US2061032A - Jet pump - Google Patents

Description

Patented Nov. 17, 1936 ,UNITED STATES PATENT OFFICE JET PUMP v Thomas H. Huil', Philadelphia, Pa. Application November 23, 1935,v Serial No. 51,315 z claims. (ci. 23o-95) This invention relates to jet pumps, and more particularly to jet pumps actuating atmospheric air by means of compressed air as driving uid. I have discovered through extensive tests that such pumps can be considerably improved in performance by proportioning and shaping the same in a novel way, namely by positioning the jet discharge nozzle, and thereby thel actuating jet, parallel but unsymmetrical to the surrounding pressure chamber or mixing portion oi the fluid conduit, and further by tapering or Haring the discharge nozzle itself, at least at its exit side, but better at the entrance side also.

It is accordingly the broad object of the present invention to provide for a jet pump with an improved performance, as regards the economy, eiiiciency, magnitude of pressure orsuction obtained, and range of different delivery volumes within which the performance is acceptable.

Another object of the invention is to provide for such jet pump having a jet nozzle parallel with the surrounding portion of the conduit but out of alignment with its axis.

A still other .object is to provide for such jet pump having a ilared discharge nozzle.

It is at last an object of this invention to provide for such jet pump having the parts, shape, and proportions described in the specification.

These and other desirable objects and advanltagesof the present invention will be illustrated in the accompanying drawing and described in the specification, a certain preferred embodiment being disclosed by way of illustration only; for since the underlying principles may be incorporated in other specific devices, it is not intended to be limited to the one here shown except as such limitations are clearly imposed by the appended claims.

In the drawing like numerals refer to similar parts throughoutthe several views, in which Fig. 1 represents a longitudinal section through the jet pump,

Fig. 2 is a cross section on the line 2--2 of Figure 1, and

Fig. 3 is a longitudinal section through the jet nozzle of Figure 1, showing the same in an enlarged scale. y

In Figure 1 there is shown an integrally cast pump body I0 having a circular inlet 22 for the working fluid to be actuated, this fluid entering therein from the open or from a supply pipe not shown in the drawing, and connected to the pump body in any suitable manner. This fluid is then conducted through a straight, round, cylindrical pressure chamber II where it passes by the nozzle I8 to be described later. The actuated fluid passes next through the straight and round converging cone I2, the circular cross sections of whichldiminish gradually in size from that of the pressure chamber II to about one fourth to one fth thereof. The fluid is then received by the straight and round diverging cone I3 with circular cross sectiors gradually increasing in size from that of the exit'cross section of the converging cone to a size substantially equal to that of the cross-section of the pressurechamber II. It will be seen from Figure 1 that the divergent cone is much longer than the convergent cone, about three times as long, the two cones combining to form a Venturi tube, the steepness of the conicity being in keeping with the scientific rules of streamlining, that is to say with more space devoted to the streamlining on the trailing side than to the streamlining on the leading side. 'Ihe divergent cone I3 discharges the uid into a discharge pipe not shown in the drawing and connected to said cone in any suitable manner, or the iiuid is discharged into the open, as the particular purpose may require. It is also seen from Figure 1 that the conduit composed of the pressure chamber II and of the two cones I2 and I3 possesses an axis of symmetry I4, which in this case is the axis of revolution common to the conduit portions II, I2 and I3, their walls being generated by rotation thereabout.

The actuating or driving fluid enters the pump `at the threaded inlet I5 from a supply pipe not shown in the drawing. It passes through a valve I6 of any suitable construction, next through the hollow bracket I1 projecting from the wall of the pressure chamber into the same, and iinally through the jet nozzle I8, from which it 'is discharged into the pressure chamber. This nozzle comprises an insert 23 screwed into bracket I1, having a straight round ared entrance conduit I9 convergent in the direction of w and a straight round conical exit portion 20 gently divergent in the direction of flow, so that the diameter of the cross section common to portions I9 and 20 is smaller than both the entrance diameter of portion I9 and the exit diameter of portion 20.

The nozzle portions I9 and 20 are coaxial, and their common axis of symmetry 2|, or axis of revolution, is parallel to the axis of symmetry Il of the pressure chamber. According to the invention, however, the two axes I4 and 2I do not coincide, but they are deliberately spaced apart from each other, so that the nozzle I9 and 20, and

the pressure chamber ll and l2, are parallel but not concentric. I have found that a distance between these two axes equal to about one twelfth of the pressure chamber diameter, or slightly more, leads to a pronounced improvement in the performance of the pump, which eccentricity is larger than any small accidental eccentricity unavoidable with ordinary manufacturing methods. I have also found that one definite and fixed eccentricity takes care of a large range of operating conditions, and that it is not necessary to make the eccentricity adjustable, for increasing the range of good performance, at least not ordinarily. I have therefore illustrated my invention by showing a fixed eccentricity, which is the embodiment I prefer.

The beneficial eiect of this eccentricity, manifested by experiment and trial, can probably be explained as follows: For an efficient pump performance it is necessary that the actuating fluid mix with the working fluid and flow then through the venturi in positive contact with the walls thereof, not separated therefrom by fluid substantially at rest. A concentric jet has the tendency to flow in the latter ineillcient way, but a separated eccentric jet is unstable and cannot maintain itself, but rather makes contact with the walls on the side nearest to it and changes then to a contacting jet.

The beneficial effect of the i'laring of the jet nozzle is believed to have special relation to the elasticity of the actuating iiuid, compressed air. It is known in the turbine art that a ared exit nozzle is conducive to large exit velocities of elastic fluids, such as steam. I would thus have discovered that the efficiency of jet pumps is increased by giving to the actuating jet a particularly high initial velocity before it mixes with the working iiuid, the iiared nozzle being a particular structure for bringing that about, and therefore of great use in connection with jet pumps.

I have found that the other proportions shown in the drawing are also important and should be f substantially adhered to for the preservation of the eiiiciency and performance of the pump. The distance of the nozzle exit from the entrance cross section of cone l2, and the steepness of the two cones l2 and I3 are of importance and should not be departed from without assurance that such departure is not harmful. With the pump as shown, using air compressed to about 100 pounds per square inch as actuating fluid, and atmospheric air as working fluid, I have obtained a very strong air flow, and a suction up to 55 inches of water.

I claim:

1. A jet pump having a substantially cylindrical casing providing a rotund conduit for receiving and discharging the pumped iiuid: said conduit comprising a substantially cylindrical portion, a first conical portion in conterminous relation to the cylindrical portion convergent in the direction of iiow, and a second conical portion in conterminous relation to said first conical portion divergent in the direction of flow; jet nozzle means in said cylindrical conduit portion positioned in spaced relation to and upstream of the entrance end of said rst conical conduit portion parallel to but out of alignment with the conduit axis; and means for supplying driving uid to the jet nozzle means.

2. In combination with a pressure supply line, a casing comprising a substantially cylindrical conduit for receiving and discharging fluid constricted by a pair of conical conduit portions converging towards each other and coaxial with the conduit, and a single nozzle connected to and receiving the entire flow from the pressure supply line, said nozzle having its discharge tip disposed eccentrically of the conduit axis but parallel thereto and positioned in spaced and upstream relation to the receiving end of the constricted portion of the conduit.

THOMAS Hi HUFF.

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