Patent Publication Number: US-2015082758-A1

Title: Pulse filter design

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates generally to a filter element and, more particularly, to a filter element having an improved filtration efficiency. 
     2. Discussion of the Prior Art 
     Inlet systems for gas turbines are generally used for treating air that passes to the gas turbine. The air can be treated by filtering the air with one or more filter elements provided within the inlet system. The filtration efficiency of the inlet system is somewhat constrained by the total number of filter elements that can be accommodated within the inlet system. Additionally, factors such as the total area of filtration media, pressure drop caused by the filter elements, etc. can also affect the filtration efficiency of the inlet system. Accordingly, it would be useful to provide a filter element having a size and/or construction that allows for a greater total number of filter elements to be provided in the inlet system so as to provide an improved filtration efficiency. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The following presents a simplified summary of the invention in order to provide a basic understanding of some example aspects of the invention. This summary is not an extensive overview of the invention. Moreover, this summary is not intended to identify critical elements of the invention nor delineate the scope of the invention. The sole purpose of the summary is to present some concepts of the invention in simplified form as a prelude to the more detailed description that is presented later. 
     In accordance with one aspect, the present invention provides a filter element including a first filter portion extending between a first end and an opposing second end. The first filter portion includes a first cross-sectional dimension that is substantially constant along a length of the first filter portion between the first end and the second end. The filter element includes a second filter portion extending between a third end and an opposing fourth end with the third end being located adjacent the second end. The third end has a third end cross-sectional dimension that substantially matches the first cross-sectional dimension, the fourth end having a fourth end cross-sectional dimension that is smaller than the third end cross-sectional dimension. 
     In accordance with another aspect, the present invention provides a filter element including a first filter portion extending along a longitudinal axis between a first end and an opposing second end. The filter element includes a second filter portion extending along the longitudinal axis between a third end and an opposing fourth end. The first filter portion and second filter portion include a plurality of sides that are substantially planar. 
     In accordance with another aspect, the present invention provides a filter element including a first filter portion extending along a longitudinal axis between a first end and an opposing second end. The first filter portion includes a substantially cylindrical shape. The filter element includes a second filter portion extending along the longitudinal axis between a third end and an opposing fourth end with the third end being located adjacent the second end. The second filter portion includes a substantially conical shape. The first filter portion and second filter portion include a plurality of sides that are substantially planar. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other aspects of the present invention will become apparent to those skilled in the art to which the present invention relates upon reading the following description with reference to the accompanying drawings, in which: 
         FIG. 1  is a schematized cross-section view of an example inlet system including an example filter element in accordance with an aspect of the present invention 
         FIG. 2  is a perspective view of the example filter element including an example partition in accordance with an aspect of the present invention; 
         FIG. 3  is a side elevation view of the example filter element of  FIG. 2 , including example dimensions of the filter element; 
         FIG. 4  is a schematized perspective view of a second example filter element in accordance with an aspect of the present invention; 
         FIG. 5  is a side elevation view of the second example filter element of  FIG. 4 , including example dimensions of the second filter element; 
         FIG. 6  is a schematized perspective view of a third example filter element in accordance with an aspect of the present invention; 
         FIG. 7  is a side elevation view of the third example filter element of  FIG. 6 , including example dimensions of the third filter element; 
         FIG. 8  is an end view of a fourth example filter element in accordance with an aspect of the present invention; 
         FIG. 9  is a cross-section view of an example of one of the second filter element, third filter element, or fourth filter element. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Example embodiments that incorporate one or more aspects of the present invention are described and illustrated in the drawings. These illustrated examples are not intended to be a limitation on the present invention. For example, one or more aspects of the present invention can be utilized in other embodiments and even other types of devices. Moreover, certain terminology is used herein for convenience only and is not to be taken as a limitation on the present invention. Still further, in the drawings, the same reference numerals are employed for designating the same elements. 
       FIG. 1  illustrates an example inlet system  10  for delivering an air flow to a device, such as a gas turbine, according to one example. An entering air flow  13  can be drawn from an exterior location and into the inlet system  10 . The entering air flow  13  can be filtered before exiting the inlet system  10 . 
     The inlet system  10  can include an inlet section  14 . It should be appreciated that the inlet section  14  is somewhat generically shown within  FIG. 1 . This generic representation is intended to convey the concept that the inlet section  14  of the inlet system  10  shown in  FIG. 1  can represent a prior art construction or a construction in accordance with one or more aspects of the present invention as will be described below. The inlet section  14  can be positioned at an upstream location of the inlet system  10 . The inlet section  14  can define an open area through which the entering air flow  13  can enter the inlet system  10 . The inlet section  14  can include one or more hoods  16 . The hoods  16  can provide a shielding function to help protect the inlet system  10  from ingesting at least some materials and/or precipitation that may otherwise enter the inlet section  14 . 
     The example inlet system  10  can further include a filter section  18  positioned adjacent to, and downstream from, the inlet section  14 . The filter section  18  can be in fluid communication with the inlet section  14 , such that the filter section  18  can receive the entering air flow  13  from the inlet section  14 . The filter section  18  defines a chamber  19  that includes a substantially open area. The chamber  19  can be substantially hollow such that air can enter and flow through the chamber  19 . 
     The filter section  18  can further include one or more filter elements  20  positioned within the chamber  19 . The filter elements  20  are shown to extend substantially horizontally within the filter section  18  and can be arranged in a vertically stacked orientation (i.e., one filter element above another filter element). However, in other examples, the filter elements  20  can be arranged in a vertically staggered position, such that a filter element  20  is not positioned directly above or below an adjacent filter element. The filter elements  20  can be positioned adjacent a bottom wall of the filter section  18  at a lower location. The filter elements  20  can be substantially evenly spaced apart from adjacent filter elements in the vertically stacked orientation upwards towards a top wall. In further examples, the filter elements  20  may not be evenly spaced apart in the vertical direction, such that some filter elements are closer or farther apart from adjacent filter elements than others. Similarly, the filter elements  20  can be arranged to be horizontally spaced apart, such that the filter elements  20  can extend across the filter section  18  in a column-like formation. It is to be understood that the filter elements  20  are only generically shown, and that the inlet system  10  could include a greater or fewer number of filter elements than in the shown example. 
     The filter elements  20  can each be attached to a partition  22  that is positioned at a downstream location of the filter section  18 . The partition  22  can include a substantially vertically oriented wall that extends across the filter section  18  in a direction substantially perpendicular to an air flow direction. Specifically, the partition  22  can extend from the bottom wall towards the top wall and between opposing side walls of the filter section  18 . The partition  22  can include a substantially non-porous structure, such that air flow is reduced and/or prevented from flowing through the partition  22 . 
     The partition  22  includes one or more apertures  23  extending through the partition  22 . The apertures  23  define openings through which the air flow can exit the filter section  18 . As such, each of the filter elements  20  can be attached to surround an aperture  23 . The entering air flow  13  can therefore pass through the filter elements  20  prior to passing through the apertures  23  and exiting the filter section  18 . After exiting the filter section  18 , the air can pass through the outlet section  24  and through an outlet  25 , whereupon the air exits the outlet  25  as exiting air flow  26 . 
     Turning now to  FIG. 2 , an example filter element  20  is illustrated. As shown in  FIG. 2 , a single filter element  20  is depicted attached to a section of the partition  22 . It is to be understood that the filter element  20  and partition  22  are somewhat generically shown within  FIG. 2 , and could take on a variety of constructions in accordance with one or more aspects of the present invention. For instance, the remaining filter elements can be similar and/or identical to the filter element  20  in the shown example or, in the alternative, could take on a number of different sizes and shapes. In some examples, the filter element  20  can include a plurality of filters (e.g., greater than two) joined together to form the single filter element  20 . In one possible example, the filter element  20  comprises a single, one-piece filter element. 
     The filter element  20  can include a first filter portion  30 . The first filter portion  30  can extend along a longitudinal axis  32  between a first end  34  and an opposing second end  36 . In an example, the first end  34  of the first filter portion  30  is attached to the partition  22 . The first end  34  can be attached to the partition  22  in any number of ways, including, but not limited to, adhesives, mechanical fasteners, snap fit means, or the like. The first end  34  of the first filter portion  30  can include a cross-sectional size (e.g., diameter, etc.) that substantially matches or is slightly larger than a diameter of an aperture  23  (shown only in phantom in  FIG. 2 , as the aperture  23  is normally not visible in such a view) through the partition  22 . The first filter portion  30  can include a first filter media  38 . The first filter media  38  can be arranged to circumferentially encircle and extend along the longitudinal axis  32 . The first filter media  38  includes any number of materials that can filter particulates from air. 
     The first filter portion  30  can have a substantially cylindrical shape, and, in particular, a circle-cylinder shape. In an example, the first filter portion  30  includes a circular cross-section with a substantially constant cross-sectional dimension (e.g., diameter) along the longitudinal axis  32  between the first end  34  and the second end  36 . The first filter portion  30  may include any selected dimensions (e.g., diameter and axial length). In an example, the first filter portion  30  includes a length of about 66 cm (˜26 inches). 
     The filter element  20  can include a second filter portion  40 . The second filter portion  40  can extend along the longitudinal axis  32  between a third end  42  and an opposing fourth end  44 . In an example, the third end  42  of the second filter portion  40  is positioned adjacent the second end  36  of the first filter portion  30 . In some examples, the third end  42  of the second filter portion  40  is attached to the second end  36  of the first filter portion  30 . The third end  42  can be positioned substantially flush with respect to the second end  36 , such that the first filter portion  30  and second filter portion  40  define a substantially contiguous filter element with limited/reduced openings, gaps, etc. through which air can pass through. The second filter portion  40  can include a truncated conical shape as one example conical shape. Also, as an example, the conical shape has a circular cross-section that varies in size along the axis (i.e., the diameter varies). In an example, the truncated conical shape of the second filter portion  40  can be tapered in a direction along the longitudinal axis  32  away from the first filter portion  30 . As such, the diameter decreases as the second filter portion  40  extends away from the first filter portion  30 . The second filter portion  40  can include a second filter media  45 . The second filter media  45  can be arranged to circumferentially encircle and extend along the longitudinal axis  32 . The second filter media  45  includes any number of materials that can filter particulates from air. 
     The filter element  20  can further include an end cap  46 . The end cap  46  can function to seal the fourth end  44  of the second filter portion  40 . The end cap  46  can be positioned at the fourth end  44  of the second filter portion  40  located opposite the first filter portion  30 . The end cap  46  is shown to be circular in shape, though a variety of sizes/shapes are contemplated. Accordingly, the end cap  46  can reduce and/or prevent the passage of air through the end of the filter element  20 . 
     Turning to  FIG. 3 , a side elevation view of the filter element  20  is illustrated. In this example, the first filter portion  30  can include a first cross-sectional dimension  54 . In an example, the first cross-sectional dimension  54  includes a diameter. In other examples, the first filter portion  30  is not limited to including a circular, cylindrical shape with a circular cross-section, and other shapes are envisioned. In an example, the first cross-sectional dimension  54  (e.g., diameter) of the first filter portion  30  is about 42 cm (˜16.5 inches). It will be appreciated, however, that the first filter portion  30  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. 
     The second filter portion  40  can include a third end cross-sectional dimension  56 . In an example, the third end cross-sectional dimension  56  includes a dimension (e.g., diameter) of the third end  42  of the second filter portion  40 . The second filter portion  40  is not limited to including a truncated, conical shape with a circular cross-section, as other shapes are envisioned. In an example, the third end cross-sectional dimension  56  (e.g., diameter) of the second filter portion  40  is about 42 cm (˜16.5 inches). It will be appreciated, however, that the second filter portion  40  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. In some examples, the third end cross-sectional dimension  56  substantially matches the first cross-sectional dimension  54 . 
     The second filter portion  40  can include a fourth end cross-sectional dimension  58 . In an example, the fourth end cross-sectional dimension  58  includes a dimension (e.g., diameter) of the fourth end  44  of the second filter portion  40 . In an example, the fourth end cross-sectional dimension  58  of the second filter portion  40  is about 32 cm (˜12.75 inches). It will be appreciated, however, that the fourth end cross-sectional dimension  58  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. In an example, the fourth end cross-sectional dimension  58  is smaller than the third end cross-sectional dimension  56  and the first cross-sectional dimension  54 . 
     The filter element  20  provides a number of benefits. In an example, the filter element  20  has a maximum cross-sectional size (e.g., diameter) of about 42 cm (˜16.5 inches) at the first cross-sectional dimension  54  and the third end cross-sectional dimension  56 . These cross-sectional sizes are smaller than in previous examples, such that a greater number of filter elements  20  can be housed within the chamber  19  of the filter section  18 , thus leading to an improved filtration efficiency of the inlet system  10 . In an example, the filter element  20  provides a larger total area of filter media (e.g., first filter media  38  and second filter media  45 ) such that filtration capability of the filter element  20  is improved. In an example, with first filter portion  30  and second filter portion  40  each comprising a length of about 66 cm (˜26 inches), the filter element  20  includes a total filtration area of about 52 m 2 . In such an example, the first filter portion  30  has a total filtration area of about 34.5 m 2  while the second filter portion  40  has a total filtration area of about 17 m 2 . By having a maximized diameter at the junction where the first filter portion  30  joins the second filter portion  40 , pressure loss is reduced across this junction, leading to a reduced pressure drop. In addition, flow distribution and filter media utilization is increased, leading to improved filtration efficiency, longer filter life, more effective pulse cleaning, etc. 
     In some examples, due to these improvements in the filter element  20 , a fewer total number of filter elements  20  may be provided in the filter section  18  while still achieving a similar or greater filtration efficiency of the inlet system  10 , thus leading to a smaller sized (e.g., reduced height) filter section  18 . In one possible example, the filter section  18  may have a reduced height of about 91 cm (˜3 ft). Further, the filter elements  20  can exhibit a lower pressure drop within the filter section  18 , which leads to a longer filter life, better filtration, efficiency, etc. In some examples, the filter elements  20  reduces pressure drop within the filter section  18  by 0.2 inches water gauge. 
     Turning to  FIG. 4 , a second example filter element  120  is illustrated. It will be appreciated that the second filter element  120  is illustrated somewhat generically/schematically so as to illustrate the structure of the second filter element  120 . In general, the second filter element  120  can be attached to the partition  22  at an aperture (not shown) in a similar manner as described with respect to the filter element  20 . The second filter element  120  can include a filter media, such as, for example, the first filter media  38  and second filter media  45 , for filtering particulates from air. 
     The second filter element  120  can include a first filter portion  130 . The first filter portion  130  can extend along the longitudinal axis  32  between the first end  34  and the opposing second end  36 . The first filter portion  130  of the second filter element  120  can be attached to the partition  22 . In some examples, the first filter media  38  comprises a plurality of different first filter media  38  for different first sides  131  of the first filter portion  130 . For example, one of the first sides  131  can include a first type of the first filter media  38  while another of the first sides  131  can include a second type of the first filter media  38 , wherein the second type of the first filter media  38  is different than the first type of the first filter media  38 . Differences in the first filter media  38  for differing first sides  131  include, but are not limited to, the type of filter media, thickness, filtration efficiency, media area, pleating, etc. 
     The first filter portion  130  can include a generally cylindrical shape with a polygonal cross-section. For example, the first filter portion  130  includes a generally constant cross-sectional dimension extending along the longitudinal axis  32 . In this example, the first filter portion  130  includes one or more first sides  131  that are substantially planar. In the illustrated example, the first filter portion  130  can include eight first sides  131 , such that the first filter portion  130  defines an octagonal cross-section. As such, the presented example is an eight-sided or octagon cylinder. The first filter portion  130  is not limited to including eight first sides  131 , and in other examples, could include any number of sides, including planar sides. In an example, the first filter portion  130  includes a length of about 66 cm (˜26 inches). 
     The second filter element  120  can include a second filter portion  140 . The second filter portion  140  can extend along the longitudinal axis  32  between the third end  42  and the opposing fourth end  44 . In an example, the third end  42  of the second filter portion  140  is positioned adjacent the second end  36  of the first filter portion  130 . The third end  42  can be positioned substantially flush with respect to the second end  36 , such that the first filter portion  130  and second filter portion  140  define a substantially contiguous filter element with limited/reduced openings, gaps, etc. through which air can pass through. 
     The second filter portion  140  can include a truncated conical shape with a polygonal cross-section. For example, the second filter portion  140  can be tapered in a direction along the longitudinal axis  32  away from the first filter portion  130 . In some examples, the second filter portion  140  has a generally decreasing cross-sectional dimension extending along the longitudinal axis  32  from the third end  42  to the fourth end  44 . In some examples, the second filter portion  140  includes one or more second sides  141  that are substantially planar. In the illustrated example, the second filter portion  140  can include eight second sides  141 , such that the second filter portion  140  defines an octagonal cross-section. The second filter portion  140  is not limited to including eight second sides  141 , and in other examples, could include any number of sides, including planar sides. In an example, the second filter portion  140  includes a length of about 66 cm (˜26 inches). 
     In some examples, the second filter media  45  comprises a plurality of different second filter media  45  for different second sides  141  of the second filter portion  140 . For example, one of the second sides  141  can include a first type of the second filter media  45  while another of the second sides  141  can include a second type of the second filter media  45 , wherein the second type of the second filter media  45  is different than the first type of the second filter media  45 . Differences in the second filter media  45  for differing second sides  141  include, but are not limited to, the type of filter media, thickness, filtration efficiency, media area, pleating, etc. 
     Turning to  FIG. 5 , a side elevation view of the second filter element  120  is illustrated. In this example, the first filter portion  130  includes a first cross-sectional dimension  154 . In an example, the first cross-sectional dimension  154  of the first filter portion  130  is about 42 cm (˜16.5 inches). It will be appreciated, however, that the first filter portion  130  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. 
     The second filter portion  140  can include a third end cross-sectional dimension  156 . The third end cross-sectional dimension  156  includes a dimension of the third end  42  of the second filter portion  140 . In an example, the third end cross-sectional dimension  156  of the second filter portion  140  is about 42 cm (˜16.5 inches). It will be appreciated, however, that the second filter portion  140  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. In some examples, the third end cross-sectional dimension  156  substantially matches the first cross-sectional dimension  154 . 
     The second filter portion  140  can include a fourth end cross-sectional dimension  158 . The fourth end cross-sectional dimension  158  includes a dimension of the fourth end  44  of the second filter portion  140 . In an example, the fourth end cross-sectional dimension  158  of the second filter portion  140  is about 32 cm (˜12.75 inches). It will be appreciated, however, that the fourth end cross-sectional dimension  158  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. In an example, the fourth end cross-sectional dimension  158  is smaller than the third end cross-sectional dimension  156  and the first cross-sectional dimension  154 . 
     Turning to  FIG. 6 , a third example filter element  220  is illustrated. It will be appreciated that the third filter element  220  is illustrated somewhat generically/schematically so as to illustrate the structure of the third filter element  220 . In general, the third filter element  220  can be attached to the partition  22  in a similar manner as described with respect to the filter element  20  and the second filter element  120 . The third filter element  220  can include a filter media, such as, for example, the first filter media  38  and second filter media  45 , for filtering particulates from air. 
     The third filter element  220  can include a first filter portion  230 . The first filter portion  230  can extend along the longitudinal axis  32  between the first end  34  and the opposing second end  36 . The first filter portion  230  of the third filter element  220  can be attached to the partition  22 . 
     The first filter portion  230  can include a truncated conical shape with a polygonal cross-section. For example, the first filter portion  230  can be tapered in a direction along the longitudinal axis  32  away from the partition  22 . In some examples, the first filter portion  230  has a generally decreasing cross-sectional dimension extending along the longitudinal axis  32  from the first end to the second end  36 . In some examples, the first filter portion  230  includes one or more first sides  231  that are planar. In the illustrated example, the first filter portion  230  can include eight first sides  231 , such that the first filter portion  230  defines an octagonal cross-section. The first filter portion  230  is not limited to including eight first sides  231 , and in other examples, could include any number of sides, including planar sides. In an example, the first filter portion  230  includes a length of about 66 cm (˜26 inches). 
     The third filter element  220  can include a second filter portion  240 . The second filter portion  240  can extend along the longitudinal axis  32  between the third end  42  and the opposing fourth end  44 . In an example, the third end  42  of the second filter portion  140  is positioned adjacent and in attachment with the second end  36  of the first filter portion  230 . The third end  42  can be positioned substantially flush with respect to the second end  36 , such that the first filter portion  230  and second filter portion  240  define a substantially contiguous filter element with limited/reduced openings, gaps, etc. through which air can pass through. 
     The second filter portion  240  can include a substantially cylindrical shape with a polygonal cross-section. For example, the second filter portion  240  includes a generally constant cross-sectional dimension extending along the longitudinal axis  32 . In this example, the second filter portion  240  includes one or more second sides  241  that are planar. In the illustrated example, the second filter portion  240  can include eight second sides  241 , such that the second filter portion  240  defines an octagonal cross-section. The second filter portion  240  is not limited to including eight second sides  241 , and in other examples, could include any number of sides, including planar sides. In an example, the second filter portion  240  includes a length of about 66 cm (˜26 inches). 
     Turning to  FIG. 7 , a side elevation view of the third filter element  220  is illustrated. In this example, the first filter portion  230  includes a first cross-sectional dimension  254 . In this example, the first cross-sectional dimension  254  represents a cross-sectional dimension at the first end  34  of the first filter portion  230 . In an example, the first cross-sectional dimension  254  at the first end  34  of the first filter portion  230  is about 42 cm (˜16.5 inches). It will be appreciated, however, that the first filter portion  230  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. In an example, a cross-sectional dimension at the second end  36  of the first filter portion  34  is about 32 cm (˜12.75 inches). 
     The second filter portion  240  can include a second cross-sectional dimension  258 . The second cross-sectional dimension  258  includes a dimension of the second filter portion  240  at nearly any location along a length of the second filter portion  240  (e.g., at the third end  42 , at the fourth end  44 , etc.). In an example, the second cross-sectional dimension  258  of the second filter portion  240  is about 32 cm (˜12.75 inches). In the illustrated example, the second cross-sectional dimension  258  substantially matches a cross-sectional dimension of the second end  36  of the first filter portion  230 . It will be appreciated, however, that the second filter portion  240  is not limited to this size, and, in other examples, could be larger or smaller than as illustrated. The second cross-sectional dimension  258  can be less than the first cross-sectional dimension  254 . 
     Turning now to  FIG. 8 , an end view of a fourth example filter element  320  is illustrated. It will be appreciated that the fourth filter element is illustrated somewhat generically/schematically for illustrative purposes. In an example, the fourth filter element  320  can include at least some structures similar to the filter elements  20 ,  120 ,  220 . For example, the fourth filter element  320  can be attached to the partition  22  and can include a filter media (e.g., first filter media  38  and second filter media  45 ). In the illustrated example, the fourth filter element  320  can include a hexagonal cross-sectional shape. The fourth filter element  320  can include six sides  331  that are planar. In an example, similar to the second filter element  120  of  FIG. 4 , the fourth filter element  320  can include a first filter portion that is substantially cylindrical and a second filter portion that is substantially conical. In another example, similar to the third filter element  220  of  FIG. 6 , the fourth filter element  320  can include a first filter portion that is substantially conical and a second filter portion that is substantially cylindrical. 
     As illustrated in  FIGS. 4 to 8 , the filter elements  120 ,  220 ,  320  having one or more substantially planar sides provide a number of benefits. In one example, the filter elements  120 ,  220 ,  320  can include a staggered arrangement within the chamber  19  of the filter section  18 . For example, the substantially planar sides (e.g., first sides  131 ,  231 ,  331  and/or second sides  141 ,  241 ,  331 ) of one filter element  120 ,  220 ,  320  can be positioned adjacent and in proximity to substantially planar sides (e.g., first sides  131 ,  231 ,  331  and/or second sides  141 ,  241 ,  331 ) of an adjacent filter element  120 ,  220 ,  320 . In some examples, adjacent substantially planar sides of adjacent filter elements can extend generally parallel with respect to each other, with a small opening, gap, space, etc. therebetween. This staggered arrangement of the filter elements  120 ,  220 ,  320  can allow for a larger number of the filter elements  120 ,  220 ,  320  to be housed within the filter section  18 , thus leading to an increased filtration capacity of the inlet system  10 . 
     As illustrated in  FIGS. 2 to 8 , the filter elements  20 ,  120 ,  220 ,  320  each include the filter media  38 ,  45  comprising a plurality of different media configurations. For example, in some examples, the filter media  38 ,  45  is arranged to have the substantially cylindrical shape (e.g., as illustrated in  FIG. 2 ). In other examples, the filter media  38 ,  45  is arranged to include one or more planar sides (e.g., sides  131 ,  141 ,  231 ,  241 ,  331 , etc.). In these examples, the filter elements  20 ,  120 ,  220 ,  320  provide a number of benefits, including, but not limited to, better flow distribution and filter media utilization, improved filtration efficiency, longer filter life, more effective pulse cleaning, etc. 
     Turning now to  FIG. 9 , a sectional view of a portion of one of the second filter element  120 , third filter element  220 , or fourth filter element  320  is illustrated. In particular, a side of one of the second filter element  120 , third filter element  220 , or fourth filter element  320  is illustrated. It will be appreciated that the illustrated side is generally planar, and can include portions of any one of the illustrated sides  131 ,  141 ,  231 ,  241 ,  331 . 
     The filter elements,  120 ,  220 ,  320  can include a filter media  400 . The filter media  400  includes any number of different materials. For example, the filter media  400  can include a variety of filtering materials that function to remove particulates from air that passes through the filter media  400 . In an example, the filter media  400  can include polytetrafluoroethylene (PTFE) or expanded polytetrafluoroethylene (ePTFE), for example. 
     In some examples, the filter media  400  can be supported by a first support device  402 . In an example, the first support device  402  can extend concentrically about the filter media  400 . The first support device  402  can have a larger diameter than the filter media  400 . The first support device  402  can define an outermost surface of the filter elements  120 ,  220 ,  320 . In an example, the first support device  402  can form a generally linear side so as to match the polygonal shape of the filter elements  120 ,  220 ,  320 . It will be appreciated that the first support device  402  may not be present in all examples of the filter elements  120 ,  220 ,  320 . Rather, in some examples, the filter elements  120 ,  220 ,  320  may not be provided with the first support device  402 . 
     The filter media  400  can be supported by a second support device  404 . The second support device  404  defines an innermost surface of the filter elements  120 ,  220 ,  320 . The second support device  404  can be spaced apart inwardly from the first support device  402  to define an opening, chamber, etc. extending between the first support device  402  and the second support device  404 . In an example, the second support device  404  can extend generally linearly to extend generally parallel to the first support device  402 . 
     It will be appreciated that the second support device  404  may not be present in all examples of the filter elements  120 ,  220 ,  320 . Rather, in some examples, the filter elements  120 ,  220 ,  320  may not be provided with the second support device  404 . In some possible examples, either or both of the first support device  402  or second support device  404  may be replaced by a scrim, adhesive, adhesive impregnated string, other support device, etc., alone or in combination. Likewise, in some examples, the filter elements  120 ,  220 ,  320  may not include both of the first support device  402  and second support device  404 . Rather, the filter elements  120 ,  220 ,  320  may instead include one of the first support device  402  or the second support device  404 . 
     The filter media  400  defines an inner surface  410  and an outer surface  412 . The inner surface  410  can at least partially be in contact with and/or supported by the second support device  404 . The outer surface  412  can at least partially be in contact with and/or supported by the first support device  402 . In some examples, the filter media  400  is arranged so as to include a plurality of pleats  420  that extend in a substantially zig-zag pattern toward and away from the first support device  402  and the second support device  404 . 
     By providing the filter elements  120 ,  220 ,  320  with one or more substantially planar sides  131 ,  141 ,  231 ,  241 ,  331 , spacing between the pleats is maintained substantially constant. For example, an outer separating distance  430  is a distance separating adjacent outer pleats  420  supported by the first support device  402 . An inner separating distance  440  is a distance separating adjacent inner pleats  420  supported by the second support device  404 . In an example, the outer separating distance  430  can substantially match the inner separating distance  440  due, at least in part, to the pleats  420  forming substantially planar sides  131 ,  141 ,  231 ,  241 ,  331 . As such, bunching of the pleats  420  at an inner location, as is known to occur in rounded/curved filter elements, is reduced. In addition to bunching (e.g., an irregular grouping of pleats), tightness of pleat exit compared to pleat entry is also reduced. As a result, in some examples, pressure loss is reduced while filtration efficiency and filter life are increased through better media utilization and improved pulse cleaning. 
     The invention has been described with reference to the example embodiments described above. Modifications and alterations will occur to others upon a reading and understanding of this specification. Example embodiments incorporating one or more aspects of the invention are intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.