Centrifugal pump with segmented diffuser

The development of this invention involved government support under N00019-04-C-0093 awarded by (identify the Federal agency). The government has certain rights in the invention.

The invention relates to a pump of centrifugal design, and more particularly to a centrifugal pump with at least one impeller flow diffuser.

A centrifugal pump for a fluid converts pump input power to kinetic energy in the fluid by means of a revolving device such as an impeller that accelerates the fluid. The most common type of centrifugal pump is the volute pump. Fluid enters the pump through the eye of the impeller and the impeller rotates at high speed. The impeller accelerates the fluid radially outward toward the pump volute or casing. This acceleration of the fluid creates suction at the impeller's eye that continuously draws more fluid into the pump.

The energy that the pump transfers to the fluid is kinetic energy, and is proportional to the velocity at the edge or vane tip of the impeller. The faster that the impeller revolves or the bigger the impeller is, the higher will be the velocity of the energy transferred to the fluid. The purpose of the pump volute or casing is to recover and convert this kinetic energy back to static pressure that a downstream system may more efficiently use. A pump of the centrifugal type may have an annular diffuser that circumscribes its impeller to help diffuse the high velocity discharge of the fluid at the impeller edge and thereby increase conversion of kinetic energy to static pressure. The annular diffuser accomplishes this diffusion with multiple diffuser passageways that extend at an angle from the impeller edge toward the volute and have an area that expands with distance from the impeller edge.

Installation of such an annular diffuser requires that the pump volute have a large diameter split line to install the annular diffuser. This results in a larger diameter volute with increased bulk and weight. Furthermore, the solid ring annular diffuser requires elaborate sealing and venting elements to eliminate leakage and axial loading.

The invention generally comprises a centrifugal pump with a volute and at least one stage with an associated impeller and removable diffuser assembly comprising: multiple diffuser segments, each diffuser segment comprising a central passage from a curvilinear inner surface to a curvilinear outer surface and a curvilinear leading engagement surface between a leading end of its curvilinear inner surface and its curvilinear outer surface; multiple curvilinear volute mounting surfaces within the volute, each curvilinear mounting surface receiving a corresponding diffuser segment to mount the diffuser segments in a generally annular pattern about the impeller to form the removable diffuser assembly, with the curvilinear inner surface of each diffuser segment proximate an outer periphery of the impeller and the curvilinear leading engagement surface of each diffuser segment engaging a trailing portion of the curvilinear outer surface of an adjacent one of the diffuser segments; and a volute connecting passage within the volute for coupling the central passages of each diffuser segment to a pump outlet.

FIG. 1 is a cut-away end view of a centrifugal pump according to a possible embodiment of the invention.

FIG. 2 is a side view of a diffuser segment according to a possible embodiment of the invention.

FIG. 3 is a top view of a diffuser segment according to a possible embodiment of the invention.

FIG. 4 is a bottom view of a diffuser segment according to a possible embodiment of the invention.

FIG. 5 is a simplified cut-away end view of the centrifugal pump shown in FIG. 1 that illustrates the installation of its diffuser segments.

FIG. 1 is a cut-away end view of a centrifugal pump 2 according to a possible embodiment of the invention. The pump 2 has an impeller 4 coupled to a drive shaft 6 . The impeller 4 receives fluid in its eye 8 from a pump inlet (not shown). A source of power (not shown) spins the impeller 4 counter clockwise to let multiple impeller vanes 10 impart kinetic energy to the fluid in a generally radial direction. A pump volute 12 receives the energised fluid and converts at least a portion of its kinetic energy to static pressure.

To control the developed pressure of the fluid in the pump 2 , the volute 12 mounts a generally annular diffuser assembly 14 that comprises multiple diffuser segments 16 . By way of example only, FIG. 1 shows five of the diffuser segments 16 within the volute 12 . Referring to FIGS. 1 through 4 together, each diffuser segment 16 has a central passage 18 , preferably of generally expanding area, from an inner curvilinear surface 20 to an outer curvilinear surface 22 . The inner curvilinear surface 20 of each diffuser segment 16 is generally concave to sit in close proximity to a generally circular outer periphery 24 of the impeller 4 . The outer curvilinear surface 22 of each diffuser segment 16 is generally convex to mate with a corresponding one of multiple curvilinear volute mounting surfaces 26 within the volute 12 . Each curvilinear volute mounting surface 26 is generally convex to establish a close fit with its corresponding diffuser segment 16 .

Each diffuser segment 16 has a curvilinear leading engagement surface 28 between a leading end of its inner curvilinear surface 20 and its outer curvilinear surface 22 . The curvilinear leading engagement surface 28 of each diffuser segment 16 is generally concave to mate with and engage a trailing portion of the outer curvilinear surface 22 of an adjacent diffuser segment 16 .

The diffuser segments 16 freely and individually mount and dismount radially through an impeller bore or cavity occupied by the impeller 4 in a generally annular or ring-like manner about the impeller 4 to form the diffuser assembly 14 . FIG. 5 is a simplified cut-away end view of the centrifugal pump 2 shown in FIG. 1 that illustrates the installation of its diffuser segments 16 . Assembly requires a rotation of the last mounted diffuser segment 16 into position as shown in FIG. 5 . Likewise, disassembly requires rotation of the first removed diffuser segment 16 opposite that shown in FIG. 5 . The central passage 18 of each diffuser segment 16 has an couples to a volute connecting core or passage 30 to discharge its fluid to a pump outlet 32 . The volute connecting passage 30 preferably has a generally expanding area to the pump outlet 32 . The outer curvilinear surface 22 of each diffuser segment 16 preferably has an elastomeric gasket 34 surrounding the discharge from the central passage 18 . The elastomeric gasket 34 insures that the higher pressure fluid discharged from its central passage 18 does not leak back around its corresponding diffuser segment 16 to the inlet of its central passage 18 . The higher static pressure at the outlet of each central passage 18 forces the curvilinear leading engagement surface 28 of each diffuser segment 16 inward to firmly engage a trailing portion of the outer curvilinear surface 22 , thereby firmly constraining the diffuser segments 16 and limiting their relative motion.

Although FIG. 1 shows a single stage of the centrifugal pump 2 , the centrifugal pump 2 may have multiple stages with the diffuser assembly 14 mounted within each stage as hereinbefore described. The described embodiment of the invention is only an illustrative implementation of the invention wherein changes and substitutions of the various parts and arrangement thereof are within the scope of the invention as set forth in the attached claims.