Slotted multi-nozzle grid with integrated cooling channels

An apparatus includes a slotted multi-nozzle grid with a plate having multiple elongated slotlettes through the plate. Each of at least some of the slotlettes has a convergent input, a divergent output, and a narrower throat portion separating the convergent input and the divergent output. At least some of the slotlettes are arranged in multiple rows. The plate further includes multiple cooling channels through the plate. At least some of the cooling channels are located between the rows of slotlettes. Each cooling channel is configured to transport coolant through the plate in order to cool the plate, such as to cool the plate as hot combustion gases pass through the plate. Each of at least some of the rows may include at least two slotlettes, and two adjacent slotlettes in one row may be separated by a structural ligament (which may have a tear-drop cross-sectional shape).

TECHNICAL FIELD

This disclosure is generally directed to propulsion systems. More specifically, this disclosure relates to a slotted multi-nozzle grid (MNG) with integrated cooling channels.

BACKGROUND

Certain types of vehicles, such as rockets, include one or more nozzles as part of a liquid propulsion system. In a liquid propulsion system, a liquid propellant is ignited, and one or more nozzles expand and accelerate the resulting combustion gases. As a result, the gases exit the nozzles at very high speeds, propelling the vehicle in a desired direction.

Cylindrical- or cone-shaped nozzles have been used for many years. Unfortunately, these types of nozzles are often quite large. As a result, these types of nozzles may not be desirable in certain situations due to volume or weight limitations. A multi-nozzle grid (MNG) is a two-dimensional or three-dimensional collection of small nozzles called “nozzlettes” in a grid pattern. A multi-nozzle grid can provide the same performance as a conventional cylindrical- or cone-shaped nozzle but in a much smaller space.

SUMMARY

This disclosure provides a slotted multi-nozzle grid (MNG) with integrated cooling channels. The cooling channels are configured to utilize a coolant to remove heat energy from the MNG, such as when hot combustion gases flow through the MNG, thereby helping to prevent the MNG from being damaged by the heat energy.

In a first embodiment, an apparatus includes a slotted multi-nozzle grid with a plate having multiple elongated slotlettes through the plate. Each of at least some of the slotlettes has a convergent input, a divergent output, and a narrower throat portion separating the convergent input and the divergent output. At least some of the slotlettes are arranged in multiple rows. The plate further includes multiple cooling channels through the plate. At least some of the cooling channels are located between the rows of slotlettes. Each cooling channel is configured to transport coolant through the plate in order to cool the plate.

In a second embodiment, a system includes a combustion chamber configured to generate combustion gases. The system also includes a slotted multi-nozzle grid connected to an outlet of the combustion chamber and through which at least some of the combustion gases pass. The slotted multi-nozzle grid includes a plate. The plate includes multiple elongated slotlettes through the plate. Each of at least some of the slotlettes has a convergent input, a divergent output, and a narrower throat portion separating the convergent input and the divergent output. At least some of the slotlettes are arranged in multiple rows. The plate also includes multiple cooling channels through the plate. At least some of the cooling channels are located between the rows of slotlettes. Each cooling channel is configured to transport coolant through the plate in order to cool the plate.

In a third embodiment, a method includes forming a slotted multi-nozzle grid having a plate. Forming the slotted multi-nozzle grid includes forming multiple elongated slotlettes through the plate. Each of at least some of the slotlettes has a convergent input, a divergent output, and a narrower throat portion separating the convergent input and the divergent output. At least some of the slotlettes are arranged in multiple rows. Forming the slotted multi-nozzle grid also includes forming multiple cooling channels through the plate. At least some of the cooling channels are located between the rows of slotlettes. Each cooling channel is configured to transport coolant through the plate in order to cool the plate.

DETAILED DESCRIPTION

FIGS. 1A and 1Billustrate an example slotted multi-nozzle grid (MNG)100with integrated cooling channels in accordance with this disclosure. As shown inFIG. 1A, the MNG100includes a plate102having multiple slotlettes104formed through the plate102. The slotlettes104allow combustion gases or other material to pass through the plate102during operation of a larger device or system. The use of multiple slotlettes104in the plate102can help ease production requirements and yet allow the MNG100to conform to the laws of fluid mechanics, thermodynamics, and structural mechanics. Moreover, the use of multiple slotlettes104in the plate102can help to shorten the overall length of the MNG100compared to conventional nozzles, which could be useful in applications where volume or mass limitations prevent use of conventional nozzles. The MNG100could be used in any suitable device or system. As particular examples, the MNG100could be used in third-stage rocket motors, divert thrusters, and thrusters of attitude control systems.

The plate102could be formed from any suitable material(s) and in any suitable manner. For example, the plate102could represent a single machined piece or a molded plate of a homogenous monolithic material or composite material. Each slotlette104could represent any suitable elongated nozzle structure. The MNG100could include any suitable number of slotlettes104in any suitable configuration.

In this example, the slotlettes104are arranged in multiple rows106, and adjacent slotlettes104in a row106are separated by structural ligaments108. The structural ligaments108help to maintain the structural strength and stiffness of the slotted plate102. The number of slotlettes104in a row106(and thus the number of structural ligaments108in a row106) can vary and may be determined by performance (such as volume flow and velocity of discharge gases) and structural requirements of the desired application. The total number of rows106in the plate102can also be determined by the desired performance and structural requirements of the MNG100. Each structural ligament108includes any suitable portion of a plate between slotlettes in a row of slotlettes.

In this example, an upper surface110of the MNG100represents the convergent side of the MNG100, and a lower surface112of the MNG100represents the divergent side of the MNG100. Gas enters the slotlettes104from the convergent side and exits the slotlettes104on the divergent side. The plate102also includes multiple flanges114that allow bolts or other connectors to couple the plate102to a combustion chamber or other structure so that material flows into the MNG100through the surface110.

As shown inFIGS. 1A and 1B, the plate102includes multiple cooling channels116. The cooling channels116denote substantially straight elongated orifices or paths through which coolant can flow through the plate102. The cooling channels116can be parallel and coplanar as shown here. The cooling channels116are interdigitated or interleaved between the rows106of slotlettes104. However, the cooling channels116could be arranged in other geometries or in a pattern with headers and multiple connecting channels between headers.

Each cooling channel116represents any suitable passageway for coolant to flow through a multi-grid nozzle. In this example, each cooling channel116represents a generally cylindrical passageway with wider ends, although any other suitable cross-sectional shape(s) could be used. Any suitable coolant can be used in the cooling channels116, such as a liquid fuel, an oxidizer, water, a water and ethylene glycol mixture, atmospheric gas, or cryogenic gas.

As shown inFIG. 3described below, the slotlettes104are supported by ribs that form three-dimensional endings of the slotlettes104, thus providing both efficient flow accelerators in converging-diverging nozzles and structural reinforcements. The rows106of slotlettes104inFIG. 1Abound the structural tubes that contain the cooling channels118, allowing coolant to flow through the cooling channels118and through the plate102to transfer heat from the plate102to the coolant.

Among other things, the use of the cooling channels116facilitates efficient heat removal from the plate102. The cooling channels116here are substantially straight, which can facilitate higher mass flow of coolant through the cooling channels116and therefore greater heat removal. Moreover, the plate102can include variable-length slotlettes104separated by structural ligaments108, which help to create a strong and stiff plate102. Depending on the application, these features could provide various advantages, such as the ability to perform longer-duration thrusts using a rocket or other liquid propulsion system.

AlthoughFIGS. 1A and 1Billustrate one example of a slotted MNG100with integrated cooling channels116, various changes may be made toFIGS. 1A and 1B. For example, the relative size and shape of each component inFIGS. 1A and 1Bare for illustration only. Each component in the MNG100could have any suitable size, shape, and dimensions. Also, the arrangement of the slotlettes104inFIGS. 1A and 1Bis for illustration only. An MNG could have any suitable number of slotlettes104in any suitable arrangement.

FIGS. 2 through 4illustrate example components in a slotted MNG100in accordance with this disclosure. As shown inFIG. 2, two slotlettes104are shown along with a cooling channel116. A conventional MNG nozzlette's geometry is typically a revolved surface. The geometry of a slotlette104can be viewed as a conventional nozzlette that is cut in half and translated (stretched) to a desired length, where surfaces connect the two halves so that the surfaces are tangent to the edges of the halves and form the desired slotlette104. InFIG. 2, each slotlette104includes a convergent input202and a divergent output204. Both the convergent input202and the divergent output204have substantially straight sides and rounded ends, and the divergent output204has a larger height than the convergent input202. Each slotlette104also includes a narrower throat portion206that separates the convergent input and the divergent output and that allows expansion of gases from the convergent input202into the divergent output204, providing acceleration.

As shown inFIGS. 2 and 3, each of the cooling channels116is located between adjacent rows106of slotlettes104. In particular, slotlettes in adjacent rows106have convergent inputs202that angle towards one another, divergent outputs204that angle towards one another, and a cooling channel116that resides within the area between the convergent inputs202and divergent outputs204of the slotlettes in adjacent rows. In some embodiments, the cooling channels116represent areas of the plate102that have been removed, such as via drilling or other suitable processing technique. Here, the cooling channels116traverse across the plate102so that during combustion, for example, heat generated in a combustion chamber is transferred through the plate102into the coolant flowing through the cooling channels116. The unique geometry of the slotlettes104allows the cooling channels116to pass through the plate102from one side and exit through the other side. This transfers heat from the convergent side of the plate102through the walls of the otherwise solid plate102and into the cooling channels116.

FIG. 4illustrates an example of the structural ligaments108in the MNG100. Each structural ligament108shown is bounded by the end of one slotlette104in a row106and the beginning of another slotlette104in the same row106. The material between the slotlettes104provides the structural material for strength and stiffness of the plate102. Each structural ligament108here has a tear-drop shape in cross-section, and the design of the tear-drop shape can be modified depending on the application.

AlthoughFIGS. 2 through 4illustrate examples of components in a slotted MNG100, various changes may be made toFIGS. 2 through 4. For example, the slotlettes104could have any suitable size and shape. Also, each structural ligament108could have any other suitable size and cross-sectional shape. In addition, note that the slotlettes104shown here are configured to receive hot gases and direct the hot gases in the same general direction. However, at least some of the slotlettes104could have angled portions to direct thrust in other directions.

FIGS. 5A through 5Iillustrate an example technique for identifying a design geometry of a slotted MNG in accordance with this disclosure. In this example, the design begins with multiple straight tubes502laying side-by-side as shown inFIG. 5A. These tubes502denote areas where the cooling channels116are to be formed. In some embodiments, the center line of each tube502lies in the same plane, the tubes502are parallel to each other, there is an equal offset distance between each adjacent pair of tubes502, and all tubes502have the same diameter. The tubes' center-to-center offset and diameter can be determined in any suitable manner, such as based on performance, cooling and structural analysis. Also, the number of slotlette rows and tubes can be determined in any suitable manner, such as the diameter of a port's bounding circle504and manufacturing limits.

As shown inFIG. 5B, the geometry surrounding each cooling tube502forms a structural rib506. In this example, the structural rib506has a tear-drop or airfoil shape in cross-section, which can help to minimize stagnation zones. This structural rib506extends across the bounding circle504of the port. The rib geometry forms half of one row of slotlettes and half of a neighboring row of slotlettes. Likewise, a tube502encased by the structure forms one of the cooling channels116described above. This is repeated for each cooling tube502, creating multiple straight structural ribs506a-506nas shown inFIG. 5C. Outboard surface slots508intersect the bounding circle504of the port as shown inFIG. 5D. The outboard surface slots508represent “unslotted” areas of the MNG adjacent to the outer cooling tubes502. With the definition of the outboard surface slots508, the geometry of the ribs is completed.

As shown inFIG. 5E, the bounding circle504is extended to form a ring510around a portion of the ribs506a-506n. Here, the ring510defines the outer limits of the ribs506a-506n. As shown inFIG. 5F, the geometry of the ribs506a-506nis bounded by the ring510, so the ribs506a-506nno longer extend outside of the ring510.

As shown inFIG. 5G, surfaces512define the outer geometry of the plate102. The surfaces512therefore identify the solid portions of the plate102(which forms the thermal mass), and the cooling tubes502traverse the entire length of the plate. The size of the plate102may be determined by a tradeoff between how much thermal mass is need versus how much mass can be saved. The side surfaces of the ribs506a-506nform the walls or outer surfaces of slotlettes to be fabricated. A portion514of the plate is raised, which could be sized to fit within a combustion chamber or other structure.FIG. 5Hshows a side view of the structure ofFIG. 5G, with each cooling cylinder502is surrounded by a rib506. The airfoil or tear-drop shape of the cross section is apparent here.

As shown inFIG. 5I, slotlettes are defined between the ribs506a-506n. A classic nozzlette516is shown here for illustrative purposes only. To form a slotlette, the nozzlette516can be divided in half, and the halves518can be separated from one another. Each slotlette is then formed using two separated halves518. Each slotlette therefore represents a nozzlette516that is stretched in one axis to make a longer slotlette. The ends of each slotlette share the geometry of the structural ligaments108. As can be seen here, the resulting cooling channels are interdigitated between slotlettes, and slotlettes are of varying length to form the structural ligaments.

AlthoughFIGS. 5A through 5Iillustrate one example of a technique for identifying a design geometry of a slotted MNG, various changes may be made toFIGS. 5A through 5I. For example, any other suitable technique could be used to design a slotted MNG.

FIG. 6illustrates an example engine and nozzle assembly600of a vehicle with a slotted MNG in accordance with this disclosure. As shown inFIG. 6, the assembly600includes a liquid propulsion system having a combustion chamber602. An outlet of the combustion chamber602is covered by a slotted MNG604. The slotted MNG604could represent the MNG100shown inFIGS. 1A and 1Babove. As noted previously, a slotted MNG can provide the same or similar functionality as a larger conventional nozzle (such as a cylindrical or conical nozzle) but in a smaller package. In some embodiments, the slotted MNG604could have a length that is roughly 20% the length of a conventional nozzle. This can provide significant volume and weight reductions. The remaining components of the assembly600are not described here as they do not relate to the use of a slotted MNG.

AlthoughFIG. 6illustrates one example of an engine and nozzle assembly600of a vehicle with a slotted MNG, various changes may be made toFIG. 6. For example, a slotted MNG could be used with any suitable larger device or system, such as any vehicle using a liquid propulsion system.

FIG. 7illustrates an example method700for forming a slotted MNG with integrated cooling channels in accordance with this disclosure. As shown inFIG. 7, the design for a slotted MNG is identified at step702. This could include, for example, using the technique shown inFIGS. 5A through 5Ito design a slotted MNG100. As a particular example, this could include identifying the number and size of multiple cooling channels116and the number and arrangement of multiple slotlettes.

A plate of material is obtained at step704. This could include, for example, forming material into the desired overall shape of the MNG100. This could be accomplished by machining a piece of material into the desired shape or using a mold to form material into the desired shape.

Cooling channels are formed through the plate at step706, and elongated slotlettes are formed through the plate at step708. This could include, for example, drilling or otherwise forming the cooling channels116through the plate102. This could also include machining or otherwise forming the slotlettes104through the plate102. Note that any suitable technique could be used to form each feature of the MNG100. Formation of the slotted MNG is completed at step710. This could include, for example, forming flanges114or other features of the slotted MNG100.

AlthoughFIG. 7illustrates one example of a method700for forming a slotted MNG with integrated cooling channels, various changes may be made toFIG. 7. For example, while shown as a series of steps, various steps in each figure could overlap, occur in parallel, or occur in a different order. As a particular example, the MNG100could be formed using a mold, and multiple features of the MNG100(such as the plate102itself along with the cooling channels116and/or the slotlettes104) could be formed at the same time.