Rotary kinetic fluid motors or pumps – Axially opposed working fluid paths to or from runner – Pump impeller means
Patent
1988-08-05
1989-11-28
Garrett, Robert E.
Rotary kinetic fluid motors or pumps
Axially opposed working fluid paths to or from runner
Pump impeller means
415 99, 416171, F01D 526, F01D 534
Patent
active
048834033
DESCRIPTION:
BRIEF SUMMARY
This invention relates to improvements in centrifugal pumps; more particularly to pumps used for pumping fluids with abrasive solids in suspension. A problem in pumping fluids of this nature is the abrasive action and wear on the components and resultant enlargement of clearances between the rotary and stationary members and consequent leakage and slippage of the fluid pumped, serious loss of head and efficiency and a reduction in serviceable life of the wearing parts, particularly the impeller and parts of the casing, or the casing liners, adjacent the sides of the impeller.
A means commonly employed to alleviate this problem is to provide the sides of the impeller with a plurality of auxilliary vanes projecting towards, and conforming with suitable running clearance to the walls of the casing adjacent the impeller. These auxillary vanes can be of various designs such a straight radial, straight inclined to radial, curved or a combination of such shapes; their objective being to minimise, by their centrifugal action on the fluid in the side clearance spaces, leakage and ingress thereto of fluid with abrasive suspended particles discharged from the impeller. Such vanes as are in use have been described for this purpose as outwardly diverging so that at the circumference of the impeller the periphery space between adjacent vanes is much greater--typically two or three times as great--as it is at the inner ends of the vanes. (see Australia Pat. No. 22513).
In more recent improvements (Australia Patent Application No. 30237/84) a ring has been extended around the periphery of the impeller to minimise the inward penetration of fluid discharged from the impeller and the associated ingress of abrasive particles into the side clearances between the impeller and casing.
A problem however with all these previous inventions is that the centrifugal pressure field generated by these auxilliary vanes causes a net flow of fluid from the inner (boss end) of the vane passage to the periphery. This flow sets up a recirculating pattern in the clearance between the rotating impeller and the stationary side of the casing as the fluid flows back along the wall of the casing to replace that which is pumped out between the auxiliary vanes (see FIG. 1). This recirculating flow of abrasive fluid causes severe wear problems which result in increased clearances which further exacerbates the resulting recirculation and wear.
It is the primary objective of the present invention to provide auxilliary impeller side vanes so designed as to restrict this recirculation and thus improve the wear life of the impeller and casing or casing liners.
In one broad form the invention comprises a centrifugal slurry pump impeller comprising: auxilliary vanes located on at least one side surface thereof; an annular projection joining the vanes, at or adjacent the periphery of the impeller; and at least one further projection extending between adjacent auxilliary vanes.
The peripheral annular projection extends all the way around the circumference however the internal projections may form an annular ring or rings or be discontinuous forming pockets between the auxilliary vanes.
The main aim of these annular projections is to disrupt the smooth flow of abrasive fluid from the impeller boss to the periphery and thus reduce the level of recirculation.
The invention will now be described by way of example with reference to the accompanying drawings in which:
FIG. 1 illustrates a sectional view of a prior art impeller in the casing of a centrifugal pump.
FIG. 2 illustrates a sectional view of the impeller according to one embodiment of the present invention in the casing of a centrifugal pump.
FIG. 3 illustrates a bottom plan view of the impeller illustrated above showing the position of the back auxilliary vanes and projections.
FIG. 4 illustrates a bottom plan view of a second embodiment of the invention showing the discontinuous annular projections and auxilliary vanes.
The embodiments of the present invention shown in the beforementioned drawings compri
REFERENCES:
patent: 3319573 (1967-05-01), Judd
patent: 3384026 (1968-05-01), Williamson, Jr.
patent: 3731940 (1973-05-01), Spruiell
patent: 4277222 (1981-07-01), Barbeau
patent: 4664592 (1987-05-01), Grzina
Garrett Robert E.
Nguyen Hoang M.
Warman International Limited
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