GB2551500A

GB2551500A - Combination air filter and separator and filter replacement method

Info

Publication number: GB2551500A
Application number: GB1610629.6A
Authority: GB
Inventors: Richard Pendrill Philip
Original assignee: VEOTEC Ltd
Current assignee: VEOTEC Ltd
Priority date: 2016-06-17
Filing date: 2016-06-17
Publication date: 2017-12-27
Anticipated expiration: 2036-06-17
Also published as: GB2551500B; GB201610629D0

Abstract

A combination air filter and vane separator for an air inlet filter system (e.g. a gas turbine air filter system) comprises an air filter portion 602, a vane separator portion 604 and a flange portion 610, 616 provided together by the air filter and vane separator portions. The air filter portion comprises a filter medium 608 and the vane separator portion comprises a vane array 614. The flange portion is adapted to be received by and secured in an air filter frame (e.g. the air inlet assembly of a gas turbine). A method of replacing an air filter for a gas turbine inlet to additionally include a vane separator is also disclosed. The method comprises removing the existing air filter from a filter frame within the air inlet assembly of a gas turbine and inserting a combination air filter and vane separator into the frame. In the method, the combination air filter and vane separator comprises a portion adapted to be received by and secured in the filter frame. The combination filter and separator may provide a means for incorporating a vane separator into an existing gas turbine inlet filter system.

Description

COMBINATION AIR FILTER AND SEPARATOR AND FILTER REPLACEMENT

METHOD

Field of the Invention

This invention relates to a combination air filter and separator and filter replacement method. Background

Gas turbines have been used in recent times as power sources for vehicles such as ships and aircraft as well as in electrical power generation applications. The basic operating principle of a gas turbine requires the intake of atmospheric air to a compressor. If the gas turbine is being operated in an environment where the atmosphere is polluted, dusty, moist or salty, it is necessary to filter out such impurities using an air inlet filter and/or vane separator / coalescer combination to maintain turbine performance and protect the turbine from damage.

An air filter is the name of the device used to filter out solid particles such as dust from the air flowing toward the gas turbine. Air filters generally comprise sheets of fibrous filter media extending perpendicularly across the entire airflow. Accordingly, all airborne particles flowing towards the gas turbine will impinge upon the filter media and be removed from the airflow. The filter media is generally supported by a frame so that the filter media can be maintained in place spanning the entire airflow. Industry standard frame sizes vary, but usually have lengths and widths ranging from 550mm to 700mm. Square frames of 597mm x 597mm are common. Typical depths between the upstream and downstream faces may be in the region of 40-100mm.

In contrast to an air filter, a vane separator is used to remove water from the air flowing toward the gas turbine. Vane separators for gas turbines are generally comprised of an array of corrugated metal (stainless steel) vanes arranged side-by-side across the airflow. Moist air is directed to the surface of the vanes where liquid and vapour are separated. From here, it may drain down under gravity and be removed from the airflow, thus substantially decreasing the moisture content of the air. The process of removing moisture from the airflow is very important, as moisture carries contaminants such as salt and dust, which may cause fouling and reduce turbine efficiency. Worse still, in freezing conditions, ice may form, causing permanent damage to the turbine. Accordingly, vane separator design has evolved to remove as much moisture as possible and to cope with the stresses and strains of extreme environmental conditions. This optimisation has meant that vane separators are exceedingly heavy, weighing up to as much as 1000kg or more. Moreover, compared to air filters, vane separators have significantly longer lifespans and should therefore be significantly more robust.

In some instances, at the time of installation, the environment in which a gas turbine inlet filter system is situated may have been considered to be sufficiently dry that provision of a vane separator was not required. Subsequent testing of the gas turbine in operation may determine that excessive levels of water are entering the gas turbine, reducing efficiency or, in freezing conditions, causing permanent damage due to ice build-up. When it is determined that excess water is entering the gas turbine, a vane separator is typically bolted on to the upstream end of the existing inlet filter system. This solution is not ideal. Normally, vane separators are large and heavy, the structures in place for the existing filter systems may not be sufficient to support the extra weight of the vane separator. In some instances, there is not enough space to include a vane separator in this way.

Other solutions in which the vane separator is not simply attached to the upstream end of the existing filter system involve more significant modifications and are therefore difficult to effect and even more expensive.

In other circumstances, a vane separator may be present in an existing gas turbine inlet filter system, but excess moisture is still reaching the gas turbine inlet. In this case, a simple method to provide additional moisture separation is desirable.

Aspects of the present invention provide elegant, cost-effective solutions to the problem of how to incorporate a vane separator into an existing gas turbine inlet filter system.

Other features and advantages of exemplary embodiments of the present invention will be apparent from the following description taken in conjunction with the accompanying drawings.

Summary

In accordance with a preferred embodiment of the invention, a combination air filter and vane separator for an air inlet filter system (e.g. a gas turbine air filter system) is provided comprising an air filter portion, a vane separator portion and a flange portion provided together by the air filter and vane separator portions. The flange portion is adapted to be received by and secured in an air filter frame (e.g. the air inlet assembly of a gas turbine).The air filter portion comprises filter media and the vane separator portion comprises a vane array.

In some embodiments, the air filter portion and the vane separator portion are separate units, and the flange portion is comprised of respective flange portions of the air filter and the vane separator portions adapted to be received by the air filter frame. In such embodiments, the size and shape of the respective flange portions (of the filter and vane separator) in a plane perpendicular to the direction of flow (the depth dimension) are the same. The combined depth of the respective flange portions is sized to fit between downstream and upstream limits of the filter frame when the filter frame is in position in the air inlet filter system such that the combination air filter and vane separator are secured in place.

Some embodiments may provide that the vane separator portion comprises a vane array surround portion and/or the air filter portion comprises a filter medium surround portion, wherein each of the vane array surround portion and the filter medium surround portion extend in the depth dimension away from their respective flange portions. The vane array surround portion and the filter media surround portion may surround the vane array and the filter media respectively in all directions perpendicular to the depth dimension. The size and shape of the vane array surround portion and the filter media surround portion in the plane perpendicular to the depth dimension may be the same as the size and shape of respective apertures in the filter frame in a plane perpendicular to airflow when the filter frame is in position in the air inlet filter system

In some embodiments, the separator flange portion, the filter flange portion, the vane array surround portion or the filter media surround portion may have a square or rectangle shape in the plane perpendicular to the air flow (the depth dimension).

Some embodiments may provide for the vane array surround portion to further comprise top and bottom support members. The vane array may comprise vanes made of plastics material.

In some embodiments, the separator flange portion and the filter flange portion have the same size and shape in the plane perpendicular to the depth dimension (the vane array surround portion the filter media surround portion may also have the same size and shape in the plane perpendicular to the depth dimension). In this embodiment, when arranged back-to-back in the depth direction, the separator flange portion and the filter flange portion are suitable to be received by and secured in the air filter frame.

In a further preferred embodiment in accordance with the invention, a method of replacing an air filter (e.g. for a gas turbine inlet) to additionally include a vane separator is also provided. The method comprises removing the existing air filter from a filter frame within the air inlet assembly and inserting a combination air filter and vane separator into the frame. In the method, the combination air filter and vane separator comprises a portion adapted to be received by and secured in the filter frame.

Various embodiments are now described by way of example only, with reference to the accompanying drawings.

Brief Description of the Drawings

Figure lisa plan view of a typical existing gas turbine and inlet filter system.

Figure 2 is a perspective view of the air filter frame suitable for the inlet filter system in Figure 1.

Figures 3, 4 and 5 are perspective views of various alternative air filter frames, alternative to that of Figure 2.

Figure 6 is an exploded cross-sectional view of an air filter and vane separator suitable for a gas turbine air inlet.

Figure 7 is a perspective view of the air filter and vane separator of Figure 6 in place in an inlet filter system.

Figure 8 is a perspective view showing the air filter of Figure 6 in greater detail.

Figure 9 is a perspective view showing the vane separator of Figure 6 in greater detail.

Detailed Description

Figure 1 shows a plan view of a prior art gas turbine and inlet filter system. Gas turbine 102 is connected at its air inlet 104 to inlet ducting 106. At the upstream end of the inlet ducting 106, an air filter 108 is arranged to extend across substantially the entire cross-sectional area of the inlet ducting 106 so that all air flowing towards the gas turbine inlet 104 passes through the filter media. The air filter 108 is kept in place by air filter frame 110. Although shown as comprising two separate planar members, it will be appreciated that filter frame 110 may comprise a single unit having a substantially U-shaped cross-section.

As indicated above, filter frames are available having standard dimensions. This ensures interoperability in different inlet filter systems. Standard filter frame dimensions are chosen to fit tightly into ducting, which itself has standard dimensions. For example, frames may be 597mm x 597mm, as previously stated. Another standard dimension of filter frames is the depth, which defines the extent of a filter frame parallel to the airflow. In Figure 1, the depth 112 is defined by the separation of the two planar members of the frame 110. Depth 112 is sufficient to accommodate and secure the air filter 108 in place. Typical depths 112 may be in the region of 40-100mm.

Vane separator 114 is secured upstream of the air filter 108. Such an arrangement is preferable, as any water contacting the filter media may decrease its efficacy and/or reduce the lifetime of the filter media. Vane separator 114 is supported in separator frame 116. As indicated above, the vanes of the vane separator 114 are generally made of stainless steel can be heavy. Thus, in general, separator frames are formed of lengths of heavy-duty metal welded together to provide sufficient support for the vanes.

Figure 2 shows a perspective view of air filter frame 110 from Figure 1. The depth 112 between the planar members of the air filter frame 110 can be readily seen. The downstream planar member includes downstream aperture 202 and the upstream planar member includes upstream aperture 204. Although inlet ducting 106 is shown extending upstream and downstream of filter frame 110, one skilled in the art will appreciate that the air filter frame 110 may be at the upstream limit of the inlet ducting 106.

In accordance with the present invention, the existing support structure provided by filter frame 110 is used to provide support for a novel combination of an air filter and vane separator. Such an arrangement allows a vane separator to be retrofitted to an existing gas turbine inlet filter system.

Figure 3 is a perspective view of an air filter frame, alternative to that of Figure 2. Air filter frame 302 represents a simpler construction for air filter frame 110 than that of Figure 2. In an existing filter system with such a filter frame, a filter is slid along the channel formed by the upstream and downstream planar members. An equivalent channel may also be formed at the top of the inlet ducting by further planar members.

While filter frame 110 has been shown as including planar members displaced apart along the direction of airflow, it will be appreciated that other air filter frame designs are possible. Figure 4 is a perspective view of an air filter frame, alternative to that of Figures 2 and 3. Air filter frame 402 is ‘L’ shaped. It comprises vertical flat section 404 and horizontal flat section 406, which lie flat on the inner surface of inlet ducting 106, and horizontal flange section 408 and vertical flange section 410 extending inward from the inlet ducting 106. In an existing filter system with such a filter frame, filters are kept in place by clips 412 and 414. Note that a further clip may be provided on the opposite end of the bottom flat section. Such a design enables easy access to the filter from the side opposite flange sections 408 and 410. Typically, the flange sections are arranged on the upstream side, so filter frame 402 provides easy access from the downstream side.

In addition to the planar members of shown in Figure 2, the filter frame may further comprise portions surrounding the filter media in all directions perpendicular to the airflow toward the gas turbine. Air filter frame 502 in Figure 5 is such a filter frame.

Figure 6 is an exploded sectional view of an air filter and vane separator suitable for a gas turbine air inlet in accordance with a preferred embodiment of the invention. Air filter 602 and vane separator 604 are provided as separate units having substantially the same size and shape. Having separate units is particularly advantageous because the lifetime of air filter 602 may be substantially shorter than that of vane separator 604. Thus, should filter 602 require replacing, one need only replace air filter 602, and not vane separator 604.

Air filter 602 comprises two main sections: filter media surround portion 606, surrounding filter media 608; and filter flange portion 610 arranged substantially concentrically with filter media surround portion 606. Filter media surround portion 606 has a height and width such that, when in position in inlet ducting 106, filter media surround portion 606 fits into downstream aperture 202 without leaving any gap for airflow toward the gas turbine 102 except through filter media 608. Filter media surround portion 606 and filter media 608 may have height and widths in the range of 500mm to 650mm and 490mm to 640mm, respectively. In a preferred embodiment, filter media surround portion 606 is square with height and width of 553mm, surrounding filter media 608 having height and width of 536mm and a depth in the range 25mm to 60mm, and more particularly a depth of 44mm. Filter flange portion 610 is dimensioned to fit within inlet ducting 106, to allow airflow through filter media 608, and so that it is supported by air filter frame 110. Filter flange portion 610 may have a height and width in the range of 550mm to 700mm. In a preferred embodiment, the filter flange portion 610 is square, having an aperture through which air may flow to the filter media 608. The height and width of the filter flange portion 610 in this embodiment is 592mm. Whereas dimensions are specified herein to some precision, it will be understood that such detail merely coincides with preferred standard dimensions and that there is considerable scope for variation in the height and width dimensions (e.g. ± about 8mm) provided that the flange fits within the housing and scope for variation in the thickness (depth dimension) of the flanges provided that the combination fits within the housing (e.g. ± about 8mm each and ± about 4mm in combination).

In a preferred embodiment, filter media 608 is largely composed of polyester, although one skilled in the art will recognise that many materials may be used for filter media 608. Whatever material is used, filter media 608 is light, so the strength requirements of the filter media surround portion 606 and filter flange portion 310 are not particularly onerous. Indeed, filter media surround portion 606 and filter flange portion 610 may be composed of high-impact polystyrene.

Similar to air filter 602, vane separator 604 also comprises two main sections: vane array surround portion 612, surrounding vane array 614; and separator flange portion 616 arranged substantially concentrically with vane array surround portion 612. Again, vane array surround portion 612 has a height and width such that, when in position in inlet ducting 106, filter media surround portion 612 fits into upstream aperture 204 so that airflow toward the gas turbine 102 must pass through vane array 414. Vane array surround portion 612 and vane array 614 may have height and widths in the range of 500mm to 650mm and 490mm to 640mm, respectively. In a preferred embodiment, vane array surround portion 612 is square with height and width of 553mm, surrounding vane array 614. Vane array surround portion 612 may further comprise drainage holes (not shown) toward the upstream end to enable increased drainage.

Separator flange portion 616 is dimensioned to fit within inlet ducting 106, to allow airflow through vane array 614, and so that it is supported by air filter frame 110. Separator flange portion 616 may have a height and width in the range of 550mm to 700mm. In a preferred embodiment, the separator flange portion 616 is square, having an aperture through which air may flow from vane array 614 to filter media 408 in air filter 602. The height and width of the separator flange portion 616 in this embodiment is 593mm.

In a preferred embodiment, the vanes of vane array 614 are composed of PVC. Alternatively, PPTV or other plastics material may be used. Use of plastic as opposed to metal for the vanes, although not strictly necessary, has the advantage that the weight of vane array 614 is reduced. Accordingly, vane array surround portion 412 and separator flange portion 616 need not be as bulky as may otherwise be the case. This in turn may allow existing filter frame 110 to support the combined weight of air filter 602 and vane separator 604. While plastic vanes may not be as durable as metal vanes, in many systems that did not originally include vane separators, the stresses on the vane array are less than those that always comprised vane separators. Plastic vanes therefore provide adequate performance. Vane separator 604 must still support vane array 614, so it must be strong compared to air filter 602. To achieve this, vane array surround portion 612 and separator flange portion 616, like filter media surround portion 608 and separator flange portion 610 are composed of high-impact polystyrene. However, vane array surround portion 412 and separator flange portion 616 are further reinforced at top and bottom by top vane support member 618 and bottom vane support member 620. Preferably, top vane support member 618 and bottom vane support member 620 are composed of aluminium. Bottom vane support member 620 may be taller than top vane support member 618. It may form a trough that assists in the collecting of water. The vane array surround portion 612 may further comprise drainage holes on a lower face to provide drainage away from the gas turbine.

Filter flange portion 610 and separator flange portion 616 have respective depths 618 and 620. The sum of depths 622 and 624 is substantially the same as depth 112 of the existing filter frame 110, so that the combined filter and separator is secured within filter frame 110 against movement within the inlet ducting 106. In a preferred embodiment, each of depths 622 and 624 are in the range of 15-30mm, more particularly each of 622 and 624 may be 22mm.

Figure 7 shows a perspective view of the air filter and vane separator of Figure 6 in place in the inlet filter assembly. In operation, air flows from the upstream end of inlet ducting 106 through vane array 614. After this stage, the moisture has been separated out of the airflow so that the airflow is relatively dry, but still contains dust and other solid particles. The airflow then passes through filter media 608 after which there is no significant moisture or solid particles remaining in the airflow, so that the air can pass into a gas turbine without reducing turbine efficiency or causing damage.

Figure 8 is a perspective view showing air filter 602 of Figure 6 in greater detail. In particular, Figure 8 shows that filter media surround portion 606 is composed of four elongate filter surround sections 802, connected at four comers by filter surround comer sections 804 to form a square. Both elongate filter surround sections 802 and filter surround corner sections 804 are preferably made of high-impact polystyrene. Strips (not shown) extending from filter surround comer sections 804 are configured to extend into slots in two elongate filter surround sections 802 to join them at a particular comer. The strips may be glued into place in the elongate filter surround section to prevent disconnection. Filter flange portion 610 employs a similar construction to filter media surround portion 606 in that it is also composed of elongate filter flange sections 806 and filter flange comer sections 808. Preferably, both elongate filter flange sections 806 and filter flange comer sections 808 are also made of high-impact polystyrene.

Figure 9 is a perspective view showing vane separator 604 of Figure 6 in greater detail. Vane separator 604 has substantially the same construction as air filter 602. Vane array surround portion 612 is composed of elongate vane array surround sections 902 and vane array surround comer portions 904. Likewise, separator flange portion 616 is composed of elongate separator flange sections 906 and separator flange corner portions 908. All these components are preferably made of high-impact polystyrene.

In certain embodiments, the flange portion may be provided by one or other of the air filter portion and vane separator portion in a manner whereby, when placed together, they are able to be secured in place by the same frame or other fixing means. In certain preferred embodiments, each may contribute to the flange portion (e.g. side by side or at the top and bottom) so that securing the flange portion causes the two to be secured in place.

Filter Replacement Method

The following method uses the combination vane separator and air filter described above to allow a vane separator to be added to an existing gas turbine air inlet filter system.

The existing filter must first be removed from its filter frame 110. Depending on the filter’s construction, this may entail different processes. For example, for the air filter frames in Figure 3, the existing filter can be slid out of the filter frame without dismantling the filter frame. Similarly, the filter frame 402 of Figure 4 may be unclipped and removed from the downstream side. The filter frame may also employ a similar method of construction as air filter 602 and vane separator 604 of the present invention. That is, the filter frame may comprise a square formed of elongate sections connected at corners by corner sections. Removing the existing filter frame may therefore also entail dismantling the sections to remove the existing filter/filter media.

Depths (thicknesses) 622 and 624 are such that they can be accommodated securely within filter frame 110. For filter frame 302 in Figure 3, combination air filter 602 and vane separator 604 may be slid into place. If not already present, drainage holes can be made in the channel formed between the planar members of the filter frame to provide drainage for any water collecting in that channel. Vane separator 604 can be sealed at its upstream side to the filter frame and to inlet ducting 106. Similar sealing can be applied to air filter 602 on its downstream side.

For filter frame 402, any water leaking downstream of flange section 404 may flow toward the gas turbine. Accordingly, it may be beneficial to provide a ‘chair’ component to provide a barrier to that flow and to support the air filter. Such a component may have an ‘h’ shaped cross-section when viewed from the side of the inlet ducting 106. The ‘chair’ is secured to the bottom of the inlet ducting 106 and sealed at its upstream end to prevent water leaking from the separator flowing further downstream. If not already present, drainage holes can be made in the channel formed between flange section 404 and the upstream end of the ‘chair’ to provide drainage for any water collecting in that channel. Vane separator 604 can be sealed at its upstream side to the filter frame and to inlet ducting 106.

For filter frame 502, after removal of the existing filter/filter media, the existing filter frame can be reconstructed around portions of the combination air filter 602 and vane separator 604 of Figure 6. In particular, the existing filter frame can be reconstructed around flange portions 610 and 616 air filter 602 and vane separator 604 of Figure 6, with filter media surround portion 606 extending through downstream aperture 202 and vane array surround portion 612 extending through upstream aperture 204.

The filter frame 110 is then reconnected to inlet ducting 106 and the filter system with increased moisture separation is ready to be used.

As many apparently different embodiments of the present invention can be made without departing from the scope thereof, it is to be understood that the invention is not limited to the specific embodiments thereof.

Claims

1. A combination air filter and vane separator for an inlet filter system, comprising: an air filter portion comprising a filter medium; a vane separator portion comprising a vane array; and the air filter and vane separator together providing a flange portion adapted to be received by and secured in an air filter frame.

2. The combination air filter and vane separator of claim 1, wherein the air filter portion and the vane separator portion are separate units, and the flange portion is comprised of respective flange portions of the air filter and the vane separator portions adapted to be received by the air filter frame.

3. The combination air filter and vane separator of claim 2, wherein each of the respective flange portions has substantially the same size and shape in a plane perpendicular to airflow when the filter frame is in position in the air inlet filter system, and wherein the combined depth of the respective flange portions parallel to the airflow secures the combination air filter and vane separator in place between downstream and upstream limits of the filter frame when the filter frame is in position in the air inlet filter system.

4. The combination air filter and vane separator of claim 3, wherein the shape of the respective flange portions in the plane perpendicular to the depth dimension is a rectangle or square.

5. The combination air filter and vane separator of any of claims 2-4, wherein the vane separator portion comprises a vane array surround portion extending in the depth dimension away from the flange portion of the vane separator portion.

6. The combination air filter and vane separator of claim 5, wherein the vane array surround portion surrounds the vane array in all directions perpendicular to the depth dimension.

7. The combination air filter and vane separator of claim 6, wherein the vane array surround portion has a substantially same size and shape in a plane perpendicular to the depth dimension as the size and shape of an aperture in the filter frame in a plane perpendicular to airflow when the filter frame is in position in the air inlet filter system.

8. The combination air filter and vane separator of claim 7, wherein the shape of the vane array surround portion in the plane perpendicular to the depth dimension is a rectangle or square.

9. The combination air filter and vane separator of any of claims 5-8, wherein the vane array surround portion further comprises top and bottom support members.

10. The combination air filter and vane separator of any of claims 5-9, the vane array surround portion further comprises one or more drainage holes to allow separated water to drain on the upstream side of the filter frame.

11. The combination air filter and vane separator of any of claims 2-10, wherein the vanes of the vane array are made of plastics material.

12. The combination air filter and vane separator of claims 2-11, wherein the air filter portion comprises a filter media surround portion extending in the depth dimension away from the flange portion of the air filter portion.

13. The combination air filter and vane separator of claim 12, wherein the filter media surround portion surrounds the filter media in all directions perpendicular to the depth dimension.

14. The combination air filter and vane separator of claims 2-13, wherein: the separator flange portion and the filter flange portion have the same size and shape in the plane perpendicular to the depth dimension; and when arranged back-to-back in the depth direction, the separator flange portion and the filter flange portion are suitable to be received by and secured in the air filter frame

15. A gas turbine inlet filter system comprising: the filter frame and the combination air filter and vane separator of any preceding claim.

16. The gas turbine filter system of claim 15, wherein the vane separator is arranged upstream of the air filter.

17. The gas turbine inlet filter system of claim 15 or 16, further comprising a gas turbine.

18. A combination air filter and vane separator for a gas turbine air inlet assembly substantially as described herein, with reference to Figures 4 to 7.

19. A method of replacing an air filter for a gas turbine inlet to additionally include a vane separator, comprising: removing the existing air filter from a filter frame within the air inlet assembly of a gas turbine; and inserting a combination air filter and vane separator into the frame, wherein the combination air filter and vane separator comprises a portion adapted to be received by and secured in the filter frame.

20. The method of claim 19, further comprising sealing the combination air filter and vane separator to the filter frame and/or inlet ducting to prevent water leaking downstream.