US2969748A

US2969748A - Ejector

Info

Publication number: US2969748A
Authority: US
Inventors: William A Staats; William J Conery
Original assignee: FE Myers and Bro Co
Current assignee: FE Myers and Bro Co
Priority date: 1959-02-12
Filing date: 1959-02-12
Publication date: 1961-01-31
Anticipated expiration: 1978-01-31

Description

1961 w. A. ISTAATS ET AL 2,969,748

EJECTOR Filed Feb. 12, 1959 3 Sheets-Sheet 1 I 98 INVENTOR.

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EJECTOR Filed Feb. 12, 1959 5 Sheets-Sheet 2 Z.".VENTOR.

Jam 1961 w. A. sTAATs ETAL 2,959,748

EJECTOR Filed Feb. 12, 1959 fie-J0 3 Sheets-Sheet 3 P/?SS PROP 7 5/ z IZOW R072" 6PM f, G JZ v INVENTOR.

w/A 5734. 75 W%% tall ER? EJECTOR William A. Staats and William J. Conery, Ashland, Ohio, assignors to The F. E. Myers & Bro., (10., Ashiand, Ohio Filed Feb. 12, 1959, Ser. No. 792,788 7 Claims. (Cl. 103-271) This invention relates to hydropneumatic'systems and in particular to an ejector for such a system for introducing air into the system and to a method of introducing air into a hydropneumatic system. I

Ejectors in hydropneumatic systems are known and may take the form of the combination of a jet nozzle and a venturi tube into which the nozzle discharges so that a low pressure is created in the throat of the venturi which is availed of for causing the air to be introduced into the hydropneumatic system. Such devices are affected by several factors with the principal considerations in the design of such an ejector including:

(1) The pressure differential from the inlet to the outlet which is necessary for fluid flow to take place;

(2) The converging inlet and diverging outlet which assures that the fluid will be accelerated as it approaches the venturi throat and will then be decelerated as it approaches the outlet, this taking place with a minimum of shock loss of the pressure of the fluid;

(3) The discharge pressure of the ejector is'important because the lowered pressure at the throat of the venturi is dependent upon the discharge pressure and increases rapidly with small increases in discharge pressure; and

(4) The flow rate range of the ejector follows the square law'of hydraulics, which is to say that the capacity or flow rate through the ejector increases in proportion to the square root of the pressure differential between the inlet and outlet of the ejector.

A particularly restrictive factor of the foregoing is the flow rate range limitation. Ordinarily, the ejector has a relatively limited flow rate range and thus is not properly operative under circumstances where the flow rate varies widely.

Heretofore, attempts have been made to avoid the flow rate range limitation by providing bypass arrangements around the ejector. These attempts have not been completely satisfactory, however, due to the fact that any such bypass arrangement offers a substantially fixed restriction in the system and the pressure differential across the ejector would continue to increase with an increase in flow rate. Such a bypass would thus have more the effect of shifting the flow rate range limits rather than extending the limits.

With the foregoing in mind, it is a primary object of the present invention to provide a novel ejector arrange merit for a hydropneumatic system, and the like, in which improved operation is had, particularlywith re spect to substantial widening of the flow rate limitations ofjthe ejector.

A still further object of thisinvention is the provision of a relatively simply constructed ejector arrangement which can readily be incorporated in a hydropneumatic system, or the like, and which will operate at improved efliciency throughout an extended flow rate range.

A still further object of this invention is the pro-vision of an ejector-venturi arrangement for hydropneumatic nited States Patent systems, and the like, in which an extremely low presice sure is developed at the aspirating port under all conditions of flow through the ejector-venturi.

It is also an object of this invention to provide an improved method of aspirating fluids into a hydraulic system over an extremely wide range of flow rates through the system, and to accomplish this without any excessive loss of pressure in the system.

In general, the objects of this invention referred to above as well as still other objects are attained by providing an ejector consisting of a jet nozzle and a venturi into which the nozzle discharges with a bypass which is effective for bypassing fluid around the nozzle and venturi without any substantial change in pressure between the inlet and outlet of the ejector over relatively wide'changes in flow rate. This is accomplished by surrounding the venturi portion of the ejector with a resilient diaphragm which defines a variable bypass around the venturi and which bypass varies extremely rapidly with small changes in pressure ditferential thereacross whereby there is little change in the pressure drop between the inlet and outlet of the ejector for large changes in the rate of =flow therethrough.

The present invention also contemplates the provision of a second ejector arranged in parallel with the nozzle of the main ejector so that the inlet end of the second ejector is at the same pressure as the inlet of the nozzle while the discharge end of the second ejector communicates with the throat of the main venturi and is thus-at a greatly reduced pressure. Because of this an extremely low pressure is established in the throat of the second ejector and this is connected with the aspirating port to draw the secondary fluid, which may be air or another liquid, into the ejector for introduction into the main liquid stream through the ejector.

The manner in which the several objects and advantages of the present invention are attained will become more apparent upon reference to the following detailed description taken in connection with the accompanying drawings in which:

Figure 1 is a diagrammatic view showing a typical hydropneumatic system with the ejector of the present invention being employed to introduce air into the system when needed,

Figure 2 is a diagrammatic view showing an iron re moval filter arrangement with an ejector according to the present invention incorporated in the system,

Figure 3 is a diagrammatic view showing a chemical treatment system in which an ejector according to the present invention is employed for introducing measured quantities of reagent into the water stream,

Figure 4 is a longitudinal sectional view through the ejector according to the present invention with the bypass completely closed,

Figure 5 is a transverse cross sectional view indicated by line 5-5 on Figure 4 showingthe aspirating port and the groove with which it communicates that is connected with the throat of the venturi of the Second ejector, 1

Figure 6 is a sectional view like Figure 5 .but shows the diaphragm pertaining to the bypass channel deflected to the point of opening to initiate the bypassing of fluid around the ejector, 7

Figure 7 is a sectional view like Figure ,6 but show.- ing the diaphragm deflected to the point that fluid is being bypassed around the ejector,

Figure 8 is a fragmentary view drawn at scale showing the second ejector,

Figure '9 is a diagrammatic view illustrating the action of the diaphragm for difierent size venturi tubes,

' Figure 10 is a diagrammatic view illustrating the ejector with gauges attached thereto to indicate the points of detecting pressures in the system during operatiom and Figure 11 is a graph illustrating pressure conditions enlarged 3 that obtain during operation of the ejector over the normal limits of flow therethrough.

Referring to the drawings somewhat more in detail, in Figure 1 .there is a tank containing water 12 supplied thereto by conduit 14 leading from a pump. Water is drawn from tank 10 by conduit 16. The upper end of the tank at 18 contains air and there is an air level control device at 20 connected with the tank at about the desired water level therein. This control includes a snifter valve 22 through which air is admitted into the control when the water level closes the inner end of the control device and which becomes inoperative when the water level falls below the inner end of the control device. A conduit 24 connects the air control device with ejector 26, according to this invention, and by the described arrangement the volume of air within the tank is maintained substantially constant.

In Figure 2 there is shown an iron removal filter arrangement with raw water entering via conduit 28 through ejector 26 and flowing from the ejector through conduit 30 that delivers the water to a pipe 32 opening into the upper end of tank 34. The aspirating port of the ejector is connected by tube 36 with a control device 38 which is quite similar to the control device 20 of Figure 1. When the upper end of tank 34 contains air, this air is drawn through control device 38 and tube 36 into ejector 26 and recirculates back to the top of tank 34. When the liquid level in the tank gets to the top, then a snifter valve 39 in control 38 admits outside air and thus the tank 34 always has a predetermined amount of air in the upper end;

The lower end of the tank contains filtering material 40 and the filtered water discharges through conduit 42 to a service conduit 44.

In Figure 3 the ejector 26 is located in a conduit 46 which receives raw water from the left and discharges treated water toward the right. The treatment of the water is accomplished by adding reagent 48 thereto which flows through tube 50, shutofl valve 52, and check valve 54 to the aspirating port of the ejector 26.

Turning now to Figures 4 through 7, the ejector of the present invention is shown in detail. The ejector comprises a body part 56 having a threaded inlet port 58 and bolted to body part 56 by screws 60 is a second body part 62 having a threaded outlet 64. The body parts engage therebetween the peripheral portion of a resilient diaphragm 66 which extends inwardly. The center of diaphragm 66 has a round aperture 68 therein somewhat smaller than the outside diameter of a venturi tube 70 which is advantageously formed integrally with body part 56.

The discharge end of the venturi tube is disposed at the inner end of the threaded outlet port 64 and at the inlet end of the venturi there is a jet nozzle 72 adapted for directing a jet into throat 74 of the venturi tube. The nozzle has an inlet end at 76 that communicates with the inlet port 58 while the space between the nozzle and the inlet port communicates by way of passage means 78.

with chamber 80 located on the upstream side of diaphragm 66. On the downstream side of diaphragm 66 is another chamber 82 communicating directly with threaded discharge port 64.

The jet nozzle 72 comprises a convergent inlet passage 84 and a portion 86 that defines the nozzle diameter. The venturi tube 70, downstream of the throat 74 thereof, has a divergent section 88. r

The nozzle 72 has a second smaller ejector formed directly therein with a converging inlet end 90, a throat 92 and a diverging discharge end 94. Discharge end 94 discharges directly into space 96 surrounding the discharge end of nozzle 72 and which space communicates with throat 74 of venturi tube 70 and is at the same pressure as the said throat.

Nozzle 72 is formed with an annular groove 98 that communicates directly with aspirating port 100 and also communicates, by way of the radial annular slot 102, with the throat 92 of the second ejector.

In operation, fluid enters the ejector through inlet port 58. The fluid is accelerated in converging passage 84 and passes through portion 86 of the nozzle at high velocity and thence into throat 74 of the venturi 70. The fluid is then decelerated in diverging portion 88 of the venturi tube and then passes out through discharge port 64 at the initial fluid velocity.

When the fluid is moving at high velocity through nozzle 72 as above described, a greatly reduced pressure is established in space 96. This establishes a high diflerential pressure across the second ejector and accordingly fluid enters through the convergent inlet portion 90 thereof and is accelerated to an extremely high velocity in the throat portion 92 and is then discharged through the diverging discharge portion 94 into space 96. The extremely high velocity through the throat portion of the second ejector causes an extremely low pressure to be established therein which is communicated via slot 102 in groove 98 with aspirating port 100. This reduced pressure in port 100 is utilized for introducing air or other liquids into the system, as heretofore described.

As the demand for fluid increases and fluid flow through the ejector from inlet port 58 to discharge port 64 increases, the pressure diflerential across the ejector increases. The inlet pressure, which is communicated directly to chamber 80 on the upstream side of diaphragm 66, accordingly increases and this causes deflection of the diaphragm.

The center hole 68 in the diaphragm is normally somewhat smaller than the outside diameter of the venturi tube and the diaphragm is thus somewhat preloaded and will not deflect sufiicient to open the center hole until there is a substantial pressure diflerential established across the diaphragm. The position which the diaphragm occupies at the time stretching of the center hole to a diameter larger than the venturi tube is imminent, is illustrated in Figure 6. This figure indicates the condition of maximum pressure difierential across the ejector and which is the pressure differential between the

chambers

80 and 82 on opposite sides of the diaphragm.

Figure 7 illustrates the ejector by-passing fluid through the center hole of the diaphragm. According to the present invention, the pressure dilferential between opposite sides of the diaphragm as it moves from its Figure 6 position to its Figure 7 position, increases gradually as the flow rate increases but increase is at a much reduced rate from what would normally be expected. This comes about by a proper selection of the material and the thickness of the diaphragm, and by selecting the size of the center hole 68 thereof relative to the size of the venturi tube 70. The free diameter of the diaphragm is also of importance in determining its characteristics under a pressure differential.

The opening of the diaphragm to permit fluid to pass through the center hole thereof at substantially no increase in pressure differential between the inlet and outlet of the ejector comes about because as the flow increases from chamber 80 through the center hole of the diaphragm to the discharge port of the ejector, a low pressure region is established at the annulus formed by the inner edge of the diaphragm and the outside diameter of the venturi tube 70.

The low pressure thus established in chamber 82 thus establishes a pressure difierential across the diaphragm 66 which is substantially greater than the relatively low pressure differential between inlet 58 and outlet 64 of the ejector. As the flow rate through the ejector increases, the velocity and the fluid through the bypass increases thereby causing a further drop in pressure in chamber 82 causing the diaphragm 66 to deflect still further as is indicated in Figure 7.

The selection of the size of the venturi and the size of the hole in the diaphragm together with other factors influencing the action of the diaphragm, such as the resilience thereof and the outer clamped diameter, eflect the action of the diaphragm as will be seen in Figure 9.

In Figure 9 there is illustrated diagrammatically venturi tube 101 of a small diameter and a second venturi tube 103 of a larger diameter. The diaphragm 105 is illustrated at the point where opening of the bypass is imminent and also where the bypass has been opened about each venturi tube. Under the same conditions of pressure differential across the diaphragm, the diaphragm hole in the case of the smaller venturi tube will expand from diameter 611 to diameter d2 Whereas in the case of the larger venturi tube the hole in the diaphragm would expand from diameter D1 to diameter D2. The ratios of the respective flow areas thus established will be the ratio of the squares of the difierences in the diameters.

It will be apparent that the area established about the larger venturi tube is substantially greater than thearea established about the smaller venturi tube, and this will occur for the same pressure differential which will cause the same degree of defection of the diaphragm. By selecting a predetermined prestress of the diaphragm, which is predetermined by the size of the center hole in the diaphragm, and by selecting the proper size venturi tube, it is possible actually to have a negative rate of pressure drop from inlet to outlet for a predetermined range of flow rates.

In one particular application in which the present invention has been applied, it was desired to maintain pressure less than atmospheric in port 100 for all flow rates through the ejector from 5 gallons per minute to 100 gallons per minute and at a discharge head of 50 pounds per square inch. Tests indicated that a 12 pound per square inch pressure differential was necessary at all times between inlet port 58 and outlet port 64 of the ejector to satisfy these conditions. The prestressing of the diaphragm and the selection of the material thickness thereof and the outside or clamped diameter provide for establishing a bypass channel that gives substantially a constant pressure drop across the ejector throughout the flow range referred to above, namely, from 5 gallons per minute to 100 gallons per minute.

From the foregoing it will be seen that the present invention provides an arrangement whereby a bypass is established through the ejector that will greatly extend the flow rate range of the ejector while at the same time maintaining an extremely low pressure in the aspirating port throughout the entire range of fiow rates.

The particular conditions in which the ejector could be employed and the fiow rate range desired therethrough will determine the size of the ejector and the particular conditions pertaining to the diaphragm controlled bypass, and it will be understood that modifications of this nature in the disclosed structure of this nature are considered to fall within the purview of the present invention.

To illustrate specific examples, reference may be had to Figures and 11 wherein there is shown an ejector arrangement according to this invention with the diaphragm comprising /a inch thickness gum rubber with a 2 inch clamped diameter, which is to say, the diaphragm is flexible inwardly from a 2 inch diameter.

The main ejector comprises a nozzle diameter of .170 inch, and the venturi tube throat is .1875 inch.

The second ejector comprises a nozzle diameter of inch and a throat diameter of M inch.

The graph of Figure 11 shows the action of the ejector With flow rates ranging from 0 gallon per minute up to 50 gallons per minute, and the lines indicate the pressure drop across the entire ejector which is the pressure drop that would be obtained by subtracting the reading of gauge 3 from the reading of gauge 1.

In Figure 11 there are 4 graph lines which indicate the variation in conditions as the prestress on the diaphragm is varied. It is understood that the prestress is obtained by the selection of the size of the center hole. The outside diameter of the venturi tube is /2 inch, and the center hole sizes for the diaphragm are ,4 inch for graph line I; graph line- II is for a diaphragm having a 1 inch center hole; graph line III indicates the conditions for a diaphragm center hole of inch; and graph line IV indicates the conditions for a diaphragm center hole of M inch.

The line marked V shows the conditions which obtain when there is no bypass channel and the ejector operates as a simple unit with all the flow passing through the nozzle and the venturi tube.

It will readily be seen from the graph, which are records taken under actual test conditions, that there is substantially no change in pressure drop across the ejector once the bypass channel commences to open. It will also be observed that in the absence of a bypass channel the pressure drop across the ejector rises extremely rapidly and that, accordingly, an extremely limited range of flow rates only would be possible without the bypass.

To indicate the manner in which the pressure drop across the diaphragm itself increases with increasing rates of flow through the ejector-bypass combination, reference may be had to line VI on the graph which shows the pressure differential across a diaphragm in which the conditions are the same as have previously been described except the diaphragm has a inch center hole and is fitted over a venturi tube which is inch in outside diameter. 7

It will be evident from line VI of the graph that the pressure differential across the diaphragm rises as the flow therethrough increases thus causing greater flexing of the diaphragm increasing the area of the bypass channel and thus contributing to the substantially constant overall pressure drop between the inlet and outlet of the e ector.

The pressure diiferential curve numbered VI is obtained by subtracting the reading of gauge 2 from the reading of gauge 1.

We claim:

1. An ejector for a fluid system; a body part having an inlet and an outlet, a nozzle and venturi tube within the body part in series between the inlet and outlet, a passage leading to the throat of said venturi tube through a wall of said body part, a bypass channel through the body part bypassing the nozzle and venturi tube, and a resilient diaphragm having its periphery clamped in the body part and surrounding the venturi tube normally closing said bypass channel, said diaphragm being yieldable outwardly from said venturi tube in response to a predetermined diflerential pressure between the opposite sides thereof for permitting fluid to flow through the said channel.

2. In an ejector for a fluid system; a body part having an inlet and an outlet, a nozzle and venturi tube connected in series between the inlet and outlet, a passage leading to the throat of said venturi tube through a wall of the body part, a bypass channel extending through the body part from the inlet to the outlet in parallel with the nozzle and venturi tube, and a resilient diaphragm having its periphery clamped in the body part extending into engagement with the outside of the venturi tube whereby the said channel is normally closed but whereby the diaphragm will yield outwardly from said venturi tube at a predetermined differential pressure on the opposite sides thereof for establishing said channel.

3. In an ejector for fluid systems; a body part comprising a first portion having an inlet and a second portion having an outlet, said portions being secured together, a nozzle and venturi tube in series in the first body portion arranged so the nozzle receives fluid from the inlet and the venturi tube discharges into the outlet, a passage leading from the throat of the venturi tube through a wall 7 of the said first portion of the body part, a channel leading 'from the inlet to the outlet in parallel with the nozzle and venturi tube,.and a resilient diaphragm clamped between said first and second portion of said body part having a central aperture through which the venturi tube extends, said aperture being normally smaller than the venturi tube whereby the bypass channel remains closed until a predetermined differential pressure is developed across the diaphragm whereupon the diaphragm will yu'eld outwardly from said venturi tube to establish said channel.

4. In an ejector for fluid systems; a hollow body having an inlet inone end and an outlet in the other end and being divided between the ends to form two body parts, a nozzle supported within the body on the axis of the inlet and spaced therefrom, a venturi tube supported within the body in alignment with the nozzle and terminating adjacent the outlet of the ejector, a passage leading from the throat of the venturi tube through a wall of the ejector so fluids will be drawn into the venturi tube, the arrangement of the nozzle and venturi tube providing a bypass channel from the inlet to the outlet around the nozzle and venturi tube, a resilient diaphragm member having a peripheral portion clamped between the parts of the ejector body and having a central aperture through which the venturi tube extends so the said channel is normally closed, the said aperture being normally smaller than the venturi tube whereby the channel will remain closed until a predetermined pressure difierential is established across the diaphragm whereupon the diaphragm will yield outwardly from said venturi tube to establish said bypass channel, and the ejector body .being formed to define a cavity within which the diaphragm expands when subjected to differential pressure whereby fluid flowing through the aperture in the diaphragm will create a condition of reduced pressure on the downstream side of the diaphragm.

5. In an ejector for fluid systems; a hollow body having an inlet at one end and an outlet at the other end, a nozzle in the body in alignment with the inlet and adjacent thereto, a venturi tube extending from adjacent the nozzle to adjacent the outlet so that a supply of fluid through the nozzle will cause a reduced pressure in the throat of said venturi'tube, means adjacent the nozzle forming a venturi passage having its inlet end connected to receive fluid from the inlet of the ejector and having its outlet connected with the throat of said venturi tube and a passage extending through the side of the body and communicating with the throat of the said venturi passage, there beinga channel through said body from the inlet thereof to the outlet in parallel with the nozzle and venturi tube, a resilient diaphragm fixed to the body and extending inwardly and having a central aperture normally smaller than the venturi tube through which the venturi tube extends, said diaphragm being yieldable outwardly from said venturi tube to permit fluid to pass therethrough.

6. In an ejector arrangement for a fluid system; a hollow body having axially aligned inlet and outlet at opposite ends, said body being divided laterally between its ends into two body parts, a nozzle and venturi tube in series between the inlet and outlet and coaxial therewith, a venturi passage adjacent the nozzle having its inlet end arranged to receive fluid from the inlet of the ejector and having its discharge end connected with the throat of the venturi tube whereby extremely high fluid velocities are established in the throat of the venturi passage resulting in an extremely low pressure condition therein, a passage extending from the throat of said venturi passage through the side wall of the ejector body so that air or fluids can be drawn into the ejector body, and'a bypass channel through the ejector body in parallel with the nozzle and venturi tube, there being means normally closing said channel responsive to a predetermined pressure differential between the inlet and outlet for establishing said channel, said means comprising a resilient rubberlike diaphragm disc clamped between the parts of the ejector body and extending inwardly and having a central aperture normally smaller than the outside diameter of the venturi tube through which aperture the venturi tube extends.

7. In an ejector for fluid systems; a substantially cylindrical body formed in two parts arranged end to end with an inlet in the end of one body part and an outlet coaxial therewith in the other end of the other body part, a nozzle supported in the one body part coaxial with said inlet and spaced therefrom, a venturi tube also supported in said one body part coaxial with said nozzle and having its discharge end disposed at the inner end of the outlet, a passage leading from the throat of the venturi tube to the side of said one body part, a resilient diaphragm having a central aperture normally smaller than the venturi tube clamped between said body parts with the venturi tube extending through the central aperture, there being a bypass channel from the inlet to the outlet around the nozzle and venturi tube which the diaphragm normally closes, and said bypass channel tapering inwardly from the downstream side of the diaphragm toward the discharge end of the venturi tube so that a cavity of substantial size is provided on the downstream side of the diaphragm whereby fluid passing through the aperture in the diaphragm when it is deflected by pressure on the upstream side thereof will cause a reduced pressure region on the donwstream side of the diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS