US1828409A - Reaction blading - Google Patents

Description

Octa 2o,`1931. B. v. DENSMORE 1,828,409-

REACTION BLADING Filed Jan. ll, 1.929

F l 14 Y WITNESS 5 INVENTOR 6&1". BMDensmm-e a v l' Bf GMP3] ATTORNEY Patented Oct. ZO, 1931 BENJAMIN V. DENSMORE, OF RIDLEY PARK HOUSE ELECTRIC av MANUFACTURING CoMPANYyA vco aioitlirrloiv oF rrnivlvsvr.`

REACTToNjTlAnINe Application filed January 11,1929.' Serial. k111'0.

' VANIA 'j My invention relates to elastic fluid turbines, and more particularly to the reaction blading for such turbines, and it has for an object to improve the efficiency of apparatus of this character.

It is one of the inherent characteristics of reaction turbines, or of the reaction stages of any turbine, that the pressures on the opposite sides of each row of blades are different. This is due to the fact that the steam expands in the moving as well as in the stationary blades and there is a drop in pressure between the two sides of every row of blades. Hence, there is a tendency for steam, or other working fluid to pass ina Continuous stream around the tips of the blades toward the region of lower pressure.

To counteract this tendency, it is customary to provide a relatively small clearance between the tips of the moving blades and the casing, in one instance, and between the tips of the stationary blades and the rotor, in the other. Under such conditions, rubbing sometimes occurs at the tips'of the blades, causing the latter to chatter, or vibrate. Then this rubbing occurs, thetip of ai blade is temporarily retarded soV that the blade is bent backwardly until it is free of the rubbing surface, or until its resiliency causes it to snap forward and thus, to thrust its tip portion directly toward, or into any adjacent, or rubbing surface, andthe blade is. again bent backwardly, and so on; themotions just described being those which occur when the blade is in a vibratory condition. Y

The more serious consequences are due to impacts, or-other Contacts resulting from the forward swing of the tip ofthe blade and which cause the rubbing surface to seize the tip, or to otherwise arrest this forward Inotion, for such contacts tend. to push the tip of a blade directly into any adjacent surface. It will be apparent, therefore, that a relatively slight rubbing at the tip of a blade may easily Cause suicient chattering, or vibration, to eventually produce a failure by breakage. Y- Y It isa more particular object of this invention, therefore, to provide turbine blades with 'means for Vrubbing occurs.

`preventingserious vibration when l This and otherobjects areeflected by my invention, aswill vbe lowing vdescription and claims taken in connection with the accompanying drawings,

wherein Figflis an elevation of a'reaction blade; 'and f Fig. 2 is a fragmentary sectional view of a turbinehavlng blades y,1n accordance wlththe present invention)` Accordingto one preferred formofinyV invention, thetip of a reaction blade'is proyvided with a Abendable extension. whichis formed as continuation'ofa working surface of thefblade, and inclinedbaclawardly with respect to "thefdir'ection of rotation. jyfvir` tue of this backwardly inclined extension, it

isassured that,should any rubbing occur, fthe'eizte'nded portion willme'rely be bent over, the point Iof contact will 'always follow the blade and the tip portion Vwillnot be pushed directly 'but.willdrag'overitin such amanner as to `destructive vibration.

y.tend to dampen vibration, thus 'avoiding any This'will be'more apparent from the draw"- sisting of ablade portionl, as usual, and a relatively'thin, 'extension l2. As

.showninfFig 2, theblade is :mounted on a turbine rotorl', the tip end of the blade portion 1l being disposed, adjacent the casr apparent from1 the foltoward, or intothe rubbing surface, j

ingswher'ein I have shown theblade 10, conpreferably as a continuation of the face of the blade, and thisl extension is also initially inclined backwardly with lrespect to the direction of rotation, or with respect to the direction of relative the blade and any tip might come in rubbing Contact. A close radial sealing clearance, indicated at`15`, is provided between the bendable extension 12 vand the adjacent surface of the casing'll, so

that the bendable extension is normally not in contact with said surface. By arranging movement of the tip of surface with which this this bendable extension so that it is initially inclined backwardly in the manner just described, it will be clear that the radial clearance 15 may be exceedingly small, and in the event any rubbing occurs, the point of contact will always follow the :blade ii-11d hence, will cause .the rubbed metal t0 flow 'iil One direction and tend to prevent vibration when the rub takes place. Should any rub occur With-my Anovelib'lade, -it Wil-l thus bevseen that no serious consequences Will'resultand that, when access is had to the blading, the rubbed edgeJ portion may be trimmed andstraightened and the original clearance restored. The extension l2, as will be noted from the .(lraxvings, extends 'transversely .of the blade. When the edge coines 'into contact with ininnte irregularities of ,the adjacent surface of .the casing 14, the ,edge ,wll'yield or ,bend ,in 4the Alongiimdinal Adirection Aofthe blade. Thus the blade is A,not held .back and does not ,vibrate.

It will .be .readily app arent, therefore, that I have provided a turbine blade with means for preventing vibration due to rubbing.

While I have shown .my invention .in .bu-.t one forni, it Will be obvious,tofthoseslilled ,in the .art ,that .it is not so limited, .but is sus ceptibleof various changesand modifications y without departing from ,the spirit thereof,

,and l desire., therefore, that only such .limitaltions' shall .be pla-ced thereuponas v,are imposedyby .the prior .art or as are `specifically set orthin theqappendedlaims, .3.5 What I .claiin is; Y Y

1. Ina turbine, Athe combination of a rotor .and ,a cas-ing, ,a turbine ,blade .carried by one of `said `parts with its ,tip .endradjraeent the otherofsaid parts, said tip `end ,being formed Y .40 with a relatively .thin extension bendable lon- `gitndinally .of the blade vand having close sealing clearance With said other part, .said extension being bent backwardly with respecttothe direction odi rotationof theblld 4.5 relative .to said othen-part.

2. rlhe combination defined in claim l, which .the bendable extension 'is tormed .as `a continuation of one of the working faces Kof `the blade,

.50 In testimony WhereohlV have hereunto subscribed `lny naine .this 27th day lof December,

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