US2501614A

US2501614A - Compressor construction

Info

Publication number: US2501614A
Application number: US788350A
Authority: US
Inventors: Nathan C Price
Original assignee: Lockheed Aircraft Corp
Current assignee: Lockheed Corp
Priority date: 1947-11-28
Filing date: 1947-11-28
Publication date: 1950-03-21
Anticipated expiration: 1967-03-21

Description

Patented Mar. 21, 1950 COMPRESSOR CONSTRUCTION Nathan C. Price, St. Helena, Calif., assigner to Lockheed Aircraft Corporation, Burbank, Calif.

Application November 28, 1947, SerialNo. 788,350

This invention relates to compressors or blowers and has more particular reference to axial flow type compressors. It-is a. general object of the invention to provide an axial ow compressor characterized by a simple, inexpensive and extremely light weight rotor construction.

'I'his application is a continuation-in-part of my co-pendng application, Serial No. 583,152, led March 16, 1945, which, in turn, is a division of my co-pending application, Serial No. 488,029, filed May 22, 1943, now Patent No. 2,468,461, issued April 26, 1949.

23 Claims. (Cl 230-122) It is another object of the invention to provide an axial blower or compressor of the axial flow multiple blading row type which has an extremely light weight rotor that preserves its circularity and maintains adequate blade tip clearance even during high speed operation. The light weight rotor particularly adapts the compressor for use in aircraft power plants, and the like, where weight is an important consideration.

Another object of the invention is to provide a compressor of the class referred to characterized by a light weight rotor shell of thin metal effectively reinforced by internal hoops which.

carry the axially spaced rows of radially projecting blades to relieve the shell of the major loading. This form of rotor construction is well suited for mass production methods, is inexpensive, and results in a strong, dependable, light weight wheel or rotor.

Another object of the invention is to provide an axial flow compressor in which the rows of impeller blades in upstream and downstream relation to one another are slotted and have their interiors in communication with one another so that the pressure differential in the main passage oi' the blower causes air flow into the slots of the blades in one row and the discharge of air from the slots of the other row to increase the boundary layer flow over the surfaces of the blades thereby assuring eilicient blade operation throughout the wide range of coefllcients of lift that may be encountered as a result of variation in ambient air density and pressures at the rst rows of diffuser vanes. vThe augmented boundary layer flow reduces the tendency of the boundary layer to separate from the blade surfaces and lessens the drag so that the main air flow follows the blade surfaces to greater angles of attack.

When the compressor is embodied in a power plant for propelling high altitude aircraft, it must, of necessity, operate at varying pressure altitudes and function at variable compression ratlos. stant operative pressures within the combustion zone and gas turbine of the power plant, the first stage compressor is regulated to operate at lower speeds in the denser ambient air of low altitudes and to function at higher speeds in the low density ambient air of the higher altitudes. This variation of operating conditions requires that the impeller blades of the rst stage compressor and, particularly,- the rst rows of such blades operate through a wide range of angles of attack relative to the entering air and with respect to the partially compressed air leaving the' first rows of intermediate diffuser vanes, that is the initial rows of impellers must operate over a wide range of coeflicients of lift. This range of coeflicients of lift is greatly in excess of the range for emcient impeller operation and under certain conditions at low altitude the rst rows of impeller vanes may operate under practically stalled conditions. The increased boundary layer ow obtained by the present invention brings about eiiicient vane or blade operation through the wide range of coeilicients of lift.

It is a further object of the invention to provide an axial compressor of the class referred to in which the hollow rotor shell constitutes a common means of communication between the several hollow slotted blades with appropriate metering means being provided for the blades to assure the required or proper relationship between the Volume of air flow through the slots of the spaced blading rows.

Other objectives and advantages of the invention will become apparent from the following detailed description of typical preferred embodiments, throughout which description reference is made to the accompanying drawings wherein:

Figure l is a fragmentary side elevation of a compressor `of the invention with a portion broken away to illustrate the rotor and adjacent parts in cross section;

Figure 2 is an enlargedfragmentary sectional view of the compressor shell showing the blades in side elevation;

Figure 3 is a fragmentary sectional View taken as indicated by lines 3 3 of Figure 2;

Figures 4 and 5 are enlarged transverse sectional views of the blades of different rows;

Figure 6 is a fragmentary sectional view of another form of blade attachment; and

Figure 7 is a fragmentary perspective view oi a blade and blade shank employed in the structure of Figure 6.

In the drawings the invention is illustrated In order to maintain substantially conthe impeller varies.

embodied in a blower or compressor for an internal combustion turbo power plant of the type disclosed in my co-pending application Serial No. 488,029. The compressor may be considered the first stage compressor arranged at the forward end of the power plant to receive the ram air and may be considered as driven by the turbine of the power plant through the medium of a suitable drive. However, it will be apparent that the features of the invention may well be embodied in compressors designed for other applications and installations.

The illustrated structure includes an elongate cylindrical housing ||l which may constitute the forward portion of the power plant casing and the case or shell of the compressor. The forward end of the housing l is open and provided with a grooved spigot |2 which constitutes the inlet'of the compressor. v

The blower or compressor includes a rotor arranged longitudinally and coaxially within the housing III. The construction of the wheel or rotor is a feature ofthe invention. The improved rotor comprises a shell 20 preferably constructed of relatively thin sheet metal or the like. While the thickness of the sheet metal of the rotor shell will depend upon the overall size of the compressor, and upon other considerations, the thickness of the shell in most instances is between thirty-five and ninety onethousandths of an inch. The rotor shell 20 is in the form of a truncated cone of rearwardly increasing diameter and may be fabricated from a thin metal tube spun or otherwise-'worked to the required shape. The compressor rotor further includes internal rings or hoop-like reinforcing and blade carrying elements. In the construction illustrated there is a plurality of axially spaced pairs of reinforcing rings 2| and 22 of angular cross section. The pairs of rings 2| and 22 are graduated or varied in diameter to conform to the tapering shell 2l and their axially extending flange parts are fixed to the internal surface of the shell by riveting, welding, braining. or the like. As best illustrated in Figure 2 the hoops or rings of each pair are spacedl apart axially of the rotor and are related to have their inwardly projecting circumferential flanges i3 in spaced generally parallel relation. The pairs of rings 2| and 22 are spaced longitudinally throughout the length of .the shell 20 or at least throughout that portion of the shell which carries The rings 2| and 22 mount the impeller vanes as will be later described and their spacing is determined by the required spacing of the blading rows.

The rotor shell 20 constructed of the `thin sheet metal and reinforced by the spaced internal hoops or rings 2| and 22,-.as just described, is light in weight and inexpensive to manufacture. and yet possesses ample strength and rigidity to maintain its circularity and the blade tip clearance during high speed operation.

I have shown the forward end of the rotor shell 20 provided with a forwardly projecting h ollow spindle 48 rotatably supported in suitable bearings 49. The bearings 49 are mounted within a streamlined housing 50 centrally suplported in the compressor inlet by spaced radial vanes 5| of the spigot I2. The vanes 5| may be set at an angle of incidence with respect to the axis of the compressor to impart an initial swirl to the air entering the compressor. The

direction of this swirl is counter to the direc-y tion of rotation of the rotor 20 to increase the A efficiency of the initial compression stage. The

rear portion of the rotor 20 is suitably supported in the housing lil or the power plant case by supporting and driving means not shown.

The rotor 20 of the blower carries a plurality of axially spaced rows of impeller blades 25. In accordance with this invention, the blades 25 are hollow and are preferably constructed from relatively thin sheet metal. The blades 25 are closed at their tips except for small vent holes 85, and are provided at their root ends with metal Shanks or fittings 24. The vent holes 85 are for the purpose of preventing accumulation of oil within the blades, whichmight occur over a period of time d-ue to seepage past bearing seals. The fittings 24 are separately formed elements engaged within the root portions of the hollow blades at 21 and secured therein by welding or furnace brazing. The portions of the fittings 24 which project beyond the ends of the blades are reduced in cross section leaving shoulders 23 flush with the root ends of the blades. The reduced tongues of the fittings 24 are passed through correspondingly shaped slots or openings 9 in the wall of the rotor shell. The openings 9 are provided in spaced circumferential rows and are located so that the inwardly projecting fittings are received between the inwardlyl extending flanges of the adjacent rings 2| and 22. These projecting parts of the fittings 24 are employed as anchor lugs for the blades. Each fitting 24 has a transverse opening 3 receiving a bolt or pin 26. The pins 26 serve to secure the fittings to the adjacent rings 2| and 22. The parts are related so that the shoulders 23 at the root ends of the blades 25 engage and conform to the external surface of the rotor 20 when the pins 26 are engaged in their openings 3 to ilx the blades to the mounting rings. With this mode of attaching the blades 25 the pairs of hoops or rings 2| and 22 carry the concentrated centrifugal forces of the blades, relieving the shell of the major loads so that the shell may be fabricated from relatively-thin light sheet metal for minimum weight. Furthermore, ther blade attaching means assures uniform spacing of the blades and facilitates fabrication by mass production methods.

In the form of construction illustrated in Figures 1, 2 and 3, the root fittings 24 are ported or provided-with passages to maintain the interiors of their respective blades 25 in communication with the internal cavity of the hollow rotor 20. Thus, as shown in Figure 3, the shank fitting 24 has a pair of

ducts

29 and 30 leading from the interior of the respective blade 25 to the interior of the hollow rotor. The blades 25 of the several forward rows of blading are designed to provide for the circulation air therethrough, thereby effecting boundary layer control action for the blades. It is contemplated that boundary layer control apertures or slots of various configurations and in diierent locations may be provided in the blades. However, the invention provides an improved arrangement of slots for effecting a most efilcient boundary layer control action throughout substantially the entire lengths of the blades.

The bodies of the blades 25 in the several forward rows are each provided with a plurality of relatively narrow longitudinally extending -slots 3| to 34. The slots 3| to 34 are provided in the convex or anti-lift walls of the blades ln-or ad\ jacent the chordwise portion of maximum thickness. As shown in Figures 4 and 5, the substantially airfoil-shaped blades 25 are designed so that their portions of maximum thickness are forward of the medial axial planes, and the slots ting of the blade walls throughout practically the entire lengths of the blades without materially weakening the blades or lessening their rigidity.

The number of forward rows of impeller blades 25 provided with slots 3| to 34 as just described, will vary in blowers intended to function under erent operating conditions. In most instances it will be found sufficient to provide the slots in the three or four initial rows of blading. Figure l shows the three forward rows of blades 25 provided with the slots 3| to 34, it being understood that this is merely typical. It is preferred that the slots in certain rows be forwardly directed for the inspiration-or the reception of air, while th'e slots of other rows be rearwardly directed for the discharge or expiration of air. Where there are three rows of slotted blades, as illustrated, it is preferred to make the slots in the two rearward rows forwardly directed for the reception or inux of air and to make the slots in the forward row, rearwardly directed for the discharge or efflux of the air. The blade walls at the forwardly directed slots 3| to 34 may have internal lips 1 while the blade walls at the rearwardly directed slots 3| to 34 'may have internal v lips 6, the lips 6 and 1 serving to assist in directing the air and to give the slots a-substantially nozzle shape. As above described, the

ducts

29 and 30 in the blade root fittings 24, maintain the interiors of the blades 25 in communication with the internal cavity of the hollow rotor so that the air received by the slots of the said two rearward rowsof bladesenters the interior of the rotor and passes forwardly therein to the forward row of blades for discharge from the slots thereof. Thus the cavity of the hollow rotor 20 forms a common means of communication between the interiors of the several rows of hollow blades. With this simple construction, the slotted blades are maintained in communication with one another without the necessity of providing special ducts or passages.

The invention provides means for distributing air flow through the slotted blades to obtain a balanced or desired boundary layer control effect at the blades of the several rows. It is contemplated that the width or capacity of the slots 3| to 34 of slotted blading rows be related to obtain the desired proportionate or balanced boundary layer control action, or the

ducts

29 and 30 of the several blading rows may be proportioned in so far as capacity is concerned to balance the air flowv through the several rows. Furthermore, the capacity of both the slots and the ducts may be controlled or related to bring about a preferred relationship of air flow. Unless such provision is made for a distributed ilo-w of boundary layer control air there may be a substantially neutral condition in the intermediate row or rows of slotted blades, with little or no air flow therethrough.

rows. Thus, where there are three rows of slotted blades as illustrated, the root ducts 29 and 3l of the blades in the third or rearward row are constricted to bring about a substantially balanced or equalized air flow through'the second and third rows of blades Air will ow into the second and third rows of blades and pass out through the initial row of blades.

A plurality of rows of radial inwardly extending diffuser or countervanes 58 is provided on the inside of the housing I0. The stationary vanes 58 are arranged to stand with small clearance between the impeller fblades 25 of the rotor 20.

Figures 6 and 7 illustrate another form of rotor construction and blade attachment of the invention. In this case the rotor shell 20a may be a simple thin walled sheet metal member of the desired configuration as in the previously described embodiment. Axially spaced rings 19 are provided on the internal surface of the shell 2|! to reinforce the same Iand to carry the rows of blades 12. y

The rings 10 correspond in function to the above described rings 2| and 22.and are suitably fixed to the rotor shell 20a by riveting, spot welding, brazing or the like. However, in this case there is a single ring 10 at each row of impeller blades 12 and each ring 10 is somewhat channelshaped in transverse cross section having two spaced flanges 1| which project inwardly toward the axis of rotation of the rotor. The hoops or rings 10 have a wall thickness at the wall of the shell 20a approximately the same as the thickness of the shell wall to facilitate the welding or securing of the rings to the shell. The flanges 1| are provided at their inner or opposing sides with shoulders 14. The shoulders 14 of the sets of flanges 1| are directly opposite or in common plane and face inwardly toward the axis of rotation of the rotor. The rings 10 are further provided with circumferentially spaced radial openings 13 for receiving the shanks of the blades 12. The openings 13 are centrally spaced struction as the blades 25 described above, beings I have found it desirable to employ the

root ducts l

29 and 30 as metering passages. For example, the ducts 29 and 39 of certain blading rows are constricted with relation to the ducts of the other between the sidesof the rings 19 to -join their channels and have radially outward facing seats 15. The seats 15 are flat and perpendicular to the axes of the openings 13 but have llets or radii where they join the openings 13. Openings 16 are formed in the wall of the rotor shell 29a `to register with the seats 15 and to be coaxial with the openings 13. The openings 13 and 16 and the seats 15 are round or cylindrical and are equally spaced about the circumference of the rotor 29a in accordance 'with the precalculated location of the blades 12.

The blades 12 may be of the same general conhollow formed sheet metal elements of the required configuration. Each blade 12 is provided with a separately constructed shank tting having a shank 11 for engaging in an opening 13, and an intermediate circular or .cylindrical head 'I8 for reception in an opening 16 and for engaging a seat 15 and a transverse tongue 19 to' be secured ina blade. The Shanks 11 are cy-lindrical to conform with the openings 13 of the rings 10 and their inner ends are adjacent the shoulders 14 of -the'rings. The heads 18 are fiange-like parts presenting flat inner surfaces for cooperating with the seats 15 to establish the perpendicularity of the blades with respect to the rotor. The tongues 19 of the shank fittings are shaped to conform to the internal configuration of the blades 12 and in the construction illustrated are substantially airfoil shaped to-correspond with the -blade shape. The shank fittings are preferably precision castings in which case the tongues 19 require no -machining and the shanks 11 and heads 18 need only slight machining. The hollow blades 12 are securely fixed or bonded to thetongues 19 of their shank llttings, for example the blades and tongues may be furnace bonded. Thus the shear areas of the blade assemblies are securely joined to dependably withstand the operational loading. In practice it may be found advantageous to construct the blades 12 and the shank fittings, or at least the tongues 19 of `the ttings, of the same material to assure a good bonding of blades and tongues. The inner end or base surfaces of the blades 12 and their tongues 19 are ground or otherwise machined to substantially fit the external surface of the rotor shell 20a.

The blades 12 are secured to the rotor assembly by cap screws 88 screwed into bores in the inner ends of the Shanks '.11 so that their heads cooperate with the above described shoulders 14. It is preferred to arrange washers 8l between the shoulders 14 and the heads of the cap screws 80. It will be seen that Awhen the blades 12 have been set at the proper angle, the screws 80 maybe tightened down to secure the blades in position. The cap screws 80 may be locked in place by safety wires 82. Pins 88 may engage in openings in the rings and shank fitting heads 18 to preserve the angular setting of the blades 12. The cap screws 80 are preferably tubular and where desired or necessary, ports or air passages 83 extend through the tongues 18 and heads 18 to communicate with the tubular screws so that the interiors of the blades 12 and rotor shell 20a are connected for the circulation of boundary layer air as in the previously described form of the invention.

From the foregoing it will be seen that I have provided a blower or compressor rotor construction that is extremely simple and inexpensive to manufacture and that islight in weight. The

exceptionally small weight of therotor well suits it for embodiment in aircraft power plants and. of course, minimizes centrifugal forces and inertia effects. While the construction is light in weight, the reinforcing hoopsor rings 2l and 22 within the housing, a plurality of rows of hollowy blades projecting from the rotor and having fluid apertures in their walls, the interiors of the blades being in communication with the internal cavity of the hollow rotor so that fluid may flow -from one blade to another through said cavity,

and means for restricting the flow through the blades of certain rows to substantially equalize the flow through the blades of the several rows.

2. An axial blower comprising a housing, a ro- -tor in the housing including a hollow thin walled shell, and internal hoops reinforcing the shell, hollow impeller blades projecting from the shell and anchored to said hoops, the blades having communication with the interior of the shell, and

means for producing air flow through the shell hollow rotor shell, internal reinforcing hoops for the shell, hollow blades for vprojecting from the rotor, and fittings secured to the roots oi' the blades and attached to said hoops to mount the blades on the rotor.

5. A rotor for an axial blower comprising a thin walled hollow rotor shell, internal reinforcing hoops on the wall of the shell, hollow blades for projecting from the rotor, fittings fixed in the root portions of the hollow blades, and means for securing the fittings to said hoops to attach the blades to the rotor.

6. A rotor for an axial blower comprising a hollow rotor shell, internal reinforcing hoops for the shell, the hoops having inwardly projecting circumferential flanges, blades for projecting from the rotor, root parts on the blades received between said ilanges, and means for attaching said paots to the flanges to secure the blades to the ro r. l

'7. A rotor for an axial blower comprising a hollow rotor shell, internal reinforcing hoops for the shell, the hoops having inwardly projecting circumferential flanges, blades for projecting from the rotor, root parts on the blades received between said flanges, and means for attaching said parts to the flanges to secure the blades to the rotor, including pins received in axial openings in the flanges and parts.

8. A rotor for an axial blower comprising a hollow rotor shell, internal reinforcing hoops for the shell, hollow blades for projecting from the rotor, root fittings brazed inthe hollowv blades, and means for securing the fittings to said hoops.

9. A rotor for an axial blower comprising a hollow rotor shell, internal reinforcing hoops for the shell, hollow blades for projecting from the rotor, ttings projecting from the root ends of the blades and secured to said hoops, there being ducts in the fittings placing the interiors of the blades in communication with the interior of the shell and boundary layer slots in the blades arranged to cause the flow of air throimh the blades and the interiorof the shell.

10. A rotor for an axial blower comprising a hollow rotor shell, internal reinforcing hoops for the shell, hollow blades for projecting from the rotor, fittings projecting from the root ends of the blades and secured to said hoops, there being ducts in the fittings placing the interiors' of the blades in communication with the interior of the shell and boundary layer slots. in the blades arranged to cause the flow of air through the blades and the interior of the shell, said ducts of certain blade fittings being restricted to meter the flow of air through such blades.

11. A rotor for an axial blower comprising a hollow rotor shell, internal hoops on the wall of the shell, hollow blades for projecting from the rotor, fittings projecting from the root ends oi' the blades and secured to said hoops, therebeing ducts in the fittings placing the interiors of the blades in communication with the interior of the shell and boundary layer slots in the blades, said slots of downstream blades being forwardly directed for the influx of air and the slots of upthin-walled light weight hollow shell having rows of circumferentially spaced openings, circumferential internal stiffening rings on the shell, and hollow blades secured to the rings and extending through said openings to projecti'from the shell.

.the assembly of the shell, rings, and blades constituting a structure having great liexural rigidity and minimum inertia.

13. In an axial compressor, a hollow sheet metal rotor shell having a row of circumferentially,

spaced openings, a ring secured to the interior of the shell at said row of openings to reinforce the shell, a row of blades at the exterior of the shell, and shanks on theblades extending through said openings and secured to said ring tomount the blades on the rotor.

14. A compressor rotor comprising a hollow sheet metal rotor shell having axially spaced rows of circumferentially 'spaced openings, rings s ecured to the interior of the shell at said rows of openings to reinforce the shell, rows of circurn-i ferentially spaced blades at `the exterior of the shell, shanks on the blades extending through said openings, and means securing the shanks to said rings to attach the blades to the rotor.

15. A compressor rotor comprising a thinwalled rotor shell of generally tubular form having at least one row of circumferentially spaced openings in its peripheral wall, a reinforcing ring secured to the interior of the shell at said row of openings, a row of hollow blades at the exterior of the shell, shank fittings bonded to the interiors of the blades and extending into said openings, and means for securing said fittings to the ring to attach the blades to the rotor. 16. A compressor rotorcomprising a thinwalled rotor shell of generally tubular form having at least one row of circumferentially spaced openings in its peripheral wall, a reinforcing ring secured to the interior of the shell at said row of openings, a row of hollow blades at the exterior of the shell, shanks extending into said openings, parts on the shanks conforming to and bonded with the interiors of the blades, and means for securing the shanks to said ring.

17. A compressor rotor comprising a thinwalled rotor shell, a reinforcing ring on the shell, a row of hollow blades for the rotor, shanks for the blades including tongues conforming to and bonded with the interiors of the blades, and means for securing the shanks to said ring.

18. A compressor rotor comprising a thinwalled shell, a reinforcing ring secured within the shell to reinforce the same, there being a row of openings passing through the wall of the shell and said ring, a row of blades at the exterior of the shell, shanks projecting from the root ends of the blades and received in said openings, and screwv threaded means securing the shanks to the ring.

19. A compressor rotor comprising a thinwalled shell, a reinforcing ring secured within the shell to reinforce the same, there being a row of openings passing through the wall of the shell and said ring, outwardly facing seats on the ring at the openings. a 20w of bladesat the exterior of the shell. Shanks on the blades received in said openings, parts on the shanks bearing in-v wardly against said seats, and screws threaded into the Shanks and clamping outwardly against the ring to secure the blades to the ring. 5 20. A compressor rotor comprising a thinwalled rotor shell, a thin-walled reinforcing ring ,secured to the interior of the shell, there being a row of openings passing substantially radially through the wall of the shell and ring, a row of4 l0 hollow blades at the exterior of the shell, vShanks received in said openings, parts on the Shanks conforming to and bonded with the interiors of the blades, and screws threaded into the shanks to cooperate with the ring to secure the blades i3 thereto, the shanks and screws having passages for placing the interiors of the blades in communication with the interior of the shell.

21. A compressor rotor comprising a thinwalled shell, a reinforcing ring secured within go the shell to reinforce the same, there being a row of openings passing through the Wall of the shell and said ring, outwardly facing seats on the ring at the openings, a row of blades 'at the ex-V ing at least one row of circumferentially spaced openings in its peripheral wall, a reinforcing ring secured to the interior of the shell at said row of openings, a row of hollow sheet metal blades at the exterior of the shell, precision-cast shank fittings extending into said openings and having parts conforming to and bonded with the interiors 40 of the blades, and means for securing the fittings to the blades. Y

23. In an axial compressor, a hollow sheet metal rotor shell having a row of circumferentially spaced openings, a ring secured to the interior of the shell 'at said row of openings to reinforce the shell, the ring having a peripheral flange of approximately the same thickness as the shell wall engaging thereagainst and secured thereto, a row of blades at the exterior of the shell, and shanks on the blades extending through said openings and secured to said ring to mount the blades o the rotor.

` NATHAN C. PRICE.

REFERENCES CITED The following references are of record in the ille of this patent:

UNITED STATES PATENTS 0 Number Name Date 752,340 Holzwarth Feb. 16, 1904 1,014,350 Wales et al Jan. 9, 1912 1,967,962 Metten July 24, 1934 2,213,940 Jendrassik Sept. 3, 1940 5 2,241,782 Jendrassik May 13, 1941 2,314,058 Stalker Mar. 16, 1943 2,337,619 Miller Dec. 28, 1943 2,344,835 Stalker Mar. 21, 1944 2,405,768 Stalker Aug. 13, 1946 FOREIGN PATENTS Number Country Date 20,818 Great Britain Sept. 19, 1906