US3835886A

US3835886A - Porous tube injector

Info

Publication number: US3835886A
Authority: US
Inventors: L Zajac
Original assignee: Rockwell International Corp
Current assignee: Boeing North American Inc
Priority date: 1972-12-14
Filing date: 1972-12-14
Publication date: 1974-09-17
Anticipated expiration: 1991-09-17

Abstract

A fluid injection system for uniformly mixing gases comprising a primary gas conduit; and a plurality of banks of injector tubes with each of said tubes formed with a plurality of radial openings communicating the interior of said tubes with the interior of said conduit, said tubes extending transversely across said conduit with the tubes of each of said banks extending perpendicular to the tubes of each adjacent bank and having the number of tubes in each bank and the size and spacing of said tubes determined so as to provide the maximum tube area possible while maintaining a predetermined minimum Reynolds number of primary gas flowing through said primary gas conduit and ensuring sufficient cooling of said tubes to maintain structural integrity.

Description

United States Patent [1 1 Zajac Sept. 17, 1974 [54] POROUS TUBE INJECTOR Primary Examiner-Robert G. Nilson Inventor: Lawrence J. Zajac, Thousand Oaks Attorney, Agent, or Firm-L. Lee Humphries; Robert M. Sperry Calif.

[73] Assignee: Rockwell International Corporation,

El Segundo, Calif. ABSTRACT [22] Filed: Dec. 14, 1972 A fluid injection system for uniformly mixing gases comprising a primary gas conduit; and a plurality of [21] Appl 3l5038 banks of injector tubes with each of said tubes formed with a plurality of radial openings communicating the [52] U.S. Cl. 137/604, 48/180 C, 259/4 interior of said tubes with the interior of said conduit, [51] Int. Cl. F16k 19/00 said tubes extending transversely across said conduit [58] Field of searchn 259/4; 4l180 C with the tubes of each of said banks extending perpendicular to the tubes of each adjacent bank and having [56] References Cited the number of tubes in each bank and the size and UNITED STATES PATENTS spacing of said tubes determined so as to provide the l 178 960 M19 Smith 48mm C maximum tube area possible while maintaining a predetermined minimum Reynolds number of primary gas FOREIGN PATENTS OR APPLICATIONS flowing through said primary gas conduit and ensuring 766,006 l/l957 GreatBritain 259/4 sufficient cooling of said tubes to maintain structural integrity.

7 Claims, 2 Drawing Figures l2 IO -IO -|O lO f a a I x alarm PAIENTEBsm mu H: a q 8 5 H M w/mf H C a a H 5 M mvmvmy s l FIG-2 m r 6 m A D V Q] 6 o 6 (m. w 6 m. w r n FIG.

POROUS TUBE INJECTOR BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to fluid mixing and is particularly directed to apparatusfor uniformly mixing gases in a combustion chamber.

pssa atiaasiitbslit qr Art It is frequently necessary or desirable to mix gases in a combustion chamber in order to ignite or control combustion therein and it is usually desired that such mixing be accomplished uniformly throughout the combustion chamber. Innumerable devices have been proposed heretofore for accomplishing such mixing. However, in recent years, interest in non-polluting engines, gas dynamic lasers, and the like, have led to far more stringent requirements for uniformity of mixing and have demanded higher combustion temperatures than have been employed previously and it has been found that the prior art fluid injection systems would not satisfy these new requirements. Thus, many of the prior art fluid injection systems have not provided truly uniform distribution and, hence, have permitted creation of hot spots or, in the case of gas dynamic lasers, have caused non-homogeneous species distributions which result in laser beam distortion. Furthermore, these new techniques frequently require temperatures which would be above the melting point of conventional materials, whereas the newer high temperature materials, such as those developed forspace vehicle nose cones, are prohibitively expensive.

BRIEF SUMMARY AND OBJECTS OF INVENTION These disadvantages of the prior art are overcome with the present invention and a fluid injection system is disclosed which provides truly uniform mixing throughout the combustion chamber and permits conventional materials to be employed, even where the temperature in the combustion chamber exceeds the melting point of such materials.

The advantages of the present invention are preferably attained by providing a fluid injection system comprising a primary gas conduit; and a plurality of banks of injector tubes with each of said tubes formed with a plurality of radial openings communicating the interior of said tubes with the interior of said conduit, said tubes extending transversely across said conduit with the tubes of each of said banks extending perpendicular to the tubes of each adjacent bank and having the number of tubes in each bank and the size and spacing of said tubes determined so as to provide the maximum tube area possible while maintaining a predetermined minimum Reynolds number (e.g., 6000) of the primary gas flowing through said primary gas conduit. With this arrangement, transpiration of the injected fluid through the openings in the injector tubes provides a barrier to the heat flux from the primary gas and serves to protect the structural integrity of the injector tubes.

Accordingly, it is an object of the present invention to provide improved fluid injection means.

Another object of the present invention is to provide a fluid injection system which assures uniform mixing of the injected fluid with the primary fluid.

An additional object of the present invention is to provide a fluid injection system therein the injected fluid forms a heat barrier to protect the structure of the injector tubes against heat flux from the primary fluid.

A specific object of the present invention is to provide a fluid injection system comprising a primary gas conduit; and a plurality of banks of injector tubes with each of said tubes formed with a plurality of radial openings communicating the interior of said tubes with the interior of said conduit, said tubes extending transversely across said conduit with the tubes of each of said banks extending perpendicular to the tubes in each adjacent bank and having the number of tubes in each bank and the size and spacing of said tubes determined so as to provide the maximum tube area possible while maintaining a predetermined minimium Reynolds number of the primary gas flowing through said primary gas conduit.

These and other objects and features of the present invention will be apparent from the following detailed description, taken with reference to the accompanying drawing.

BRIEF DESCRIPTION OF DRAWING FIG. 1 is an end view, partly in section, of a combustion chamber embodying the present invention; and

FIG. 2 is a longitudinal section through the combustion chamberof FIG. 1, taken on the line 22 thereof.

DETAILED DESCRIPTION OF INVENTION In that form of the present invention chosen for purposes of illustration, FIGS. 1 and 2 show a combustion chamber, indicated generally at 2, having a primary gas conduit 4 through which primary gas from a suitable supply. is delivered. A plurality of injector tubes 6 extend transversely across the primary conduit 4 and are disposed in a plurality of banks, as seen at 8, l0, l2, and 14 in FIG. 2, with the tubes 6 of each bank, such as 10, extending perpendicular to the tubes 6 of each adjacent bank, such as banks 8 and 12. The injector tubes 6 are formed of a cylindrical mesh of wire made of heat resistant metal, such as stainless steel or nickel, to give the desired tube porosity.

The diameter and spacing of the tubes 6 and the number of tubes 6 in each of the banks 8, l0, l2, and 14 may be varied, substantially as described, within the constraint that the total tube area should be made as large as is possible, while maintaining the structural integrity of the tubes 6 and while maintaining a predetermined minimum Reynolds number of the primary gas flowing through the conduit 4. Moreover, the Reynolds number of the primary gas flow through conduit 5 should be greater than 200 and preferably greater than 6000..This assures that the flow through the primary conduit will be turbulent and enhances mixing of the primary gas with the secondary gas from the injector tubes 6. The provision of the plural banks 8, l0, l2, and 14 of injector tubes 6 also serves to promote turbulence and improve mixing of the gases, and it is found that the degree of turbulence and mixing increases with the number of such banks provided. On the other hand, the flow of secondary gas through the injector tubes 6 forms a heat barrier which serves to protect the tubes 6 against heat flux from the primary gas and, since the volume of the secondary gas to be injected must be divided between all of the injector tubes 6, the number of the injector tubes 6 and, thus, the number of banks,

such as

banks

8, 10, 12, and 14, must be limited sufficiently to assure that the flow rate of the secondary gas through each of the injector tubes 6 is adequate to protect the structural integrity of the tubes 6.

In a gas dynamic laser installation embodying the present invention, the diameter of the primary conduit 4 was five inches and the injector tubes 6 were onefourth inch diameter tubes formed of a single layer mesh of 10-20 gauge stainless steel wire obtained commercially, under the trademark Rigimesh," from Poraloy Company, El Monte, Calif. Obviously, however, other porous tubes may be employed. Ten of the injector tubes 6, spaced on one-half inch centerlines, were disposed transversely across the primary conduit 4 in each of four banks, 8, 10, 12, and 14, with the tubes 6 of

banks

10 and 14 extending perpendicular to the tubes of banks 8 and 12. The banks 8, l0, l2, and 14 were spaced approximately one-half inch apart along the longitudinal axis of the primary conduit 4. The temperature of the primary gas (for example, CO N was about 5,600F and the secondary gas (for example, N was supplied at a temperature of 80F and at a flow rate approximately twice that of the primary gas flow rate. With these conditions, the injection system of the present invention permitted continuous operation of the installation, without failure of the injector tubes 6 and provided a distribution of the secondary gas that corresponded to a standard deviation of 0.56 percent.

Obviously, numerous variations and modifications may be made without departing from the present invention. Accordingly, it should be clearly understood that the form of the present invention described above and shown in the accompanying drawing is illustrative only and is not intended to limit the scope of the invention.

What is claimed is:

l. A fluid injection system comprising:

a primary fluid conduit, and

a plurality of porous injector tubes extending transversely across said conduit with each of said tubes formed of a mesh material having a plurality of openings communicating the interior of said tubes with the interior of said conduit.

2. The device of claim 1 wherein:

said injector tubes are disposed in a plurality of banks spaced axially along said conduit with each of said banks comprising a plurality of said tubes.

3. The device of claim 2 wherein:

the tubes of each of said banks extend perpendicular to the tubes of each adjacent bank.

4. The device of claim 1 wherein:

the number, size and spacing of said tubes is such as to provide the maximum tube area possible while maintaining a predetermined minimum Reynolds number of the primary fluid flow through said conduit.

5. The device of claim 1 further comprising:

a primary fluid flowing through said conduit with a Reynolds number greater than 200.

6. The device of claim 5 wherein:

the Reynolds number of the primary fluid flow through said conduit is greater than 6000.

7. The device of claim 5 further comprising:

secondary fluid supplied through said injector tubes at a flow rate approximately twice that of the flow rate of the primary fluid flow through said conduit.

Claims

1. A fluid injection system comprising: a primary fluid conduit, and a plurality of porous injector tubes extending transversely across said conduit with each of said tubes formed of a mesh material having a plurality of openings communicating the interior of said tubes with the interior of said conduit.

2. The device of claim 1 wherein: said injector tubes are disposed in a plurality of banks spaced axially along said conduit with each of said banks comprising a plurality of said tubes.

3. The device of claim 2 wherein: the tubes of each of said banks extend perpendicular to the tubes of each adjacent bank.

4. The device of claim 1 wherein: the number, size and spacing of said tubes is such as to provide the maximum tube area possible while maintaining a predetermined minimum Reynolds number of the primary fluid flow through said conduit.

5. The device of claim 1 further comprising: a primary fluid flowing through said conduit with a Reynolds number greater than 200.

6. The device of claim 5 wherein: the Reynolds number of the primary fluid flow through said conduit is greater than 6000.

7. The device of claim 5 further comprising: secondary fluid supplied through said injector tubes at a flow rate approximately twice that of the flow rate of the primary fluid flow through said conduit.