US1166316A - Turbine-rotor. - Google Patents

Description

0. D. H. BENTLEY.

I TURBINE ROTOR. APPLICATION FILED 0CT.23, 19l2.-

Patented Dec. 28, 1915.

OLIVER D. H. BENTLEY, 015 BOSTON, MASSACHUSETTS, ASSIGNOR TO B. F. STURTEVANT COMPANY, OF BOSTON, MASSACHUSETTS, A CORPORATION OF MASSACHUSETTS.

TURBINE-ROTOR.

Specification of Letters Patent.

Patented Dec. 26, T9915.

Application filed October 23, 1912. Serial No. 727,343.

To all whom it may concern: I

Be it known that I, OLIVER D. H. BENT- LEY, a citizen of the United States, residing at Hyde Park, Boston, in the county of Suffolk and State of Massachusetts, have invented certain new and useful Improvements in Turbine-Rotors; and I do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

The present invention relates to improvements in turbine rotors.

Turbine rotors and similar elements which run at high rotative speeds must be not only statically balanced so that the center of mass lies in the axis of rotation, but must also be dinamically balanced so that no unbalanced centrifugal forces will exist which would set up a couple at right angles to the axis of rotation. Turbine rotors are usually statically balanced by mounting them on two parallel knife blades and removing metal until there is no tendency of the rotor to roll on the knife blades. It is much more difficult to dynamically balance a rotor. In some instances, the high speed rotor has been mounted upon a flexible shaft which bends sufficiently under the couple set up by the dynamically unbalanced condition of'the rotor to allow the rotor to be dynamically self-balanced. In other instances the rotor is rigidly mounted upon a rigid shaft and then is carefully machined into a shape which, as far as' care in workmanship can attain, is symmetrical about the axis of the shaft. In this case the stresses set up because of any dynamically unbalanced condition, which machining is unable to obviate, is withstood by the strength of the rotor structure and the shaft bearings. The complications and disadvantages involved in the use of a flexible shaft on a turbine rotor have been considerable, so great in fact that in all cases where it was possible to avoid the use of the flexible shaft it has been eliminated, so that the flexible shaft is used only in certain types of turbines having extremely rapid running and light rotors. The expense and degree of care necessary to machine a rigid rotor mounted on a rigid shaft to a symmetrical condition are very great and even with the most careful workman- 'sists of two disk-like plates 3 ship it is found almost impossible to machine a rotor for perfect dynamic balance.

The object of the present invention is to produce a turbine rotor of such construction as in a state of rotation to automatically assume a condition of dynamic balance, and to this end the invention consists in the turbine rotor hereinafter described and particularly defined in the claims.

In the accompanying drawings illustrating the preferred form of the invention Figure 1 is a side elevation of a portion of said rotor, and Fig. 2 is a sectional elevation of a turbine rotor embodying the preferred form of the invention.

The illustrated embodiment is described as follows: The rotor shaft 1, mounted in rigid bearings in the casing, has secured upon it the hub 2 of the rotor, which conand 4c supporting at their periphery between them the blades 5. The plates 3 and 4: are circular in form. They have holes at their centers through which extends the boss 6 of the hub 2. The central holes in the plates 3 and 4 fit the boss 6, and the plates 3 and 4 are thereby centered on the shaft. A hexagonal nut 7 screwed upon the boss 6 holds the plates 3 and 4: in position. From the center the plates diverge from each other to their periphery, as seen in Fig. 2, where the series of blades 5 is supported. These blades v5 are made of extruded metal, and are cut from bars of uniform section and indefinite length, after which they have turned upon their ends the pins 8 which are received in the holes spaced around the disks 3 and t in the peripheries of the disks to receive them. These holes are slightly counter-sunk on the outside, and the studs 8 are riveted into the counter-sinks in order to secure the blades in position in the disks. In order securely to hold the blades from accidental turning in the plates, each counter-sink is scored with a radial groove. "When the ends of the studs 8 are riveted in the counter-sinks,

the metal of the studs flows into such scores.

and securely holds the blades from turning. The rotor illustrated in the drawing is intended to receive the steam from the expanding nozzle or nozzles upon its periphery and to discharge it into its center, whence it escapes through the openings 9 in the disks 3 by a continuous wreath of nozzles, the exhaust will be through the disks 3 and 4, but

where the nozzles are separated, the exhaust, or' part of the exhaust, will or may be thrgrtgh the inoperative inter-blade spaces.

his to be observed that the rotor is of triangular cross-section, and is supported atthe apex of the cross-section; This construction lends itself to facility of springing of the plates 3 and 4 during the rotation of the rotor in order to enable the rotor to bring itself into a condition of dynamic balance. While the greatest of care is exercised in the construction of these rotors, it is a matter requiring the utmost nicety of workmanship in order to secure the static balance of the structure, let alone the dynamic balance, and so the rotor of the present invention, being one which self-actingly brings itself to a condition of dynamic balance, contributes substantially to the excellence of running, conditions of the engine. In the case of a rigid rotor out of dynamic balance when rotated at the high speed incident to the operation of the turbine, .even if the parts are strong enough to stand the stresses to which they are subjected, the unbalanced condition subjects the parts to excessive and unpermissible wear, which has operated in many cases to forbid the use of speeds which in the case of a heavy self-centering dynamically balanced rotor would not only be permissible but highly desirable, because of the higher speeds capable of being obtained,

' and the excellence of the running conditions of a dynamically balanced rotor.

The gist of the present invention resides in making the rotor flexible, so that it may in operation automatically assume a condi- 1 tion of dynamic balance.

The present lnvention is not limited to the illustrated embodiment, as it may be eming from their point bodied in other forms within the scope of the following claims 1. A turbine rotor for turbine engines having a rigid shaft and a flexible dynamically self-balancing rotor consisting of a hub on the shaft, a series of blades, and two sheet metal disk-like plates for connecting the hub and the blades, said plates diverg of junction at the hub to their point of junction at the blades.

2. A turbine rotor for turbine engines having a rigid shaft, a hub on the shaft, :1 series of blades and two flexible sheet metal disk-like plates uniting the blades and hub, said plates being contiguous to each other at their point of junction with the hub, and separate from each other and receiving the blades between them at their point of junction with the blades.

3.'A turbine rotor for turbine engines having a rigid shaft, a hub on the shaft, a series of blades, and two disk-like plates uniting the hub .and blades, said plates being contiguous at their point of junction with the hub, and diverging in straight lines to their point of junction with the blades.

4. A turbine rotor for turbine engines having a rigid shaft, a hub on the shaft, a series of blades and two disk-like plates uniting the. hub and blades, said plates forming conical surfaces, with their apexes contiguous and their bases separate.

5. A turbine rotor for turbine engines having a rigid shaft, a hub on the shaft, a. series of blades and two flexible sheet metal disk-like plates uniting the blades and hub, said plates forming conical surfaces with their apexes abutting each other and oppositely directed longitudinally of the shaft, and having very obtuse angles at their apexes.

OLIVER D. H. BENTLEY. Witnesses:

HORACE VAN EVEREN, GEORGE E. STEBBINs.

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