Compound ejector

Abstract

Apparatus and methods of operation are disclosed for combining injected high-energy primary flow fluid (normally a gaseous medium) and induced or entrained secondary flow fluid (frequently air) at and in the essentially conventional throat and diffuser sections of an ejector to significantly increase ejector performance efficient with limited injection slots or openings of limited size and with minimum diffuser lengths, to achieve high diffusion rates and substantially reduced system energy losses attributed to fluid flow blockage and flow separation, and to obtain other important ejector operating characteristics.

Parent Case Text

CROSS REFERENCES

This is a continuation, of application Ser. No. 310,723, filed Nov. 30, 1972, now abandoned.

Description

SUMMARY OF THE INVENTION

Ejector apparatus having conventional throat and diffuser sections in its operating configuration is provided with center injector means and additionally with Coanda injector means, and is operably connected to a source of high-energy primary flow fluid. The injected primary flow fluid from both said injector means is combined with entrained secondary flow fluid, induced through the ejector inlet opening, at and in the ejector throat and diffuser sections to both significantly increase ejector output force-to-input force performance ratio (thrust augmentation ratio) and minimize ejector system energy losses in comparison, for instance, to the performance of comparably sized and configured conventional multi-tube injector ejector apparatus. The invention achieves thrust augmentation ratios at least to as great as approximately 1.55 employing a secondary flow entrance (slot) area ratio of approximately 12.5, and is especially significant with respect to short length ejector configurations wherein the desired ratio of ejector diffuser length to ejector throat diameter is in the range of approximately 1 to 2.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic plan view of an embodiment of the compound ejector of this invention having a throat section with circular planform;

FIG. 2 is a schematic sectional view taken at line 2--2 of FIG. 1;

FIG. 3 is a schematic plan view of an embodiment of the compound ejector of this invention having a throat section with a rectangular planform;

FIG. 4 is a schematic cross-sectional view taken at line 4--4 of FIG. 3; and

FIG. 5 graphically illustrates thrust augmentation ratio performance achieved by the instant invention in comparison to thrust augmentation ratio performance achieved with various conventional ejector apparatus arrangements.

DETAILED DESCRIPTION

The embodiment of the invention illustrated schematically and in sectional detail in FIGS. 1 and 2 is distinguished from the other embodiment illustrated in the drawings primarily by the planform of the ejector throat configuration. The principal elements comprising the FIG. 1 arrangement are separately described in the following subparagraphs, each identified initially by the appropriate reference numeral in the drawings, and additionally as to element nomenclature, details of form and construction, and statement of principal function or functions:

11; ejector high-energy fluid source; normally in the form of a source of pressurized gaseous medium at a pressure ratio of approximately 1.3 or greater (e.g. 1.3 to 30 depending on type and location of source available) at the source discharge face such as a high-pressure gas supply, a gas compressor, a turbo-fan engine fan, or a turbo-jet engine turbine section; provides primary flow fluid to the ejector and such fluid may comprise, in some applications, products of combustion at an elevated temperature (e.g. 65.degree.C. to 600.degree.C.) relative to ambient or atmospheric temperature (nominal 15.degree.C.).

12; supply duct sections; normally of metallic construction or of fibre-reinforced thermosetting resin construction and in conventional duct cross-sectional configurations preferably sized to minimize internal fluid flow pressure or energy losses and to achieve flow velocities of about 0.25 Mach Number in typical applications but sometimes to as great as about 0.4 Mach Number; directs primary flow fluid from source 11 to primary flow distribution ductwork:

13; distribution duct sections; similar in construction and cross-sectional configuration to duct sections 12; direct proportioned primary flow fluid to system injectors;

14; duct fittings; similar in construction to duct sections 12 and 13 and of conventional fitting configuration; join system duct sections together and to other system fluid distribution elements;

15; primary flow control valve; essentially of metallic construction and conventional valve configuration but in some applications may take form of plug nozzle with cooperable diverter; regulates/diverts flow of primary flow fluid from source 11 through supply duct sections 12;

16; proportioning valves; of conventional metallic construction and configuration; proportioning of primary flow fluid to minimize system energy losses preferably and normally is accomplished by varying duct diameters of slot and nozzle opening sizes but if elements 16 are provided in the ejector arrangement, such function to further control the primary flow fluid from source 11 for proper distribution to individual injectors in the apparatus, and in either case proportioning normally is with from 30 to 70 percent of total primary fluid flow to the ejector center injector and the balance to the ejector Coanda injector;

17; center injector; of streamlined duct-like or tube-like construction using materials comparable to the materials comprising duct sections 12 and 13 and having a location above the ejector throat section and an operating orientation downwardly along the general flow direction of the ejector diffuser section; directs primary flow fluid to the center of the ejector throat section for downward projection essentially along the ejector diffuser section flow axis;

18; nozzle opening; an opening in the center injector sized to achieve a desired percentage primary fluid and a flow velocity approaching or in excess of approximately 0.7 Mach Number and located preferably slightly above or at the plane of the ejector throat section; provides downward primary air flow at the throat center and at a proper velocity;

19; coanda injector supply duct; generally similar to injector means 17 in construction materials but of annular planform configuration with the toroidal inside diameter essentially corresponding to the ejector throat section diameter and the toroidal average diameter corresponding to the diameter of the ejector circular inlet area; typically directs primary flow fluid to the perimeter of the ejector inlet for injection into system 10, for approximately 90.degree. to 110.degree. angular rotation (15.degree. to 30.degree. minimum), and for mixing and downward projection essentially in nonseparated relation to the diverging walls of the ejector diffuser section;

20; Coanda slot opening; ring-like slot opening in the Coanda injector supply duct substantially coextensive with the perimeter of the ejector circular inlet area and sized to achieve a primary fluid flow in the desired 30 to 70 percent total flow range and with a velocity approaching or in excess of approximately 0.7 Mach Number; the opening, by virtue of its location and orientation essentially injects primary flow fluid radially inwardly toward the inlet area center and approximately at right angles to the lift ejector operating longitudinal axis whereupon it is rotated by the Coanda effect typically approximately 90.degree. to 110.degree. into a downward path generally along the direction of the walls defining the ejector divergent diffuser section; and

21; diffuser section wall; of metallic composition of fibre-reinforced thermosetting resin composition in plate-like, circumferentially continuous form and joined and faired to the wall of Coanda injector means 19 to provide a smooth transition from the ejector throat to the divergent ejector diffuser section exit opening; length essentially accomplishes mixing of ejector primary and secondary fluid flows and diffusion allows pressures produced at the inlet to induce ejector secondary fluid flow and develop improved ejector thrust.

In addition, the drawings are provided with certain of the following reference symbols identifying features or characteristics of the ejector construction of the invention useful for analytical purposes:

L; ejector length (height); extends from the plane of the ejector exit opening to the plane of ejector inlet opening, the latter normally being positioned a relatively small distance above the plane of the ejector throat section;

D; ejector diameter; essentially the diameter of the ejector throat section except that in cases of non-circular throat section planforms the dimension may correspond to the average planform dimension of the throat area affected by the center injector and the ejector cross-section being analyzed;

A.sub.th ; cross-sectional (planform) area of ejector throat section;

A.sub.i ; cross-sectional (planform) area of ejector inlet;

A.sub.e ; cross-sectional (planform) area of ejector exit;

A.sub.p ; cross-sectional area of primary fluid flow exits which in most instances is the sum of the discharge area of the center injector nozzle opening and the Coanda injector slot opening;

A.sub.s ; cross-sectional area of secondary or entrained fluid flow which in most instances, because of relative absence of blockage in the ejector throat section by the center injector means 17, essentially corresponds to the ejector inlet area A.sub.i ; and

.alpha.; ejector diffuser section wall divergence angle (half-angle) relative to the lift ejector axis in the general direction of principal fluid flow.

Heavied arrow showings in the drawings indicate principal air flow direction for the primary, secondary, and combined fluid flows. The ejector discharge flow at the exit face is particularly noteworthy in view of the fact that it is substantially of improved distribution across the exit face.

FIG. 3 illustrates an ejector apparatus embodiment 30 having the features of this invention combined with supporting structure referenced generally as 31. In addition to a different throat section planform, those FIG. 3 (and FIG. 4) elements of the embodiment which differ significantly from FIG. 1 and FIG. 2 in detail are as follows:

32; straight-line center injector; has characteristics, except for principal planform configuration, of center injector 17; directs primary flow fluid in the operating position for downward projection essentially along the ejector diffuser section flow axis;

33; slot opening; in center injector 32 and similar in all other characteristics, excepting an elongated planform configuration, to the nozzle opening 18 described in connection with ejector embodiment 10;

34 and 35; straight-line Coanda injector; each of construction and form characteristics similar, except as to planform configuration, to Coanda injector 19 of the FIGS. 1 and 2 arrangement; comprised of a slotted, duct-like straight-line Coanda injector; each projects part of the primary flow fluid (approximately one-half of the typical 30 to 70 percent proportion of total primary flow) from source 11 into the ejector inlet and throat section regions for downward projection essentially along the ejector diffuser section interior wall surfaces and for mixing;

36 and 37; Coanda slot opening; straight-line openings in injectors 34 and 35 and otherwise similar in characteristics and function to slot opening 20.

Another embodiment of the instant invention is generally similar to embodiment 30 but is not shown in the drawings. Such additional embodiment differs from the FIGS. 3 and 4 arrangement in that it includes two center injector assemblies 32 positioned intermediate injectors 34 and 35 and in spaced-apart relation relative to each other. By this alternate arrangement a proportionately greater center injection of primary flow fluid can be developed.

FIG. 5 provides quantitative information regarding the performance capabilities and characteristics of the instant invention. Curves 41 and 42 indicate the magnitude of thrust augmentation obtained with the instant invention at L/D ratios of 2.5 and 2, respectively. Although the instant invention is important with respect to ejectors having a L/D ratio of 2.5 or less, it is particularly significant with respect to ejector apparatus having a ratio (L/D) in the range of approximately 1 to 2. In the case of curve 41, which is in part based on actual test data and in part on theoretical projection, the test embodiment of the compound ejector was operated with a divergence half-angle (.alpha.) of 7.5.degree.. Curve 42, on the other hand, involved a divergence half-angle of 12.degree..

The performance of the ejector of this invention, as manifested by curves 41 and 42, also is compared in FIG. 5 to the performance of conventional ejectors of comparable design and operating parameters having only Coanda injection (curves 43 through 45) at 6.degree. half-angle divergence or only conventional center injection (curve 46) at 7.5.degree.. It is apparent from curves 43 through 46 that for comparable ratios of ejector throat area to primary slot area, significantly improved thrust augmentation ratios are obtained with the present invention. Shorter design lengths (L) are achieved by practice of the invention as a result of permitting utilization of high divergence half-angles (.alpha.) with improved diffuser wall boundary layer control.

In considering the foregoing described invention, careful distinction must be made between introducing primary flow fluid into the ejector system by means of a Coanda slot opening in comparison to introducing such primary flow fluid into the ejector by tangential injection over the diffuser wall as such is typically accomplished from a region near the ejector throat. In one test arrangement involving injection from opposed Coanda slot openings as in the FIG. 3 arrangement an obtained thrust augmentation ratio of 1.35 was reduced to a value of 1.2 when one opposed ejector inlet Coanda slot opening was replaced with a wall-tangent throat area injector operated at otherwise identical fluid flow conditions. Studies of flow separation from the ejector diffuser wall as a function of diffuser divergence angle established that in a case of distinct wall separation at a 6.degree. half-angle with center injection only, no separation was observed with the additional introduction of Coanda slot injection as described in connection with this invention.

Also, opposed Coanda slot opening injection is considered to efficiently turn high pressure ratio (e.g. 3.5 to 4) fluid flows over a relatively small arc. From the standpoint of effecting Coanda flow turning without separation, the ratio of vane radius or turn curvature adjacent the slot opening to slot height is important and fortunately is not considered highly critical. With a small radius to a slot-height ratio (approximately 5), flow detachment from the ejector wall becomes apparent at a pressure ratio of about 1.8 and is based on observed detachment after about 50.degree. of turning. Increasing the ratio of surface turning radius to slot-height functions to improve the obtained thrust augmentation ratio particularly when at values in the range of approximately 10 to 15.

Claims

I claim:

1. In ejector apparatus immersed in a body of secondary flow fluid and producing an augmented thrust vector oriented along an ejector longitudinal axis, in combination:

perimeter injector means having opposed discharge slots that are positioned at opposite sides of said longitudinal axis and that are oriented and sized to each discharge primary fluid flowed therethrough in a direction toward and substantially at right angles to said longitudinal axis at a discharge velocity greater than approximately 0.7 Mach number;

convergent inlet surfaces each extending from immediately adjacent a respective one of said perimeter injector means opposed discharge slots and continuing in the direction of fluid flow along said longitudinal axis through a rotational angle in the range of approximately 80.degree. to 110.degree. to form an ejector apparatus throat having a minimum dimension D in a direction normal to said longitudinal axis;

center injector means having a discharge nozzle that is positioned intermediate said perimeter injector means discharge slots and above said ejector apparatus throat minimum dimension D and that is oriented and sized to discharge primary fluid flowed therethrough in a direction generally along said longitudinal axis at a discharge velocity greater than approximately 0.7 Mach number;

divergent diffuser surfaces continuing from said convergent inlet surfaces in the region of said ejector apparatus throat minimum dimension D to a termination at an interface with said body of secondary flow fluid and with an average divergence with respect to each other of angle 2.alpha.; and

duct means flowing high energy primary flow fluid to said perimeter injector means discharge slots and to said center injector means discharge nozzle at pressure ratios greater than approximately 1.3 relative to said body of secondary flow fluid and at flow rates sufficient for maintaining said discharge velocities,

said perimeter injector means opposed discharge slots and said divergent diffuser surfaces termination being separated in a direction along said longitudinal axis by a distance L that is less than approximately 2.5 times said ejector apparatus throat minimum dimension D, and said divergent diffuser surfaces average divergence angle 2.alpha. being at least approximately 15.degree..

2. The invention defined by claim 1 wherein said opposed discharge slots each have a height H in the direction of said ejector longitudinal axis and wherein said convergent inlet surfaces each have a mean radius of curvature R for said rotational angle, said height H and said radius of curvature R being in a ratio substantially in the range of from 1:5 to 1:5

3. The invention defined by claim 1 wherein said divergent diffuser surfaces termination is separated from said perimeter injector means opposed discharge slots in a direction along said longitudinal axis by a distance L that is substantially less than approximately 2.0 times said ejector apparatus throat minimum dimension D.

4. The invention defined by claim 1 wherein said duct means high energy primary flow fluid is proportioned with approximately from 30 to 70 percent being flowed to said center injector means and the balance being flowed to said perimeter injector means.

5. The invention defined by claim 4 wherein said duct means high energy primary flow fluid is proportioned with approximately 50 percent being flowed to said center injector means and the balance being flowed to said perimeter injector means.

6. The invention defined by claim 1 wherein said divergent diffuser surfaces average divergence angle 2.alpha. is at least approximately 24.degree..

7. A method of augmenting the thrust of a primary fluid flow in ejector apparatus which is immersed in a body of secondary fluid and which has joined in succession along a longitudinal axis a convergent inlet section, a throat section of minimum dimension D in a direction normal to said longitudinal axis, and a divergent diffuser section, comprising the steps of:

injecting part of said primary fluid flow into said ejector apparatus in a direction generally along said longitudinal axis as a free core jet centrally of a secondary fluid inlet opening in said convergent inlet section and generally from above and toward said throat section at a discharge velocity greater than approximately 0.7 Mach number and entraining and mixing secondary fluid flowed through said inlet opening into and with primary fluid from said free core jet;

simultaneously injecting the balance of said primary fluid flow into said ejector apparatus in a direction generally at right angles to said longitudinal axis as wall jets and from opposite sides of said secondary fluid inlet opening in said convergent inlet section, toward said longitudinal axis, and at discharge velocities greater than approximately 0.7 Mach number over opposed curved inlet surfaces in said convergent inlet section adjacent thereto;

turning said primary fluid flow injected as wall jets over said curved inlet surfaces in said convergent inlet section and entraining and mixing additional secondary fluid flowed through said secondary fluid inlet opening in said convergent inlet section into and with the primary fluid of said wall jets;

diffusing said free core jet and wall jet primary fluid flow and entrained and mixed secondary fluid in said ejector apparatus intermediate opposed wall surfaces extending from said throat section and defining said divergent diffuser section; and

discharging said diffused free core jet and wall jet primary fluid flow and entrained and mixed secondary fluid from said ejector apparatus and into said body of secondary fluid a distance from the region at which said primary fluid flow is injected into said ejector apparatus that is in the direction of said longitudinal axis greater than approximately 1.0 times but less than approximately 2.5 times said throat section minimum dimension D,

said primary fluid flow and entrained and mixed seconary fluid thereby having a thrust at the region of discharge into said body of secondary fluid at least 50 percent greater in magnitude than the magnitude of thrust of said primary fluid flow.

8. The method defined by claim 7 wherein said primary fluid flow injected as a free core jet and as wall jets is injected into said ejector apparatus at a pressure ratio of approximately 1.3 or greater with respect to the pressure of said body of secondary fluid.

9. The method defined by claim 7 wherein said primary fluid flow injected into said ejector apparatus as wall jets has a height in the direction of said apparatus longitudinal axis in a ratio to the mean radius of curvature of said opposed curved inlet surfaces in said convergent inlet section in the range of approximately from 1:5 to 1:5 initially.

10. The method defined by claim 7 wherein said primary fluid flow injected into said ejector apparatus is proportioned in a manner whereby approximately from 30 to 70 percent is injected as said free core jet and the balance is injected as said wall jets.

11. The method defined by claim 7 wherein said primary fluid flow injected into said ejector apparatus is proportioned in a manner whereby approximately 50 percent is injected as said free core jet and the balance is injected as said wall jets.

12. The method defined by claim 7 wherein said primary fluid flow injected as wall jets is turned over said opposed curved inlet surfaces in said convergent inlet section through an angle in the range of approximately from 30.degree. to 110.degree..

13. The method defined by claim 7 wherein said primary fluid flow injected as wall jets is turned over said opposed curved inlet surfaces in said convergent inlet section through an angle in the range of approximately from 80.degree. to 110.degree..

14. The method defined by claim 7 wherein said free core jet and wall jet primary fluid flow and entrained and mixed secondary fluid is diffused intermediate opposed wall surfaces extending from said throat section that diverge with respect to each other through an average angle that is at least approximately 15.degree..

15. The method defined by claim 7 wherein said free core jet and wall jet primary fluid flow and entrained and mixed secondary fluid is diffused intermediate opposed wall surfaces extending from said throat section that diverge with respect to each other through an average angle that is at least approximately 24.degree..