US1218223A - Centrifugal blower. - Google Patents

Description

C.,H. sMooT.

CENTRIFUGAL BLOW'E. /APPglcAT'loN msn Auml. 1913.

Patented Mar. 6, 1917.

\ WITNESSES ATTORNEY for operation at veryv high speeds.

UNITED STAT-Es PATENT omer.

CHARLES H. SMOOT, 0F NW YORK, N. Y., ASSIGNOR T0 RATEAU, BATTU, SMOOT COMPANY, OF NEW YORK, N. Y.,

A CORPORATION OF NEW YORK.

CENTRIFUGAL BLOWER.

Specication of Letters Patent.

Patented Mar. 6, 1917.

To all 'whom it may concern.'

Be it known that I, CHARLES H. SMoo'r,l

a citizen of the United States of America, residing in the city, county, and State of New York, have invented certain new and useful Improvements in Centrifugal Blowers, of which the following is a true and exact description, reference being had to the accompanying drawings, which form a part thereof.

My present invention relates to centrifugal blowers, and particularly to centrifugal blowers adapted for operation at high speed, as, for instance, one directly connected to and driven by a steam turbineor a high speed electric motor.

' The general object of my invention is to provide animproved blower of the type referred to.

More specifically, one object ofmy invention is to provide an impeller structure adapted by its strength, weight, and shape ac-y complish this object of my inventionv .by forming the impeller blades integral with the impeller shaft in order to get the necf essary strength on. the one Hhand and onthe other hand to increase theso called crltical speed of the blower.` A second object of.,

the invention is to provide means for de livering the air to each set' o fimpeller blades employedin such a manner as to reduce the shock losses. This feature of my invention is Vvof special importance vin connection with the type of impeller which I prefer to employ and 'in which the airis kdelivered to the spaces betweenadjacent radial impeller blades comparatively close to the axisof'the impeller. This object of my inventionI attain by providing directing nozzles adjacent the inlet to the impeller chambers and arranged to convertthe pressure yof the fluid passmg to the unf peller chamber into velocity directed 1n the direction of rotation' of the impeller so that the fluid is-given a. rotary motion about the axis of the impeller approximately equal to the rotational velocity of the impellen A third object of the invention is tofprovide an impeller and diffusion chamber construction and arrangement which will minimize the leakage through the clearance spaces between the edges of the impeller blades and the sides of the impeller chamber from the space between, and at the side edges of one pair of impeller blades, and the corresponding spaces between adjacent pairs of lmpeller blades; and which will permit the impeller blades to be made of sufficient width to avoid mechanical ditliculties when the impeller operates at high speeds in cases where the volume of the fluld discharged is small and the diffusion chamber surrounding the impeller chamber is correspondingly narrow. This I accomplish by making the diusion chamber substantially narrower measured in a direction parallel to the axis of the impeller than the tips of the impeller blades and of course narrower also than the impeller` chamber.

The various features of novelty which characterize jmy invention are pointedv out with particularity in the claims annexed to andforming a part of this specification. For a better understanding of the invention, however, and of the advantages possessed by it, reference should be had'to the accompanying drawingsV and descriptive matter in which lI have illustrated a form in which my invention may be embodied.

Of the drawings:

. Figure 1 is a sectional elevation taken on the line l-1 of Fig. 2;

Fig. 2 is a transverse section taken on the Fig.v 3is a transverse section taken on the linie 3 3 of F ig. .1 but on a smaller scale.

In the drawings A represents the casing of. a'centrifugal blower and is formed with an inlet A for air or other gaseous fluid to be compressed which opens into the annular inlet chamber A2. The chamber A2 communicates adjacent its center with an impeller chamber A3 which is surrounded-by a diffusion chamber A4. The diffusion Ichamber A4 communicates at itsy outer edge with the intermediate inlet chamber A5. The lattercommunicates adjacent its center v with the high pressure impeller chamber A6. The impeller 'chamber A6 is open at its periphery to a dil'usion chamber A7V 4which communicates vat its periphery in turn with the usual volute collecting chamber A8.l The impeller casing is also formed with bearing `boXes A9 in which are journaled the reduced shaft end portions B of the rotary impeller B. The impeller B is provided with one set of radial blades B2 working in the wheel chamber A3 and with a second set of radial blades B3 working in the high pressure impeller chamber A, In the preferred construction illustrated, the body, blades B2 and B3, and shaft end portions B of the impeller, are formed in one integral structure. peller in a one piece structure as described 4is highly advantageous where high rotative speeds are desired, and when it is also desired that the machine should operate below its so called critical speed.

Those skilled in the art will understand that the integral shaft and blade construction inherently tends toward a high critical speed of the shaft, since the critical speed of a shaft of given length is increased by increasing the stiffness of the shaft, and is decreased by increasing the weight of the shaft and the parts carried by it. The construction obviously gives the maximum .stiffness of shaft and strengthvof connection between the shaft and blades possible with a given radial depth of blade and diameter of circle touched by the tips of the blades and thus permits of a high peripheral speed at the tipsof the blades. Furthermore, the fact that the inner ends of the blades come closer to the axis of the shaft than would be possible if a separate hub structure were employed or the blades were not integral with the shaft, makes it possible to keep the diameter of the circle touched by the tips of the blades, when the latter are of a given radial depth, smaller than would otherwise be possible. This in turn makes it possible to obtain an increased angular velocity with a given peripheral velocity than would otherwise be possible. There is a distinct advantage also, in a blower of the type described, in admitting the air, to be compressed, to the blades as close to the axis of the impeller wheel as is possible, and the integral shaft and blade construction described permits of the admission of the air at the least possible distance from the axis of "sponding impeller chamber largely into velocity and to give this fluid a rotational velocity in the same direction as, and approximately equa-l to the rotational velocity of the impeller. This permits the fluid to enter the impeller without the shock due to an abrupt change in velocity or direction of velocity and thus greatly minimizes the so The formation of the imcalled shock losses commonly occurring at the point at which the fluid passes into the impeller. This feature of my invention is especially important in the case of the impeller of the kind shown in which the blades are radial and extend into close proximity ofthe axis of rotation ,of the impeller shaft. The blades C and C may be used with or without the usual guide blades D employed to guide the fluid fromthe upper circumference of the inlet chamber for each impeller to the point of entering the impeller wheel and to prevent the formation of a vortex in which energy and pressure would be wasted. In practice I ordinarily prefer to employ the guide blades or vanes D.

In the preferred construction illustrated the` annular diffusion chambers A4 and A7 surrounding, and opening at their inner edges to the impeller chambers are each made substantially narrower, measured in a direction parallel -to the axis of the impeller, than the corresponding' impeller blades at theirouter ends or tips. This arrangement possesses two important advantages in the case of high speed impellers. In the first place the thickness of the diffusion chamber is fixed by the conditions of operation and particularly by the volume of the fluid discharged into the diffusion chamber from the impeller chamber which it surrounds. lVhen the volume of fluid thus discharged is comparatively small and the diffusion chamber consequently narrow, the practice heretofore followed of making the axial width of the tips of the blades as small as, or less than the thickness of the diffusion chamber results in blades which are not wide enough to have the desired strength and thickness .to resist the mechanical strains to which they are subjected. In the second place and of even more importance under some operating conditions I find that the leakage from the space between, and open at the side edges of, one pair of impeller blades into the corresponding spaces between adjacent pairspf impeller blades, through the clearance space necessarily provided between the side edges ofthe impeller blades and the side walls of the impeller chamber is su-bstantially reduced by the increased width of the impeller blades which is permitted when this width is not controlled by the thickness of the diffusion chai'iiber. This decreased leakage follows from the fact that the total pressure which each impeller blade exerts upon the air passing through the space between that impeller blade and an adjacent blade is fixed and constant for a particular discharge volume. and for par- I ticular pressures at which the fluid passes' to and is discharged from the impeller, and is independent of the width of the blade. If the impeller blades be made narrow the differential of the pressures per square inch j on the front and back faces `of each blade is high, whereas if vthe impeller blades be wide this pressuredifference is low, and the greater the area of the impeller blade the less the difference in pressure on thev opposite sides of the blade. The reduction in the diiference in the pressuresl on the opposite sides of each blade of course tends directly to a corresponding reduction in the amount of leakage from the side edges of.4

each blade anda consequent reduction in" the energy losses resulting from such leakage.

It will be apparent to those skilled in the art that the lnovel features of construction and arrangement specified are of e general utility in`single stage as well. as in multistage blowers. They are lof especial utility, however, in the case of multistage blowers wherein the difficulties incident to the use of single -stageblowers are multiplied.

While in accordance with the provisionsA of the statutes I have illustrated and dei' scribed the best form of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the form of the apparatus disclosed without departing from the spirit of my invention, and that under some'conditions certain features of my invention may be used without a corresponding use of other features.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is: 4 e

l. In a centrifugal blower, the combination with a rotary impeller having the spaces between adjacent blades open at the sides of the impeller, of a casing 'formed with an impeller chamber and a surrounding diffusion chamber opening from the periphery of the impeller chamber and of a thickness measured axially of the impeller substantially lessthan the width of the impeller blades at their outer ends.

2.v In a centrifu al blower, the combina-` tion with a rotary laded impeller, of a casi duce the '.Witnesses:

and to give said fluid a rotational velocity .in the direction of the impeller rotation.

3.; In a centrifugal blower the combina'- tion with arotary bladed impeller having radial blades, 'of a casing formed with an impeller chamber, a diffusion chamber into which the impeller chamber opens at its outer edge, an inlet chamber along side of the impeller 'chamber and a central lateral opening, across which the inner ends of the ,impeller blades project, connecting said inlet and impeller chambers and al set of nozzles located in said inlet chamber and surrounding said opening, andadapted to reressure and increase the velocity of the iiuid passing into the impeller chamber from said inlet chamber and togive said iuid a rotational velocity the direction of the impeller rotation.

4. A rotary impeller adapted forjoperation at .ver high peripheral speeds comprising a s aft or body portion and unshrouded radial blades integral Vtherewith l and projectingradially therefrom.

5.- A rotary impeller adapted for opera.v

tion at very high eripheral speeds comprising a shaft or v ody portion and two integral therewith and projecting radially CHARLESIJI.l SMOOT.

, L. L. BATTU,

C. S. BRooKs.

therefrom.

A8 5 sets of unshrouded radially extending blades

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