US3664588A - Platelet injector - Google Patents

Abstract

PLATELET INJECTOR HAVING A MANIFOLD RING, AND A PLURALITY OF VANES ARRANGED IN GROUPS OF VANES SECURED TO SAID MANIFOLD. EACH GROUPS OF VANES HAVING A RADIALLY EXTENDING VANE, WITHT EH REMAINING VANES OF THAT GROUP PARALLEL THERETO. THE VANES OF EACH GROUP BEING A CONSTANT WIDTH APART FORMING A PASSAGE THEREBETWEEN. IN OPERATION THE FUEL IS INJECTED FROM SAID VANES WHILE THE OXIDIZER PASSES THROUGH SAID PASSAGE BETWEEN SAID VANES.

Description

May 23 1972 4 J. H. MITCHELL vEI'AI.` 'f 3,664,588

,PLATELET INJEc'ro 2 Sheets-Sheet 'l Filed oct." 22,"1969 I :Fuz

INVENTORJ. n. Mln-,wu

May 23, 1972 J, H, MlTCHELL ET AL 3,664,588

PLATELET INJECTOR 2 Sheets-Sheet 2 Filed Oct. 22, 1969 INVENTORJ. M170-lil 1- Marana United States Patent O 3,664,588 PLATELET INJEC'IOR .lames H. Mitchell, Rancho Cordova, and Hans H.

Mueggenburg, Diamond Springs, Calif., assgnors to the United States of America as represented by the Secretary of the Air Force Filed Oct. 22, 1969, Ser. No. 868,980 Int. Ci. F23d 11/10 U.S. Cl. 239-418 1 Claim ABSTRACT F THE DISCLOSURE A platelet injector having a manifold ring, and a plurality of vanes arranged in groups of vanes secured to said manifold. Each groups of vanes having a radially extending vane, with the remaining vanes of that group parallel thereto. The vanes of each group being a constant width apart forming a passage therebetween. In operation the fuel is injected from said vanes While the oxidizer passes through said passage between said vanes.

BACKGROUND OF THE INVENTION This invention relates generally to injectors for rocket engines, and more particularly to a new design for an injector which finds its main utility in the gas-liquid injection system.

The purpose of any rocket engine injector is to provide a means whereby the propellants; that is, the oxidizer and fuel are uniformly distributed, thoroughly mixed and atomized prior to vaporizing, igniting and combusting. Complete combustion must take place within a minimum of chamber volume for optimum efficiency. Injectors normally incorporate a manifolding system in which the propellants are physically distributed in specific areas adjacent to each other on the backside of the injector face. Orifices are then located into these areas to provide a pattern of oxidizer and fuel streams or sprays. The injection pattern is usually such that the fuel is in close proximity to the oxidizer at the proper mixture ratio; that is, the ow rate of the oxidizer with respect that of the fuel must be constant at any incremental area of the injector face. The pattern of propellant orifices thus create-d, primarily determines the effectiveness of the combustion process.

The development of injectors has by necessity followed empirical lines of approach. As a consequence there are many different types. The objective of the injector is to break up the liquid into droplets in order to increase the liquid surface and effect rapid mixing and vaporization. It has a similar function to the carburetor of an automobile engine.

There are many types of injectors which can be used. In the pressure injector, most commonly used, the uid is under pressure, and break-up into droplets results from the inherent instability of the fluid and its impact on the atmosphere, on another jet, or on a fixed plate. Such injectors can be formed in numerous patterns so that different uid streams will impinge upon one another or upon a common target plate. Special designs may contain within themselves deecting vanes, inverted cones, mixing chambers, or unique spiral flow paths.

In some injectors the assembly is a flat plate, the orifices being formed by drilling directly into the plate. The angle of liquid impingement is fixed by the angle used for drilling the orifices. Mixing can be improved by the addition of a target plate upon which the liquid streams can impinge, or by various arrangements of the orifices. Unless mixing is accomplished rapidly, especially during the ignition process, burning cannot take place before an ex- ICC cessive amount of propellant has accumllated in the combustion chamber. Such hard starts are not desirable.

Personal experience plays an important role in the particular design of the injector. The very individualistic ignition and burning properties of the various propellant systems adds to the specific nature of the injectors. The weight of the device also enters into its design. For example, poor mixing, which usually requires a long combustion chamber, can be improved by using a larger injector. However, if the increase in Weight of the large injector is greater than the reduction in weight obtained by using a shorter combustion chamber, there is no need to change the injector design.

Generally the greater the number of orifices the finer the pattern, and the more closely the criteria of uniform distribution, optimum mixing and atomization prior to combusting can be achieved. Assuming an injector has been designed to satisfy this criteria, the injector durability must then be established. The propellants once ignited produce extremely high temperature combustion gases (up to 6500 F.) which may be detrimental to the injector face. This is particularly an acute problem if the injection pattern is suc-h as to allow local recirculation of corrosive combustion 'gases from coming in contact with the face. Finally, combustion instability may be encountered having adverse effects on the entire rocket engine.

SUMMARY OF THE INVENTION The instant invention is a device (commonly called an injector) which overcomes all of the problems heretofore encountered in injector design.

A primary difference between various rocket engine injectors is in the fluid state of the propellants. In conventional liquid engines the injector employs both fuel and oxidizer in the liquid state; in some advanced engine concepts one yof the propellants enters the injector in the gaseous state while the other propellant is in the liquid state. It is the gas-liquid injection system for which the subject injector has been successfully developed and for which it finds its primary utility. There are other applications, however, that this invention may be applied to. In general, the invention can be employed in any gas-liquid injection system including air augmented rocket engines and jet engines as well as any commercial gas-liquid spraying systems. This injector provides a more uniform propellant distribution through a micro-orifice injection pattern than found in any previous injector for gas-liquid injection systems. This results in a highly efficient propellant combustion. The concept of this injector is also applicable to other related injection systems as will be pointed out hereinbelow.

The platelet injector of this invention is composed of a plurality of vanes, arranged in symmetrical groups of vanes. The vanes of each group vary in length. Uniform propellent distribution is achieved by locating the longest vane in each of the groups radially and the remaining vanes in each group parallel to it, so that a constant Width oxidizer passage remains between each vane. The radius of the leading edge of each vane is such so as to decrease oxidizer gas boundary turbulence, whereas the trailing edge of each vane has been chamfered to minimize the area exposed to the combustion zone.

Each vane is composed of a left hand and a right hand platelet, which are brazed together to form the finished vane. The inner sides of each platelet have matched chemically etched passages which form the internal fuel circuits when the halves are joined together. The fuel passages are designed in two alternative injection patterns. In one design, all fuel exits from the vanes in an axial direction, giving a showerhead pattern. In another design, the exit orifices are arranged in pairs which impinge at an included angle of approximately sixty degrees. The fuel is impinged upon itself as it leaves the vane which causes the fuel streams to break up into a ne fuel fog.

The vanes are secured to an injector manifold ring. In operation the oxidizer passes through the oxidizer passages between the vanes while the fuel is sprayed through the vanes after entering the vanes from the manifold.

It is therefore clearly evident that the instant invention not only accomplishes the two primary objectives of distribution and atomization, but it also has overcome the problem of reproduciblity. Because the critical low passages are manufactured into the part employing photographic techniques (i.e., the same negative can be used repeatedly over and over again) the invention lends itself to mass production of precise identical parts. Furthermore, it has been estimated that the cost of the injector (without taking cost advantage of mass production into consideration) is approximately one-half of the cost of a conventional injector.

Furthermore the injector of the invention can also be applied to liquid-liquid injection systems whereby the constant Width gap between the vanes would be filled with a second set of vanes being fed from above rather than the outer periphery. Doing this could have far-reaching implications for liquid-liquid rocket engine injectors, where proper propellant distribution, atomization, and stability have been a continuous problem. In a liquid-liquid injection system this invention offers several distinct additional advantages. The first two of which aid the combustion stability characteristic of the engine. By allowing a small controlled gap between adjacent platelets an acoustic injector face is obtained. Secondly, any number of vanes may be extended beyond the remaining vanes to act as baffles. Both of these features suppress combustion instability modes.

An additional important advantage that this invention offers a liquid-liquid system is that because the vanes are chamfered on the trailing edge, the metal most likely to be eroded, as on a conventional injector face, simply is not there to be eroded. Furthermore, the propellant velocity through the orifices in the exposed edge of the rvane is relatively high to aid the atomization of the injected propellant, thereby regeneratively cooling the trailing edge of the vane as well. Also, because the propellant circuits are bolted together and not permanently joined, several fuel injection patterns may be evaluated with one oxidizer injection pattern and vice-versa without building the entire injector over again.

Finally, it would seem reasonable that any manifolding system which lends itself to optimum propellant distribution in a gas-liquid injection system would also make an excellent heat exchanger. This is particularly true of this invention in that large surface areas are in contact with the fluids at a minimum of pressure drop.

It is therefore an object of this invention to provide an injector which finds its main utility in the gas-liquid injection system by providing a more uniform propellant injection system.

It is a further object of this inventionto provide an injector which produces extremely high fuel injection velocity.

lt is another object of this invention to provide an injector which is extremely durable in construction.

It is still another object of this invention to provide an injector which is economical to produce and which utilizes conventional, currently available components that lend themselves to standard mass production manufacturing techniques.

For a better understanding of the present invention, together with other and further objects thereof, reference is made to the following description taken in con- 4 nection with the acompanying drawing and its scope will be pointed out in the appended claim.

DESCRIPTION OF THE DRAWING FIG. 1 is a schematic top elevational view of the injector of this invention;

FIG. 2 is a pictoral view of a plurality of vanes of the injector of this invention;

FIG. 3 is a cross-sectional side elevational view of a portion of one side of the showerhead pattern vane of the injector of this invention;

FIG. 4 is a cross-sectional side elevational view of a portion of the other side of the showerhead pattern vane shown in FIG. 3 of the injector of this invention;

FIG. 5 is a cross-sectional side elevational View of a portion of one side of the impinging pattern vane of the injector of this invention;

FIG. 6 is a cross-sectional side elevational lview of a portion of the other side of the impinging pattern vane shown in FIG. 5 of the injector of this invention; and

FIG. 7 is a pictoral view of a completed vane of the injector of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT The platelet injector 10 of this invention shown schematically in FIG. 1 iinds its main utility in the gas-liquid type injection system. The injector 10 is made up of a plurality of vanes 12 and 12. The number of vanes 12 and 12 may vary, however, optimum results may be obtained `by utilizing 88 of such vanes 12 and 12' (as shown in FIG. 1) about 1A; inch thick and arranged in eight symmetrical groups of 11 vanes each. The vanes 12 vary in length from anywhere between 0.850 to 4.5 inch. The longest vane 12 of each group of vanes is located radially with respect to the center of an inlet manifold ring 14 with the remaining vanes 12 in each group parallel to vane 12. As the -vanes 12 in each group of vanes extend outward from vane 12 their length decreases proportionally. The injector construction of this invention further provides a constant width passage 16 for the oxidizer between each vane 12, Although the width of passage 16 may vary from injector to injector, best results are usually achieved if the width remains a constant 0.175 inch. The radius of the leading edge 18 (see FIG. 2) of each vane 12 is such as to decrease the oxidizer gas boundary turbulence, whereas the trailing edge 20 of each vane 12 has been chamfered to minimize the area exposed to the combustion zone.

The vanes 12 (as shown in FIGS. 1 and 2) are secured to the injector inlet manifold 14 by any suitable securing means such as by a weld joint around the inlet 21 of each vane 12. Additional strength may be obtained by further furnace brazing the joint to achieve a solid braze fillet around each vane 12 where it departs from the inlet manifold 14. Spacers 22 are iixedly secured (preferably by brazing) between the vanes 12. These spacers 22 not only assure the constant width passages 16 between the vanes 12, but also increase the resonant frequency of the vane 12, thereby minimizing the possibility of vane flutter.

Referring now to FIGS. 3-6, two alternative vane designs 24 and 26 are shown. Each of these vane designs 24 and 26 are composed of a left hand platelet 28 and 30 respectively and a right hand platelet 32 and 34, respectively. These platelets 28, 32 and 30, 34 when secured t0- gether by any suitable securing means such as welding, form the finished vane 12 shown in FIG. 7. The inner sides of each platelet 28, 30, 32 and 34 have chemically etched passages which form the internal fuel circuit passages 36 and 50 when the halves are joined together. The fuel circuit passages 36 and 50 are designed in two alternative configurations-the showerhead pattern vane design 26 of FIGS. 5 and 6.

In the showerhead pattern vane 24 shown in FIGS. 3 and. 4 each platelet 28 and 32 has a fuel flow circuit passage 36 etched into one side. The etched ow circuits 36 may be of any suitable depth but are preferably 0.015 inch deep so that when opposing sides are brazed together, a very accurate fuel ow circuit is achieved. To assure proper distribution within the vane 24, inlet lands 40 are spaced in such a way that the longest fuel flow path has the same resistance as the shortest path. A common manifold 42 at the end of the inlet lands assures further uniform distribution. Flow is then directed through a high pressure drop flow control zone 44. Flow is controlled by etching the passages on one side 32 only of the two platelet halves. Upon leaving the flow control zone 44, the high velocity fuel at approximately 160 ft./sec. enters a common diffusion zone 46 formed by the tapered portion of lands 40 prior to entering the injection orices 48. Fuel is injected in discrete streams from the trailing edge of the vane 24 at approximately 50 ft./sec. through a total of over 2000 such individual orices in the injector. The primary combustor oxidizer gas passes between the lvanes at approximately 125 ft./ sec.

The impinging pattern platelet vane 26 shown in FIGS. and v6 is identical in construction to the showerhead platelet vane 24 with the exception of the configuration and depth of the photo-etched fuel circuit passages 50 within the vanes. Whereas the showerhead vane injector has over 2000 orices 48, the impinging pattern vane injector is composed of over 3500 orifices 52. These orilices 52 are arranged in pairs which impinge at an included angle of substantially 60 degrees and are smaller in size compared to the showerhead orifices 48. The reduction in fuel orifice area allows the fuel injection velocity to be increased from approximately 50 to 90 ft./sec. thereby increasing the atomization of the impinging fuel. The increase in injection velocity, however, increases the pressure drop of the vane across the injection orifices 52. Thus, to obtain the same total pressure drop through the vanes as in the showerhead design 24, the flow control zone 44 is etched on both the left and right hand side 30 and 34 to a combined depth of approximately 0.030 in. instead of 0.015 as in the showerhead pattern.

In use either the showerhead vane design 24 or the impinging vane design 26 may be utilized with the inlet manifold 14 'as shown in FIG. 1. The fuel enters the manifold 14 through inlets 15 and from manifold 14 enters inlets 21 in vanes 12. The oxidizer gas passes through the passages 16. Due to the internal fuel circuit passages 36 and the fuel is expelled at a high velocity. By the use of the injector 10 of the instant invention the propellants are uniformly distributed and thoroughly mixed and atomized prior to vaporizing, igniting and combusting in a rocket.

Although the invention has been described with reference to a particular embodiment, it will be understood to those skilled in the art that the invention is capable of a variety of alternative embodiments within the spirit and scope of the appended claim.

We claim:

1. A platelet injector comprising a main manifold in the shape of a ring, a plurality of vanes arranged in groups of vanes, one vane of each of said groups of vanes being located radially with respect to the center of said manifold and the remaining vanes of each of said groups of -vanes being parallel thereto, said vanes of each of said groups of vanes being a constant width apart from each other forming a passage therebetween through which an oxidizer can pass, each of said vanes being formed of identical left and right hand platelets having a plurality of ilow passages etched therein connected at one end to a plurality of injection orifices and at the other end to a common inlet manifold within each of said platelets, said inlet manifold being lixedly secured to said main manifold and said orices being arranged in pairs which impinge at an included angle of substantially sixty degrees whereby fuel enters said inlet manifold from said main manifold and exits from said orifices.

References Cited UNITED STATES PATENTS 3,141,301 7/1964 Whitney 60-39.46 3,200,589 8/1965 Mower et al 60-39.74A 3,413,704 12/1968 Addoms, Jr., et al. 60-258 SAMUEL FEINBERG, Primary Examiner

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