US2962206A

US2962206A - Centrifugal compressor for a gas turbine engine

Info

Publication number: US2962206A
Application number: US379568A
Authority: US
Inventors: David M Borden; Samuel B Williams
Original assignee: Chrysler Corp
Current assignee: Old Carco LLC
Priority date: 1953-09-11
Filing date: 1953-09-11
Publication date: 1960-11-29
Anticipated expiration: 1977-11-29

Description

Nov. 29, 1960 D. M. BQRDEN ETAL- 2,962,206 I CENTRIFUGAL COMPRESSOR FOR A GAS TURINE ENGINE Filed Sept. 11. 1953 4 Sheets-Sheet 1 IN V EN TORS- 174044 M 50 is 72. Samuel ,5; Mllzamsz gwmwwfm Nov. 29, 1960 D. M. BORDEN ETAL 2,962,206 CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE q "&

I 1N VEN TORS 2 Jan I67 M 5a 74% 77.

Nov. 29, 1960 n. M. BORDEN EI'AL 2,962,206

CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE Filed Sept. 11, 195: 4 Sheets-Sheet s INVENTORS fiat z; M 5 orJe 71, air 727116] 5. 144/]:127719.

Nov. 29, 1960 D. M. BORDEN EI'AL 2,962,206

CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE' Filed Sept. 11, 1953 4 Sheets-Sheet 4 49 INVENTORS. R Jan '21 M Zariere United States Patent Q CENTRIFUGAL COMPRESSOR FOR A GAS TURBINE ENGINE David M. Borden, Huntington Woods, and Samuel B. Williams, Birmingham, Mich., assiguors to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Sept. 11, 1953, Ser. No. 379,568

Claims. (Cl. 230-119) This invention relates to gasturbine power plants and more particularly to a centrifugal compressor for use with gas turbine power plants for compressing the'intake air used for combustion.

It is a common practice in the present stage of gas turbine development to provide the power plant with an air compressor at a position which is upstream from the burner. The compressor may be either of the positive displacement type or of the centrifugal type and it may be powered by means of a separate bladed turbine wheel interposed in the high velocity combustion gases which leave the burner. Suitable coupling means may be used for interconnecting the rotating turbine wheel with the compressor.

The compressor of the present invention includes a bladed fluid inlet structure or inducer which is associated with a rotary compressor element and which is effective to increase the overall working efliciency of the compressor unit.

A few of the advantages in increasing the pressure of the air before combustion intlude a resulting increase in the density of the combustible charge, an accompanying increase in the temperature of the charge which results in increase in the combustion efiiciency, andan improvement in the distribution characteristics of the charge in the burner.

The present invention includes features which may readily be adapted to be used with centrifugal compressors and pumps in a variety of different installations. The present disclosure is directed to several forms of a centrifugal compressor in combination with one particular gas turbine power plant design, but it is not intended that the scope of the present invention should be limited to installations of the type herein disclosed.

An object of the present invention is to provide a centrifugal air compressor for use with gas turbine power plants or the like, said compressor including a bladed air intake portion disposed on the upstream side of the compressor blades.

Another object of the present invention is to provide a bladed rotary centrifugal air compressor having a means associated therewith for imparting a rotary motion to the intake air while the same is conducted to the bladed portion of the compressor.

Another object of the present invention is to provide a rotary centrifugal air compressor having an air intake portion which comprises an axial hub portion, a plurality of stages of radial blades disposed about the hub and a shroud surrounding the peripheral edges of the blade.

Another object of the present invention is to provide a rotary centrifugal air compressor having an intake portion disposed on the upstream side thereof for imparting an initial axial acceleration to the intake'air.

Another object of the present invention is to provide a rotary centrifugal air compressor with a bladed'air intake portion in which the blades thereof are secured to an axial hub by means of suitableinsertsformed integrally with the blades which permit the blades to be readily assembled to the hub.

Another object of the present invention is to provide a centrifugal air compressor with a bladed air intake portion, as described in the preceding object, wherein the blades are retained in place and supported by a peripheral shroud.

Another object of the present invention is to provide a centrifugal air compressor having a bladed rotor portion with a pair of radial shrouds, a bladed air intake portion on the upstream side of the rotor portion, and a peripheral shroud about the blades in the air intake portion to support the same, the peripheral shroud being formed integrally with one of the pairs of radial rotorshrouds.

Another object of the present invention is to provide a centrifugal compressor as described in the preceding object in which the peripheral shroud is constructed separately from the radial rotor shroud.

Another object of the present invention is to provide a centrifugal air compressor having a rotor portion and a bladed air intake portions disposed on the upstream side thereof about an axial hub and having a peripheral shroud disposed about the blades, the blades of the air intake'portion being secured to the hub and shroud by means of welding.

Another object of the present invention is to provide a centrifugal compressor with an air intake portion having a plurality of stages of radially disposed blades, the angle of pitch for the blades of the successive stages being progressively smaller as the air travels therethrough.

In general, the compressor of the present invention com prises a rotor element which is suitably mounted for rotation about its geometric axis. The rotor is provided with an annular opening at the intake end thereof for the purpose of providing an inlet passageway'forthe intake air. The air is then conducted axially throughthe rotor within an annular passageway which is a continuation of the annular opening previously mentioned. The air then enters the base or mouth of a circular bladed portion of the rotor which extends radially outward from the geometric axis. The blades in this bladed portion may be radially disposed or may be formed with entrances or exit angles other than The number of such blades may be varied as appropriate.

The air is discharged from the bladed portion peripherally in a radial direction into a diffuser housing which comprises a spiral structure of progressively increasing cross sectional area and which is effective to reduce the velocity of the air discharged from the rotor andto convert a substantial percentage of the air velocity pressure into static pressure. Such a conversion is necessarily accompanied by an increase in the air temperature. The path followed by the air throughout the components of the power plant with become obvious from the following brief description of the present embodiment with reference to Figure 1 of the drawings.

An important feature of the present invention resides in the structure which forms the annular passageway extending axially from the inlet opening of the rotor to the mouth of the rotor blades. This structure will be hereinafter referred to as the inducer portion of the centrifugal compressor.

One or more stages of inducer blades of the airfoil type maybe fixed within the inducer passageway in order to impart rotary motion to the axially moving intake air. Such blading is also effective to increase the total pressure to a certain extent as the air approachesthe leading edges of the radial rotor blades.

Such a bladed inducer portion is effective to reduce the'energy losses due to sudden changes in the direction of the intake air stream. Also the impact losses,-due to unfavorable angles of'attack at the leading edgeof" 14 to the surrounding atmosphere.

the radial blades, are reduced. Also, energy losses due to excess turbulence and local eddies in the flow pattern are reduced and the tendency of the air stream to break away from the contour of the rotor blades is reduced.

In addition to the above, the bladed inducer portion is effective to increase the overall pressure ratio since the total pressure at the inlet or leading edge portion of the radial rotor blades is increased. Each of these factors contributes to increase the overall operating efliciency of the compressor unit.

The blading which is associated with the inducer portion of the rotor is disposed in the disclosed embodiments of the invention in two axially spaced stages about the geometric axis. Suitable means are provided for mounting the individual inducer blades which permit them to be readily assembled on a production basis. Further, an inducer shroud is provided which surrounds the outer peripheral edges of the inducer blades for the purpose of adding support to the blades and for defining the axially extending inducer passageway.

The various disclosed embodiments will be described in more particular detail with reference to the accompanying drawings wherein:

Figure 1 is a cross sectional view of a gas turbine power plant of the automotive type which incorporates one form of the compressor of the present invention;

Figure 1A is an enlarged subassembly view of the centrifugal compressor of Figure 1;

Figure 2 is a sectional view of one embodiment of the compressor rotor showing the bladed inducer portion;

Figure 3 is a detail sectional view showing the welded blade construction of a second form of the compressor of the present invention;

Figure 4 is a sectional view of the structure shown in Figure 2 and is taken along the section line 44 of Figure 3;

Figure 5 is a cross sectional view of a third form of the present invention;

Figure 5A is a detail elevation view of the inducer blade adapted for assembly in the structure shown in Figure 5;

Figure 6 is a cross sectional view of a fourth form of the present invention;

Figure 6A is a detail elevation view of an inducer blade adapted for assembly in the structure shown in Figure 6.

Having reference first to the gas turbine assembly view of Figure 1, the compressor unit is shown generally by means of numeral 10 and it comprises the bladed inducer portion, shown at 11, and the rotor portion 12 in adjacent relationship with respect to each other.

. The air intake means for the gas turbine power plant includes an intake housing 13 having an intake opening The outer portion of the housing 13 partly defines an annular passageway 15 which extends radially inward from the opening 14. The cross sectional shape of the passageway 15, as seen in Figure l, is that of a funneled configuration the center line of which forms a reverse curve. The passageway 15 terminates in an axially extending annular conduit structure, shown at 16, near the geometric axis of the housing 13.

The inducer portion 11 defines an annular space about the hub 17 of the compressor rotor 10, said annular space forming a continuation of the conduit structure 16.

The hub 17 extends outwardly through the central axis of the housing 13 and is positively connected to an accessory drive shown generally at 18. Suitable bearing means are provided in the housing structure 13 to provide end support for the rotor and inducer.

The inducer portion 11 of the compressor unitltl is sealed by suitable sealing means formed in the structure 16 and the hub 17 may be provided with a similar type of sealing means 20. The rotor portion 12 of the compressor unit 10 is adapted to discharge the intake air radially through bladed passages formed therein into an 4 annular inlet opening 19 in a diffuser structure shown generally at 21.

The diffuser 21 comprises a volute-shaped housing, which forms a part of the gas turbine housing proper. The volute housing has a cross sectional area which becomes progressively greater as'the air discharged from the rotor portion 12 travels therethrough.

After the air completes substantially a 360 degree turn in the diffuser 21, the static pressure thereof is increased. This high pressure air is collected in the regenerator housing portion 22 and from there it is allowed to pass through a section of a rotary regenerator shown at 23.

The rotary regenerator 23 is rotatably mounted at 24 and is provided with suitable axially extending passages through which the compressed air is allowed to pass into the annular chamber designated by means of the numeral 25.

The chamber 25 is defined by the gas turbine outer wall structure 26 and the circular baffle structure 27 disposed internally of the wall structure 26.

The air is then passed under pressure from the chamber 25 into a burner, not shown. A suitable means is associated within the burner for mixing fuel with the compressed air and for igniting the mixture. The burned gases then pass from the burner into the chamber designated in Figure 1 by means of numeral 28.

The chamber 28 is annular in shape and is defined by the baffie structure 27 and by another bafiie 29 disposed within the structure 27. The direction of motion of the expanded and heated combustion gases passing from the burner is such that they pass through the chamber 28 in a spiral path. The cross sectional area of the chamber 28 progressively decreases as it progresses about the axis of the engine. The expanded combustion gases pass from the chamber 28 and enter an annular space 30 defined by turbine housing structure 31 and the bafiie structure 29.

A cascade of stator blades 33 is disposed about the axis of the engine Within the annular space 30. The blades 33 are succeeded by an annular cascade of primary turbine blades 34 disposed within space 30 upon the periphery of turbine wheel 35.

A second cascade of stator blades is mounted as shown at 36 adjacent the blades 34 and these are followed by the secondary turbine blades 37 mounted about the periphery of the secondary turbine wheel 38.

The gases which are exhausted from the turbine blades 37 are allowed to pass into a chamber designated by means 24 thereby permitting the heated section of the regenerator to come in contact with the relatively cooler air passing into the burner and also permitting the cooler sections thereof to come in contact with the hot exhaust gases being exhausted from the engine.

The turbine wheel 38 is provided with a shaft which is drivably connected to the input pinion of a reduction gear box shown generally by means of numeral 42. The output gear of the reduction gear box 42 is connected to the output shaft 43 from which useful power may be obtained.

The primary turbine wheel 35 is formed with a central shaft 44 which is drivably secured to the hub member 17 of the compressor unit 10. The high velocity gases passing through the annular space 30 are effective to drive aaeaaoa '5 unitis shown in more particular detail. The shaft 44 carries at one end thereof the turbine wheel 35. The other end of shaft 44 is threa'dably'secured at 65 within the hub member 17. The hub member 17 is disposed in abutting relationship with one end of a hub member 61 for the rotor portion 12.

An adaptor 53, which maybe substantially cylindrical in shape, is disposed coaxially about shaft 44 in abutting relationship with the other side of the rotor hub member 53. The adaptor 61 is formed with an extension 62 upon which a suitable bearing and sealing structure may be assembled.

The shaft 44 is effective to maintain the turbine wheel 35, the adaptor 53, the rotor 12 and the hub member 17 in axially stacked relationship.

The rotor 12 includes a circular row of blades 45 disposed about the axial shaft 44 and between a pair of blade shrouds 48 and 49. The inner periphery of shroud 48 is assembled at 55 to a cylindrical inducer shroud shown at 58, by any suitable means. For example, the

shrouds

58 and 48 may be brazed together'or they may be assembled by means of a force fit.

The annular passageway defined by the inducer shroud 58 and hub 17 has disposed therein a pair of blade stages shown by means of members 73 and 72. The blades may be secured to the hub 17 by means of integral inserts 76 formed at the blade roots. The inserts are adapted to fit within suitable slots in the hub 17.

The projected angle formed by the principal axis of the blade slots and the axis of the shaft 44 may be varied for each stage as appropriate. It is preferable to form the blade slots so that the direction of the chordal lines for the successive blade stages will progressively approach the axial direction defined by the rotor axis. If desired, the blade angles of the successive stages 73 and 72 may be progressively varied so that the blade exit angle for the last stage is substantially equal to the entranceangle for the rotor blades 45.

Having reference next to Figure 2, another form of the compressor unit is shown in more particular detail and is generally designated-by means of numeral 110. The rotor 112 thereof is shown extending radially outward and it includes a circular row of blades 145 forming therebetween channels which originate at the leading edges 146 of the blades 145 and which terminate at the tip edges 147 at the outer peripheral edge. The blades 145 are enclosed by the shroud structures 143 and 149.

The rotor 112 is centrally apertured at 151 to receive the shaft 44. Suitable means may be provided for securing the rotor 112 to the shaft 44, such as the pins 152 secured to the shoulder piece 153. The rotor structure comprising shrouds, 148 and 149, and the blades 145 may be cast as an integral unit.

The rotor 112 is provided with a shoulder 154 against which an inducershroud member is abutted. The shroud member includes a centrally apertured hub portion 155 which receives the shaft 44 therethrough and upon which a circular cascade of blades 156 is radially disposed. The blades 156 are adapted to mate with the leading edges 146 of the blades 145 thereby forming one continuous blade structure from the leading edges 157 of the blades 156 to the tip edge 147 of the blades 145.

An inducer shroud 158 is formed integrally with the blades 156 and it extends axially from the tip edges of the blades 156. The shroud 158, blades 156 and the hub 155 may be cast as one integral unit.

The hub 155 has formed thereon a shoulder surface 159 against which a secondary stage bladed assembly of the inducer 111 is positioned. This secondary stage assembly includes a hub 161which is also centrally bored at 162 to receive the shaft 44. The hub 161 is counterbored at 163 to receive therein an extension 164 of a hub 165 which is associated with a primary stage bladed assembly of the inducer 111. The hub 165 is also counterbored at 166 and it receives therewithin a holding adaptor 167 which may be splinedt at. 168 upon. the shaft-44 and is efiective to hold the members 165, 161,155 and the rotor 112 in a fixed axial position. A suitable snap ring may be provided as shown at 167' to prevent axialmovement of the bladedassembly.

The hubs 161-and are each provided Witha circular row of slots shown by means of dotted lines at 169 and 170 respectively. Within these slotsare received, respectively, a rowof secondary stage inducer blades 172 and a row of primary stage inducer blades 173.

The

inducer blades

172 and 173 are each provided with suitable base portions which are adapted to fit into the associated slots in the members 161. and 165. The extension 164 in the hub member 165 serves as aradial spacer for the blades 172 and the adaptor 167 serves as a radial spacer for the blades 173.-

The slots 169 and 17 0-may be formed at various angular positions with respect to the axis of thecompressor 110 in order to suitably position the associated inducer blades.

The shroud 158 is adapted to extend over the outer tip edges of the inducer blades in order to provide a means of support for. theblades andto define a suitable axial annular inducer passageway. The inducer 158 has formed thereon two rows of holes adapted to. receive 7 pins 174 which maybe formed.

onthe inducer blades

172 and 173 to provide additional blade support.

A key 175 is received within suitable key slots formed in shaft 44-and hubs 155,161, and165 for the purpose of preventing rotation of the rub members upon shaft 44.

Figures 3 and 4 illustrate a modified inducer shroud assembly. The hub 155 shown in Figures 3 and 4 corresponds to'hub 155 shown inFigure 2 and the blades 156' correspond to blades 156 of Figure 2. The blades, as shown'in Figures 3 and 4,. are secured to the hub 155 by means of weld metal '176.

The inducer shroud is shown in Figures 3- and 4 at 158 and itcomprises a separatemember which is slotted at 177 to receive the tip edge of blades 156'. The blades 156' maybe welded to.the shroud as-shown at 178.

.Referringnext to Figure 5, another modified form of the invention is illustrated. The rotor portion 212 of the compressor unit .210. of Figure S includes a radial shroud 249 and integrallyformed rotor blades 245. Only one. radial shroud-isprovided in this embodiment of the invention, the pump stationary housing serving to perform the functionof a secondshroud.

A first hub member is shown at 255 uponwhich the radial blades256 are radially secured. The blades 256 are adapted-to meet the leading edges246 of the blades 245 and to form extensions of the blades 245'. t

The inducer shroud 210 is integrally secured to the tip edges of the blades 256. The assembly consisting of shroud 210, blade 256 and hub 255 corresponds to the shroud 158, blades 156, and hub 155 of the assembly "of Figure 2. r

The hub members for the second and first stages of the inducer are shown at 261 and 265 respectively. Each of the hubs 261 and 265 are provided with slots shown in Figure 5 at 269 and 270, respectively, within whichtthe inducer blades are disposed. The hubs 255, 261, and 265 are held in a fixed axial position by the nut 267 threaded at 268 upon the shaft 44.

The inducer blades are shown in Figure 5 at,272 and 273. Figure 5A is a detail view of one of the blades which include a base portion 271 having fore and aft extensions thereon to: provide added. blade support. The base 271 of each blade is adapted to fit into the associated

slots

269 and 270. Axial displacement of the blades 272 and 273 isprevented bymeans of the abutting relationship of the ends of the base portion 271-with the adjacent hub 255 and the nut 267. Radial displacement of the blades 272 and 273 is preventedby the shroud '210 which surrounds the blades and contacts the tip edges thereof. If desired, suitable pinsor other supporting means may be provided to secure thcblades 272 and 273 7 to the shroud 210 to provide added support to withstand bending loads.

Referring next to Figure 6, another modified form of the compressor unit is illustrated. The rotor portion of the unit is shown at 312 and it comprises a shroud 349, radial blades 345 and a second shroud 348. The inducer shroud is shown at 358 and is formed integrally with the rotor shroud 348. The rotor 312 and the shroud 358 may be cast in one piece as an integral unit.

The inducer portion, shown at 311, comprises a hub member 365 which has an axially extending portion 361 formed thereon. The hub 365 is retained upon shaft 44 by the threaded engagement shown at 368.

The secondary stage and primary stage inducer blades are shown at 372 and 373 respectively. One of the blades is illustrated in detail in Figure 6A. It is seen that each of the blades is provided with a base portion which is formed with a tongue 371 having a projection 360 extending therefrom. Mating slots are provided in the hub 365 and the extension 361 to receive the tongues 371 and projections 360 on the associated inducer blades. Radial displacement of the inducer blades is prevented by the shroud 358 which contacts the tip edge of each of the blades.

It should be noted from the various views of the inducer portions, and especially from Figures A and 6A, that the blades are shaped to provide an air foil having sections of increasing chordal length as the radial distance of the respective sections from the central axis increases. In other words, the chordal length of any one section from the root to the tip edge is substantially directly proportional to the radial distance of that section to the axis. Such a configuration is considered desirable because the aerodynamic characteristics of the blades are such that the efficiency is higher if the ratio of the chordal length at any one radius to the spacing between the blades at that same radius is kept constant. This ratio is known as the solidityratio.

Further, the need for a diverging chordal length for the inducer blades may become apparent when it is observed that in order to maintain a uniform angular velocity of the inlet air stream through the inducer shroud, the linear tangential velocity of a particle of air at any radial position must be proportional to the radial distance of that particle from the axis of rotation. Therefore, it is apparent that the particles of air near the outer tip edge of the inducer blades must be accelerated over a longer period of time than the particles of air nearer the axis of rotation in order to maintain a uniform angular velocity. By providing the blade near the outer edge with a longer chordal length than that of the portion of the blade radially inward, the air near the tip edge is so acted upon for a relatively longer period of time.

The blades may also be provided with a variable double camber cross sectional shape as shown in Figures 5A and 6A. The blunt nose leading edges and the relatively thin trailing edges of the blades may also be provided with appropriate entrance and exit angles, respectively, in order to obtain optimum performance.

The composition of the cast structure of the various compressor units herein disclosed may be of aluminum or magnesium, or alloys thereof, in order to reduce the total Weight. The inducer blades may be formed, if desired, of a suitable plastic such as Bakelite in order to reduce manufacturing costs and to acilitate the blade forming process.

The blade support which is provided by the various inducer shrouds contributes to the vibrational stability of the assembly and prevents fatigue failures at the blade roots.

It is contemplated that the present invention may be used in kinetic machinery which makesuse of or which acts upon fluids other than air or gases. The device of the present invention may, for example, be readily adapted to be used with centrifugal machines employing liquids such as water, liquid fuel, or the like.

The number of inducer blade stages may be varied as appropriate and also the entrance and exit angles of the blades may be varied. It is preferably to provide the blades of the successive inducer stages with progressively varying entrance angles which approach in value the magnitude of the entrance angle of the rotor blades.

The inducer blades may also be of the single camber type or the zero camber type if such a design is desired. Such blades might well be used on low capacity units without an appreciable loss in operating efiiciency.

While various embodiments of the invention have been disclosed, it is understood that the invention is not limited thereto since many variations may readily become apparent to those skilled in the art, and the invention is to be given its broadest possible interpretation within the scope of the following claims.

We claim:

1. In combination, a high speed rotor for a gas turbine engine, an air compressor including a central rotatable hub coaxial with said rotor and driven thereby, at least one annular outer one-piece shroud coaxial with said hub, a plurality of generally radially extending blades, each blade having a root portion at its radially inner end, key and socket means so constructed and arranged between said inner end and hub as to prevent relative axial and angular movement of said blade with respect to said hub and so that said blade is freely shiftable radially with respect to said hub, the diameter of the inner periphery of said shroud being substantially equal to twice the distance from the tip of said blade to the axis of said hub when the blade, shroud, and hub are in unstressed and assembled condition prior to rotation thereof, so that forced engagement between said shroud and the radially outer end of the blade under the infiuence of centrifugal force during high speed operation of said compressor takes place, said shroud closely encircling the radially outer ends of said blades and providing radial support for said outer ends when said blades are forced outwardly against said shroud by centrifugal force during said operation.

2. The combination according to claim 1 and comprising in addition means interconnecting said shroud and the radially outer ends of said blades.

3. The combination as in claim 1 wherein said key and socket means includes a generally radially opening socket in said hub mating with one of each of said root portion, the root portion of each blade comprising an out-of-round tongue and a narrow finger of the radially inner end of the tongue, said tongue and finger extending radially inwardly and seating snugly within the mating socket therefor.

4. The combination according to claim 3 wherein said tongue is compartively thin and said finger is of reduced width with respect to the width of said tongue.

5. In combination, a high speed rotor for a gas turbine engine, an air compressor comprising a compressor rotor having a central rotor hub and an annular rotor shroud coaxial with said hub and spaced radially therefrom to define an annular rotor passageway, an inducer hub rotatable coaxially with said rotor hub, at least one annular one-piece inducer shroud distinct from said rotor shroud, said inducer shroud being coaxial with said inducer hub and spaced radially therefrom at the upstream end of said rotor shroud to define an annular inducer passageway in communication with said rotor passageway, the rotor and inducer hubs being rotatable coaxially with said engine rotor and being driven thereby, a plurality of generally radially extending inducer blades, each blade having a root portion at its radially inner end, key and socket means so constructed and arranged between said inner end and inducer hub as to prevent relative axial and angular movement of said blade with respect to said inducer hub and so that said blade is freely shiftable radially with respect to said inducer hub, the diameter of the inner periphery of said inducer shroud being substantially equal to twice the distance from the tip of said blade to the axis of said inducer hub when the blade, inducer shroud, and inducer hub are in unstressed and assembled condition prior to rotation thereof, so that forced engagement between said inducer shroud and the radially outer end of the blade under the influence of centrifugal force during high speed operation of said compressor takes place, said inducer shroud closely encircling the radially outer ends of said blades and providing radial support for said outer ends when said blades are forced outwardly against said inducer shroud by centrifugal force during said operation.

References Cited in the file of this patent UNITED STATES PATENTS 953,526 Green Mar. 29, 1910 10 Havill Oct. 8, 1935 Szydlowski Aug. 6, 1940 Werther Dec. 8, 1942 Rockwell et al Mar. 30, 1948 Miller June 19, 1951 Szczeniowski Oct. 2, 1951 Jonker Sept. 2, 1952 Lysholm Dec. 2, 1952 Klein Nov. 24, 1953 Travers Oct. 19, 1954 Jandasek Dec. 7, 1954 Zeidler et al Dec. 15, 1959 FOREIGN PATENTS Austria May 26, 1924 Germany Jan. 29, 1941 Great Britain Apr. 1, 1936 Great Britain July 9, 1947 Italy Ian. 14, 1939 UNITED STATES PATENT OFFICE CERTIFICATION OF CORRECTION Patent NO. 2,962,206 Novembr 29, 1960 David M. Borden et al.

pears in the above numbered pat- Itis hereby certified that error ap d Letters Patent should read as ent requiring correction and that the sai corrected below.

Column 2, line 20, for "portions" read portion 53, for "with". read will column 4, line 53, for "the" read this column 6, line 29, for "rub' read hub column 8, line 5, for "preferably" read preferable line 50, for "of the" read on the Signed and sealed this 6th day of June 1961. ii

(SEAL) Attest:

ERNEST W. SWIDER Attesting Officer DAVID L. LADD Commissioner of Patents