US1934013A - Centrifugal pump - Google Patents

Description

Nov. 7, 1933. J SJM 1,934,013

CENTRIFUGAL PUMP FiledMarch 29, 1935 a 1 7 I: Q 4 f v Patented Nov. 7, 1933 CENTRIFUGAL PUMP James Sim, Cathcart, Glasgow, Scotland, assignor to G. & J. Weir, Limited, Cathcart, Glasgow,

Scotland Application March 29, 1933, Serial No. 663,411, and in Great Britain May 4, 1932 2 Claims.

When centrifugal pumps, particularly extraction pumps, are operating at reduced loads, trouble is sometimes experienced with water hammer at the entrance edges of the blades due to the circumstance that the designed capacity of the pump impeller is in excess of the requirements. This phenomenon frequently manifests itself in what is known as gulping, i. e., the impeller gulps water at the entrance edges of the blades, thus setting up heavy shocks.

The object of the present invention is to obviate this drawback.

According to the invention the impeller is formed opposite the inlet eye with a cavity presenting an annular chamber located on the side of the discharge plane of the impeller remote from said inlet eye and bounded by the impeller structure so that the rotating surfaces of the impeller drag round the liquid in the chamber and cause rotation thereof.

The rotation in the chamber will be small at the full capacity of the pump, but will increase progressively as the quantity passing through the pump is reduced, the speed of rotation of the liquid in the chamber varying inversely as the quantity or" liquid passing through the pump.

At full capacity of the pump the relative velocity at the inlet edges of the blades will beat or near the designed figure and the inlet blade angle will be correct for the conditions; at reduced output the relative velocity and inlet angle will be incorrect for the conditions, but owing to the increased rotation in the chamber the consequent reduction in relative velocity will bring the inlet blade angle nearer the ideal angle and automatic compensation will be obtained for such incorrect blade angles at reduced output. As a result there is realized smooth working throughout the whole range of load with no gulping.

The rotation in the chamber may be assisted by vanes rotating with the impeller and disposed within the annular chamber.

The figure of the accompanying drawing illustrates a single-stage single-inlet pump according to the present invention.

Referring to the drawing, (1 denotes the rotary impeller arranged in the casing b and driven by the shaft 0.

d denotes the suction branch and e the discharge branch of the casing b. The impeller a is formed with an annular chamber f disposed opposite the impeller eye and located on the side of the discharge plane of the impeller remote from the inlet eye.

It will be seen that the Water, after entering the inlet eye of the impeller a, is presented with a large rotating surface effecting rotation of the water.

To further such rotation, vanes,

which may be tapered, may be incorporated in the impeller structure as shown in dotted lines at g.

It will be seen from the drawing that the annular pocket or chamber f is bounded by spaced lateral walls both extending in a direction more nearly parallel to the axis of rotation of the impeller than transverse to said axis beyond the entrance edges of the impelling blades and away from the impeller inlet.

What I claim is:--

1. In a centrifugal pump, a rotary impeller presenting an inlet eye and having impelling blades extending outwardly from said eye, said impeller formed opposite said eye with an annular pocket having spaced lateral walls both extending in a direction more nearly parallel to the axis of said impeller than transverse to said axis beyond the entrance edges of said blades and away from the inlet.

within said pocket.

JAMES SIM.

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