US 3710617 A
An eductor system consists of an augmentor tube, with a suitable termination which may be a blast tube. Each tube has one end thereof fixedly anchored and has its other end free to move due to thermal expansion with respect to the first end. Four flexible or resilient plates extend downwardly from a pair of overhead structural beams, the lower ends of the flexible plates being fixedly attached to flanges encircling the tube. In this way, the tube is supported by the flexible plates, yet it is free to expand longitudinally due to the hot gases flowing therethrough. Also, the plates, together with the beams and the way they are mounted, appreciably lessen any tendency for the basket to vibrate vertically or horizontally.
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Description (OCR text may contain errors)
United States Patent 1 Andersen 1541 MEANS FOR FLEXIBLY SUPPORTING AN EDUCTOR TUBE USED IN TESTING JET ENGINES 1  Inventor: Ronald E. Andersen, Minneapolis, Minn.
[ 73] Assignee: Central Engineering Company, Minneapolis, Minn.
22 Filed: June 16, 1971 21 Appl.No.: 153,625
3,710,617 1 Jan. 16, 1973 2,515,028 7/1950 Wert ..248/58 2,713,397 7/1955 Klausmeyer ..181/33 HC 2,823,756 2/1958 Bridge et al ..181/33 HC Primary Examiner--Jerry W. Myracle AttorneyRalph L. Dugger et al.
 ABSTRACT An eductor system consists'of an augmentor tube, with a suitable termination which may be a blast tube. Each tube has one end thereof fixedly anchored and has its other end free to move due to thermal expansion with respect to the first end. Four flexible or resilient plates extend downwardly from a pair of overhead structuralbeams, the lowel ends of the flexibleplates being fixedly attached to flanges encircling the tube. In this way, the tube is supported by the flexible plates, yet it is free to expand longitudinally due to the hot gases flowing therethrough. Also, the plates, together with the beams and the way they are mounted, appreciably lessen any tendency for the basket to vibrate vertically or horizontally.
' 6 Claims, 6 Drawing Figures PATENTEDJAH 16 1915 SHEET 1 0F 3 l mm Q PATENTEDJAN 16 I975 3.710.617 sum 2 BF 3 Fig 3 INVENTOR RONALD E. ANDERSEN BY 20, (Mum,
Arlorneys PATENTEDJAH 16 I973 SHEET 3 [IF 3 coo 00 0 O INVENTOR RONALD E. ANDERSEN f/orneyj BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to the testing of jet engines, and pertains more particularly to a flexible means for supporting the augmentor or blast tube, the latter sometimes being called a perforated basket, normally used in conjunction with jet engine testing.
2. Description of the Prior Art Augmentor tubes and blast tubes are conventional with respect to the testing of jet engines. These tubes, however, are in close communication with the exhaust nozzle of the jet engine undergoing test. The augmentor tube, which is the nearer of the two, mixes air with the exhaust gases coming directly from the engine, thereby providing a cooling effect. Also, the augmentor tube functions to prevent recirculation of the engine exhaust gases which otherwise might feed back into the air intake of the jet engine.
The purpose of theblast tube or perforated basket, which receives the mixed air and hot gases from the augmentor tube while still at an elevated temperature, is to produce a uniform temperature throughout the exhaust room by compelling the gases to exit therefrom along the entire length and circumference of the basket, doing so through the multiplicity of perforations formed therein. It is imperative that the gases after leaving the blast tube or perforated basket be as uniform in temperature as possible in order to provide the maximum degree of protection to the various silencing panels mounted in the exhaust stack through which the gases must travel on their way to the outside atmosphere. In achieving this aim, it is important also that the gases flowing through the basket not impinge on the back wall of the exhaust room because the elevated temperatures would cause deterioration and crumbling of the concrete of which the back rear wall is constructed, as well as adversely affecting other exposed concrete surfaces forming the interior of the exhaust room.
Furthermore, the fast moving exhaust gases in the augmentor tube, these being the gases coming from the exhaust nozzle of the engine under test, must be pushed through the augmented air which is being drawn or injected into the augmentor tube. In other words, the resulting shearing action of the rapid airflow with the slower airflow produces a low rumbling noise. The resulting single blast of air must be broken up into smaller streams, thus shifting the acoustical energy from its low frequency to a higher frequency to enable a more efficient absorption of the sound energy by the silencingpanels. Not only is the noise a'problem, but another problem has existed with respect to vibration.
It should be apparent from the foregoing explanation that the mixed gases and air passing through both the augmentor tube and the perforated basket are at an elevated temperature. Such temperatures produce a severe amount of thermal expansion, approximately 1 k inches in eductortubes having a length approximating 35 feet. Because of the relatively large amount of movement of the free rear end of the tube, whether it be the augmentor or blast tube, with respect to the fixed front end thereof, wheeled carriages or dollies have been employed, the wheels rolling along the floor or on tracks to permit the thermal expansion to occur. Not only are the carriages or dollies quite costly, but they contribute virtually nothing to the reduction of vibration that is normally present as far as either the augmentor or blast tube they support.
SUMNIARY OF THE INVENTION Accordingly, one object of the invention is to provide a low cost means for supporting an eductor system while it is being used in the testing of jet engines. In this regard, an aim of the invention is to utilize a plurality of flexible plates that effectively support the weight of the tubes, yet enabling the tubes to expand as much as they need to under different thermal conditions. In the achieving of a low cost support for a tube, use is made of the wall structure constituting part of the exhaust room and two overhead beams having their opposite ends carried in the walls. Two flexible plates extend downwardly from each beam with which they are associated, being secured at their upper edges to the beam and at their lower edges to the eductor tube so that the tube is free to move in a longitudinal or axial direction while it is being supported.
Another object of the invention is to minimize the amount of vibration, both vertically and transversely, that would otherwise occur in the eductor system. More specifically, the employment of four flexible plates that can flex horizontally in the direction in which the thermal expansion takes place resist vertical and transverse movement of the tube, these being the directions in which most of the vibration occurs.
Briefly,'the invention contemplates the use of a steel augmentor tube and a steel blast tube or perforated basket, the end of the augmentor tube nearer the exhaust nozzle of the jet engine being fixedly anchored in the rear wall of the test room and the open end of the basket being similarly anchored in a fixed relationship in the front wall of the exhaust stack with the discharge end of the augmentor tube projecting loosely thereinto so that the discharge end of the augmentor tube is free to move. Extending transversely above the augmentor tube is a pair of parallel beams having their ends supported by the concrete side walls flanking the augmentor tube. Extending longitudinally above the blast tube or perforated basket in a parallel relationship with the longitudinal axis thereof are a pair of beams having their ends supported by the forward and rear concrete walls of the exhaust stack. Attached to the underside of each beam and extending downwardly'therefrom are two flexible plates. The upper ends or edges of these plates are secured by welding to the beams, whereas the lower ends or edges are welded to annular flanges extending circumferentially around the body of the particular tube. Although one end of the tube in each instance is fixedly anchored, the resiliency of the flexible plates enable the other end to move as much as is required under various thermal conditions.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a vertical sectional view of the test facility but with a portion of its intake having been removed for the sake of drawing compactness;
FIG. 2 is a horizontal sectional view taken in the direction of line 2-2 of FIG. I;
FIG. 3 is an enlarged sectional view taken in the direction of line 3-3 of FIG. 2 in order to show the manner in which the fixed end of the blast tube or perforated basket is anchored;
FIG. 4 is a sectional view takenin the direction of line-4-4 of FIG. 1 in order to show to better advantage two of the flexible plates and their mode of connection to the beam above and the perforated basket below, the view being on an enlarged scale as compared to FIG. 1;
FIG. 5 is a horizontal sectional view taken in the direction of line 5-5 of FIG. 1, and
FIG. 6 is a fragmentary side elevational view taken in the direction of line 6-6 of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now in detail to the drawings, it will be helpful to illustrate a conventional test facility for testing jet engines. This facility has been denoted generally by the reference numeral 10 and includes an intake 12 (a considerable portion of which has been removed) via which air enters a test room 14 and an exhaust room Describing further the construction of the augmentor tube 72, it will be perceived that an annular angle 16. Although not pertinent to the understanding of the invention, acoustical panels labeled 18 are located inside the intake 12, only one of which has been shown.
Within the confines of the test room 12 is a thrust stand 20, being suspended from the ceiling. A jet engine 22 is shown supported by the thrust stand 20 and the jet engine, as is conventional, has an air inlet 24 and an exhaust nozzle 26.
At this time, greater attention is called to the exhaust room which already has been generally assigned the reference numeral 16. This room 16, as normally considered, extends from the rear wall 28 of the test room 14. For ease of description, though, the exhaust room 16 can be said to include two sections or compartments 30, 32. The first compartment 30 includes a concrete floor 34, a front wall (which is the rear wall 28 of the test room 14), a rear wall 38, side walls 40, 42 and a ceiling 44. The compartment 32 includes a floor 46, a front wall 48 (which includes the rear wall 38 of the compartment 30), a rear wall 50, and side walls 52 and 54. The walls extend upwardly to form an exhaust stack 56 having an open top 58 through which the gases leave the exhaust room 16 to the outside or atmosphere.
As best viewed in FIG. 3, there is an annular channel 60 having flanges 62a and 62b. An annular angle member 64 has one edge abutting the edge of the flange 62b. The channel 60 is held in place by means of anchor studs 66 which are simply embedded in the concrete constituting the front wall 28 of the compartment 30. Additional studs 68 hold the angle member 64 in place. It will be seen that the studs 66 and 68 are welded to a number of U-shaped rods 69 before pouring theconcrete to form the wall 28. Also shown are threaded bolts 70 which function to mount or anchor the educ-tor tube described below.
The first eductor system tube to be described is the generally cylindrical augmentor tube 72. The thickness of the augmentor tube 72 in practice is on the order of one-half inch and its diameter is on the order of IS feet, whereas its length is approximately feet. Some conception as to the size of this tube is believed desirable in order to better appreciate the benefits to be derived from a practicing of the invention.
member 74 having an L-shaped cross section, as can be discerned from FIG. 3, provides a cylindrical band portion 76 and a radially extending flange portion 78. The flange portion 78 has a number of angularly spaced apertures therein so as to accommodate the ends of the previously mentioned bolts 70, nuts 82 being threadedly attached to the bolts so as to fixedly anchor the forward end of the tube 72 to the front wall 28 of the compartment 30 of the exhaust room 16. More specifically, owing to the presence of the fixedly anchored channel 60, the tightening of the nuts 82 pull the tube 72 against the flange 62b. It will, of course, be appreciated that the band portion 76 of the angle member 74 is welded directly to the cylindrical tube 72. Resembling the annular member 74, especially as to its L-shaped cross section, are apair of angle or L- shaped annular members 84 each having a cylindrical or band portion 86 and a radial flange 88. However, the radial flange 88, unlike the radial flange 78, is not apertured in the illustrated example, and this will be better understood as the description progresses.
Before describing the manner in which the first eductor system tube, that is the augmentor tube 72, is supported in order to accommodate or allow the rather large amount of thermal expansion to occur,it will be easier to refer to the second eductor tube that is employed in the exemplary eductor system. Accordingly, the second eductor tube, more specifically the blast tube or perforated basket has been denoted by the reference numeral 90. Size-wise it is similar to the tube 72. Unlike the tube 72, though, it is formed with a mu]- tiplicity of perforations 92 having a diameter approximating 1 V4 inches with a spacing between hole centers of 2 A inches. The tube also differs in that its rear end is closed, there being an end plate at 94, which is unperforated.
Two structural beams of reinforced concrete have been labeled 96, 98. These beams 96, 98 are of identical construction, each including, as can be seen in FIG.
4, horizontal reinforcing steel rods 100 and vertical reinforcing rods 102. These rods 100, 102 being embedded in concrete which has been indicated by the reference numeral 104. It will be understood that the opposite ends labeled 106 of the structural beams 96, 98 are carried within the walls 48 and 50 of the exhaust room 16. In other words, the beams 96, 98 are placed in the exhaust room 16, more specifically the compartment 32, with their longitudinal axes parallel to the longitudinal axis of the tube 90 and spaced laterally from each other as can be discerned in FIG. 4. Of course, these beams 96, 98 are spaced a preferred distance above the tube 90.
At this time, it will be mentioned that two pairs of angle members 108, each having ahorizontal flange 110 and a vertical flange 112, has its horizontal flange 110 in each case welded to a plate 114 as can be readily discerned from FIG. 4 (and also to some extent in FIG. 6), the plate 114 in each instance being welded to the lower ends of the vertical reinforcing rods 102 (as shown in FIG. 4).
Playing a very important role in the practicing of the present invention, as far as the tube 90 is concerned, are four flexible steel plates 116a, 116b, 116a and 116d being approximately one-half inch thick and having a width approximating] 8 inches and alength or vertical height equal to approximately 24 inches. The elongated configuration of each flexible plate 116 results in an upper marginal end portion 120 which is welded to the vertical flanges 112 of the angle members 108 in each instance and a lower marginal end portion 122 which is welded to the radial flange 88 in each instance.
It will be recalled that the augmentor tube 72 has a pair of angle or L-shaped annular members 84 encircling it; likewise, a pair of such members 84 encircle the blast tube 90 and it is the radial flanges 88 of these two members 84 to which the respective marginal portions 122 are attached. From FIG. 4, it is important to note that the two flexible plates 116a and 116b appearing in this view (and also as is apparent from FIG. 5 in which the plates 1 16a, 116b, 1 160 and 116d sectionally appear) are laterally spaced. Consequently, the portion of the blast tube 90 that expands is not only supported by the four flexible plates ll6a-1l6d, but due to the resulting intermediate resilient portions which have been indicated by the reference numeral 124 these plates permit rearward longitudinal movement of the closed end 94 of the tube 90 to whatever degree is necessary to accommodate for the thermal expansion that axially occurs. This, as already mentioned, can be approximately 1 75 inches. Additionally, the vertical planes in whichthe parallel plates 116 are located resist vertical vibratory motion of the perforated tube due to the rigidity of these plates in a vertical direction and the lateral spacing of the plates 116a, 1161; and the plates 1160, 116d resist horizontal vibratory motion as well.
It will be understood that the forward end of the blast tube 90 is anchored in the same way as the augmentor tube 72. In other words, the blast tube 90 has an angle member 74 bolted to afixedly mounted annular channel 60, the only difference being that the channel in this instance is set in the wall 38 in contradistinction to the wall 28 as in the case of the augmentor tube 72.
With the foregoing in mind, attention is directed to the use of two transverse beams 126, 128 having their opposite ends supported in the upper portions of the side walls 40, 42 in the same fashion as are the ends 106 of the beams 96, 98 supported in the walls 48 and 50. The design of the transverse beams 126 and 128, however, is the same as the construction of the beams 96 and 98 which has already been described. Likewise, even though arranged transversely, each beam 126, 128 has a pair of plates 116 attached thereto, these being identified as 116e, 116f, 1163 and 116 which correspond to the previously mentioned plates 116a, 116b, 116a and 116d. The rear end of the augmentor tube 72 has a slightly smaller diameter than that of the forward end of the blast tube or perforated basket 90, resulting in the tube 72 loosely and slidably projecting into the forward end of the tube 90.
Although a plurality of silencing panels 132 have been pictured rather schematically in FIG. 1, the plane inwhich the sectional view constituting FIG. 2 has been taken makes it such that these panels do not appear in FIG. 2. It is not believed necessary to illustrate the manner in which the panels are supported, although it can be mentioned in passing that they are supported on cross beams which have an angle cross section. Also, inasmuch as the silencing panels are conventional, ac-
I the main fluid stream and also to reduce the temperature of this mixed air and gases such that the mixture will not be detrimental to the various panels 132.
OPERATION l-Iaving presented the foregoing information, the manner'in which my inventive combination functions should be obvious. Nonetheless, a brief summary should be of assistance in appreciating the benefits to be derived. With this in mind, it will be understood that the forward ends of each eductor system tube 72, is fixedly anchored to the walls 28 and 38, respectively. Owing to the shear action that takes place within the augmentor tube 72, there is rumbling or low frequency noise that must be changed as far as its frequency is concerned so as to be absorbed by the various silencing panels 132. Consequently, both eductor system tubes 72, 90 are subjected to severe amount of vibration in performing the task of mixing the hot gases from the exhaust nozzle 26 of the jet engine 22 undergoing test. In this regard, it may be of some help to indicate the flow of exhaust gases from the engine 22 by arrows 134 and the flow of air to be mixed therewith by arrows 136. Inasmuch as the blast tube 90 has the task of breaking up the hot stream of mixed gases and air flow ing through the augmentor tube 72, it also is subjected to a severe amount of vibration. However, due to the fact that each eductor system tube 72, 90 is supported by four flexible plates 116 with each pair of such plates being laterally spaced, both vertical and horizontal vibrational components are effectively damped or absorbed. g
The amount of thermal expansion resulting from the heated fluids flowing through the eductor system tubes 72, 90 is quite appreciable in each instance. However, the unanchored or rear ends of both tubes 72, 90 are free to move a considerable distance by reason of the inherent flexibility afforded by the plates 116. More specifically, due to the resiliency of the intermediate plate portions 124 of the flexible plates 116, the thermal expansion can be accommodated, the plates 116 simply flexing to the requisite degree in accommodating for the expansion. At the same time, though, the vibrations encountered in the tubes 72, 90 are dampened by virtue of the rigidity accorded the supporting means via the vertical planes in which the plates 116 reside. In other words, although the plates 116 can flex to permit longitudinal movement of the eductor system tubes 72, 90, any tendency for movement in the vertical planes is transmitted directly through the plates to the structural beams 96, 98, 126 and 128, as the case may be. Inasmuch as the ends of the beams are carried in certain of the walls of the exhaust room 16, the vibration is for all intents and purposes eliminated because of the massive walls of the exhaust room and the inherent damping action they provide.
The mixed gas and air leaves the exhaust room 16 through the stack 56 and the open top 58. Not only is the average temperature of the gases leaving the exhaust room 16 appreciably reduced, but the blast tube or perforated basket 90 has broken up the blast of air and gases delivered to it by the augmentor tube 72 to the extent that the various smaller and individual streams of fluid flow have a higher sound frequency such that the acoustical energy can be more readily absorbed by the various silencing panels 132. in this regard, it will be appreciated that my invention does not detract from the efficiency of either eductor system tube 72, 90 in any way, actually absorbing the vibrations that would otherwise be present where the wheel carriages or dollies are used, as already mentioned, while at the same time permitting an unlimited amount of expansion to take place.
1. In combination, an eductor system tube for use in testing jet engines, an exhaust room comprising a section having vertical front, rear and side walls forming a chamber in which said tube is located, said tube having one end fixedly mounted to said front wall and its other end residing near said rear wall, an overhead beam having its ends fixedly supported by two of said vertical walls so that said beam is fixedly supported above said tube, first and second parallel flexible plates spaced from said one end of the tube and from each other, the upper marginal edge portions of said parallel plates being anchored to said beam and the lower marginal edge portions thereof being anchored to said tube so as to at least partially support said tube and at the same time permit longitudinal movement of said other end thereof with respect to its said one end due to thermal expansion, said beam residing in one plane and said tube having its longitudinal axis residing in a second plane generally parallel to said one plane, said plates residing in at least one plane perpendicular to said planes and to said longitudinal axis.
2. The combination set forth in claim 1 including channel means fixedly contained in said front wall, a flange secured to said tube adjacent said one end thereof, and means fixedly connecting said flange to said channel means.
3. The combination set forth in claim 2 in which said front wall is of concrete.
4. In combination, a horizontal eductor system tube for use in testing jet engines, structural'means, first and second elongated means rigid along their longitudinal axes and flexible along a transverse axis in each instance perpendicular to their said longitudinal axes, said first and second elongated means each having first and second ends, means connecting said first ends to laterally spaced locations on said structural means so that said first ends are anchored against movement relative said structural means, means connecting said second ends to laterally spacedlocations on said tube so that said second ends are anchored against movement relative said tube and are movable therewith as said tube expands and contracts along its longitudinal axis, third and fourth elongated means rigid along their longitudinal axes and flexible along a transverse axis in each instance perpendicular to said longitudinal axes, said third and fourth elongated means each having first and second ends, means connecting said last-mentioned first ends to laterally spaced locations on said structural means so that said last-mentioned first ends are anchored against movement relative said structural means, said last-mentioned first ends being spaced from said'first-mentioned first ends, means connecting said last-mentioned second ends to laterally spaced locations on said tube so that said last-mentioned second ends are anchored against movement relative said tube and are movable therewith as said tube expands and contracts along its longitudinal axis, said last-mentioned second ends being longitudinally spaced from said first-mentioned second ends, whereby movement of said tube is resisted in all directions perpendicular to its said longitudinal axis.
5. The combination set forth in claim 4 in which sai first and second elongated means constitute a pair of resilient plates residing in one vertical plane and said third and fourth elongated means constitute a second pair of resilient plates residing in a plane parallel to said one plane.
6. The combination set forth in claim 4 in which said tube constitutes a perforated basket, the combination further including an exhaust room in which said basket is located, and an exhaust stack extending upwardly from the top of said exhaust room, said structural means including a pair of beams extending across the top of said exhaust room at an elevation beneath said stack, said first ends of said first, second, third and fourth elongated means being fixedly attached to said beams.