Particle Separator With Scroll Scavenging Means

Abstract

A particle separator for removing extraneous matter from the inlet flow to the compressor of a gas turbine engine has improved efficiency provided by a scroll type of scavenging means. The scroll scavenging means provides for removal of the particles from the collection chamber of the separator and limits the circumferential travel of the particles within the collection chamber before removal, so as to reduce the likelihood that the particles will be rebounded back out into the engine inlet. The invention herein described was made in the course of or under a contract or subcontract thereunder, (or grant) with the Department of the Army.

Parent Case Text

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a continuation of Application Ser. No. 201,421 filed Nov. 23, 1971 now abandoned.

Description

BACKGROUND OF THE INVENTION

This invention generally relates to an improved engine inlet particle separator, and more particularly to an improved inlet particle separator for use with a gas turbine engine wherein the improvement comprises a scroll scavenging means disposed within the collection chamber of the particle separator for reducing the likelihood that particles of extraneous matter entrained within the collection chamber are rebounded back into the engine inlet.

Aircraft gas turbine engines are particularly susceptible to damage from foreign objects introduced into the air inlets of the engines. This problem has been most acute in the past with respect to relatively large foreign objects such as stones, gravel, birds, hail and the like. With the advent of gas turbine powered helicopters and other vehicle take-off and landing (VTOL) aircraft, smaller particles of foreign matter such as sand and water have become increasingly troublesome due primarily to the conditions under which such aircraft may be operated. Because of its VTOL capability, this type of aircraft may be utilized in areas where conventional airfields are nonexistent, such as in combat zones, and in other isolated areas. Helicopters and other VTOL aircraft are also especially suited for certain low altitude missions on both land and sea, including close combat support, search and rescue, and anti-submarine warfare. Under these and related conditions, substantial quantities of small foreign objects such as sand and dust particles and droplets of water may become entrained in the air stream supplied to the gas turbine engine. These particles, which individually have little effect on the engine, can cause very substantial damage when introduced into the engine in large quantities. For example, it has been found that the engine of a helicopter operating at low altitude in a desert environment can lose performance rapidly due to erosion of the engine blading by high velocity particles. In addition to erosion, extraneous matter, particularly salt water, introduced into the engine in this manner can cause rapid and destructive erosion.

It is, therefore, desirable to provide means for separating out the particles of sand, dust, water and the like before the air stream is supplied to the engine. To be satisfactory, it is essential that the separator chosen to provide this function be effective in removing the unwanted particles from the air stream. High efficiency is particularly desirable in an aircraft separator in view of the large quantities of air and, consequently, the large quantities of extraneous particles consumed by a gas turbine engine.

Heretofore, particle separators have included collection chambers which either retained the extraneous matter until the engine was shut down, whereupon the particles were removed through a clean-out port by means of a vacuum hose, or alternatively removed the particles during engine operation through a single outlet port. Retaining particles of extraneous matter within the collection chamber of the separator during engine operation is disadvantageous due to the likelihood that particles striking the walls of the collection chamber will eventually be rebounded back into the passageway and hence into the engine inlet. Also, the collection chamber of the separator may fill and overflow into the passageway. Removal of the particles from the collection chamber through a single outlet during engine operation eliminates the possibility of the collection chamber overflowing, but still retains the risk that particles might rebound back into the passageway before passing through the outlet port. The likelihood of particles rebounding back into the passageway increases with the circumferential distance that the particles must travel before exiting through the outlet port. In conventional separators, many of the particles must travel entirely around the collection chamber before being evacuated through the outlet port which increases the probability that the particles will strike an interior surface and rebound back into the passageway.

Therefore, it is an object of this invention to provide an improved engine inlet separator wherein separator efficiency is materially increased by reducing the risk that particles entrained within the collection chamber of the separator will be rebounded back into the engine inlet.

It is also an object of this invention to provide an improved engine inlet separator wherein the risk of entrained particles rebounding back out of the collection chamber is reduced by limiting the circumferential distance which the particles need travel before evacuation from the chamber.

It is a further object of this invention to provide an improved engine inlet separator having a scroll type of scavenging means communicating with the collection chamber of the separator so as to limit the circumferential distance traveled by the particles before evacuation from the chamber.

SUMMARY OF THE INVENTION

A gas turbine engine assembly includes an improved engine inlet particle separator for removing extraneous matter from the stream of air supplied to the compressor. The particle separator includes a pair of spaced apart walls which define an annular passageway therebetween, having at opposite ends thereof, an annular inlet and an annular outlet for flow communication with the engine inlet. Additional wall means define a collection chamber in flow communication with the annular passageway for receiving and removing extraneous matter from the stream of air supplied to the engine inlet through the passageway. Means for centrifuging the extraneous matter out of the air stream within the passageway into the collection chamber are also provided. The improvement comprises a scroll scavenging means communicating with the collection chamber for reducing the likelihood that particles of extraneous matter entrained within the collection chamber are rebounded back into the passageway. The scroll scavenging means acts to inhibit particles which enter the collection chamber from rebounding back into the passageway by limiting the circumferential travel of the particles around the collection chamber.

DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims distinctly claiming and particularly pointing out the invention described herein, it is believed that the invention will be more readily understood by reference to the discussion below and the accompanying drawings in which:

FIG. 1 is a cutaway perspective view of the improved particle separator of this invention as attached to the inlet of a gas turbine engine.

FIG. 2 is a cross-sectional view of an alternate embodiment of the separator of FIG. 1 as attached to the inlet of a gas turbine engine.

FIG. 3 is a cross-sectional view taken along the line 3--3 of FIG. 2.

FIG. 4 is a cross-sectional view of still another alternate embodiment of the separator of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1 there is shown the inlet portion of a gas turbine engine assembly 10 including a gas turbine engine inlet 12 and an axial flow separator 14 having improved scroll scavenging means 16 formed in accordance with the present invention. The engine, of which only the inlet portion is shown, typically includes in axially spaced serial flow arrangement, a compressor, an annular combustor, a gas generator turbine for driving the compressor and a power turbine for driving an output shaft, all of which are conventional and well known to the gas turbine art. The turboshaft engine described may be suited for helicopter applications in which a helicopter rotor (not shown) is driven by the output shaft through suitable speed reduction means (not shown).

The improved separator of this invention is a static component having no moving parts. More particularly, the separator 14 has an outer casing or housing indicated generally by the numeral 18 and an inner fairing 20, defining therebetween an axially extending annular passageway 22 having at opposite ends thereof an annular inlet 24 and an annular outlet communicating with the engine inlet 12 and an annular particle collection chamber 26. A row of circumferentially spaced, radially extending turning vanes 27, having a desired turning configuration which will be described presently, is located adjacent the annular inlet 24. Another row of circumferentially spaced, radially extending, compressor inlet guide vanes 28 is located adjacent the engine inlet 12, the vanes 28 also having a required turning configuration. The annular particle collection chamber 26 is defined by the outer surface of the engine housing 30, a first axially and circumferentially extending wall 32, a second radially and circumferentially extending wall 34, and a third radially and circumferentially extending wall 36 connecting with the separator housing 18 so as to form a radially outward extending gutter.

The improved scroll scavenging means includes a plurality of circumferentially spaced turning vanes 38 which radially extend from the engine housing 30 to the axially and circumferentially extending wall 32. The vanes 38 axially divide the particle collection chamber 26 and define an annular extraction manifold 40 at the aft portion of the collection chamber. Means for ducting extraneous matter from the extraction manifold 40 is provided by a scavenge duct 42 which cummunicates with the manifold, and preferably extends in a tangential direction away from the outer periphery of the extraction manifold 40. The outside end of the scavenge duct is in flow communication with a scavenge blower (not shown) for establishing a reduced pressure within the duct, and drawing out extraneous matter entrained within the annular manifold.

During operation of the gas turbine engine, the low pressure area existing at the inlet 12 of the engine causes air to flow through the annular passageway 22 at high velocity. As the air passes over the stationary turning vanes 27, it is turned or centrifuged circumferentially such that downstream of the vanes 27 the air stream has both angular and axial velocity. This is known as imparting "swirl" to the fluid stream. Small particles of foreign matter entrained in the air stream are also centrifuged, this centrifuging resulting primarily from the particles, which have small mass, being carried along with the swirling air. To assure that particles having greater mass are also centrifuged by the turning vanes, it may be desirable to overlap adjacent vanes circumferentially so that a particle cannot pass axially between adjacent vanes without striking a vane and thereby being turned. A particle entrained in the air stream and centrifuged will have both tangential and axial velocity downstream of the turning vanes 27. In theory, a particle leaving the vanes 27 with both tangential and axial velocity, and not being subject to any external forces, will follow a straight line path to the outer periphery of passageway 22 at some point downstream of the vanes. In practice, however, the swirling air has a significant effect on the particle's trajectory which can be compared roughly to that of a helix having increasing diameter in the downstream direction. The compressor inlet guide vanes 28 may be configured as deswirl vanes to remove the circumferential velocity component of the main air stream before entering the compressor.

In the preferred practice of the present invention, the turning vanes 27 have a turning configuration which will cause the entrained extraneous matter to reach the outer periphery of the passageway 22 upstream of the engine housing 30, and either flow directly into the collection chamber 26 or strike the interior surface of the separator housing 18 and rebound therefrom into the chamber 26. Once the particles enter the chamber 26, they are prevented from rebounding back into the passageway 22 by entrainment through the turning vanes 38, and into the extraction manifold from which the particles are scavenged through the duct 42 by means of a blower. Turning vanes 38 are arranged to maintain the same circumferential direction of flow initially imparted to the input air stream by turning vanes 27. To assure that particles do not rebound from the extraction manifold 40 back into the passageway and hence to the engine inlet, turning vanes 38 may also be overlapped circumferentially so that a particle cannot pass axially between adjacent vanes without striking a vane and thereby rebounding back into the manifold. It has been found that the scroll scavenging means of this invention provides significantly improved separator efficiency to the extent that particles entering the engine passage have been reduced from 20 percent to 12 percent of the total mass of particles entering the separator inlet when using standard AC coarse test dust.

The turning vanes of the scroll scavenging means of this invention limit the circumferential distance which particles must travel before entrainment within the manifold 40 so as to reduce the likelihood that the particles will rebound back into the engine inlet. As becomes readily obvious from the drawings, once a particle travels aft of the turning vanes into the extraction manifold, nearly all possible rebound paths back into the engine inlet are blocked by the turning vanes. For the configuration of FIG. 1 showing three turning vanes each of which extends an arcuate distance of approximately 120.degree., it can be seen that no particle need travel more than a cirumferential distance of 120.degree. before entering the extraction manifold from which the likelihood of rebound back into the engine inlet is substantially reduced. The intended scope of invention is by no means limited to the number of turning vanes shown and the scroll scavenging means may include any number of turning vanes as required to meet a particular separator efficiency.

Referring to FIGS. 2 and 3 where like numerals refer to previously described elements, there is shown generally at 16' an alternate embodiment for the scroll scavenging means of this invention. A plurality of circumferentially spaced and radially extending inlet openings 50 are disposed around the outer periphery of the collection chamber 26. Each opening 50 communicates with a scavenge duct 52 wherein the outside end of each scavenge duct is in flow communication with a scavenge blower (not shown) for establishing a vacuum within the duct and drawing out extraneous matter entrained within the collection chamber. Each scavenge duct is defined by a circumferentially extending inner wall 54 and a circumferentially extending outer wall 56 wherein each inner wall gradually extends radially outward from the inlet opening to the outer wall of the adjacent duct. The walls of each duct may be either curvilinear or rectilinear in cross-section, and are not particularly limited, so long as an enclosed fluid passageway is defined therebetween for drawing out particles entrained within the collection passageway.

For the arrangement of FIGS. 2 and 3, showing three openings, each of which is circumferentially spaced approximately 120.degree. apart, it can be seen that no particle entrained within the collection chamber need travel more than a circumferential distance of 120.degree. before entering a scavenge duct from which the likelihood of rebound back into the engine inlet is substantially reduced. Again the intended scope of invention is by no means limited to the number of openings and the scroll scavenging means may include any number of openings as required to meet a particular separator efficiency.

FIG. 4 shows generally at 16" still another embodiment for the scroll scavenging means of this invention whereby circumferentially spaced, axially extending, turning vanes 60 are provided instead of openings 50 as shown in FIGS. 2 and 3. The turning vanes 60 in combination with the outside axially and circumferentially extending wall 32 define an annular extraction manifold 62 therebetween, which functions in substantially the same manner as previously described. Again particles entering the colletion chamber need only travel a limited circumferential distance before passing radially outward into the extraction manifold from which the likelihood of rebound back into the engine inlet is substantially reduced.

Having above described preferred embodiments of the invention though not exhaustive of all possible equivalents, what is desired to be secured by Letters Patent is distinctly claimed and particularly pointed out in the claims appearing below.

Claims

What is claimed is:

1. In a gas turbine engine assembly wherein an improved engine inlet particle separator includes a pair of spaced apart wall members defining an annular inlet and an annular outlet for communication with the engine inlet, wall means defining a collection chamber in flow communication with the annular passageway for receiving and removing extraneous matter from the stream of air supplied to the engine inlet through the passageway and means for centrifuging the extraneous matter out of the air stream within the passageway into the collection chamber, the improvement comprising:

scroll scavenging means having a plurality of turning vanes with the leading edge of each vane spaced upstream of the trailing edge of an adjacent vane to divide the collection chamber and define an annular extraction manifold at the downstream portion thereof thereby reducing the likelihood that particles of extraneous matter entrained within the extraction manifold are rebounded back into the passageway, whereby all particles entering the collection chamber may be inhibited from rebound back into the passageway after only limited circumferential travel around the collection chamber, and

means for continuously ducting extraneous matter from the extraction manifold including a blower for establishing a vacuum within the extraction manifold and drawing out the extraneous matter entrained within the manifold.

2. The improved inlet separator of claim 1 wherein the wall means defining the collection chamber includes spaced apart inner and outer generally axially extending circumferential wall members and an interconnecting wall member, and the plurality of turning vanes extend radially from the inner wall member to the outer wall member with the leading edge of each vane spaced axially forward of the trailing edge of an adjacent vane, thereby dividing the collection chamber so as to define the annular extraction manifold at the aft portion thereof.

3. The improved inlet separator of claim 1 wherein the scroll scavenging means comprises:

a plurality of axially extending turning vanes with the leading edge of each vane spaced radially inward of the trailing edge of an adjacent vane thereby dividing the collection chamber and, in combination with the outer wall of the collection chamber, defining the annular extraction manifold.

4. An improved particle separator for removing extraneous matter from a fluid stream comprises:

means forming an axially extending passageway having an inlet and an outlet at opposing ends thereof;

wall means defining a collection chamber around the passageway in flow communication with the passageway for receiving and removing extraneous matter from a fluid stream flowing through said passageway;

means adjacent said inlet for imparting swirl to the fluid stream flowing through said passageway whereby extraneous matter is centrifuged out of the fluid stream into the collection chamber, and

scroll scavenging means having a plurality of turning vanes with the leading edge of each vane spaced upstream of the trailing edge of an adjacent vane to divide the collection chamber and define an annular extraction manifold at the downstream portion thereof thereby reducing the likelihood that particles of extraneous matter entrained within the, extraction manifold are rebounded back into the passageway, whereby all particles entering the collection chamber may be inhibited from rebound back into the passageway after only limited travel around the collection chamber,

and means for continuously ducting extraneous matter from the extraction manifold including a blower for establishing a vacuum within the extraction manifold and drawing out the extraneous matter entrained within the manifold.

5. The improved particle separator of claim 4 wherein the wall means defining the collection chamber includes spaced apart inner and outer generally axially extending circumferential wall members and an interconnecting wall member, and the scroll scavenging means includes a plurality of turning vanes which radially extend from the inner wall member to the outer wall member with the leading edge of each vane spaced axially forward of the trailing edge of an adjacent vane thereby dividing the collection chamber so as to define the annular extraction manifold at the aft portion thereof.

6. The improved inlet separator of claim 3 wherein the scroll scavenging means comprises:

a plurality of axially extending turning vanes with the leading edge of each vane spaced radially inward of the trailing edge of an adjacent vane thereby dividing the collection chamber and, in combination with the outer wall of the collection chamber, defining the annular extraction manifold.