Inertial separator and method of use

Abstract

To provide an inertial separator for removing particulates in engine intake air.SOLUTION: An inertial separator 500 comprises: an inlet tube 50 having an inlet 51 at an inlet end 52, an outlet 55 at an opposite outlet end 56 including an undercut 200, and a central passage 65 between the inlet end and the outlet end; a deflector 10 having a plurality of spaced centrally joined helical vanes 11 abutting on a wall of the central passage; an outlet tube 100 positioned within the outlet end of the inlet tube, the outlet tube having an outlet tube central passage 150 between an inlet 101A and an outlet 120A in fluid communication with the central passage of the inlet tube, the inlet of the outlet tube having a smaller diameter than the central passage of the inlet tube, the outlet tube having an outer surface having a spiral ramp 300 having a first ramp end 301 and a second ramp end 302, the spiral ramp having a portion 310 angled downwardly toward the second ramp end and the undercut; and a scavenge flow outlet 250 adjacent to the undercut and the second ramp end.SELECTED DRAWING: Figure 1A

Description

[Background technology]

[0001]

[0001] Engines, whether gas turbine, gasoline, diesel, or hybrid, require airflow to the engine during operation. Some engines, especially in aircraft, military, or industrial gas turbine vehicles, require extremely high airflow to the engine due to the high power generated. Because particulates in the air can damage these engines, inertial separators (e.g., vortex air cleaners, inlet particle separators (IPS), and engine air particle separators (EAPS)) are sometimes used with engines that operate under conditions where the air may contain large amounts of particulates, which are removed before entering the engine inlet. Inertial separators are particularly useful for use with aircraft, especially those that are turbine-driven (e.g., helicopters), because they kick up large amounts of dirt and dust when operating close to the ground.

[0002] A single inertial separator or multiple inertial separators may be used with an engine, and typically each separator includes an inlet pipe having a central passage with an inlet and an outlet at either end, a deflector for creating swirls in the incoming air to concentrate airborne contaminant particles at the periphery of the passage to clean the air in the center of the passage, and an outlet pipe having a central clean air passage communicating with the central passage of the inlet pipe. The relatively clean air in the center of the passage flows through the central clean air passage of the outlet pipe. Typically, the outer wall of the outlet pipe defines a generally annular contaminant trapping and removing passage within the central passage of the inlet pipe, through which the contaminant particles pass while the relatively clean air in the center of the passage flows through the central clean air passage of the outlet pipe.

[0003]

[0003] However, there is a need for improved inertial separators.

[0004]

[0004] The present invention seeks to ameliorate at least some of the shortcomings of the prior art. These and other advantages of the present invention will become apparent from the description set forth below. Summary of the Invention

[0005]

[0005] One aspect of the present invention provides an inertial separator comprising: (a) an inlet pipe having an inlet at an inlet end, an outlet at an opposite outlet end, an undercut, and a central passage between the inlet end and the outlet end including the undercut; (b) a deflector mounted within the central passage, the deflector having a plurality of spaced apart and centrally joined helical vanes abutting a wall of the central passage; (c) a coaxially disposed outlet pipe located within the outlet end of the inlet pipe, the outlet pipe having a first end having an inlet and a second end having an opposite outlet, and an outlet pipe central passage between the inlet and outlet that is in fluid communication with the inlet pipe central passage, the outlet pipe inlet being smaller in diameter than the inlet pipe central passage, the outlet pipe having a helical ramp having a first sloped end and a second sloped end, the helical ramp having a portion that slopes downwardly toward the second sloped end and the undercut; and (d) a capture removal outlet adjacent the undercut and the second sloped end.

[0006] In some versions of the inertial separator, the outlet tube includes a pair of separated tabs that prevent rotation of the outlet tube during use.

[0007] In one aspect, an inertial separator apparatus is provided that includes a housing containing an inertial separator according to an aspect of the invention.

[0008] In another aspect, an inertial separator array is provided that comprises a housing containing two or more inertial separators according to an aspect of the invention.

[0009]

[0009] In another aspect, a method for treating an air flow to an operating engine includes the steps of passing air through an inlet of an outlet tube of an inertial separator according to one aspect of the present invention, passing the depleted air through an outlet of the outlet tube to the operating engine, and passing the depleted flow from the inertial separator to a depleted flow outlet. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1 illustrates a side view of an inertial separator including an inlet pipe, an undercut, a deflector (sometimes called a "swirler" or "spinner"), an outlet pipe with anti-rotation tabs, a helical ramp, a scavenge flow outlet, and a scavenge flow in accordance with one embodiment of the present invention. [Figure 1B] FIG. 1B is a perspective bottom view of the inertia separator shown in FIG. 1A, also showing a pair of spaced apart anti-rotation tabs. [Figure 1C] FIG. 1B illustrates a side view of the inertial separator shown in FIG. 1A. [Figure 2A] FIG. 1B shows a top view of the inlet tube shown in FIG. 1A. [Figure 2B] FIG. 1B shows a top view of the outlet tube shown in FIG. 1A. [Diagram 3] FIG. 1B is a perspective side view of the outlet tube shown in FIG. 1A showing pairs of spaced anti-rotation tabs positioned to contact spaced anti-rotation tabs on an adjacent inertial separator. [Figure 4A] FIG. 2 is a diagrammatic representation of air flow and entrapment flow through an inertial separator according to one aspect of the present invention. [Figure 4B] FIG. 2 is a top view diagrammatically illustrating aligned entrapment flow through multiple inertial separators and entrapment flow outlets according to one embodiment of the present invention, also showing particles constantly moving in the same direction at high velocity. [Figure 4C] FIG. 13 is another top view diagrammatically illustrating aligned entrapment removal flows through multiple inertial separators and entrapment removal flow outlets according to an embodiment of the present invention. [Diagram 5] FIG. 1B illustrates an inertial separator apparatus according to one embodiment of the present invention, the apparatus comprising a housing containing an inertial separator as shown in FIG. 1A according to one embodiment of the present invention, and also illustrates the air flow and entrapment removal flow through the inertial separator apparatus. [Figure 6] 1B shows an inertial separator array according to one embodiment of the present invention, the array comprising a housing containing a plurality of inertial separators as shown in FIG. 1A according to one embodiment of the present invention, and also shows the air flow and the entrapment flow through the inertial separator array, the entrapment flow gradually increasing in flow towards the entrapment outlet of the system due to the individual contribution of each inertial separator. [Figure 7A] FIG. 4 illustrates a side view of multiple outlet tubes arranged for use in an inertial separator array, where the outlet tubes include pairs of spaced apart anti-rotation tabs as shown in FIGS. 1B and 3. [Figure 7B] FIG. 7B illustrates a top view of the multiple outlet tubes shown in FIG. 7A, where pairs of spaced anti-rotation tabs on adjacent outlet tubes prevent further rotation of the tubes (and inertial separator) during use. [Figure 8A] FIG. 1 illustrates an inertial separator array in accordance with an aspect of the present invention in communication with a fan, the inertial separator array may be used with a gas turbine engine. [Figure 8B] FIG. 1 illustrates an inertial separator array in accordance with an aspect of the present invention in communication with an air ejector, the inertial separator array being usable with a gas turbine engine. [Figure 8C] FIG. 1 illustrates an exemplary turbine engine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011]

[0018] According to one aspect of the invention, there is provided an inertial separator comprising: (a) an inlet pipe having an inlet at an inlet end, an outlet at an opposite outlet end, an undercut, and a central passage between the inlet end and the outlet end including the undercut; (b) a deflector mounted within the central passage, the deflector having a plurality of spaced apart and centrally joined helical vanes abutting a wall of the central passage; (c) a coaxially disposed outlet pipe located within the outlet end of the inlet pipe, the outlet pipe having a first end having an inlet and a second end having an opposite outlet, and an outlet pipe central passage between the inlet and outlet that is in fluid communication with the inlet pipe central passage, the outlet pipe inlet being smaller in diameter than the inlet pipe central passage, the outlet pipe having a helical ramp having a first sloped end and a second sloped end, the helical ramp having a portion that slopes downwardly towards the second sloped end and the undercut; and (d) a capture removal outlet adjacent the undercut and the second sloped end.

[0012]

[0019] In one aspect of the inertial separator, the helical ramp includes a helicoidal ramp.

[0013]

[0020] In some aspects of the inertial separator, the outlet tube includes an anti-rotation element that includes a pair of separated anti-rotation tabs that prevent rotation of the outlet tube during use.

[0014]

[0021] In another aspect, an inertial separator array is provided that comprises a housing containing two or more inertial separators according to an aspect of the invention.

[0015]

[0022] In another aspect, a method for treating an air flow to an operating engine includes the steps of passing air through an inlet of an outlet pipe of an inertial separator according to one aspect of the invention, passing the depleted air through an outlet of the outlet pipe to the operating engine, and passing the depleted air from the inertial separator to a depleted flow outlet.

[0016]

[0023] An embodiment of a method for treating an airflow into an operating engine may include passing air through an inlet of an outlet pipe of an inertial separator device according to an embodiment of the present invention or through two or more inlet pipes of an inertial separator array, passing the depleted air through an outlet(s) of the outlet pipe(s) to the operating engine, and passing the depleted air from the inertial separator(s) to a depleted flow outlet(s).

[0017]

[0024] In an exemplary embodiment of the method, the collected removal stream comprises dirt particles (eg, dust).

[0018]

[0025] Aspects of the method for treating airflow to an engine during operation may also include preventing and / or minimizing rotation of the inertial separator(s) during use. In one aspect of the method, a pair of anti-rotation tabs of one inertial separator contact a pair of anti-rotation tabs of an adjacent inertial separator to prevent further rotation of the inertial separator. In one aspect of the method, two or more inertial separators each include an outlet tube including a first pair of first and second anti-rotation tabs and a second pair of first and second anti-rotation tabs, the first and second anti-rotation tabs of the first pair of anti-rotation tabs being spaced apart greater than the first and second anti-rotation tabs of the second pair of anti-rotation tabs, and the first and second anti-rotation tabs of one pair of one inertial separator contact the first and second anti-rotation tabs of one pair of an adjacent inertial separator to prevent further rotation of the adjacent inertial separator.

[0019]

[0026] Advantageously, the inertial separator according to the aspect of the present invention allows airflow with reduced interference and requires less trapped airflow. The circular flow inside the central part of the separator is enhanced by the trapped airflow low pressure and the rotational motion. Furthermore, the trapped airflow from multiple separators can be aligned to more efficiently convey the trapped airflow (e.g., containing dust) away from the separator at high speed in the same direction, thereby reducing the possibility of backflow.

[0020]

[0027] Another advantage is that the collected removal flow is directional and defined, rather than being emitted in all directions.

[0021]

[0028] Each of the components of the present invention will now be described in more detail below, with like components having like reference numerals.

[0022]

[0029] 1A and 1B for reference, an inertial separator 500 includes an inlet tube 50 having an inlet 51 at an inlet end 52, an outlet 55 at an opposite outlet end 56, an undercut 200, a wall 60 having an inner wall surface 60A and an outer wall surface 60B, and a central passage 65 between the inlet end 52 and the outlet end 56, the central passage being bounded by the inlet tube inner wall surface 60A and the outlet end 56 including the undercut 200; a deflector 10 mounted within the central passage, the deflector 10 having a plurality of spaced apart, centrally joined helical vanes 11 abutting the inner wall surface 60A; The outlet tube 100 has a first end 101 having an inlet 101A and a second end 120 having an opposite outlet 120A, and an outlet tube central passage 150 between the inlet 101A and the outlet 120A that is in fluid communication with the inlet tube central passage 65, the outlet tube inlet 101A being smaller in diameter than the inlet tube central passage 65, the outlet tube 100 having an outer surface with a helical slope 300 having a first sloped end 301 and a second sloped end 302, the helical slope having a portion 310 that slopes downwardly toward the second sloped end and an undercut; and a collection removal outlet 250 adjacent the undercut and the second sloped end.

[0023]

[0030] Typically, the central passage of the inlet pipe has a constant inside diameter from the inlet end to the outlet end.

[0024]

[0031] The first end 101 of the outlet tube facing the deflector may define a thin annulus that separates the clean core flow in the passage 150 from the peripheral flow containing contaminants. To ensure that only clean air reaches the passage, some excess air may be lost in the trapped removal flow. The end may include a lip, e.g., a conical lip, at the end of the outlet member that is within the tubular housing. The lip, if present, may form a baffle, e.g., to direct contaminants, e.g., dust particles, to the periphery of the tubular housing for evacuation.

[0025]

[0032] In some embodiments, for example as shown in FIG. 1A, the inlet of the inlet tube further comprises a collar 53 that typically deforms when the separator is installed in the housing.

[0026]

[0033] The deflector is coaxially mounted in the central passage at the inlet of the inlet pipe, for example by injection molding (e.g., "one shot" molding), at the point where the vanes 11 abut the inner wall of the inlet pipe. The deflector 10 has a plurality of spaced apart, centrally joined helical vanes 11 abutting the walls of the central passage and disposed at an angle to the line of airflow from inlet to outlet to create a vortex in the incoming air to centrifugally concentrate airborne contaminant particles at the periphery of the passage and keep the air in the center of the passage relatively free of contaminant particles.

[0027]

[0034] The illustrated wings are helical and formed at a pitch length. The deflector can have any suitable length, and in a typical embodiment, the wings range from about 2% to about 20% of the length of the inlet pipe. In the embodiment shown in FIG. 1A, the deflector 10 has a cylindrical hub 12 (typically hollow) that extends beyond the wings upstream to form a tip 13 (shown as a blunt tip) and downstream to form a tip 14, which can be in the form of, for example, a blunt tip or a conical tip, for example, formed at a cone angle ranging from about 30° to about 60°. Other shapes for any of the tips are encompassed by the invention, for example, the upstream tip can have a dome-like shape.

[0028]

[0035] The undercut 200 allows a portion 57 of the inlet tube outlet end 56 to extend further downward toward the second end of the outlet tube than another portion 58 of the inlet tube outlet end (see FIG. 1C). In the illustrated embodiment (see FIGS. 1A-1C), the undercut has a generally vertically disposed edge 201 (the vertically disposed edge has an upper end 201A near the first end of the outlet tube and a lower end 201B near the second end of the outlet tube, see FIG. 1B) that generally corresponds to the vertical axis "A" of the inertial separator, and a generally horizontally disposed edge 202 that is perpendicular to the vertically disposed edge, with the upper surface of the second angled edge located between the upper end 201A and the lower end 201B of the vertically disposed edge 201, and the second angled end 302 generally aligned with the vertically disposed edge. In some other embodiments (not shown), the second angled end 302 is not generally aligned with the vertically oriented edge, e.g., the end 302 is angled downward relative to the vertically oriented edge.

[0029]

[0036] The outlet tube 100 is coaxially disposed within the outlet end 56 of the inlet tube, the outlet tube having an inlet 101A at a first end 101 (the first end extends into the outlet end of the first tube), an outlet 120A at an opposite second end 120, and an outlet tube central passage 150 between the first and second ends for delivering clean air from a central portion of the first tube central passage (i.e., the outlet tube central passage between the inlet and outlet of the outlet tube is in fluid communication with the central portion of the inlet tube central passage). In the illustrated embodiment, the outlet tube is generally tapered (e.g., has a frusto-conical shape).

[0030]

[0037] In the embodiment shown, the outlet tube includes a peripheral or circumferential ring 102 attached to the outlet tube near the inlet end. The ring can provide some flow restriction and potentially "bounce" particles back toward the collection removal passage.

[0031]

[0038] The outlet tube includes a circumferential spiral ramp 300 attached to / projecting from an outer surface of the outlet tube between a first end and a second end of the outlet tube. The spiral ramp has a first ramp end 301 and a second ramp end 302, a top ramp surface 307 (see FIG. 3 ) extending from the first ramp end to the second ramp end, and a ramped outer sidewall, with the first ramp end above the second ramp end (i.e., the first ramp end is closer to the first end of the outlet tube than the second ramp end, and the second ramp end is closer to the second end of the outlet tube than the first ramp end). Preferably, as shown in Figures 1A and 3, the spiral ramp is a single passage, e.g., the ends of the spiral ramp do not overlap or only slightly overlap, and the second ramp end does not extend beyond the first ramp end or extends somewhat (e.g., about 15%) relative to the vertical axis of the separator.

[0032]

[0039] Typically, the ramp defines a flow restriction, reducing the diameter of the inlet pipe's central passage at the ramp to provide a trap flow path (shown formed in Figures 1A, 4A, 5 and 6 for removing contaminant particles, e.g. dust, from the separator via a trap outlet adjacent the inlet pipe undercut. The ramp may restrict flow through the annular passage and ensure that the pressure in the central passage 65 is higher than the trap outlet. Preferably, the outer sidewall / edge 320 of the ramp contacts (and more preferably is sealed, e.g. by a friction fit) the inner wall surface 60A of the inlet pipe, e.g. to support the outlet pipe in place within the inlet pipe (preferably, the outer sidewall / edge 320 contacts and seals from one end of the ramp to the other).

[0033]

[0040] In the illustrated embodiment, helical ramp 300, which may include a helicoidal ramp, has second ramp end 302 and portion 310 that slopes downward toward undercut 200, and first ramp end 301 has little or no downward angle at portion 305 (see FIGS. 1A and 3). For example, second ramp end and portion 310 that slopes downward toward undercut have an angle ranging from about 1° to about 15°. In some embodiments, portion 305 and groove 303 have a greater thickness to provide an improved seal against the inlet and outlet pipes.

[0034]

[0041] If desired, the entire helical ramp 300 can be angled downward toward the second ramp end 302, and the undercut 200 and / or the second ramp end can be angled further downward from the remainder of the ramp.

[0035]

[0042] As shown, the inlet (first end) of the outlet tube is smaller in diameter than the central passage 65 of the inlet tube. The first end of the outlet tube facing the deflector may define a thin annulus that abruptly separates the clean core flow in the passage from the peripheral flow containing contaminants. The end may include a lip, e.g., a conical lip, at the end of the outlet tube that resides in the inlet tube. The lip, if present, may form a baffle, e.g., to direct contaminants, e.g., dust particles, to the periphery of the inlet tube for discharge.

[0036]

[0043] Using the embodiment shown in FIG. 5 for reference, the inertial separator apparatus 600 comprises an inertial separator 500 according to one embodiment of the present invention disposed within a housing 650 .

[0037]

[0044] 6 for reference, an inertial separator array 700 comprises at least two (i.e., a plurality) of inertial separators 500 according to an embodiment of the present invention disposed within a housing 750. An inertial separator array can comprise any number of inertial separators according to an embodiment of the present invention (e.g., tens of inertial separators, hundreds of inertial separators, thousands of inertial separators) disposed within a housing.

[0038]

[0045] FIG. 8A shows an inertial separator array 800 according to one embodiment of the present invention in communication with a fan, and FIG. 8B shows an inertial separator array 800 according to one embodiment of the present invention in communication with an air ejector, each array comprising a plurality of separators 500 mounted on an inlet tube plate 801 and an outlet tube plate 802; the inertial separator arrays shown in FIGS. 8A and 8B can be used with a gas turbine engine, and FIG. 8C shows an exemplary turbine engine.

[0039]

[0046] As shown in Figures 4B, 4C, 6, 8A and 8B, the trapped removal flows from multiple separators can be aligned to more efficiently convey the trapped removal flows (e.g., including dust) away from the separators at high speed in the same direction, and the trapped removal flows do not enter the engine inlet.

[0040]

[0047] In some aspects of the inertial separator, the outlet tube includes a pair of separated anti-rotation tabs that prevent rotation of the outlet tube during use.

[0041]

[0048] For example, using the embodiment shown in Figures IB, 3, 7A and 7B for reference, the outlet tubes each include a pair of outwardly extending anti-rotation tabs 180 (including a first tab 180A and a second tab 180B) and a pair of anti-rotation tabs 190 (including a first tab 190A and a second tab 190B). The distance between the tabs in one pair is greater than the distance between the tabs in the other pair. Thus, as shown in Figure 7B, the tabs of one pair with the smaller distance between the tabs can mate with and contact another pair of tabs on an adjacent inertia separator, preventing further rotation because the tabs with the smaller distance between the tabs cannot rotate over the tabs with the larger distance between the tabs.

[0042]

[0049] If desired, the components of the inertial separator can be fabricated from any suitable rigid impermeable material, including any impermeable thermoplastic material, that is compatible with the fluid being processed. Typically, the inlet tube can be fabricated from a polymer such as acrylic, polypropylene, polyethylene, polystyrene, or polycarbonate resin.

[0043]

[0050] If desired, inertial separators according to embodiments of the invention can be monolithic, and can optionally be manufactured by additive manufacturing (sometimes referred to as "additive manufacturing" or "3D printing"). Inertial separators are typically formed by repeated deposition of metal powders bonded together by an activatable binder (e.g., binder jetting, sometimes referred to as "drop-on powder"), followed by consolidation of the powder, typically by, for example, sintering. The components can be manufactured together by additive manufacturing in continuous operations at substantially the same time. Any suitable additive manufacturing equipment can be used, and a variety of manufacturing 3D printers are suitable and commercially available.

[0044]

[0051] All references cited in this specification, including publications, patent applications, and patents, are herein incorporated by reference to the same extent as if each reference was individually and specifically indicated to be incorporated by reference and was set forth in its entirety herein.

[0045]

[0052] The use of the terms "a" and "an" and "the" and "at least one" and similar referents in the context of describing the present invention (particularly in the context of the claims below) should be construed to encompass both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The use of the term "at least one" followed by a list of one or more items (e.g., "at least one of A and B") should be construed to mean one item (A or B) selected from the listed items or any combination of two or more of the listed items (A and B), unless otherwise indicated herein or clearly contradicted by context. The terms "comprising," "having," "including," and "containing" should be construed as open-ended terms (i.e., meaning "including, but not limited to"), unless otherwise indicated. The recitation of ranges of values ​​herein is merely intended to serve as a shorthand method of individually referring to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated herein as if it were individually recited herein. All methods described herein can be performed in any suitable order, unless otherwise indicated herein or clearly contradicted by context. The use of any and all examples or exemplary language (e.g., "etc.") provided herein is intended merely to better clarify the invention, and does not limit the scope of the invention unless specifically claimed. No language in this specification should be construed as indicating any non-claimed element as essential to the practice of the invention.

[0046]

[0053] Preferred embodiments of the present invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of these preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors expect that such variations will be utilized by those skilled in the art as appropriate, and the inventors intend for the invention to be carried out in ways other than as specifically described herein. Accordingly, the present invention includes all modifications and equivalents of the subject matter recited in the appended claims as permitted by applicable law. Moreover, the present invention encompasses any combination of the above-described elements in all possible variations thereof unless otherwise indicated herein or clearly contradicted by context.

Claims

1. (a) an inlet pipe having an inlet at an inlet end, an outlet at an opposite outlet end including an undercut, and a central passage between said inlet end and said outlet end, said outlet end including said undercut; (b) a deflector coaxially mounted within the central passage, the deflector having a plurality of spaced apart, centrally joined helical vanes abutting a wall of the central passage; and (c) a coaxially disposed outlet tube located within the outlet end of the inlet tube, the outlet tube having a first end having an inlet and a second end having an opposite outlet, and an outlet tube central passage between the inlet and the outlet in fluid communication with the central passage of the inlet tube; an outlet pipe, the inlet of the outlet pipe being smaller in diameter than the central passage of the inlet pipe, the outlet pipe having an outer surface with a helical slope having a first sloped end and a second sloped end, the helical slope having a portion that slopes downwardly toward the second sloped end and the undercut; (d) a capture removal outlet adjacent the undercut and the second angled end; Equipped with an inertia separator, wherein the outlet tube includes a first pair of first and second anti-rotation tabs and a second pair of first and second anti-rotation tabs, the first and second anti-rotation tabs of the first pair of anti-rotation tabs being spaced apart greater than the first and second anti-rotation tabs of the second pair of anti-rotation tabs.

2. The inertial separator of claim 1 , wherein the helical ramp comprises a helicoidal ramp.

3. 3. The inertial separator of claim 1 or 2, wherein the helical ramp comprises an outer sidewall sealed against an inner wall surface of the inlet pipe.

4. 1. A method for treating airflow to an engine during operation, comprising: (a) an inlet pipe having an inlet at an inlet end, an outlet at an opposite outlet end including an undercut, and a central passage between said inlet end and said outlet end, said outlet end including said undercut; (b) a deflector coaxially mounted within the central passage, the deflector having a plurality of spaced apart, centrally joined helical vanes abutting a wall of the central passage; and (c) a coaxially disposed outlet tube located within the outlet end of the inlet tube, the outlet tube having a first end having an inlet and a second end having an opposite outlet, and an outlet tube central passage between the inlet and the outlet in fluid communication with the central passage of the inlet tube; an outlet pipe, the inlet of the outlet pipe being smaller in diameter than the central passage of the inlet pipe, the outlet pipe having an outer surface with a helical slope having a first sloped end and a second sloped end, the helical slope having a portion that slopes downwardly toward the second sloped end and the undercut; (d) a capture removal outlet adjacent the undercut and the second angled end; passing the air through separate inlets of two or more inertial separators, each comprising: each of the two or more inertial separators comprises an outlet tube including a first pair of first and second anti-rotation tabs and a second pair of first and second anti-rotation tabs, the first and second anti-rotation tabs of the first pair of anti-rotation tabs being spaced apart more than the first and second anti-rotation tabs of the second pair of anti-rotation tabs, and the first and second anti-rotation tabs of a pair of one inertial separator contact the first and second anti-rotation tabs of a pair of an adjacent inertial separator to prevent further rotation of the adjacent inertial separator; passing the depleted air from separate outlets of separate outlet pipes of the two or more inertial separators to the operating engine and passing the depleted air from the inertial separators to separate depleted air outlets; A method comprising:

5. The method of claim 4 , wherein the collected removal stream comprises debris.

6. 6. The method of claim 4 or 5, comprising preventing or minimizing rotation of the inertial separator.

7. (a) an inlet pipe having an inlet at an inlet end, an outlet at an opposite outlet end including an undercut, and a central passage between said inlet end and said outlet end, said outlet end including said undercut; (b) a deflector coaxially mounted within the central passage, the deflector having a plurality of spaced apart, centrally joined helical vanes abutting a wall of the central passage; and (c) a coaxially disposed outlet tube located within the outlet end of the inlet tube, the outlet tube having a first end having an inlet and a second end having an opposite outlet, and an outlet tube central passage between the inlet and the outlet in fluid communication with the central passage of the inlet tube; an outlet pipe, the inlet of the outlet pipe being smaller in diameter than the central passage of the inlet pipe, the outlet pipe having an outer surface with a helical slope having a first sloped end and a second sloped end, the helical slope having a portion that slopes downward toward the second sloped end and the undercut, the helical slope having a portion at the first sloped end that has little or no angle downward; (d) a capture removal outlet adjacent the undercut and the second angled end; An inertial separator comprising:

8. 1. A method for treating airflow to an engine during operation, comprising: (a) an inlet pipe having an inlet at an inlet end, an outlet at an opposite outlet end including an undercut, and a central passage between said inlet end and said outlet end, said outlet end including said undercut; (b) a deflector coaxially mounted within the central passage, the deflector having a plurality of spaced apart, centrally joined helical vanes abutting a wall of the central passage; and (c) a coaxially disposed outlet tube located within the outlet end of the inlet tube, the outlet tube having a first end having an inlet and a second end having an opposite outlet, and an outlet tube central passage between the inlet and the outlet in fluid communication with the central passage of the inlet tube; an outlet pipe, the inlet of the outlet pipe being smaller in diameter than the central passage of the inlet pipe, the outlet pipe having an outer surface with a helical slope having a first sloped end and a second sloped end, the helical slope having a portion that slopes downward toward the second sloped end and the undercut, the helical slope having a portion at the first sloped end that has little or no angle downward; (d) a capture removal outlet adjacent the undercut and the second angled end; passing air through the inlet of an inertial separator; passing entrapped air from the outlet of the outlet pipe to the operating engine and passing entrapped air from the inertial separator to the entrapped air outlet; A method comprising:

Images