US2911137A - Rotary aspirator pump - Google Patents

Description

Nov. 3, 1959 M. L. EDWARDS ROTARY AsPIRAToR PUMP Filed Nov. 18. 1955 INVENTOR.

44- 1111 lllllllllllllllllll M-r HM MILES LOWELL EDWARDS `ll f 1l NFH-...llllIll lllllllllllfI/l 2 vBY MM# ATTORNEYS United States Paret- This invention relates to a suction pump o f the rotary aspirator type for pumping gases, vapors or liquids, and particularly volatile liquids having vapor entrained or liberated in the pumped liquid.

Objects of the invention are to provide an improved rotary aspirator pump of higher efllciency than conventional pumps of this type and to provide a pump of this type which willidevelop a relatively high suction.

Ancillary to the attainment of the foregoing general objects, a more particular object is to provide an aspirator type of pump having an impeller passageway with a rectangular aspirating orifice arranged to deliver a rectangular or flat sheet, of pumping liquid in broad surface contact with the pumped fluid in order more effectively to entrain and carry the pumped fluid along the impeller passageway with the pumping liquid.

In a rotary aspirator pump the impeller is flooded in a reservoir of' liquid, which is referred to as the pumping medium or pumping liquid. The pumped fluid may be a gas or vapor, but preferably it is a wet gas or vapor or a combination of gas or vapor with a liquid which willl maintain an adequate supply of pumping liquid in the reservoir. The pump irnpeller is disposed in the bottom of the reservoir, and the pumped fluid is discharged from the reservoir at a higher point so as to retain suflicient pumping liquid to keep theimpeller submerged at all times. The pumping liquid is re-circulated through the impeller and is not discharged from the reservoir unless the pumped yfluid contains `additionalliquid to fill the reservoir. Thus, the pump is inherently self-priming and is well adapted for the pumping of volatile liquids which must be raised from a tank at a lower level under su-ction.

The present pump is to be regarded as a jet pump. The conventional jet pump is a device for pumping a fluid by means of a high velocity jet. The jet may be the same or'it may be a different fluid from that being pumped. The, usual jet pump is made up of three primary elements; (1) a nozzle in which fluid under pressure is converted into, the high velocity jet; (2) a contact or mixing chamber comprising an area of low pressure in which the fluid to be pumped engages by friction and receives momentum from the jet; and (3) a recovery tube into which the joined fluids flow and, by orderly deceleration, pressure is recovered.

The conventional jet pump, having no moving parts, is the simplest of all pumping mechanisms but it has the disadvantage of being very low in efficiency. It is notable that the energy introduced into the jet pump comes in hydraulic form from pressure in the pumping fluid. The low eflicicncy of the jet pump is commonly attributed to the extreme difference in velocity ofthe two fluids at the point where they are joined. The transfer of momentum occurs in a very short space interval with an accompanying high loss of energy in turbulence. To be successful, the jet pump must be carefully proportioned and the three elements must lbe in proper relative location to provide maximum area of contact between the two mixing fluids and to direct the combined flow into proper space relationy 2,911,137 Patented NOV- 3.,. 19,59

2 ship with the recovery tube to obtain maximum pressure recovery with a minimum of back flow.

The present invention employs a pumping and a pumped fluid in a manner similar to the conventional jet pump. The two fluids are mixed, however, at low relative velocities and the pumping energy is supplied in mechanical form by means'of a revolving pump impeller. The two fluids are drawn into the impeller near the center of rotation and are brought into frictional contact at a relatively small diameter where velocity and energy are low.

There is a unique relationship of the two fluids. asv they are brought together in which the pumping fluid is introduced to the mixing chamber in a rectangular sheetv in a position advanced in rotation with respect to the Pumped fluid. At the point of mixing, velocities, both absolute and relative, and energy, are low. Flowing outward ir the impeller to large diameters where high velocity oecurs, the accelerating forces bring about enforced inter mixture of the two fluids. The pumped fluid is forcefully trapped hy the pumping fluid and carried outward to a position where velocity and energy are high.

The impeller has passages for conducting the two fluids The two fluids may be the same, but, preferably, they are different, in that the first or pumping fluid is of greater density than the fluid to be pumped. The pumpingk fluid after being introduced intoA the impeller at a central position, is conducted outward in a passage at a relatively low velocity in the passage to an intermediate radius in the impeller, where it is forced by centrifugal pressure through an enclosed orice or nozzle. The nozzle is directed tc produce a flow in a direction counter-rotationally to the impeller motion, developing thereby within the impeller a low absolute fluid velocity.

Within the mixing chamber, the two fluid streams are brought into contact with each other. The. heavy pumping fluid is injected in a blanketing sheet of relatively low absolute velocity disposed in the chamber remote from the accelerating wall on ythe trailing side of the chamber` The fluid to be pumped enters the chamber in a blanket disposed between the heavier fluid and the accelerating wall. The primary feature of the invention is the squeezing or trapping effect brought about by the accelerating forces which act between the accelerating wall and tht blanket of heavy fluid.

An important feature of the invention is the high pump.4 ing efllciency which is obtained bythe blanket relation ship of the two fluids within the mixing chamber. Ther( is an equal distribution of the fluids across the areas ove] which the forces act on them which prevents the escape ofthe pumped fluid without being acted upon by tht pumping fluid. Of importance in attaining a high efli ciency is the low relative velocities of the fluids at tht tme'they are mixed. The pumping work of the impellei is done after the fluids are in contact with each other Thus, in reiteration, it is to be emphasized that the twc fluids are brought into contact in a revolving impeller a a point where momentum and energy are relatively low From such point of contact, the fluids are conductec through impeller passages in which momentum and energj are imparted to the joined fluids.

The invention has particular advantage in the pumping of fluids of different densities, such as a gas and a liquid or in the pumping of volatile liquids Where the problem o: withdrawing an evolved gas is difllcult. In such cases the liquid acts as the pumping medium for pumping the ga:

or vapor. y

In the revolving impeller, flow velocities, inertia forces and fluid pressures are in complex form. The complexity of ow velocities involves both relative and absolut; movement of fluids. The forces involved include cen trifugal force and the force of acceleration which occurs as a fluid progresses in the impeller passage to a large diameter. It is a law of physics that any mass will resist acceleration, and, when the mass is a fluid, pressures are developed within the lluid. This occurs in the revolving impeller wherein the acceleration may be of a centrifugal nature due to a change in direction as the fluid revolves around a center at constant diameter, or due to an increase in peripheral velocity as the fluid llows in the impeller passage from a small to a large diameter.

In the preferred embodiment of the invention illustrated on the accompanying drawing, the novel impeller is characterized by passageways extending from a central inlet chamber for the pumping liquid to the periphery of the impeller disc. These passageways are preferably curved, with the leading side of each passageway extending in a smooth spiral curve from the said inlet chamber to the discharge end at the periphery of the disc. A weir extends across the trailing side of each passageway and has a straight overflow edge parallel with the axis of rotation spaced from the leading side of the passageway to form a rectangular nozzle orifice on the leading side. Behind each weir on the trailing side of the passageway is a suction inlet opening for the pumped lluid.

High speed rotation of the impeller disc moves the trailing side of the passageway constantly into collision with the jet of liquid discharged from the rectangular orifice, the spiral curvature of the passageway causing the collision to take place at an angle substantially tangential to the trailing side of the passageway whereby the jet is thereafter impelled toward the discharge'end of the passageway at high velocity by the crowding action of the trailing wall which imparts radial acceleration to the liquid as in a centrifugal pump. A convergence of the passageway prevents cavitation within the passageway by insuring that the outer end remains full and sealed with the pumping liquid or a mixture of the pumping liquid and the pumped fluid admitted through the lluid inlet openings behind the weirs. Relative to the impeller, the ilat jet from the overflow edge of the Weir falls like a waterfall toward the trailing wall of the passageway, which may be referred to as its working face. Pumped fluid introduced through a lluid inlet opening behind a weir is thus trapped between the flat underside of the jet and the working face, whereby the pumped fluid is carried along by frictional contact with the jet and entrained therein for the rest of its travel through the passageway, the action being the same regardless of whether the pumped fluid is a gas, vapor or liquid.

The haphazard frictional engagement and intermingling of the pumped iluid with the pumping liquid in conventional rotary aspirator pumps has been regimented and improved in the present impeller by reason of the cornplete entrapment of the pumped lluid between the flat undersurface of the jet and the ilat working surface of the impeller passageway. The pumped lluid is introduced into a triangular space behind the weir which converges to an apex at the point where the working surface in high speed rotation collides tangentially with the jet of pumping liquid from the rectangular orifice. There is no escape from this triangular space except by intermingling with the pumping liquid, and so the momentum of the pumping liquid which completely fills and seals the discharge end of the pasageway maintains a highly effective pumping, action by reason of its density and consequent response to the centrifugal pumping action which takes place in the outer end of the passageway. The pumping liquid supplies the necessary density to maintain this pumping action, and the evacuation of pumped fluid removed thereby maintains a steady and constant suction at the inlet opening behind the Weir. The pumping liquid re-circulates within the reservoir and the excess of pumped Iluid is discharged from the elevated outlet.

The invention will be better understood and additional objects and advantages will become apparent from the following detailed description of the preferred embodiment illustrated on the drawing. It is to be understood,

however, that various changes in construction and arrangement may be made, and all such modifications within the scope of the appended claims are included in the invention.

In the drawings:

Figure 1 is a vertical sectional view of the pump of the invention, showing the impeller in elevation with parts broken away;

Figure 2 is a sectional view of the impeller taken on the line 2 2 of Figure 3;

Figure 3 is a view taken on the line 3 3 of Figure 1;

Figure 4 is a view taken on the line 4-4 of Figure 1;

Figure 5 is a fragmentary enlarged view of a portion of the impeller showing the pumping action; and

Figure 6 is a sectional view taken on the line 6-6 of Figure 5.

Referring specifically to the drawings, the aspirator pump of the present invention has a reservoir 10 provided with a bottom removable cover or bowl 11. Formed in the upper portion of the reservoir 10 is a suction chamber 12 in which is mounted a vertical hollow impeller shaft 14 driven by a suitable motor 15 and carrying on its lower end a rotary member or impeller disc 16 of the pump. The shaft 14 is journaled in a sealing bushing 18 mounted in the bottom wall of chamber 12 and is journaled at the top in a bushing 20 threadedly mounted in a sleeve 21 secured to the top wall of the chamber 12. Suitable packing 22 is provided within the sleeve around the shaft 14 and also in the bushing 18, if necessary, to prevent leakage between reservoir 10 and suction chamber 12. f

The impeller shaft 14 has a plurality of radial apertures 25 in communication with the chamber 12 for permitting iluid within the chamber 12 to be drawn downwardly through the interior of said shaft into the impeller 16. Chamber 12 is supplied with iluid from an inlet conduit 26 which is connected at its other end to a supply tank, not shown, which may be disposed at a lower level than the pump assembly. The reservoir 10 is provided with an outlet conduit 28 for delivery of the pumped fluid. Fluid, which may be gas or vapor, is drawn into the chamber 12 through inlet conduit 26 by suction created by the impeller 16, and is referred to herein as the pumped fluid. The impeller is submerged in a liquid, referred to herein as the pumping medium or pumping liquid, and if the pumped iluid be a wet gas or vapor, a liquid, or a combination of gas or vapor and a liquid, it'will ll the reservoir and discharge through outlet conduit 28.

For convenience of construction, the impeller 16 preferably comprises a pair of mating parts 30 and 31 having aligned apertures 32, Figures 3 and 4, for receiving screws or the like to hold the parts together in an integral unit. The upper part 30 has a hub portion 33 with internal threads 34 for threadedly engaging the lower end of impeller shaft 14. Hub 33 has a pair of inclined inlet ducts 35 which are in communication with the interior of the hollow impeller shaft 14 for receiving pumped tluid from the inlet conduit 26. impeller part 31 has a central inlet 36 through which pumping liquid enters the impeller.

Referring particularly to Figures 3 and 4- which are face views of the mating surfaces of the impeller parts 30 and 31, respectively, each of the parts is grooved to form in assembled relation a central liquid inlet chamber 40 communicating with inlet opening 36 whereby pumping liquid which is present in the reservoir 10 can freely enter the impeller. A pair of oppositely directed passageways, designated generally by the numeral 41, establish communication between the central chamber 40 and the peripheral edge of the impeller, these passageways prefterminate at' the periphery of the impeller in a rectangularV discharge orice 44. Rotation of the impeller at high speed causes a jet of fluid to be impelled from the discharge orifice 44 at high velocity creating suction within the Vpassageways 41 and drawing pumping liquid in through the bottom inlet 36. The pumping liquid thus isre-circulated through the impeller so that a suction isv created in the impeller constantly during rotation thereof, the outlet conduit 28 for the reservoir 10 being disposed at a higherl point than the impeller to insure submergence of the impeller in the pumping liquid at all times.

A restriction in the form of a weir 4S extends across the trailing side 45 of each passageway 41 andhas a straight overflow edge 49 parallel with the axis of rotation of the impeller. The edge 49 of the weir is spaced from the leading edge of passageway 41 so as to form a restricted rectangular nozzle orifice 50 on the leading side, and the weir is shaped so that the approach end of the passageway 41 between the orifice 50 and the central chamber 40 comprises a tapered space 51 forming a prepumping passage. Wall 42 is concurrent with the outward, leading side of the nozzle 50. 'I'he upstream face of Weir 48 forms a spirally curved accelerating wall 46 extending to the inlet chamber 40 to engage the pumping liquid therein and accelerate it in a radial direction longitudinally of the passage by rotational movement O f said wall in a circumferential direction with respect to the liquid. The passage wall on the leading side 42 and the passage walls on the trailing side at 45 and 46 are kall flat in an axial direction as shown in Figures 2 and 6.

The weir 48 has a rear side 52, Figure 5, which joins at the bottom with the trailing or lagging side 45 of the passageway 41. An enlarged, substantially triangular space S4 forms a mixing chamber between the side 52 of the weir and the trailing side of the passageway 41. The parallel side walls of the mixing chamber are concurrent with opposite sides of the nozzle. When the impeller is rotating at highA speed and the Apumping liquid is being circulated through the impeller, the trailing side 45 of the passageway 41, moving in the'direction of arrow 53, is in constant collision with the jetA 56 of pumping liquid being discharged from the rectangular oriiice 50. The collision between the jet and the trailing side is substantially tangential to said trailing side and the jet is thereafter impelled toward the discharge opening 44 at high velocity by the crowding action of the spiral curve of the trailing side which imparts radial and circumferential acceleration tothe liquid, giving it an increasingly high velocity as it progresses along the passageway to the periphery of the impeller. The portion of passageway 41 between mixing chamber 54 and discharge end 44`is designated as a pumping passage.

The jet 56 of pumping liquid, which is ejected from the restricted orifice 50, is rectangular in cross section and has a dat undersurface, the area of tangential collision between the undersurface ofthe jet land the trailing side of the passageway 41 being designated by the reference numeral 55 and being referred to herein as the working surface. Relative to the working surface 55, the jet may be envisioned as falling in a direction counter to arrow 53. The absolute velocity of the jet, however, is low because the revolving nozzle is moving away from the jet `at a speed almost equal to the stream velocity of the jet and the working surface 55 is to be regarded as moving at high speed into the jet which is in an advanced rotative position.

The inclined ducts 35 in the hub 33 of impeller part 30 open into the mixing chambers 54 to provide suction inlet openings 1oehind the weirs 48. Pumped uid is thus drawn from inlet conduit 26 into the suction chamber 12, thence into hollow impeller shaft 14 through apertures 25, and finally into the ducts 35 in the impeller 16. By the suction created in the impeller, the pumped uid is drawn intoV the mixing chambers 54 behind the weirs. As hereinbefore stated, the triangular spaces conned under the at surfaces of jets 56 oder the only means ol escape for the pumped fluid which has been drawn therein to intermingle with the pumping liquid of the jets. In the spaces 54 the introduced gas, vapor or liquid is blanketed over a large area and exposed to frictional contact with the flat jets and is entrained and carried forward thereby. In thepumping passages in the outer converging ends of passageways 41 the pumped liuid is completely entrapped inthe re-circulating pumping liquid and accelerated by the crowding action of the trailing walls 45 of the passages. Thus, the continuous removal of pumped fluid from spaces 54 produces a continuous suction in these spaces which is communicated to inlet conduit 26 to keep the pump primed even during intervals when no liquid is present in conduit 26.

An important feature of the present impeller structure is the positive and complete entrapment of the pumped liuid as above desscribed. The pumped fluid is blanketed by the at undersurfacc of the jet and isl readily intermingled with said jet in a mixing chamber where the absolute velocities and energies of both fluids are low, thereby avoiding excessive losses from turbulence in the mixing chamber. After the mixing of the two fluids is completed, the mixture is accelerated to produce the desired pressure and suction heads at the outlet and inlet connections of the assembly. There is thus provided a mixing stage separate and distinct, and prior to the pumping stage, whereas in conventional jet pumps and rotary aspirators, the mixing stage is incidental to and simultaneous with the pumping stage. A more eiective vacuum is thereby produced in the impeller whereby the eliiciency of the pump is increased for drawing up a liuid from a supply tank.

Having now described my'invention and in what manner the same may be used, what I claim as new and desire to protect by Letters Patent is:

l. A rotary aspirator pump impeller comprising an impeller disc having a central liquid inlet chamber for a pumping liquid, passageways of rectangular cross section extending from said chamber to the periphery of the disc, each of said passageways having a wall on its leading side relative to the direction of rotation extending from said inlet chamber in a smooth spiral curve to the discharge end of the passageway at the periphery of the disc, a restriction in the trailing side of each passageway adjacent said inlet chamber and remote from said discharge end having a straight overflow edge parallel with the axis of rotation and spaced from said wall on the leading side to form a rectangular orifice extending across the leading side of the passageway, and suction inlet openings in said passageways on the trailing sides thereof behind said overflow edges for a pumped fluid.

2. An impeller as defined in claim 1 in which the walls on the leading and trailing sides of the passageways converge from said suction inlet openings to the discharge ends and the other two walls of the passageways are parallel.

3. A rotary pump comprising a rotary impeller having a prepumping passage connected with an inlet for a pumping fluid of relatively high density, said passage being spirally curved to accelerate said pumping lluid said pre-pumping passage having a nozzle outlet close tc the axis of the impeller to discharge said fluid at a moderate relative velocity but low yabsolute velocity, a mixing chamber and -pumping passage extending in continuatior of said pre-pumping passage to receive the discharge frorr said nozzle, and an inlet for pumped fluid of relatively low mass in said mixing chamber, said nozzle and last inle` being relatively positioned to place all of said pumping iiuid in an advanced rotative position with respect to saitl pumped fluid inlet whereby the accelerating forces of the lagging side off said pumping passage will generate ar entraining action of said pumping uid upon said pumped 7 uid, thereby causing said pumped uid to be carried long through said pumping passage at high Velocity.

4. A rotatable uid pump impeller having a centrally )cated inlet on the axis of the impeller for a pumping ,uid and a centrally located inlet forV a pumped fluid, aid pumping uid inlet connecting with a generally adial passage extending to an intermediate radius within aid impeller and there connecting with a rectangular tozzle, said nozzle forming a restriction for accelerating iow of` said pumping fluid in said passage, a mixing hamber in said impeller receivingthe discharge from aid nozzle, said nozzle being positioned to direct said low into said mixing chamber in a direction counterotationally to the rotation of the impeller, said mixing hamber having parallel side walls concurrent with two pposing sides of said nozzle, said mixing chamber being longated and generally rectangular in cross section and lisposed in a generally lagging outward direction with espect to the rotation of the impeller, the leading wall of aid chamber concurring with the outward, leading side f said nozzle, said pumped fluid inlet having a passage eading to said mixing chamber and connecting therewith Vt' a pointadjacent said nozzle and in a position conurring with the lagging surface of said mixing chamber vherein the accelerating forces of the lagging surface of aid chamber will force into intimate frictional relationhip any two iluids which may enter the two said inlets s the combined fluids are accelerated in said mixing :hamber to the full radius of the impeller.

5. In a pump for liquid and gaseous fluids, a rotary mpeller having a spiral wall extending to an inlet openng in the center of the impeller to engage a high density iquid component in said inlet opening and accelerate ;aid liquid in a radial direction by rotational movement )f said wall in a circumferential direction with respect o said liquid, an overflow edge on said accelerating wall rrranged to release a sheet-like ilow of said liquid to et in a generally lagging direction relative to the direc- `ion of movement of said wall, and a port on the lagging side' of said overow edge communicating with a low iens'ity gaseous fluid component in said pump, said port Jeingclosely adjacent said overflow edge so that uid :merging from said port is immediately blanketed on the agging side of vsaid jet and entrained therein for dis- :harge from said impeller along with said liquid whereby iuction pressure is maintained at said port for aspirayion of said low density gaseous component.

6. In a pump for liquid and gaseous fluids, a rotary mpeller having a pumping liquid inlet opening on the axis of the impeller, a spiral wall in said impeller ex- ;ending from said opening to engage liquid in said opening and accelerate said liquid in a radial direction by novement of said wall in a circumferential direction,

an overflow edge on said accelerating wall arranged to release a sheet-like flow of said liquid to jet in a genera ally lagging direction relative to the direction of moves ment of said Wall, a port in said impeller adjacent said,

overiowy edge and entirely on the lagging side of said accelerating wall and said overflow edge communicating with a low density gaseous fluid component in saidA pump, said overow edge being disposed rotatively in advance of said port so that fluid emerging from said port is completely blanketed over its entire leading side. by said jet and entrained therein for discharge from the impeller along with said liquid whereby suction pressure is maintained at said port for aspiration of said low density gaseous component.

7. A rotary aspirator pump impeller comprising a rotary impeller disc having a central liquid inlet chamber on the axis of the impeller for a pumping liquid, passageways of rectangular cross section extending from said chamber to the periphery of the disc, each of said passageways having a wall on its leading side relative to the direction of rotation extending from said inlet chamber in a smooth spiral curve to the discharge end of the passageway at the periphery of the disc, each of said passageways having a iirst wall portion on itsA trailing side extending from said inlet chamber and converging abruptly toward said leading wall, said first wall portion terminating in a straight overflow edge parallel with and spaced from said leading wall and forming the trailing side of a rectangular orifice extending across the leading side of the passageway at a point near said inlet chamber and remote from said discharge end, each of said passageways having a second wall portion on its trailing side offset immediately behind said overflow edge in a lagging direction from said overow edge and converging gradually toward said leading wall in the direction of said discharge end, and suction inlet openings in said passageways for a pumped fluid adjacent said oiset portions of said trailing walls immediately behindv said overflow edges.

References Cited in the le of this patent UNITED STATES PATENTS 1,312,588 Skidmore Aug. 12, 1919 2,319,230 Harrington May 18, 1943v 2,349,731 Hornschuch May 23, 1944 2,630,963 Schlichtig Mar. 10, 1953' 2,780,175 Thoren et al Feb. 5, 1957' FOREIGN PATENTS 328,851 Germany Nov. 8, 1920 417,903 Italy Feb. 1, 1942' 643,177 France Sept. 11, 1928

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