US3091520A - Radial outflow catalytic pack - Google Patents

Description

May 28, 1963 F. A. NEWBURN RADIAL OUTF'LOW CATALYTIC PACK 3 Sheets-Sheet 1 Filed Dec. 19, 1958 INVENTOR. FLOYD A. NEWBURN ATTORNEY May 28, 1963 F. A. NEWBURN RADIAL OUTFLOW CATALYTIC PACK 5 Sheets-Sheet 2 Filed Dec. 19, 1958 INVENTOR. FLOYD A. NEWBURN fit S, W M MM ATTORNEY May 28, 1963 F. A. NEWBURN 3,091,520

RADIAL OUTFLOW CATALYTIC PACK Filed Dec. 19, 1958 3 Sheets-Sheet 3 FIG. 3

INVENTOR. FLOYD A. NEWBURN ATTORNEY 3,091,520 Patented May 1963 3,091,520 RADIAL OUTFLOW CATALYTMI PACK Floyd A. Newburn, Woodland Hills, Calif., assignor to North American Aviation, Inc. Filed Dec. 19, 1953, Ser. No. 783,641 3 Claims. (Cl. 23-288) The present invention is directed to a catalytic pack assembly. More particularly, the invention concerns a propellent injection system including a catalytic screen pack for decomposing a propellent for driving a turbine or for operation of a rocket engine.

The catalytic pack of the present invention permits radially outward flow of a propellent through a screen pack wherein the propellent is decomposed and the hot gases of the reaction products directed in such a manner as to do useful work. Heretofore various types of screen packs have been used in gas generators for driving turbines or for generating gases usable in the propulsion of missiles, rockets, airplanes, torpedoes or the like. The most common type of screen pack has included a series of stacked screens either made of a catalytic substance or having a coating of catalytic substance thereon in which the propellent is passed axially through the stacked screens, i.c. perpendicular to the screens. The major disadvantages of this axial flow type pack are (1) that the device has the same cross-sectional area for both the liquid inlet and the gas outlet, which is undesirable since the gaseous products have several times the volume of the liquid, and (2) a high pressure drop which is further aggravated by (3) compression of the screens during use. This type of screen pack also is characterized by the flow of silver or other catalytic material from the top screens to the lower screens thereby blocking the openings in the mesh of the lower screens. Further, a large diameter chamber is required for large flow rates and unwanted heat can not flow by conduction from the hot down-stream screens to the cool up-stream screens to prevent over heating of the down-stream screens. Various modifications have been made of the axial flow type packs but each has retained flow characteristics which are axial and thus suffer from the disadvantages set out above.

Basically, the present invention is directed to an injector system including a catalytic pack particularly adapted for the above mentioned applications in which a series of annular parallel catalytic members recited herein as screens are formed into a stack having inlet means at the internal periphery of the series of stacked screens allowing flow of propellent radially or laterally outwardly through the pack of screens in a direction parallel to the screens themselves. By this construction compression of the screens is prevented along with the resultant tendency for screen pack pressure drop'to increase with run time. Further, the present construction provides a thermal heat flow path for conduction of heat from the hot part of the screen to the cool part, thereby reducing the tendency of the screens to melt when used with a liquid propellent having high inlet temperatures. Further, the screen pack of applicants invention may be assembled as a package which is easily insertable within a gas generator or propulsion engine. The device by its novel features lends itself to a small diameter assembly of relatively light weight.

An object of this invention is to provide a novel catalytic pack.

A further object of this invention is to provide a catalytic screen pack assembly having radially outward flow of fluid through the pack laterally through the screens therein.

A still further object of this invention is to provide a hydrogen peroxide screen pack usable in gas generator and rocket engine applications.

An additional object of this invention is to provide a propellent injection system for a rocket engine.

The above objects as well as other objects of this in vention will be apparent from the description of the accompanying drawings in which:

FIG. 1 is a partial cross-sectional view of a screen pack within a rocket engine;

FIG. 2 is a top view of the screen pack per se taken on the lines 2-2 in FIG. 1;

And FIG. 3 is a partial cross-sectional view of a gas generator screen pack.

The catalytic pack is designated generally .by the numeral 11 and is shown inserted into the forward end of a rocket engine thrust chamber assembly 10. The thrust chamber 10 comprises an annular shell 12 made in the form of a double wall or abutting, longitudinallyextending, peripheral tubes which extends from the forward portion of the thrust chamber to and including the rocket nozzle portion. Intermediate the ends of chamher well 12 the usual constrictive nozzle throat section 12a is formed. As is known, the rocket engine thrust chamber has an open divergent opening through which combustion gases are ejected providing the propulsive thrust delivered by the rocket engine assembly. On the end of the thrust chamber 10 opposite the exit nozzle portion is a dome 13 which generally seals the thrust chamber against the pressures developed during the combustion processes.

The catalytic screen pack is adapted to be placed within the thrust chamber and likewise be sealed externally by the dome 13. The screen pack 11 comprises a first forward support plate 14 of generally circular configuration and a rear support plate 15 of generally circular configuration between which are stacked a series of abutting annular, flat catalytic screens 16 parallel to each other and generally parallel to plates 14 and 15. While the parallel catalytic members are herein described as screens which are desirable due to high surface area, the present invention contemplates the use of discs, perforated or imperforated, stacked to allow lateral flow of fluid therethrough. It is to be realized that in a typical rocket engine application of the present combination over two hundred screens are stacked in an axial distance between five and six inches. In this particular application inert screens are generally alternated with active screens. The inert screens prevent fusion of active screens to each other, a characteristic which is especially typical with silver type catalyst. They also provide a means for con trolling the pressure drop through the pack. The pressure drop increases with increased number of mesh per inch. It has been found to be advantageous to have several (i.e. three) active screens at each end of the screen pack in order to prevent liquid by-pass of the pack. The active screens fuse together at the ends of the pack to block liquid flow. The pack of screens 16 are held in a prescribed amount of compression by the end plates 14 and 15 and are held in lateral alignment by a pair of perforated cylinders 17 and 18 extending around the exterior periphery of the screens and the internal periphery of the screens, respectively. The forward support plate 14 is provided with an inlet aperture or apertures 19 extending around an inner peripheral portion having a maximum diameter no greater than the internal diameter of the inner perforated cylinder 18. The inlet aperture 19 permits flow of monopropellent, in the case of hydrogen peroxide, to the inner perforated cylinder at a desired pressure drop. The propellent then passes through the inner cylinder and radially outward in parallel flow through the parallel screens wherein the propellent is decomposed and the gaseous products forced out laterally through the outer peripheral perforated cylinder 17 into a relatively large volume space between the cylinder 17 and the inner periphery of the wall 12 of the thrust chamber 19. It can thus be seen that a relatively small liquid volume chamber is provided internally of the pack and a relatively large gaseous volume chamber provided radially externally of the pack. A bafile extending from the inlet apertures 19 to the forward support plate 15 forms a constant liquid velocity inlet cone for directing the monopropellent radially outward in substantially constant flow through the entire axial length of the stacked screens. The pressure drop through the catalyst pack is thus controlled by apertures 19 obviating the necessity of accurately drilling holes in inner cylinder 18. The gaseous products exiting from the perforated cylinder 17 are deflected by the baffie 21 rearwardly toward a fuel injector which has a face exposed to the combustion chamber volume 24 within thrust chamber 10. Injector 25 is normally spaced from the interior walls of shell 12 as shown at 25a. Gases extending from the catalytic pack pass through the annular space 25a as well as being deflected by a deflector ring 22 attached to the injector 25. The gases so deflected are forced through various openings 43 between fuel injection rings in injector 25 The hot gases and the fuel react in the combustion chamber 24 on the downstream side of the injector face.

Flanges 26 and 27 are provided on the dome 13 and shell 12, respectively, and are adapted to be brought into sealing engagement by a nut and bolt combination or other clamping means 28 which exerts pressure on a copper tube seal 29 sealing the thrust chamber assembly at the forward end. The flow path of the propellent, explained hereafter in terms of hydrogen peroxide, enters the thrust chamber assembly at an inlet 30 ordinarily from a turbine pump or other source of pressurized propellent (not shown). The inlet 30 along with an annular ring forms a manifold which is connected to a series of tubular passages 32 around the periphery of the thrust chamber nozzle and within the walls of shell 12. In a preferred type of construction the tubular passages are formed from rectangular tubes which abut each other to form shell 12. The tubes are laid up in a jig, are brazed to each other and are held by circumferential bands 9. The propellent acts to regeneratively cool the nozzle, throat area 12a and the interior wall of shell 12 in the area of the combustion chamber and the inserted screen pack. Flow of hydrogen peroxide from the tubes 32 exists at the dome 13 and flows radially inward through channel 33 to the inlet apertures 19 from where the flow passes radially outward through the screens 16 as here tofore explained.

In the particular tubular thrust chamber disclosed the products of decomposition are mixed and combusted in combustion chamber 24 with fuel which is passed into the thrust chamber through an entrance connection 40 externally of the screen pack to an internal passage 4-1 to fuel injector 25. Injector 25 is attached to the aft end of injector stem 40. The fuel flows through the main passage 42 of the injector and into various lateral passages 44 and is spray injected at 46 into the combustion chamber wherein it intimately contacts corresponding sprays 45 of gaseous products from the screen pack and combusts forming combustion products which are expanded through the nozzle of the thrust chamber to provide the propulsive force.

The screen pack is assembled between the support plates 14 and 15 by providing end annular plates 62 and 64 which rest on ridges 61 and 65 in the rear and forward support plates, respectively. Tabs 60 and 63 are adapted to be bent over the exterior surfaces of plates 62 and 64 to hold the plates 16 in compression. In a typical installation the screens are compressed under a preload of approximately 2,000 pounds when the end plates are flat. Therefore, the cartridge bulges outward at the ends when not assembled in a rocket motor or into a turbine gas generator as the end plates 62 and 64 act as Belleville type springs. This preloading provides a spring characteristic to the assembly which in turn provides a load which is concentrated at end surfaces 66 and 67 on the active screens to provide a seal. The cartridge is held in place by the flanged holding means discussed above. It will be readily apparent that other means such as a thread or nut combination on the central shaft 40 could be used to keep the catalytic pack 11 in assembled condition. Such a construction is seen in FIG. 3.

As is well-known in the art, liquid hydrogen peroxide flowing through a suitable catalyst is decomposed into oxygen and super heated steam. The deflector ring 22 which is at an approximately 45 angle to the injector Z5 distributes the hot gases more uniformly through the injector. Without the deflector ring 22 the main gas flow would be along the walls of the chamber due to the high gas momentum in that direction. For a gas turbine drive a deflector ring is not necessary as the gases would enter the turbine manifold around the circumference of the screen pack as shown in FIG. 3.

FIG 2 shows a top view of the inserted cartridge taken on the line 22 of FIG. 1. The annular plates 62 and 64 are shown held in nearly perpendicular position to the peripheral perforated cylinder 17 by means of a series of tabs 63 adapted to be bent over onto the top surface of the annular end disc 64. A clear showing of one of the main advantages of the present invention is shown in FIG. 2 wherein the entering liquid volume is in the crosssectional area between diameters 18 and 20 whereas the needed higher volumetric area for the gaseous products is situated in the larger annular area formed between diameters 17 and 21.

FIG. 3 shows the screen pack described with respect to FIG. 1 in use in a gas generator. The gas generator, generally denoted 70, comprises an outer casing 71, an end dome containing a liquid inlet 72, the screen pack 90, a partition wall 73 opposite the inlet 72 and having multiple peripheral nozzle exits 7 therein, and a turbine wheel 75 which is driven by the gases exiting from nozzles '74 against turbine blade tips 76 as is known in the art. The turbine drive shaft 77 is coupled (not shown) to suitable pumps (not shown) or generators for doing useful work. Turbine exhaust gases are removed through passage 86. The screen pack assembly is held on stud 78 between a shoulder 7% and a retaining nut 80 exterior of the dome end 85. The assembly 90, and more particularly the end plate 87, abuts the casing 71 at shoulder 81 and is held within the casing by the clamping means 82 associated with flanges 33 and 84 integral with casing 71 and demo 85, respectively. 'In operation liquid flows through inlet 72, flows radially outwardly through the pack 90 as described in FIG. 1 and is directed to the nozzles exiting against the turbine Wheel driving the same.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. A catalytic screen pack assembly comprising a forward support plate, a rear support plate spaced from and in parallel alignment with said forward support plate, a series of co-extensive abutting alternate catalytic and inert annular screens parallel to and in the space between said support plates, said series comprising at least one catalytic screen adjacent said plates for preventing a fluid by-pass thereat, means laterally holding said screens between said support plates, and a constant velocity fluid inlet means at the inner annular periphery of said screens for passing -a substantially constant fluid flow radially through said screens to the exterior periphery thereof.

2. A catalytic screen pack assembly comprising a series of alternate catalyst and inert screens stacked one next to another in parallel relationship, perforated wall means radially confining the screens at peripheral edges thereof, support means at each end of the stacked screens holding the screens together in said stack, a tapered fluid inlet extending between said support means for uniformly passing fluid radially outward through said screens and said perforated Wall means at a substantially uniform velocity, and a baflle means constructed and arranged radially of said Wall means for controlling the flow of the products of a reaction catalyzed by said screens and for limiting radial heat transfer.

3. A catalytic screen pack assembly comprising a series of alternate annular open mesh catalyst and inert screens stacked one next to another in parallel relationship, per forated wall means radially confining the screens at inner and outer peripheral edges thereof, support means at each end of the stacked screens holding the screens together in said stack, a fluid inlet means comprising a first predetermined volume extending between said suppont means for passing fluid radially outward through said screens and said perforated wall means, and means comprising a second predetermined volume larger than said first predetermined volume for collecting and controlling the flow of fluid exiting radially of said screens.

References Cited in the file of this patent UNITED STATES PATENTS 1,979,187 Bindley Oct. 30, 1934 2,639,224 McAfee May 19, 1953 2,865,721 Lane et al. Dec. 23, 1958 2,887,456 Halford et a1 May 19, 1959 FOREIGN PATENTS 274,952 Great Britain July 28, 1927 727,720 Great Britain Apr. 6, 1955 771,896 Great Britain Apr. 3, 1957 793,300 Great Britain Apr. 16, 1958

Claims (1)

1. A CATALYTIC SCREEN PACK ASSEMBLY COMPRISING A FORWARD SUPPORT PLATE, A REAR SUPPORT PLATE SPACED FROM AND IN PARALLEL ALIGNMENT WITH SAID FORWARD SUPPORT PLATE, A SERIES OF CO-EXTENSIVE ABUTTING ALTERNATE CATALYTIC AND INERT ANNULAR SCREENS PARALLEL TO AND IN THE SPACE BETWEEN SAID SUPPORT PLATES, SAID SERIES COMPRISING AT LEAST ONE CATALYTIC SCREEN ADJACENT SAID PLATES FOR PREVENTING A FLUID BY-PASS THREAT, MEANS LATERALLY HOLDING SAID SCREENS BETWEEN SAID SUPPORT PLATES, AND A CONSTANT VELOCITY FLUID INLET MEANS AT THE INNER ANNULAR PERIPHERY OF SAID SCREENS FOR PASSING A SUBSTANTIALLY CONSTANT FLUID FLOW RADIALLY THROUGH SAID SCREENS TO THE EXTERIOR PERIPHERY THEREOF.

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