US1871747A - Impeller for centrifugal pumps - Google Patents

Description

15, 1932- H. SCHLACHTER 1,871,747

IMPELLER FOR CENTRIFUGAL PUMPS Filed July 5, 1929 h. ScHmcr/Tm HENRY scrrLAcrrrEn, or BEATRICE,

Patented Aug. 16, 1932 PATEN- ll FACTURING coMrAN A conroan rron orfr Eimeszrm IMPELLER ron oENTRIrUGAn III-Mrs Application filed my 1929. Serial No. 375,999.

invention relates to pumps of thecentrifugal type and its object is the provlsion offa centrifugal'pump which will be more.

efficient in operation than the prior pumps.

' ler Another object of the invention is the pro vision of a centrifugal pump in which the balance is as nearly absolute as it'is possible to obtain. T

Another object of the invention is the.

eliminationof parts and of machine work to thereby reduce the cost of manufacture with-v out sacrificing efficiency.

Another object whichI have in viewli's,

the provision whereby the total pressures on the twosides of the impeller may be either balanced or unbalanced in such a Way as to create any requisite amount of'end thrust. n

It is also my object to provide a pump in which higher pressure may b. maintained on v Q- the inner side of the gland.

Having ill'VlQW these objects and others which will be pointed out in thefollowing description, I will nowrefer to the drawing, in which i a a Figure 1 is a plan view. of the face or blade side of the impeller. p l is t T Figure 2 is a. sectional View of the impeland casing, the section being taken along the diameter ofthe impeller,

"Figure 3 is a diagram on which certain calculations are based, the calculations being intended to locate an aperture in the impeller in a position where it will have its maximum efliciency in balancing the pressure on opposite sides of the impelleror-rotor. f

The impeller is of a more or less com-i mon form having a shroud on a central shaft 11 and spiral blades 12. The shaft 11 has its hearings in an extension 13 of the'casing 14.: The impeller 10 is accurately machined at its periphery for rotation in the casing wallat 15. The water drawn into the cas ing is engaged by the blades 12 of theimpeller 10 to build up a pressure or head as is usual in pumps of this type. Whilethe joint at 15 between the'shroud andthe cas ing is as tight as can be made, a certain amount of leakage occurs which carries a portion of water to the rear-side of-the. iinpeller. The head is. produced not only on NEBRASKA, assreuonmo DEMPSTER MILL MANU- the blade side of the impeller shroud but also on the rear side but there is normally a great. difie'rence in pressure on the twosidesof thej'imp'eller' shroud. .It has been recognized; however, that an equality of pressure on the two sidesof the impeller shroud would be desirable, but so faras I efl'ectivelmeans for equalizing these pressiuresgex'cept by the use of additional parts. Effective operation of the impeller requires had to Figure 3 of the drawing. Pressure or head at any pointon the impeller shroud is proportional to the square of the velocity,

and since the velocity is proportional to the radius, the relation maybe expressed in the form of a formula thusz (l h=lcr in which it represents the head built up oii 3 know, none of the prior constructions show either sideof the impeller-at a point at a dis- 7 tance r from theaxis of rotation. To this, however, must be added the pressure p at the center, so that thegeneral formula willrea'd (2)"h=.k7' 1). dius of the impeller and the headat Ifthe r" the periphery of the impeller be expressed by the characters a and H respectively, the formula will read" 7 (pH-ram V and the value of It may be expressed thus:

the value of h in1-Formula (2),

The two curves of Figure 3, representing pressure or head on the two sides of the 1m peller, may be expressed thus:

2 1= +19 and Total pressures built upbytthe impeller i will then be represented by solids generated by the revolution of the diagramin Figure about its vertical axis. The two curves of Figure 3 are parabolas, as may readily'be determined by inspection of Equations (6) and,

(7). The revolution of the'entire diagram in Figure 3 will generate. a right circular cyl-' inder while the revolution of-the upper portions above the parabolas, will generate pa raboloids ofrevolution. In the Figure 3 dia gram, it will be observed that the totalpres sures built up on the two sides of the impeller are represented by the volumes underneaththe solids described by rotating the parabolas about their vertical axis. These volumes may readily be determined by subtracting the volumes of the paraboloids from the volume of the cylinder, the equation being expressed in general terms thus:

which may readily be reduced the form (9) v= g The total pressures, as represented by the volumes underneath the parabolas, on the two sides of the impeller must be equal. It follows that if-o and '0 are equal, then i or n 2i-H1 2i.p1+p2 Under the condition imposed by Equ ti b q n (13) becomes from whence it follows that 1 1% or In other words, the balance hole in the impellermust be positioned a-distance from the axis equal to'the fraction of the radius of the impeller expressed in Equation (14:)

The position of the aperture l6 is deter. mined by means of the above formula. It is necessary also that the area of the aperture .16 be great enough to equalize the pressures without being any greater than is necessary. It must be largeenough to permit a flow of liquid at low velocity,equal to the leakageat the peripheral joint 15, where leakage occurs at a relatively high velocity. The areaof the aperture 16 is therefore determined by the area of the 'clearance'between the periphery of the impellershroudlO and the casing at the joint 15, or in othe'rwords, the clear ance'of the running joint formedby the cas-. ing and the impeller shroud. While my drawing shows only: one aperture 16, it is apparent that the impeller shroud maybe provided with any desired number of apertures similar to the aperture 16. These apertures must, however, be located equidistantly from the center in accordance with the above formula. 1 V i I have also shown a very specific form of 1 impeller together with a very specific form of casing; The principles herein set forth are,

however, adapted for application to nearly all pumps of a similar kind and I wish it to be understood that Figures 1 and 2 aremerely illustrative of "the general type of pump. It isalso' obvious that it'may be desirable in some cases to createunequal pressures in a certain ratio to'ea'chother .on opposite sides of the impeller. If a certain amount of .end thrust is desirable in. one directionorfthe other, the balancelhole 16 may be positioned in accordance with the" calculations to produce thejdesired inequality of pressures't By creating a requisiteamou'ntlof end thrust in a vertical centrifugali'pump it would be pos sible tocarry' hydraulically the entire weight. of the shaftijng and'other rotating parts, thereby eliminating the .7 load on: the. thrust bearings. f i y.

i 'In prior impellers ofgthis type, the pressure built up on the rear sideis about "one fourth" as much as that built up on the blade side, dueto the factthat the water in this cavity revolves only about onehalf asrapidly as it does in the blades',rthe pressure being proportional to the square of the velocity. This results in end'thrust and in loss. of power,'{ both of which objections are; elimi-' nated infthe'construction which]: have de-V scribed, and especially in the provision ofia balance hole which is so positio'ned and which is of such .size'that it will effectively balance the pressures on the two sides of the impeller,

or which may be so positioned that the total pressures on the two sides of the impeller will behin any desired predetermined ratio to each ot er. b Having thus described my invention in such full, clear, and exact terms that its construction and operation will be readily understood by others skilled in the art to which it pertains, what I claim as new and desire to secure by Letters Patent of the United States is 1. In a rotary pump or the like, a shrouded impeller having an opening through the shroud, the opening having an area greater than the area of the peripheral clearance of the running joint formedv by the casing and the impeller shroud and being so positioned that the total pressures on the two sides of said impeller shroud will be in apredetermined ratio to each other.

2. In a rotary pump or the like, a shrouded impeller having means for conducting fluid through the shroud at a velocity less than that of the fluid flowing through the peri heral clearance of the runningjoint forme by the casing and the impeller shroud and being so positioned that the total pressures on the two sides of said impeller shroud will be in a predetermined ratio to each other. I

3. In a rotary pump or the like, a shrouded impeller having an opening through the shroud, the opening being located at a radial distance from the axis of said impeller equal to the fraction of the radius of the impeller expressed in the equation.

in which 4" represents the radial distance. of the aperture in said impeller shroud and a represents the radius of said impeller.

4. In a rotary pump or the like, a shrouded impeller having an opening through the shroud, the opening being so located as to equalize the pressures on both sides of said impeller shroud, the position of the opening in the impeller being determined by the formula in which 7- represents the radial distance of the aperture in said impeller shroud and a represents the radius of said impeller, the opening in said impeller having an area greater than the area of the clearance of'the running joint formed by the casing and the im eller shroud. V

n testimony whereof I affix my signature.

HENRY SCHLACHTER. .7

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