US2266180A - Impeller for centrifugal pumps - Google Patents

Description

Dec. 16, 1941. R. P. EMERICK IMPELLER FOR CENTRIFUGAL PUMPS Filed Jan. 20, 1939 INVENTOR.

Patented Dec. 16, 1941 IMPELLER FOR CENTRIFUGAL PULIPS Raymond P. Emerick, New Haven, Miclp, assignor to Raymond F. Goltz, Detroit, Mich.

Application January 20, 1939, Serial No. 251,957

Claims. (01. 103-115) My invention relates to impellers for centrifugal pumps, and more particularly, to the shape and curvature of the radially disposed vanes which form a part th'ereof.

The invention hereinafter disclosed is specially applicable to the large centrifugal pumps used in dredging operations, 1. e. the pumping of conglomerate mixtures with water of sand, clay, gravel or rock, and the pumping of oil or water.

Heretofore centrifugal pumps have been accompanied in operation with hammering or slugging with resulting loss of power and efiiclency. Hammering is caused by the sudden release of vacuum areas produced by velocity changes in a pumped aggregate at different points along the radially and circumferentially spaced fluid passages of an impeller.

The velocity of flow of pumped material at different points within the fluid passages is directly dependent upon the initial velocity, the shape and curvature of the vanes defining said fluid passages, and upon centrifugal force.

If the velocity of a pumped material is greater at the point of discharge of the fluid conducting channels than at the intake end thereof or at other points along the same, an irregularity of flow develops which intermittently produces the aforesaid low pressure or vacuum areas.

Another cause of hammering is the sudden piling up of pumped aggregate within the fluid passages caused by temporary reduced velocity at the discharge end of the vanes. With the conventional circular curvature of the vanes an excessive frictional 'forceis developed. This force, which is due to the sudden changes in direction of the circular vanes, operates against the flow of any pumped mixture. It is this force which causes a decrease in velocity of a pumped aggregate. When the initial velocity is not maintained, the suction pressure at the intake end of the fluid .conducting passages is irregular. It is also these irregularities which produce variations in fluid velocity throughout the fluid channels of the impeller; and consequently with such irregularities of flow producing intermittent low pressure areas, hammering" is to be expected.

It is the object of my invention to eliminate the hammering or slugging which very often accompanies the operation of centrifugal pumps, specially when pumping conglomerate mixtures with water of sand, clay, gravel or rock.

It is the object of my invention to thereby mixtures thus accomplishing greater efllciency.

It is the further object of my invention to cut down power costs.

The objects of my invention are accomplished by the novel impeller hereinafter described which is so designed as to overcome the existing dimculties of operation of centrifugal pumps here,- inbefore described.

For a better understanding of my invention, reference should now be had to the following more specific description and drawing of which:

Figure 1 is a front elevational view of an im-- peiler, partiall in section.

Figure 2 is a rear elevational view of the same.

Figure 3 is a side elevational view thereof.

Figure 4 is a partial isometric view'of the impeller blades and shroud.

Referring to the drawing, the impeller II, which forms the important part of a centrifugal pump, is cast in one piece of some hard abrasion resisting material.

A plurality of vanes I2 are radially and circumferentially disposed about the axis of the impeller.

The shrouds or discs l3 and I4, forming pm of the impeller, support the blades or vanes l2, and are integral therewith.

The opening IS in the impeller shell provides intake means through which fluids are drawn. This opening extends through the impeller shell to the shroud l4 conducting pumped fluids through the openings It to the fluid conducting channels l1 defined by the vanes or blades The impeller H is providedwith circumferentially spaced discharge oriflces l8 on the periphery thereof through which the pumped medium is discharged, entering the casing, (not shown) within which said impeller is rotatably mounted, to be discharged through an outlet therein tangential to saidcasing.

The flanged portion l9 forming a part of the shroud I 4 is provided with an opening 20 within which would be secured the actuating means the shrouds l3 and I4 form a part thereof and are designed to prevent the return of any pumped material in the casing which might seek the low pressure area at the inlet opening of the impeller on the outside of the shroud l3. These ribs act as vanes on a small scale throwing out any escaping pumped medium by centrifugal force.

The blades or vanes l2 which define the fluid produce a regular and continuous flow of such passages of the impeller, in order to withstand wards the periphery thereof.

The profile of the vane which forms a part of my invention consists of straight line portions 22 and curved portions 23 and 24. These vanes defining the fluid passages start at the periphery of the intake opening, l5 and extend laterally through the impeller shell, and are retained by the shrouds l3 and I4. These vanes also extend radially from the said intake channel to the periphery'of the shrouds which form an part of the said impeller.

Were the vanes to radially central axis in a straight linenornialto the intake opening, the velocity of flow would so vary at different points along the fluid channel due to the increasing radii that the flow would necessarily be irregular producing the hammering effect heretofore mentioned.

In the conventional impeller, the vanes start at-the central portion and continue to the periphery at a substantially constant radius. It is this sudden change of direction of a regular curve which produces the frictional forces heretofore stated.

The straight line portions 22 nearest the suction end of the vanes l2 are designed to produce a higher initial velocity to the pumped substance than would be produced if the vanes started with a curve.

In my preferred embodiment the straight line portion comprises 25% of the radial distance from the intake opening Hi to the outer surface of the impeller. However, it is contemplated as within the scope of my invention,. depending upon the nature of the substance to be pumped, that said straight line portions comprise from 1% to 75% of the aforesaid radial distance.

In my preferable embodiment the said straight line portion extends at a 63 angle from the radial lines passing through the center of the imaginary circle defined by the interior and points of the vanes. These radial lines also pass through said end points. However, it is contemplated as within the scope hereof depending upon the nature of the substance to be pumped, that said angle be variedfrom zero to 90 from the aforesaid radial line.

It is to be understood that the measurement of the above acute angle is based upon a radial line which is defined as follows:

The interior end points of the radially spaced surfaces define the loci of a circle. The radial line referred to passes through the center of said circle and through any one of the above said points defining said circle. Thus the straight line portion of the vane is constructed at an acute angle, preferably 63 from the above described radial line.

The conventional circular vane is replaced in my invention with vane curvatures 23 and-24 defined by the curves of increasing radii.

The curvature of my preferable embodiment is essentially as disclosed in the drawing, Figure 1; however, the exact rate of change in curvature shown depends upon the materialsought to be pumped. In other words, the principle of my invention is applicable to curves defined by arcs of increasing radii within the limits of a straight line and the arc of a perfect circle.

My theory is that by supplementing the regular curved vane of impellers with a vane defined by arcs of increasing radii, the initial velocity obtained by the pumped medium is maintained so asto guarantee a continuous and regular flow i t gra sees-aims :the

the additional forces, increase in thickness tofor centrifugal pumps. This, of course, facilitates the exit of a pumped medium eliminating the aforesaid h ering" characteristic of the conventional cent fugal pump, depending, in degree, upon the amount of concentration in the pumped conglomerate.

This result is accomplished by diminishing the frictional forces which naturally act upon a flowing fluid where there are sudden changes in direction as would be the case where the vanes are shaped in the conventional circular form.

With this frictional resistance reduced to a minimum, the pumped medium is permitted to maintain its initial velocity. When this is accomplished hammering and plugging up of the pump is eliminated.

It has been this hammering and plugging up of centrifugal heavy duty pumps of the conventional type which eventually causes their destruction.

By maintaining the initial velocity of any pumped medium, I am able to guarantee uniform vacuum pressure in centrifugal pumps.

Thus by the novel shape and curvature of the vane, I am able to obtain a smooth, continuous, and uninterrupted flow of pumped medium. Consequently, I have produced an impeller for centrifugal pumps with a new efiiciency approx- 1 imately 38% greater than the usual 35% to 45% efiiciency of this type of pump.

The impeller disclosed herein is comprised of four vanes as my preferable embodiment. However, I do not limit the theory of my invention to this number, it being contemplated that any convenient number greater than one vane may be used.

Now having fully described my invention herein, reference will be had to the claims which follow for determining the scope hereof.

I claim:

1. A closed impeller for a centrifugal pump comprising a plurality of vanes defined by a plurality of separate substantially spirally spaced surfaces, and by supporting members integral therewith, one thereof having an opening for receiving a power source, and the other having an axial fiuid inlet opening, the latter communicating with a central inlet recess, the inlet openings between said vanes communicating with said inlet recess, the surfaces defining each vane consisting of a straight line portion for a substantially short part of its length, the same being disposed at an acute angle with respect to a radial line passing through the center of the circle defined by the interior ends of said surfaces, at the points where the vanes communicate with the central recess, the outer portion of said surfaces being generated by arcs of increasing radii, whereby the cross sectional areas of the vanes progressively increase out to the periphery of the impeller.

2. A closed impeller for a centrifugal pump comprising a plurality of vanes defined by a plurality of separate radially spaced surfaces, and by supporting members integral therewith, one thereof having an opening for receiving a power source, and the other having an axial fluid inlet opening, the latter communicating with a central inlet recess, the inlet openings between said vanes communicating with said inlet recess, the surfaces defining each vane consisting of a straight line portion for a substantially short part of its length, the same being disposed at an acute angle with respect to a radial line passing through the-center of the circle defined by the interior ends of said surfaces, at the points where the vanes communicate with the central recess, the outer portions of said surfaces being irregularly curved.

3. A closed impeller for a centrifugal pump comprising a plurality of fiuid conducting passages defined by a plurality of separate angularly disposed radial surfaces, and by shrouds integral therewith, there being a central inlet opening in one of said shrouds, communicating with an axial recess bounded by the said shrouds, the surfaces defining each vane consisting of 'a substantially short straight line portion adjacent the axialrecess, the same being disposed at an acute angle with respect to a radial line passing through the center of the circle defined by the interior end points of said surfaces, at the points where the vanes communicate with the central recess, and a trailing curved portion defined by arcs of increasing radii.

4. An impeller for a centrifugal pump comprising a plurality of vanes defined by a plurality of radially and spirally spaced surfaces, and by supporting members joined thereto, one thereof having an opening for receiving a power source, and the other having a fluid inlet opening, the latter communicating with an inlet recess, the inlet openings between said vanes communicating with said inlet recess, the surfaces defining each vane consisting of a straight line portion for a substantially short part of its length, the same being disposed at an acute angle with respect to a radial line passing through the center of the circle defined by the interior end points of said surfaces, and also passing through one of said end points, the outer portion of said surfaces being generated by arcs of increasing radii.

5. An impeller for a centrifugal pump comprising a plurality of vanes defined by a plurality of radially spaced surfaces, and by supporting members joined thereto, one thereof having an opening for receiving a power source, and the other having a fluid inlet opening, the latter communicating with an inlet recess, the inlet openings of said vanes communicating with said inlet recess, the surfaces defining each vane consisting of a. substantially straight line portion for a substantially shortpart of its length, the same being disposed at an acute angle with respect to a radial line passing through the center of the circle defined by the interior end points of said surfaces, and also passing through one of said end points, the outer portion of said surfaces being generated by arcs of increasing radii.

RAYMOND P. EMERICK.

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