor is preferably selected to correspond to the duct or filter housing in which it is to be installed. Since most ducts and housings have circular or square cross-sectional geometries, the hollow plate-shaped housing is preferably circular or square. The aerosol distributor shown in the figure is configured for installation in a square duct, and the housing is manufactured accordingly. The overall width or diameter of the hollow plate-shaped housing can typically be in the range of 100-1300 mm, preferably in the range of 250-650 mm.

[0081] It should be understood that the aerosol distributor can also be manufactured in other shapes to suit other pipeline contours.

[0082] Via the aerosol port 12 , the aerosol distributor 20 may be connected to an aerosol source 14 adapted to supply a test aerosol to an inlet of the housing 21 at a pressure in the range of 0.1-5 bar, preferably in the range of 0.2-3 bar.

[0083] The downstream test portion 5 is arranged between the downstream surface of the filter 10 in the filter housing portion 4 and the air flow outlet orifice 7, and includes a duct that forms a passage that guides the air flow from the filter to the air flow outlet orifice 7. An aerosol sampling probe 15 is arranged in the passage. The aerosol sampling probe 15 is located in the gas flow downstream of the filter and is used to sample gas from the gas flow to be analyzed to analyze the presence of test aerosols. The sampling probe 15 can be connected to a sampling port 16 arranged through the main body of the duct and is in fluid communication with the sampling port 16. During the test, a portion of the gas flow is extracted from the duct through the sampling probe and delivered to an external instrument 18, such as a photometer or particle counter, which is used to determine the aerosol concentration in the upstream and downstream samples. The aerosol concentration measured in the sample collected by the downstream sampling probe can optionally be compared with the aerosol concentration measured in the sample collected by the upstream sampling probe 9.

[0084] The downstream sampling probe can be moved in a plane parallel to the filter surface so that the filter surface can be scanned with the sampling probe. This type of sampling probe can not only detect the presence of a leak, but also give a rough indication of the leak location on the filter surface.

[0085] A typical sampling probe is made of a tube with several inlet holes distributed along the length of the sampling probe through the tube wall and a central outlet connected to a downstream sampling port. Different concepts for moving the probe to scan the filter surface have been proposed. One concept is to use an elongated sampling probe that extends along the length or width of the filter and can be moved back and forth in a direction perpendicular to its longitudinal extension by a manual or motor-driven mechanism (such as a cylinder, drive screw or other suitable mechanism) to scan the area near the filter surface.

[0086] In some embodiments, the sampling probe is composed of a series of fixed discrete probes that are evenly distributed across the cross-sectional area of ​​the filter housing, wherein each discrete probe can be analyzed independently. Thus, the series of discrete probes can not only detect the presence of a leak, but also provide a rough indication of the location of the leak on the filter surface.

[0087] In some cases, particularly with a movable sampling probe or a series of discrete probes arranged to scan the filter surface, it is preferred to place the sampling probe close to the filter surface. In some embodiments, the distance between the sampling probe and the filter is in the range of 5-100 mm, preferably in the range of 5-25 mm.

[0088] Alternatively, a second plate-shaped housing as defined above with reference to the first aspect of the present disclosure can be used as a fixed sampling probe. To function as a sampling probe, the plate-shaped housing is placed downstream of the filter, with the outlet opening facing or facing away from the downstream surface of the filter. During the test, a portion of the gas flow is extracted from the pipeline through the plate-shaped housing and delivered to an external instrument for determining the aerosol concentration, such as a photometer or particle counter. This configuration can be advantageous because it can be used to simultaneously extract samples from a large number of locations across the entire cross-sectional area of ​​the passageway while maintaining a low overall pressure drop.

[0089] As used herein with respect to a channel or gas conduit, the term "total cross-sectional area" refers to the total open cross-sectional area of ​​the channel or gas conduit in a plane perpendicular to the general flow direction of the gas stream.

[0090] Although the present invention has been described herein with reference to various exemplary embodiments, it will be understood by those skilled in the art that various changes can be made and that equivalents can be substituted for the elements therein without departing from the scope of the present invention. In addition, many modifications can be made to adapt specific situations or features to the teachings of the present invention without departing from its basic scope. Therefore, it is intended that the present invention is not limited to limiting the disclosed specific embodiments to the best mode for implementing the present invention, but that the present invention will include all embodiments within the scope of the appended claims. In addition, it will be understood by those skilled in the art which features of different embodiments can be combined, although not explicitly stated above.

Claims

1. An aerosol distributor for performing filter leak detection in a gas filtration system, the aerosol distributor being configured to be positioned in a gas flow upstream of a filter, the aerosol distributor comprising: A hollow shell, comprising: at least one aerosol inlet for allowing aerosol from an aerosol source to enter the chamber within the hollow housing, and a plurality of aerosol outlet holes for releasing the aerosol from the chamber into the gas flow surrounding the hollow housing, It is characterized by: The hollow shell has a plate-like shape having an upstream surface and a downstream surface, the upstream surface being configured to face the incoming gas flow and the downstream surface being configured to face the filter, wherein the hollow shell includes a plurality of channels extending between a channel inlet at the upstream surface of the hollow shell and a channel outlet at the downstream surface of the hollow shell so that gas from the gas flow can pass through the hollow shell.

2. The aerosol distributor according to claim 1, characterized in that The plurality of channels comprises a range of 100-3000 channels per square meter of overall cross-sectional area of ​​the hollow shell in a plane perpendicular to the general flow direction of the gas stream.

3. The aerosol distributor according to claim 1, characterized in that The channel inlet and the channel outlet are uniformly distributed on the upstream surface and the downstream surface of the hollow shell, respectively.

4. The aerosol distributor according to claim 1, characterized in that The passage extends between the upstream and downstream surfaces of the hollow housing in the general flow direction of the gas stream.

5. The aerosol distributor according to claim 1, characterized in that The passage extends parallel to the general flow direction of the gas stream between the upstream and downstream surfaces of the hollow housing.

6. The aerosol distributor according to claim 1, characterized in that The channels have a circular or square cross-sectional geometry.

7. The aerosol distributor according to claim 1, characterized in that The overall width or diameter of the channel is in the range of 5-50 mm.

8. The aerosol distributor according to claim 1, characterized in that The overall width or diameter of the channel is in the range of 8-20 mm.

9. The aerosol distributor according to claim 1, characterized in that The overall width or diameter of the channel is in the range of 10-15 mm.

10. The aerosol distributor according to claim 1, characterized in that The total cross-sectional area of ​​the channels is at least 20% of the overall cross-sectional area of ​​the hollow shell in a plane perpendicular to the general flow direction of the gas stream.

11. The aerosol distributor according to claim 1, characterized in that The total cross-sectional area of ​​the channels is at least 30% of the overall cross-sectional area of ​​the hollow housing in a plane perpendicular to the general flow direction of the gas stream.

12. The aerosol distributor according to claim 1, characterized in that The total cross-sectional area of ​​the channels is at least 40% of the overall cross-sectional area of ​​the hollow shell in a plane perpendicular to the general flow direction of the gas stream.

13. The aerosol distributor according to any one of claims 1 to 12, characterized in that The aerosol outlet hole is located on the upstream surface of the hollow housing.

14. The aerosol distributor according to claim 13, characterized in that The aerosol outlet orifice is located between the channels.

15. The aerosol distributor according to any one of claims 1 to 12 and 14, characterized in that The at least one aerosol inlet is located on the upstream surface of the hollow housing, between the channels.

16. The aerosol distributor according to any one of claims 1 to 12 and 14, characterized in that The hollow shell has a thickness in the range of 5-100 mm.

17. The aerosol distributor according to claim 16, characterized in that The thickness of the hollow shell is in the range of 10-50 mm.

18. The aerosol distributor according to any one of claims 1 to 12, 14 and 17, characterized in that The hollow shell is circular or square.

19. The aerosol distributor according to any one of claims 1 to 12, 14 and 17, characterized in that The aerosol distributor consists of aerosol distributor subunits, wherein each aerosol distributor subunit is an aerosol distributor as defined in any one of claims 1 to 12, 14 and 17.

20. The aerosol distributor according to any one of claims 1 to 12, 14 and 17, characterized in that The hollow shell has an overall width or diameter in the range of 100-1300 mm.

21. The aerosol distributor according to claim 20, characterized in that The hollow housing has an overall width or diameter in the range of 250-650 mm.

22. An apparatus for detecting filter leaks in a gas filtration system, comprising: - a filter housing for sealably mounting a filter within the filter housing such that a gas flow through the filter housing passes through the filter, and - an aerosol distributor located in the gas stream upstream of said filter for releasing a test aerosol from an aerosol source into said gas stream, It is characterized by: The aerosol distributor is an aerosol distributor as defined in any one of claims 1-21.

23. The device according to claim 22, characterized in that The aerosol distributor is positioned so that an upstream surface faces the incoming gas flow and a downstream surface faces the filter, and the aerosol outlet hole is positioned on the upstream surface or in the channel at a position closer to the upstream surface than to the downstream surface.

24. The device according to claim 22, characterized in that The distance between the aerosol distributor and the filter is in the range of 50-400 mm.

25. The device according to claim 22, characterized in that The distance between the aerosol distributor and the filter is in the range of 50-250 mm.

26. The apparatus according to any one of claims 22 to 25, further comprising: - a sampling probe, located in the gas flow downstream of the filter, for sampling gas from the gas flow to be analyzed for the presence of the test aerosol.

27. The device according to claim 26, characterized in that The sampling probe is movable in a plane parallel to the filter surface, such that the filter surface can be scanned using the sampling probe.

28. The device according to claim 26, characterized in that The distance between the sampling probe and the filter is within the range of 5-50 mm.

29. The device according to claim 26, characterized in that The distance between the sampling probe and the filter is within the range of 5-25 mm.

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