US2042064A - Runner for centrifugal machines - Google Patents

Description

May 26, 1936. F. KUGEL RUI INER FOR CENTRIFUGAL MACHINES 7 Filed Dec. 22. 1933 Patented May 26, 1936 UNITE STATES Fritz Kugel, Heidenheim-on-the-Brenz, Germany, assignor to American Voith Contact 00., Inc., New York, N. Y., a corporation of New York Application December 22,1933, Serial No. Masai This invention relates to runners for centrifugal machines and more particularly hasfor its object to provide an open runner without side walls, in which the normal axial thrust isequalized or counteracted. For this purpose, my in-' and Figure 2 shows a profile of an open runner.

Similar characters of reference indicate corresponding parts throughout the various views.

Before referring particularly to the drawing, it may be stated as descriptive of the environment of this invention that in the design of runners or impellers for centrifugal pumps. it is in certain instances desirable and even necessary to partly or wholly leave off the lateral end walls. This des gn, particularly with fast-running impellers,

results in decreasing or entirely eliminating the wheel friction and loss due to friction of the water on the channel walls. This design on the other hand, is advantageous in order to prevent a plugging of the pump, particularly where impure liquids, as, for instance, paper stock and similar substances are to be pumped.

In the case of impellers of the single runner radial discharge type, the elimination of the impeller side walls makes it necessary to give increased attention to the strength of the impeller blades and to the axial thrust. If the side wall at the flow entrance side only is left ed, the impeller blades may still have sumcient strength, but a very high axial thrust will be created. In 4,5 an endeavor to overcome this, it has been proposed to partly leave off also the opposite impeller side wall. However, this procedure fulfills the intended purpose in part only and furthermore weakens the strengthof the blades, so that, particularly under higher pressures, which com-4 spondingly require higher, speeds, difficulties arise with respect to taking care of the remaining axial thrust and giving the blades the necessary strength to overcome the action of centrifugal force.

Figure 1 shows a plan view of the flow paths;

In Germany December 24, 1932' 1 Claim. (Cl. 103-115) The determining factor for the strength of the blades is the moment ofinertia of the bladesections in a meridian plane in relation to their axes through the center of gravity parallel to.--the impeller axis. The difference in pressure existing- 5 on the front and rear surfaces of theimpelier blades, respectively, resulting from the work performanoaccupled with the development (shape) of the blade section, is the determining factor for J I the magnitude of the axial thrust. I l0 Theblade surface is composed of the sum of the flow paths starting from the entrance edge of I the blade. In designing the blade, a limited number of these flow paths are laid-out, and they in I turn determine the blade surface.- The accepted 15 practice in'this consists in primarily determining the flow paths on the lateral rotational surfaces limiting the impeller 'proflle, .andin addition thereto at leastone more flow path on an intermediate medium flowplane, The relative loca- 20 tion'of these flow paths in regard tothe circumference can be taken more or less at will, the determining factors on the one hand being mostly hydraulic considerations and on the other hand being the possibility of using a simple method of checking the blade profile as, for instance, that obtained by straight intake and discharge edges.

Referring to the drawing, Figure 1 shows in plan view the flow paths of an impeller. A meridian section along d-d through the blade 30 formed by theseflow paths results in the blade profile or contour shown in Figure 2. In Figure 2, a1 as, b1 b2 and 01 0: represent the meridians of the rotational surfaces on which the flow paths are located. a; bi 01 is the impeller entrance edge, a: b: or the impeller discharge edge in circular projection. Ameridian section of the blade is a section taken on a plane through the axis of the runner.

As an axial thrust K towards the entrance side 40 is always exerted by the hub disk to which the blades are attached, it is, in order to fully equalize this axial thrust, necessary to have the free end of the blades exert an opposite axial thrust.

. In order to accomplish this, it is necessary that the cords through the terminal points of the arcuate contours forming respectively the rear side and the front side of the blade in meridian cut, meet the impeller axis at the intake side of the impeller, which can be accomplished by a suitable arrangement of the various flow paths on the circumference, as herein described and shown. It is at least necessary that tangents t and t through the terminal points a and h opposite to the entrance side of the contours indicated by n, the shoulder by n and the peripheral part of the hub F of the impeller by n. As willbe seen from Figure 1, the blades B extend beyond'the periphery n of the hub F of the im-' peller, that is the outer parts of the blades overhang the hub.

Within certain limits the blade section in a meridian plane can be formed at will. when considering the blade section of the blade shown in Figures 1 and 2 with respect to the axial thrust created it will be seen that the axial component at of the force 8 resulting from the larger pressure acting upon the front side of the bladeand the smaller pressure acting upon the rear side of the blade, acts in the direction of the arrow D. Thus, the axial thrust :as indicated by'the arrows K is equalized by the force 3: acting in a direction opposite thereto.

In preference to meridian sections of the blades with straight contours, there is provided a meridian blade profile with curved contours, as illustrated by Figure 2, whereby a greater moment of inertia is obtained, that is, the greater strength of the blades creasing weight.

From the foregoing, it is seen that the improved runner has open blade .Ichannelsand blades, and that the blade sections in meridian planes of the free blade part are so inclined towards the axis that the cord through the termiis obtained without innal points of the contours forming respectively the rear side and the front side of the blade meets the impeller axis at the entrance side of the impeller. At least, however,- the tangents through the terminal points of the contours opposite the entrance side, which contours form 5 respectively the rear side and the front side of the blade, meetor cut the line of the impeller axisiat" the entrance side of the impeller.

While the invention has been shown as embodiedin a centrifugal pump, the invention has application to other types of centrifugal machines. In the foregoing I have described an embodiment of my invention, but changes may be made therein without departing from the spirit or 15 scope of the invention as defined in the subjoined claims.

I claim:

In a runner for centrifugal machines, a hub, blades on said hub, said hub acting as the sole 2 means for supportingthe blades, said blades extending beyond'the hub to form open free blade parts defining open channels, the meridian sections. of the free blade parts being of arcuate contour generally inclined toward the entrance 25 side of the axis of the runner, the meridian sections having contours which form the front and rear faces, respectively, of the blades, the lines passing through the terminal points or the front and of meridian sections intersecting the. ads of the runner at its entranceslde', and the tangents to the front and rear faces of the meridian sections at the'side of the runner remote from itsientrance side also intersecting said axis at the entrance side of the runner, whereby-reactive forces, set up when the blades are operated upon, act in opposition to the axial thrust of the runner.

.- mrrzxoonn 40 the rear faces, respectively, of said 30

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