US2880926A

US2880926A - Fabricated bladed compressor wheels

Info

Publication number: US2880926A
Application number: US495201A
Authority: US
Inventors: Edward A Stalker
Original assignee: Stalker Development Co
Current assignee: Stalker Development Co
Priority date: 1955-03-18
Filing date: 1955-03-18
Publication date: 1959-04-07
Anticipated expiration: 1976-04-07

Description

April 7, 1959 E. A.- STALKER 2,880,926

FABRICATED BLADED COMPRESSOR WHEELS I Filed March 18, 1955 2 Sheets-Shee't 1 INVENTOR.

E. A. STALKER FABRICATED BLADED COMPRESSOR WHEELS Filed March 18, 1955 April 7, 1959 2 Sheets-Sheet 2 INVENTOR. ZZZMMQMM United States Patent "O 2,880,926 FABRICATED BLADED COMPRESSOR WHEELS Application March 18, 1955, Serial No. 495,201

Claims. (Cl. 230-134) This invention relates to axial flow compressors.

An object of the invention is to' provide a fabricated bladed Wheel wherein the fatigue strength of the blades at their roots is greatly improved.

Other objects will appear from the description, drawings and claims.

The above objects are accomplished by the means illustrated in the accompanying drawings in which- Fig. l is a fragmentary axial section through an axial flow compressor showing the Wheel assembly together with fragments of associated parts of the compressor;

Fig. 2 is an enlarged fragment in section of the rim portion of a wheel;

Fig. 3 is a fragmentary section on line 3-3 in Fig. 2; Fig. 4 is a fragmentary section on line 44 in Fig. 2; Fig. 5 is a fragmentary section on line 5-5 in Fig. 2;

Fig. 6 is a fragmentary section on line 6-6 in Fig. I

l; and

Fig. 7 shows fragments of two adjacent tie rod tubes partly in section.

In fabricated wheel and blade assemblies it is diflicult to eliminate stress concentrations where a sheet metal blade abuts the rim of the wheel hub. The bending of the blade about a chordwise axis tends to cause fatigue failure in a blade along a line close to the rim surface where the stress is raised by the abruptness of the change in geometry.

In the invention of this application, means are provided for mounting the blades which alleviate the stress concentration.

Each blade tends to vibrate about a chordwise axis near the root section causing compressive stresses in the upper (convex) and tension stresses in the lower wall of the blade. The compressive stress may be offset, at least in major part by a tension stress due to the centrifugal load of the blade. However the tension stresses in the lower wall are magnified by the addition of the centrifugal tension. Thus the critical Wall stresswise is the lower wall. It should be thicker than the upper wall or it should be reinforced relative to the upper wall.

In this invention the blade envelope defined by the upper and lower walls is carried by a hollow stern. For lightness and economy it is desirable to make this stem of folded sheet metal with lapped portions of the stem walls fixed together preferably by fused metal forming a stem flange extending along a major portion of the span of the blade. (The span of a blade is the length extending substantially parallel to the radius of the bladed wheel.)

Further advantage of the type of stem construction is taken by positioning the stem flange on the lower wall to aid in resisting the magnified stress loads coming on the lower wall during vibration of the blade.

Referring now to the drawings, particularly Fig. 1, the compressor is indicated generally as 10 comprising the case 12, the wheel assembly 14, and the stators 1618.

The Wheel assembly comprises the wheels 2023, the hub spacers 26-28, the end plates 30 and 31 and the

shafts

32 and 34.

The wheel assembly is mounted in the compressor for Patented Apr. 7, 1959 rotation about the axes of

shafts

32 and 34 in suitable bearings not shown.

The wheels are substantially similar so it will be sutlicient to describe in detail only wheel 21.

Referring particularly to Figs. 1, 2 and 3, wheel 21 comprises a plurality of blades 40 peripherally spaced about a hub means 41 and secured to its disk 42. The hub means also includes a rim means 44 which encircles the disk and is fixed thereto.

As shown particularly in Figs. 2, 3 and 5 each blade or blade means 40 comprises a blade envelope 48 and a stem means both of which pass radially inward through an opening 50 in the rim means 44. Each envelope encloses and is fixed to a stem means 60 comprising a front stem 62 and a rear stem 64 spaced apart chordwise to provide a gap for accommodating an outer portion of the disk therein. The stems are secured to the disk preferably by solder or other fused metal between the stems and the disk.

Each stem is preferably secured by fused metal to the opposite or upper and lower walls of the blade envelope. See Figs. 2 and 4.

The rim means comprises a front ring 70 and a rear ring 72 which abut each other over the tabs 74 of the disk at the joint 76 and providing a front leg 77 and a rear leg 78 each radially inturned.

The blades and rim means are secured together by means of the

root connectors

80 and 86. The connector 80 is fixed to the root end portion of its blade by fused metal, preferably solder, and to the front leg-77 of the rim ring by the flange 84 also by fused metal. In a similar manner connector 86 is fixed to the blade and to the rim ring 72 by flange 88. These flanges are preferably spot-welded at to the front and rear legs at localities substantially inward from the rim surface 94 of the rim means.

The connectors each extend radially outward beyond the rim surface 94 and are secured by fused metal to the blades. See particularly Figs. 2 and 4. The portion of a connector adjacent to the rim is a fillet means. Above the rim surface the thicknesses of the fillet means is tapered to a feather edge at so that there is no abrupt change in blade cross section. As shown in Fig. 4 the fillet means has the concave surface characteristic of fillets for relieving stresses. This eliminates significant stress concentration and provides the blade with a long life relative to fatigue failure from vibration. The fillet means terminates at 100 at a distance from the rim of fillet magnitude. That is this distance is very small and not greater in radial extent than about the thickness of the blade.

The wheels are stacked in axial tandem relation between the end plates 30 and 31 by means of the cylindrical hub spacers 2628. See Fig. 1. Tie bolts pass through the spacers and the plates and draw the parts together.

As show in Figs. 6 and 1 each spacer comprises an outer cylinder 114 with inturned flanges 116 and 118 at opposite ends, Fig. l, and two adjacent inner cylinders 117 and 119 with inturned flanges 120 to provide a stiffening effect. Each spacer also includes a length of tube 122 fixed by fused metal to the inner and outer cylinders.

The tubes have a conical recess at one end and a complementary conical recess "at the opposite ends so that the tubes center one in the other and properly align the wheels one relative to the other.

It will now be clear that I have provided a novel construction which eliminates the tendency to stress concen tration in a blade at the locality where it presses against the rim means under bending forces such as fluid action and vibrations.

While I have illustrated specific forms of the invention, it is to be understood that variations may be made there in and that I intend. to claim my invention broadly as indicated by the appended claims.

I claim:

1. In combination in a bladed wheel for a compressor, a huh-means comprising a hollow. rim means having a rim with peripherally spaced openings therein, said rim means having front and rear legs extending radially inward, and a plurality of hollow separate blades spaced peripherally about said rim with each extending radially inward through a said opening for a limited radial distance and terminating nearer to said rim than to the center of said hub means, a separate connector means bonded to each said blade at the root end thereof and extending radially outward through said opening between the edges thereof and said blade for a radial distance of fillet magnitude, said connector means decreasing in thickness outward from said rim forming a fillet means of concave outer surface at said rim for alleviating stress concentration in said blade at said rim, and each said connector means having flanges secured to said legs.

In combination in a bladed wheel for a compressor, a hub means comprising a hollow rim means having a rim with' peripherally spaced openings therein, and a plurality of hollow blades spaced peripherally about said rim with each extending radially inward through a said opening-for a limited radial distance and terminating nearer tosaid rim than to the center of said hub means, a separate connector means bonded to each said blade at the root end thereof 1 and extending radially outward through said opening between the edges thereof and said blade for a radial distance of fillet magnitude, said connector' mea'ns decreasing in thickness outward from said rim forming a fillet means of concave outer surface at said rim for alleviating stress concentration in said blade ht said rim, and each said connector means being secured by fused metalto saidrim means at a locality radially inward from said rim. 7

3." In combination in a bladed wheel for a compressor, a hub means comprising a hollow rim means having a rim with peripherally spaced openings therein, said rim means including radially inturned front and rear legs, and a plurality of hollow separate blades spaced peripherallyabout said rim with each extending radially inward through a said opening for a limited radial distance and terminating nearer to said rim than to the center of said hub means, a separate connector means bonded to each said blade at the root end thereof and extending radially outward through said opening between the edges thereof and said blade for a radial distance of fillet magnitude, said connector means decreasing in thickness outward from said rim forming a fillet means of concave outer surface at said rim for alleviating stress concentration in said blade at said rim, and each said connector means being secured to a said leg at a locality radially inward fixed to said disk peripherally thereabont with peripherally spaced openings in said rim, and a plurality of hollow separate blades spaced peripherally about said rim with each extending radially inward through a said opening for a limited radial distance and terminating nearer to said rim than to the center of said hub means, a stem means within each said blade fixed to the interior surface thereof and extending out of said blade at the root end thereof and secured to said disk for supporting said blade, a separate connector means bonded to said rim means and'to each said blade for supporting said rim on said disk, said connector means extending radially outward through a said opening for a radial distance of fillet magnitude and about each said blade and having decreasing thickness radially outward from said rim means forming a fillet means of concave outer surface at said rim for alleviating stress concentration in said blade at the root end thereof.

5. In combination in a bladed wheel for a compressor, a hub means comprising a hollow rim means having a rim with peripherally spaced openings therein, and a plurality of hollow separate blades spaced peripherally about said rim with each blade extending radially inward through a said opening for a limited radial distance and terminating nearer to said rim than to the center of said hub means, said blades being secured in said hub means, fillet means for each said blade separate from that of another blade before being fixed to its respective blade by fused metal,-said fillet means extending along a major portion of the chord length of said blade at said rim and radially outwardly through a said opening between the edges thereof and said blade for a distance less than the maximum thickness of the portion of said blade at said fillet means, each said fillet means extending radially inward through said rim for a limited radial distance and terminating nearer to said rim than to the center of said hub means, each said fillet means being fixed by fused metal to its respective blade, each said fillet means progressively decreasing in thickness radially outward from said rim'to a feather edge at the radially outward edge of said fillet means providing a concave surface of said fillet means over substantially the Whole radial extent of the portion thereof outwardly of said rim, for alleviating stress concentration in said blade at the junction of said blade and rim.

References Cited in the file of this patent UNITED STATES PATENTS Germany Mar. 5, 1953