US3554668A

US3554668A - Turbomachine rotor

Info

Publication number: US3554668A
Application number: US823608A
Authority: US
Inventors: Joseph A Wagle
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1969-05-12
Filing date: 1969-05-12
Publication date: 1971-01-12
Anticipated expiration: 1988-01-12
Also published as: GB1252544A

Abstract

A TURBOMACHINE ROTOR COMPRISES A NUMBER OF RINGS FORMING A DRUM WITH END BELLS AT THE ENDS OF THE DRUM. EACH RING MOUNTS A ROW OF BLADES WITH CLEVIS-TYPE ROOTS WHICH EXTEND THROUGH OPENINGS IN THE RING AND WHICH ARE RETAINED BY PINS ON THE INTERIOR OF THE RING EXTENDING THROUGH HOLES IN THE ARMS OF THE BLADE ROOT CLEVISES. RINGS OF FIBROUS COMPOSITE WRAP EXTEND AROUND THE BLADE MOUNTING RINGS BETWEEN THE ARMS OF THE BLADE ROOT CLEVISES. CORRUGATED STANDOFF RINGS BETWEEN THE RING AND THE FIBROUS WRAP PROVIDE FOR SLIGHT GROWTH OF THE RING RELATIVE TO THE WRAP.

Description

J.-A.WAGLE TURBoMAcHNE RoToR.

` Jan. 12,-1971 f l Filed May 12, 1969 STRAINA United States Patent Office 3,554,668 Patented Jan. 12, 1971 3,554,668 TURBOMACHINE ROTOR Joseph A. Wagle, New Augusta, Ind., assigner to General Motors Corporation, Detroit, Mich., a corporation of Delaware Filed May 12, 1969, Ser. No. 823,608 Int. Cl. F01d 5/32 U-S. Cl. 416-220 14 Claims ABSTRACT OF THE DISCLOSURE A turbomachine rotor comprises a number of rings forming a drum with end bells at the ends of the drum. -Each ring mounts a row of blades with clevis-type roots which extend through openings in the ring and which are retained by pins on the interior of the ring extending through holes in the arms of the blade root clevises. Rings of fibrous composite wrap extend around the blade mounting rings between the arms of the blade root clevises. Corrugated standoff rings between the ring and the brous wrap provide for slight growth of the ring relative to the wrap.

My invention is directed to turbomachine rotors and particularly to provide a strong, lightweight rotor for turbomachines such as axial-flow compressors and turbines. In the preferred embodiment, my invention is applied to a multistage axial-liow compressor having a lightweight titanium drum rotor and blades mounted by a clevis and pin arrangement, but other adaptations of the invention are readily perceived.

The principal virtue of the invention lies in the felicitous use of very high tensile strength fibrous composite wrap to reinforce the metal rotor drum against the very high centrifugal forces exerted upon it, principally by the blades, but also by the structure of the drum itself. The structure is such that the force exerted by the blades is delivered against the interior of the rotor drum, whereas the reinforcing ring is disposed about the exterior of the rotor immediately adjacent the point of application of the centrifugal forces from the blade roots.

Another feature of my invention which is desirable in most applications is an arrangement which I call a standoff ring to allow some growth of the metal structure due to centrifugal force or temperature changes before the loads are transmitted fully to the fibrous reinforcement. This is desirable because of the usually greater yielding of the metal than of the fiber-reinforced composite, so that to exploit the full strength of the metal it should be permitted to be strained to a greater extent than the reinforcement.

The principal objects of the invention are to improve the strength and reliability of turbomachine rotors, to provide an improved rotor structure having light weight and adapted to exploit the advantages of lightweight metals such as titanium and fibrous composite wraps. A further object of the invention is to provide a structure embodying an inner ring and an outer reinforcing ring with structure providing for slight yielding of the inner ring relative to the outer ring.

A still further object of the invention is to provide an improved method of making a reinforced rotor drum ring for high speed rotating machinery.

The nature of my invention and the advantages thereof will be clear to those skilled in the art from the succeeding detailed disclosure of the preferred embodiment of the invention, which is presented to explain the principles of the invention and is not to be construed in a limiting sense.

FIG. l is a sectional view of a drum rotor taken in a plane containing the axis thereof;

FIG. 2 is an enlarged view of a portion of FIG. l;A

FIG. 3 is a still further enlarged view corresponding to FIG. 2 but illustrating the process of manufacture of the rotor;

FIG. 4 is a radial sectional view taken on the plane indicated by the line 4 4 of FIG. 2;

FIG. 5 is a fragmentary axonometric view of a rotor ring; and

FIG. 6 is a stress-strain diagram.

FIG. 1 shows a rotor for a four-stage axial-fiow compressor. The rotor comprises a drum 9 made up of four rings -10 and two end bells 11 and 13. As illustrated, the end bells are integral with stub shafts by which the drum may be mounted for rotation in suitable bearings, one stub shaft having a driving ange 14. The parts 10, 11, and 13 are held together by a tie bolt 15 and nut 17. The end bells may have any suitable shape and the tie bolt may or may not be present, depending upon the particular design.

As shown, the rings 10` progressively increase in diameter, although they may not and, in general, they are as near alike as feasible although they may differ in width and, ordinarily, in the number of blades mounted on the rings.

Each ring mounts a row of blades 18 having roots 19 which, as illustrated, are of the multiple clevis type embodying four clevis arms 21. As shown in FIG. 4, each blade may embody a platform 22 between the airfoil portion and the root. In the form illustrated, each ring 10 embodies a central blade mounting portion 23, two radial flanges 25, and axially extending marginal flanges 26.

The radial flanges contribute to the stiffness to the ring during its processing prior to the assembly into the rotor. However, these are not essential to the practice of the invention however desirable they may be in certain cases and, therefore, the ring 26 may, if desired, be a cylindrical or conical ring without offsets or radial anges. The

parts

23, 25, and 26 may be an integral machined part or, preferably, a welded or brazed structure made from a plurality of rings.

Since each blade root 19 comprises four arms 21, each ring is machined to provide four rows of apertures 27, with one aperture in each row for each blade. Semicircular holes 29 are machined through both flanges 25 to receive a sernicircular blade retaining pin 30 having a head 31. Pin 30 may be retained in a suitable manner, as by centrifugal force in the conicalstructure illustrated, by pinning, by tack welding7 or by adjacent rotor structure. The arms of the blade roots have holes 33 which are preferably cylindrical. Pin 30 extends through the holes 33 so as to mount the blade with a slight hinging action so that it may adopt a suitable position as a result of the centrifugal and gas loads in operation of the rotor. It is to be understood that such clevis and pin blade mountings are quite old and well known.

The features of my rotor which are significantly difierent from prior rotors of which I am aware involve the reinforcing of the ring by a fibrous composite wrap 34,

which is wrapped around the rotor in rings disposed be-v tween the arms 21 of the blade root, and the standoff ring or rings 35 disposed between the blade mounting portion 23 and the fibrous composite wrap 34. The materials used for the reinforcing wrap may follow known practice in the art, depending upon the nature of the installation. The use of glass fibers set by a thermosetting resin has long been known (see, for example, U.S. Pat. No. 3,095,138 to Warnken, June 25, 1963). Currently there have been extensive developments involving more exotic materials such as sapphire, beryllium, tungsten, graphite, and boron `filaments which may be bonded by a metal matrix or a suitable high strength polymer such 3 as an epoxy resin for the lightest weight and greatest strength. The presently preferred materials for the reinforced rotor are titanium for the part and a carbon or boron and epoxy resin composite for the reinforcing ring or wrap 34.

While the reinforcing ring can be wound or fitted directly onto a rotor, it is in most cases advantageous to provide a standoff ring between the blade mounting ring and the reinforcing ring. In the preferred embodiment of the invention, the standoff ring comprises three rings 35 disposed between adjacent arms 21 of the blade roots. the three rings extending around the perimeter of the blade mounting portion 23. Of course, it is possible to use a single ring provided with apertures for the blade mounting arms. However, as shown most clearly in FIGS. 3 and 4, the standoff ring is a thin ring of metal with corrugatons extending axially of the rotor so that a slightly yieldable spring is provided between the rings 23 and 34 extending entirely around the rotor drum. This standoff ring may be made of steel or any other suitable material. The

ring may be segmented with the segments located by cementing, brazing or otherwise fixing them to the ring 23.

I have devised a technique for applying the several bands of the composite wrap 34. As illustrated in FIG. 3, temporary flanges 37 are mounted, extending around the portion 23 of the mounting ring, and covering all four sets of the mounting apertures 27. The anges 37 are rings of some material of sufficient strength to confine the wrap into the spaces between the blade root arms. These rings 37 are made of some material which may be removed readily after the winding curing of the reinforcing rings are completed as, for example, a soluble ceramic. According to this mode, the rings 37 are applied to the rotor and the standoff rings 35 are put into place, after which the fiber is applied with a suitable cement or binder and wound to the desired depth on the rotor, under appropriate tension. The fiber may be applied as a tape. The drum section or ring 10 is then cured and the rings 37 removed, after which the blades are inserted and the pins 30l applied to retain them.

It will also be clear, of course, that the reinforcing rings 34 might be wound around any suitable collapsing mandrel and then put or pressed into place on the ring 10. In this case, the ring 10 must not have a flange such as extending so as to block the mounting of the reinforcing rings. The standoff rings 3-5 are provided to insure compatibility between the mounting ring and the reinforcing ring. This is illustrated by the stress-strain diagram in FIG. 6. The line TI represents the elastic deformation of the titanium rotor with stress. The reinforcing ring deformation line indicated as WRAP starts at a considerable value of strain of the rotor because of clearance provided by the standoff ring. The line marked TOTAL represents the total stress exerted by the titanium ring and the wrapped reinforcing ring. This accommodates to the fact that the metal has a lower modulus of elasticity and, therefore, will yield to a greater extent than the fibrous composite. If the fibrous composite has a direct contact with the metal, the metal would be constrained by the fiber so as not to reach its maximum allowable stress. By allowing the metal to stretch farther than the wrap, both may be brought to the maximum allowable stress.

There is another factor that may influence the need for the standoff ring, possible greater thermal expansion of the mounting ring 10 which causes it to expand more than the reinforcing ring as the rotor comes to its operating temperature. This, of course. depends upon both the materials and the temperature ranges involved.

The effect of the standoff ring could be provided by allowing a small clearnce between the inner ring at 23 and the reinforcing ring or rings 34, at least if the reinforcing ring is formed separately on a mandrel and then assembled onto the ring 10.

It is clear, of course, that a ring such as 10 could mount more than one row of blades or, alternatively, that a drum such as 9 might be made as a unit rather than as a number of separate rings. The structure illustrated is preferred, however.

My invention is not concerned with the means by which the rings are coupled together into the rotor to maintain them in proper alignment and to transfer torque between the rings. They may be piloted together, coupled by face splines, or welded, for example. Disclosures of composite rotor constructions are numerous in the art as, for example, U.S. patents to Jendrassik, No. 2,241,782, May 13, 1941; Traupel, No. 2,619,317, Nov. 25, 1952; Constantine et al., No. 2,637,521, May 5, 1953; and Willgoos, No. 2,672,279 Mar. 16 1954. Jendrassik and Willgoos also illustrate blades with clevis roots mounted by pins. In any event there are various ways of aligning and coupling the several rings 10 into a rotot drum 9 and attaching them to suitable end bells or the equivalent,

It will be clear to those skilled in the art that my invention provides a very lightweight structure particularly adapted to the requirements of practice and readily manufactured.

The detailed description of the preferred embodiment of the invention for the purpose of explaining the principles thereof is not to be considered as limiting the invention.

I claim:

1. A turbomachine rotor structure comprising, in combination, a mounting ring, an annular row of blades mounted on the ring, the blades having clevis type roots with plural arms attached to the ring, a reinforcing ring of high tensile strength material disposed around the mounting ring between the arms, and a standoff ring disposed between the mounting ring and the reinforcing ring.

2. A structure as recited in claim 1 including pins disposed within the mounting ring extending through holes in the blade roots and coupling the blades to the ring.

3. A structure as recited in claim 2 in which the reinforcing ring is a fibrous composite wrap.

4. A structure as recited in claim 1 in which the standoff ring is defined by a strip of elastically yieldable material.

5. A structure as recited in claim 4 in which the strip is corrugated.

6. A structure as recited in claim 4 in which the strip is segmented.

7. A structure as recited in claim 1 in which there are a plural number of reinforcing rings for each row of blades.

8. A turbomachine rotor comprising one or more drum sections of annular configuration and means mounting the section or sections for rotation about an axis, each drum section comprising a mounting ring and at least one row of blades distributed around the circumference of the ring, each blade having a clevis-type root defined by plural arms extending from the blade, the ring having apertures and the arms extending through the apertures to the interior of the ring, pins on the interior of the ring extending through holes in the arms to retain the blades and transmit the centrifugal force exerted by the blades to the interior of the ring, and a fibrous composite reinforcing ring extending around the exterior of the mounting ring and between the arms to reinforce the mounting ring against centrifugal forces.

9. A rotor as recited in claim 8 including also an elastically yieldable standoff ring between the mounting ring and the reinforcing ring.

10. A rotor as recited in claim 8 in which a small effective clearance is provided between the exterior of the mounting ring and the interior of the reinforcing ring to allow expansion of the mounting ring relative to the reinforcing ring.

11. A rotor as recited in claim 10 including also an References Cited elastically yieldable standoif ring disposed between and UNITED STATES PATENTS engaging the mounting ring and the reinforcing ring.

12. A rotor as recited in claim 8 in which each blade etal' root is defined by three or more arms and a reinforcing 5 3:403844 10/1968 stoer ;:I 416 230(X) I'Ilg S dSpOSed between each WO adjacent alIl'lS. 3,494,539 Littleford 13; A rotor 'as recited in claim 12 in which a standoff ring having openings for the said arms is disposed be- EVERE'ITE A. POWELL, JR., Primary Examiner tween the mounting ring and the reinforcing ring.

14. A rotor as recited in claim 13 in which the standoff 10 U-S. C1. X.R ring is segmented. 416-217, 230