Patent Description:
The present disclosure relates generally to high temperature reactor systems. In particular, the system may include at least two different types of pipes or tubes.

Tubes or pipes are used to transport fluids through high-temperature systems such as high temperature reactors. Some systems include different types of tubes, which may include different materials of construction. Joining different types of tubes may be challenging, since the different materials of construction may have different material properties.

It is known from <CIT> or <CIT> to provide a pipeline connection structure between pipes with different coefficients of thermal expansion.

It is known from <CIT> to provide a multilayer ceramic composite tube.

In general, the disclosure describes systems, such as high-temperature reactor systems, jet or rocket engines, or other similar high temperature systems which include at least two different types of tubes. The different types of tubes may have different coefficients of thermal expansion (CTE). As such, joining the different types of tubes may be difficult, as their tendency to expand and contract at different rates during temperature changes may lead to fluid leakage through gaps that form between sealing surfaces and/or cracked components. Disclosed herein is a joining assembly which allows tubes having different CTEs to be joined and cycled through time periods of relatively low temperature and relatively high temperature with reduced leaking or fracturing.

An assembly is disclosed which includes a first tube. The first tube includes a first end configured to receive a second tube. The second tube includes a first end which is configured to both slidably translate into the first end of the first tube and to receive an insert. The insert is configured to be disposed within a first portion of the second tube near the first end of the second tube. The first tube, the second tube, and the insert are configured to form a seal, and a coefficient of thermal expansion (CTE) of the first tube is similar to a CTE of the insert and different from a CTE of the second tube.

Techniques according to the present disclosure include joining a first tube and a second tube. Joining the first tube and the second tube includes slidably translating a first end of a second tube into a first end of the first tube. The technique also includes slidably translating an insert into position within a first portion of the second tube near the first end of the second tube. Slidably translating the insert into the second tube and the second tube into the first tube forms a seal. The coefficient of thermal expansion (CTE) of the first tube is similar to a CTE of the insert and different from a CTE of the second tube.

Some optional features are defined by the dependent claims.

The details of one or more examples are set forth in the accompanying drawings and the description below, where like symbols indicate like elements.

High temperature reactors and other high temperature systems may include tubes for transporting fluids. Such systems may include at least two different types of tubes, such as, for example, a ceramic tube and a metal or metal alloy tube. Ceramic tubes may be used in high temperature systems because they have excellent thermal shock resistance due to a low coefficient of thermal expansion (CTE), the inherent material property that dictates the rate at which a material expands with increase in temperature. Metal or metal alloy tubes may be used on high temperature system for various reasons, including compatibility with low temperature plumbing, allowing for the use of bellow, or other sealing and flow requirements.

Ceramic tubes may have a low CTE, such as on the order of about <NUM>-<NUM> parts per million per degree Celsius (ppm/°C), while metal or metal alloy tubes may have a higher CTE, such as on the order of <NUM>-<NUM> ppm/°C. Joining tubes with differing CTEs presents a problem in areas which are exposed to high temperatures and/or temperature swings, because the tubes expand and contract differently (e.g., different thermal displacements, different rates of expansion or contraction) in response to changes in temperature. The differing displacements and rates of expansion and contraction during temperature cycles may result in deleterious effects, such as cracked tubes or joint components, and/or gaps between sealing surfaces that allow leaks. Fittings, such as full couplings, half couplings, reducing couplings, compression couplings, and slip couplings, may not work in these applications, because the differing CTEs of the tubes may result in increased displacement between sealing surfaces that creates leaks, increased forces between tubes and/or fittings that creates cracks, increased stress built up in the tubes or fittings, especially after repeated thermal cycles, that creates material fatigue, or other problems associated with a change in forces at an interface between tubes and/or fittings. Some systems try to avoid or minimize the difficulty in joining tubes with different CTEs by using only one type of tube in areas of the system that are subject to high temperatures. However, this solution may use extra material and dedicate extra space, which may be at a premium, to piping systems, or require additional cooling.

Disclosed herein are assemblies, systems, and techniques for joining tubes that having different CTEs that may be space-efficient and/or robust. The disclosed joining assemblies may be useful in high temperature systems such as high temperature reactors (e.g., methane pyrolysis reactors), or other systems which operate in high-temperatures or pipe high-temperature fluids. In some examples, these systems may operate above about <NUM>, such as above about <NUM>. Joining systems according to the present disclosure may allow for joining tubes with different CTEs, such as ceramic tubes and metallic tubes, to be joined in these high-temperature areas, and allow for robust and reliable gas-tight (e.g., gas-tight or nearly gas-tight) sealing performance over a series of cycles between low and high temperatures. Polymeric or elastomeric sealing may not be an option in such high temperature systems, because the system may reach high temperature may be too high.

Joining assemblies according to the present disclosure are advantageous in high-temperature applications in aerospace, oil and gas, performance materials, and other industries. Ceramic pipes are being integrated into more industrial applications due to their high temperature capabilities, and transitioning ceramic pipes to metal or metal alloy pipes may be an advantageous enabling technology.

In some examples, joining assemblies according to the present disclosure may include a first tube, a second tube, and an insert. The first tube and the insert may be configured to limit radial expansion and contraction, respectively, of the second tube during thermal transients to seal the first tube against the second tube. The insert may be a short section of tube (i.e., a third tube) which has an aperture passing through it from a first end to a second opposite end. The first end of the second tube may be slidably translated into a first end of the first tube. In some examples, at least a part of a first portion of the second tube that is located near the first end of the second tube may be positioned within the first tube. An insert may then be positioned within the first portion of the second tube. The insert may fit into the inner diameter of a second tube such that intimate contact is made between the insert and the second tube. Similarly, the first end of the second tube may fit into the inner diameter or a first tube recess within the first tube such that intimate contact is made between the first tube and the second tube. Stated similarly, the outer perimeter of the insert may match the inner perimeter of the second tube, and the outer perimeter of the second tube may match the perimeter of the first tube Thus, a seal may be formed by the first tube, the second tube and the insert, which may be gas-tight and provide an elegant solution for joining tubes with different CTEs.

The assembly may be configured to operate within a range between a low temperature and a high temperature, which may correspond with on and off operational states of a high temperature reactor or an engine. In some examples, the assembly may be originally formed at the low temperature, for example room temperature. Alternatively, the assembly may be formed at the high temperature, or at an intermediate temperature between the estimated or expected high operating temperature and the low operating temperature. Accordingly, the dimensions of the tubes and inserts described herein may be configured for assembly at the low temperature, the high temperature, or an intermediate temperature. In some examples, assembling the assembly at an intermediate temperature may result in reduction of fatigue and beneficial stress behavior.

As discussed above, in some examples, the assembly may be formed by slidably translating the first end of the second tube into the first end of the first tube, and then slidably translating the insert into a first portion of the second tube near the first end of the first tube. As described herein, the first portion of the second tube may be considered near the first end of the second tube if the first portion is closer to the first end of the second tube than the first portion is to a second opposite end of the second tube. In some examples, the components may be slidably translated with minimal force required. However, in some examples, the outer perimeter of the insert may be slightly larger than the inner perimeter of the second tube in the first portion of the second tube, and force may be required to position the insert such that it is disposed within the first portion of the second tube. The force may be a manual force, such as pressing or hammering, or a force applied by one or more machines. The applied force may cause the second tube to mechanically deform around the insert, creating intimate contact and sealing the insert within the first end of the second tube. This process may be called swaging. In some examples, the insert may define an outer perimeter that is between about <NUM> to about <NUM> larger than the inner perimeter of the first end of the second tube. In some examples, the first portion of the second tube may define a longer length than both the insert and the first tube recess, such that the first portion of the second tube defines a tail portion which axially beyond the first tube recess and the insert and less constricted with respect to expansion and contraction during temperature cycles. In some examples, the tail portion may provide increased sealing performance over a greater number of temperature cycles.

The first tube and the insert may be made of materials that have the same or similar CTEs. For example, the first tube and the insert may include a ceramic material. The second tube may have a different CTE than the first tube. For example, the second tube may include a metallic material such as a metal or metal alloy having a higher CTE than the material of the first tube and the insert. The portion of the second tube may thus be sandwiched between the first tube and the insert, and forced to move with the first tube and the insert as the first tube and the insert expand during heating periods and contract during cooling periods. As the assembly is cycled through different temperatures, the intimate contact necessary to seal fluids flowing through the assembly may be maintained.

In some examples, the joining assemblies may be configured to reduce or prevent plastic deformation at the sealing interface to remain gas-tight during continuous or intermittent temperature cycling. Parameters to ensure the assembly forms and holds a seal may include geometric factors (e.g., thickness, diameter, and other geometric ratios), material factors, (e.g., elastic modulus of the materials, yield stress of the materials, temperature dependence of the CTE of the materials), manufacturing parameters, (work hardening during sealing), and other factors that may affect displacement of surfaces or generation of stresses in the joining assemblies. Since the assembly is configured to contain fluids passing through the first and second tubes, tight machining tolerances may also be desirable. Tubes and inserts of the present disclosure may be manufactured using any suitable technique, including but not limited to subtractive processes such as machining or grinding, additive processes such as additive manufacturing, or mixtures or combinations thereof.

Although described herein primarily with respect to an example assembly joining a ceramic tube to a metal tube, it is considered that assemblies described herein may be useful for other material systems, including assemblies that join two tubes having the same or similar CTEs or that include two materials with different CTEs. For example, two metallic (e.g., metal or metal alloy) tubes could be joined using an assembly in accordance with the present disclosure. In some examples, the metallic tubes could be the same material, and thus have the same CTE. In some examples, the tubes may be constructed of two different types of metals, and thus have different CTEs.

In some examples, the joining assemblies described herein may be structurally configured for reduced displacement of and/or thermal forces generated by the second tube during expansion and/or contraction. The second tube may include a first portion at the first end of the second tube that defines a smaller circumferential outer perimeter than a second portion of the second tube. The first portion of the second tube may also be called a "thin-wall section. " Inclusion of a thin wall section in the second tube may be advantageous, because the thinner walls of the second tube in the first portion may reduce thermal expansion displacements of the second tube, reducing stresses on the other components of the assembly and thus increasing useful life (e.g., extending the number of thermal cycles to failure). Furthermore, the second portion of the second tube including thicker walls than the first portion may provide structural strength and stiffness.

<FIG> illustrate example assembly <NUM> of system <NUM>. <FIG> is a conceptual perspective view illustrating example system <NUM> which includes example assembly <NUM>. Assembly <NUM> includes a first tube <NUM>, a second tube <NUM>, and an insert <NUM>. Some internal features of first tube <NUM>, second tube <NUM>, and insert <NUM> are illustrated in broken lines. First tube <NUM>, second tube <NUM>, and insert <NUM> are illustrated in a disassembled state for clarity. <FIG> is a conceptual cross-sectional view taken along a central axial axis L extending in axial direction A, illustrating the example first tube <NUM>, second tube <NUM>, and insert <NUM> of <FIG> in an assembled state. <FIG> is a conceptual cross-sectional view taken along radial plane D extending along radial direction R of <FIG>, illustrating an example assembly <NUM> of system <NUM>.

With concurrent reference to <FIG>, assembly <NUM> includes first tube <NUM> and second tube <NUM>. Each of first tube <NUM> and second tube <NUM> is configured to transport fluids within system <NUM> and constructed from materials suitable for containing fluids. In some examples, the fluids may be hot gases, which may be under pressure. First tube <NUM> defines central lumen <NUM> extending along an axial length of first tube <NUM> from first end of the first tube <NUM>, such that fluids may be transported from any part of system <NUM>, through first tube <NUM> and into second tube <NUM>. Second tube <NUM> defines central lumen <NUM> extending axially along an axial length of second tube <NUM> from first end of second tube <NUM>, such that fluids may be transported from any part of system <NUM>, through second tube <NUM> and into first tube <NUM>, or vice versa. Although illustrated as linear in axial direction A, in some examples first tube <NUM> and/or second tube <NUM> may be curved or include one or more segments disposed angularly from one another.

First tube <NUM>, second tube <NUM>, and insert <NUM> are configured to interface with each other to form a joint <NUM>. First tube <NUM> includes first end <NUM> configured to receive second tube <NUM>. Second tube <NUM> includes first end <NUM> configured to slidably translate into the first end of the first tube <NUM>. Insert <NUM> is configured to be disposed within first portion <NUM> of second tube <NUM> to form seal <NUM> at joint <NUM>.

While first tube <NUM> and second tube <NUM> may both be configured to contain gases, first tube <NUM> and second tube <NUM> may be formed from different materials. For example, first tube <NUM> may be configured to direct gases into a reactor or other high temperature system, while second tube <NUM> may be configured to interface with lower temperature tubing or include complex structures, such as bellows. As a result of these different materials, the CTE of second tube <NUM> may be different than the CTE of first tube <NUM>. Additionally, first tube <NUM> and second tube <NUM> may contain gases that fluctuate in temperature based on the operating status and/or conditions of the high temperature system that result in temperature cycles.

First tube <NUM>, second tube <NUM>, and insert <NUM> are configured to form seal <NUM>, which maintains intimate contact between first tube <NUM> and second tube <NUM> during these temperature cycles (e.g., an on/off cycle of a high temperature cycle). The coefficient of thermal expansion of first tube <NUM> is similar to the CTE of insert <NUM> and different from the CTE second tube <NUM>. For example, the difference in the CTE of second tube <NUM> and first tube <NUM> may be greater than <NUM> ppm/°C. Assembly <NUM> may be a joining solution for tubes with CTE differences, because the geometric relationship between first tube <NUM>, second tube <NUM>, and insert may cause second tube <NUM> to thermally displace at the same rate as first tube <NUM> and insert <NUM> during a temperature change across system <NUM> or local to assembly <NUM>, to maintain the location of second tube <NUM> between first tube <NUM> and insert <NUM>. In some examples, the CTE of second tube <NUM> may be different than the CTE of insert <NUM>, or different than both the CTE of first tube <NUM> and insert <NUM>. In some examples, the CTE of second tube <NUM> may be greater than the CTE of first tube <NUM>.

First tube <NUM> defines a first tube recess <NUM>. First tube recess <NUM> is configured to receive and/or releasably secure first end of the second tube <NUM> against first tube recess surface <NUM>, with first end of the second tube <NUM> fitting against first tube recess surface <NUM>, such that at least part of first portion <NUM> of second tube <NUM> is disposed within first tube <NUM>. First tube recess may be a void within first tube <NUM> that overlaps central lumen <NUM> and extends partially along the length of central lumen <NUM> in axial direction A, such that first tube recess surface <NUM> is defined at the end of first tube recess <NUM> opposite first end of the first tube <NUM>. First tube recess is configured to receive second tube <NUM>. First end of second tube <NUM> may be inserted into first tube <NUM> at first end of first tube <NUM> and slidably translated axially until first end of second tube <NUM> is in contact with first tube recess surface <NUM>. First tube recess <NUM> defines first tube recess perimeter P3, as discussed elsewhere in the disclosure. Although first tube recess <NUM> is illustrated as cylindrical in shape with smooth walls, in some examples first tube recess <NUM> may include ridges, ribs, threads, and/or other complex features configured to further secure first end of second tube <NUM> against first tube recess surface <NUM>.

Second tube <NUM> is configured to form the other half of joint <NUM> and to transport fluids about system <NUM>. In some examples, second tube <NUM> may be a pipe defining a uniform inner diameter and outer diameter, and configured such that insert <NUM> may simply be slidably translated into first end of second tube <NUM> and remain in place by friction until insert <NUM> is positioned within first portion <NUM> of second tube <NUM>.

Second tube <NUM> may include first portion <NUM> and second portion <NUM>. First portion <NUM> begins at first end of the second tube <NUM> and extends axially along an axial length of second tube <NUM>. In some examples, the axial length of first portion <NUM> corresponds to the axial length of first tube recess <NUM>. Preferably, first portion <NUM> may define a longer axial length than the axial length defined by first tube recess portion <NUM> so that first end of second tube <NUM> may contact first tube recess surface <NUM> without interference by second portion <NUM> and tail portion <NUM> of first portion <NUM> is not housed within first tube recess <NUM>. First portion <NUM> may also be called the "thin wall section," and may be an axial portion of the second tube comprising the first end of the second tube that defines outer perimeter P1. Second portion <NUM> may also be called the "thick wall section" of second tube <NUM>, and may define outer perimeter P2. Inclusion of the thin wall section may reduce the stresses on first tube <NUM> and insert <NUM> in the area of joint <NUM>, because the thin wall of second tube <NUM> in first portion <NUM> will not exert as much thermally-induced force during a change in temperature, and/or may reduce an amount of thermal displacement of second tube <NUM> in the area of joint <NUM>, as the thickness of the thin wall may be relatively small compared to the thickness of first tube <NUM> and insert <NUM>. Inclusion of the thick wall section in the area away from joint <NUM> may provide greater structural strength and stability, since the increased thermal displacement in these areas is not likely to cause other components of assembly <NUM> to stress and crack. Tail portion <NUM> of first portion <NUM> may be a length of the thin wall section that extends axially beyond first end <NUM> of first tube <NUM>, and may relieve stresses on first portion <NUM> overall because it may expand and contract during temperature cycles without being sandwiched between first tube <NUM> and insert <NUM>.

In some examples, first portion <NUM>, insert <NUM>, and first tube <NUM> may define a combined wall thickness. The ratio of the thickness of first tube <NUM> and insert <NUM> to the thickness of the first portion <NUM> may be between about <NUM>:<NUM> and about <NUM>:<NUM>, such as for example about <NUM>:<NUM> to <NUM>:<NUM>. In some examples, first portion <NUM> may define a wall thickness between the outer perimeter and central lumen <NUM> that may be between about <NUM> and about <NUM>. For example, the thickness of the wall of second tube <NUM> in first portion <NUM> may be between about <NUM> and about <NUM>, which may balance material stability and machinability against the greater thermal displacement forces exerted by thicker walls. Alternatively, as discussed above, second tube <NUM> may, in some examples, define a uniform outer perimeter along its entire axial length. Stated similarly, in some examples, P1 may be equal to P2.

As illustrated in <FIG>, first tube <NUM>, second tube <NUM>, and insert <NUM> may be cylindrical and thus define a circular outer perimeter and lumen cross-section. However, in some examples, another suitable geometric shape may be used for any or all of first tube <NUM>, second tube <NUM>, or insert <NUM>, such that one or more of the perimeters or cross-sections is ovular, elliptical, rectilinear, curvilinear, or the like. Outer perimeter P1 of first portion <NUM> may match first tube recess perimeter P3, regardless of the shape of the perimeters. Similarly, outer perimeter P4 of insert <NUM> may be configured to match second tube central lumen <NUM> in first portion <NUM> of second tube <NUM>.

Insert <NUM> is configured to stabilize joint <NUM> by providing an internal body that expands and contracts a similar amount and at a similar rate as first tube <NUM> as the temperature of system <NUM> varies, because insert <NUM> has a similar CTE as first tube <NUM>. In some examples, first tube <NUM> and insert <NUM> may be made of the same material and thus have the same CTE. Alternatively, first tube <NUM> and insert <NUM> may be different materials, such as two different ceramic materials, that have slightly different CTEs relative to the difference between the CTEs of first tube <NUM> and second tube <NUM>. For example, the difference between the CTE of first tube <NUM> and insert <NUM> may be less than or equal to <NUM> ppm/°C, such as less than or equal to <NUM> ppm/°C, thereby sandwiching second tube <NUM> and forcing second tube <NUM> to move in unison with first tube <NUM>.

Insert <NUM> may define insert lumen <NUM> extending from insert first end <NUM> to insert second end <NUM>. Accordingly, a fluid may pass through assembly <NUM> through central lumen <NUM> of first tube <NUM>, through insert lumen <NUM>, and through central lumen <NUM> of second tube <NUM>, or vice versa in the other direction, while remaining sealed inside assembly <NUM>, even at high temperature and/or pressure. As discussed above, insert <NUM> is, according to the invention, configured to be disposed within first portion <NUM> of second tube <NUM>, and thus the length of the insert between insert first end <NUM> and insert second end <NUM> is, according to the invention, less than the the length defined by first portion <NUM> of second tube <NUM>. Furthermore, in some examples, because swaging action may be desired inside first tube <NUM>, such that seal <NUM> is formed within first tube recess <NUM>, rather than at first end <NUM> of first tube <NUM>, insert <NUM> may define a shorter axial length than first tube recess <NUM>. Configured in this way, such that insert <NUM> defines a shorter axial length than first tube recess <NUM>, may be desirable to reduce material stresses over multiple thermal cycles.

In some examples, first tube <NUM> and insert <NUM> may include a ceramic material. In the illustrated example, first tube <NUM> and insert <NUM> include ceramic material, and second tube <NUM> comprises a metal material. In some examples, the ceramic material may be selected from the group consisting of carbon, carbon-carbon composites, graphite, MACOR®, available from Corning, Inc. (Corning, NY, USA), silicon carbide, silicon carbide/silicon carbide composites, oxide/oxide composites, alumina, zirconia, silicon nitrides, other ceramics, or mixtures or combinations thereof.

In some examples, second tube <NUM> includes a metallic material. Metallic materials may include any suitable metal or metal alloy. Alternatively, in some examples, first tube <NUM> and insert <NUM> may include a metal material, and second tube <NUM> may also include a metal material. In some examples, the metal material of first tube <NUM> and insert <NUM> may have a lower CTE than the metal material of second tube <NUM>. In examples where first tube <NUM> and/or insert <NUM> may include a low CTE metallic material, the low CTE metallic material may include a refractory metal. Suitable refractory metals include, but are not limited to, molybdenum, tungsten, niobium, tantalum, rhenium, or the like.

<FIG> includes arrows C and H, which illustrate the direction of forces on assembly <NUM> during periods of cooling and heating, respectively. In some examples, during periods of cooling, first tube <NUM> and insert <NUM> may contract toward axis L, the central axial axis of assembly <NUM>, at same or a similar rate, because the CTE of first tube <NUM> and insert <NUM> are the same or similar. Arrow C illustrates the direction of contraction forces during a cooling period. Accordingly, during a cooling period, perimeters P3 and P4 may become less displaced from central axial axis L. Since second tube <NUM> is trapped between first tube <NUM> and insert <NUM> in the area of seal <NUM>, perimeter P1 may become proportionally less displaced from central axial axis L during a period of cooling, maintaining the position of second tube <NUM> between first tube <NUM> and insert <NUM>. In some examples, second tube <NUM> may have a higher CTE than first tube <NUM>, and, in the absence of insert <NUM>, perimeter P1 of second tube <NUM> would contract more than first tube <NUM> toward central axial axis L, potentially creating a gap for fluids to escape from assembly <NUM>. However, insert <NUM>, having the same or similar CTE as first tube <NUM>, contracts during a period of cooling substantially the same amount as first tube <NUM> and at substantially the same rate as first tube <NUM>. Therefore, insert <NUM> may prevent second tube <NUM> from contracting away from the wall of first tube <NUM>, holding seal <NUM> substantially gas tight (e.g., gas tight or nearly gas tight) through the cooling period. The thin wall of first portion <NUM> (<FIG>) of second tube <NUM> may maintain the contraction force exerted by second tube <NUM> on insert <NUM> below a threshold force which causes insert <NUM> to crack, because first portion <NUM> of second tube <NUM> contains less material than second portion <NUM> of second tube <NUM>.

Similarly, arrow H illustrates the direction of expansion forces during periods of heating. Periods of increasing temperature may cause first tube <NUM>, second tube <NUM>, and insert <NUM> to expand according to the CTE of their material(s) of construction. In some examples, second tube <NUM> may have a higher CTE than first tube <NUM> and insert <NUM>. First tube <NUM> and insert <NUM> may have the same or similar CTE. First tube <NUM> may prevent second tube <NUM> from expanding more than insert <NUM> during periods of heating, since first tube <NUM> may be configured to expand a similar amount to insert <NUM> and at a similar rate as insert <NUM>. Accordingly seal <NUM> may be substantially gas tight through a heating period. The thin wall of first portion <NUM> (<FIG>) of second tube <NUM> may maintain the contraction force exerted by second tube <NUM> on first tube <NUM> below a threshold force which would cause first tube <NUM> to crack, because first portion <NUM> of second tube <NUM> contains less material than second portion <NUM> of second tube <NUM>.

A thermal cycle may include a heating period, where assembly <NUM> expands in a direction along arrow H in a direction away from central axial axis L, and a cooling period, where assembly <NUM> contracts in a direction along arrow C towards central axial axis L. Seal <NUM> at joint <NUM> may be configured to be substantially gas tight through a series of thermal cycles, because the expansion and contraction of tubes <NUM>, <NUM> with different CTEs may be controlled through the physical relationship of tubes <NUM>, <NUM>, and insert <NUM>.

<FIG> is a conceptual cross-sectional view of assembly <NUM> of system <NUM>, taken along a central axial axis, illustrating example first tube <NUM>, second tube <NUM>, and insert <NUM> according to the present disclosure in an assembled state. The angles illustrated may not be to scale, but rather exaggerated to illustrate the examples. Assembly <NUM> of <FIG> may be an example of assembly <NUM> of <FIG>, corresponding to the illustration of <FIG>, and differing as described below. Many elements similar to <FIG> are omitted for clarity.

In some examples, as illustrated, first tube recess <NUM> defines a first end <NUM> at the first end of the first tube <NUM> and a second opposite end <NUM> at first tube recess surface <NUM>. In some examples, first tube recess <NUM> may define a non-uniform diameter D1, D2 in an axial direction. In some examples, diameter D1 at the first end <NUM> may be greater than second diameter D2 at the second opposite end. First tube recess <NUM> configured in this way may allow second tube <NUM> to more easily slidably translate to contact first tube recess surface <NUM>, and may reduce material stresses in first tube <NUM> which may build up over a series of cycles and ultimately cause first tube <NUM> to crack or fracture. First tube <NUM>, in this example, has rounded edges at first edge of first tube <NUM>, which may assist in reducing material stresses. As assembled, first tube <NUM>, second tube <NUM>, and insert <NUM> form joint <NUM> which includes seal <NUM> preventing fluids from escaping assembly <NUM> when flowing between first tube <NUM> and second tube <NUM>. In some examples, one or more ribs <NUM> may extend from the wall of first tube recess <NUM> toward central axis L to provide a sealing surface between first tube <NUM> and second tube <NUM>. Alternatively, a rib or ribs may extend away from central axis L from the outer perimeter of first portion <NUM> of second tube <NUM> toward the wall of first tube recess <NUM> to provide a sealing surface. In some examples, second tube <NUM> or the wall of first tube recess <NUM> may define more than one ribs along the axial length of the part, and may thus provide more than one sealing surface for redundancy and/or improved sealing performance.

In some examples, first portion <NUM> of second tube <NUM> may define a smaller inner diameter than second portion <NUM> of second tube <NUM>. Configured in this way, insert <NUM> may slide or fall easily through second tube <NUM> from the end opposite first end <NUM> to first portion <NUM>, where insert <NUM> may then be forced (e.g., hammered) into position within first portion <NUM> such that insert <NUM> is disposed within first portion <NUM>. Alternatively, the inner diameter defined by second tube <NUM> may define a substantially constant cross-section. In some examples, insert <NUM> may be configured to reach its position within first portion <NUM> from the other direction, through first tube <NUM>, in examples where the inner diameter (central lumen <NUM>, <FIG>) of first tube <NUM> is configured to allow insert <NUM> to slide within it by defining an inner diameter larger than the outer perimeter (P4, <FIG>) of.

<FIG> is a conceptual cross-sectional view of assembly <NUM> of system <NUM>, taken along a radial plane, illustrating example first tube <NUM>, second tube <NUM>, and insert <NUM> according to the present disclosure. Assembly <NUM> of <FIG> may be an example of assembly <NUM> of <FIG>, corresponding to the illustration of <FIG>, and differing as described below. As discussed above with respect to <FIG>, assembly <NUM> includes first tube <NUM>, second tube <NUM>, and insert <NUM>. Lumens <NUM>, <NUM>, and <NUM> of first tube <NUM>, second tube <NUM>, and insert <NUM>, respectively, define a channel for fluids to flow through assembly <NUM> (into the page or out of the page).

As discussed above, any of perimeters P1, P2, P3, or P4 may define any suitable shape. Insert <NUM> of assembly <NUM> defines a corrugated shape, which defines a series of ridges <NUM> which extend radially a greater distance than grooves <NUM> about central axis L. Outer perimeter P4 of insert <NUM> matches the inner diameter of second tube <NUM> such that perimeter P4 of insert <NUM> contacts the surface of the inner diameter of second tube <NUM>. Second tube <NUM> defines out perimeter P1 in first portion <NUM>, which is the part of the second tube near the first end of the second tube (<NUM>, <FIG>) that is configured to slidably translate into first tube <NUM> to form seal <NUM>. In some examples, perimeter P1 defines a corrugated shape. In some examples, outer perimeter P4 of insert <NUM> may define a corrugated shape, which may define a series of ridges <NUM> which extend radially a greater distance than grooves <NUM> about central axis L. Outer perimeter P1 of first portion <NUM> of second tube <NUM> may match the size and shape of perimeter P3 of first tube recess <NUM>, such that there is contact between the walls of first tube recess <NUM> and first portion <NUM> of second tube <NUM>.

<FIG> is a conceptual cross-sectional view of assembly <NUM>, not part of the current invention, of system <NUM> taken along a central axial axis (L, <FIG>), illustrating the example first tube <NUM>, second tube <NUM>, and insert <NUM>. Assembly <NUM> may be generally described similarly to assembly <NUM> of <FIG> as described above, where like symbols indicate similar elements. Assembly <NUM> differs from assembly <NUM> (<FIG>) as described below.

In some examples, first tube <NUM> may be a relatively short section of tube (e.g., a nut), that has an axial length extending from first end <NUM> to second end <NUM>, which may not extend axially beyond a region near joint <NUM>. Rather, insert <NUM> may extend axially away from joint <NUM>, and may contain fluids to be transported to other parts of system <NUM>.

First tube <NUM> defines first tube recess <NUM>, which is configured to receive first end <NUM> of second tube <NUM>. First tube recess <NUM> defined first tube recess surface <NUM>. First tube central lumen <NUM> defines series of threads 490A on the radial inner surface of first tube <NUM>.

Insert <NUM> includes first portion <NUM> which is configured to slidably translate into first end <NUM> of second tube <NUM>, forming a mating surface between the components. Insert <NUM> also include second portion <NUM>, which extends axially beyond first end <NUM> of second tube <NUM> when insert <NUM> is slidably translated into first end <NUM> of second tube <NUM>. Outer perimeter P4 of insert <NUM> in second portion <NUM> may define a series of threads 490B along an axial length of insert <NUM>. Threads 490A defined by first tube <NUM> and threads 490B defined by insert <NUM> are configured to mate to releasably secure first tube <NUM> to insert second portion <NUM>.

First portion <NUM> of second tube <NUM> may extend from first end <NUM> to an opposite end <NUM> which interfaces with second portion <NUM> of second tube <NUM>. In some examples, second portion may have a constant, uniform outer perimeter P2 along its axial length. First portion <NUM> defines outer perimeter P1, which may increase in magnitude in an axial direction from second end <NUM> of first portion <NUM> to first end <NUM>. Stated similarly, first portion <NUM> may define a conical shape with the top section cut off. First portion <NUM>, also called the thin wall portion, may define a varying outer perimeter P1 along an axial direction, which may be desirable for increasing the performance of assembly <NUM> across more temperature cycles. Additionally, assembly <NUM> may provide advantages in ease of disassembly and reassembly, since the assembly may include a threaded coupling formed when threads are mated. In some examples, first tube recess <NUM> of first tube <NUM> and insert <NUM> may be configured to match the shape of first portion <NUM> of second tube <NUM>, such that seal <NUM> is formed at joint <NUM>.

<FIG> is a flowchart illustrating an example technique according to the present disclosure. Techniques according to the present disclosure may be used for joining a first tube and a second tube. Although described below primarily with respect to example assembly <NUM> of system <NUM> of <FIG>, other assemblies may be used to perform the described technique, and the described technique may be performed using another assembly. In some examples, the described technique may be used to join tubes <NUM>, <NUM>, to form assembly <NUM>, that may be part of a larger system <NUM>. In some examples, system <NUM> may be a high-temperature reactor.

Joining the first tube and the second tube may include slidably translating first end <NUM> of second tube <NUM> into first end <NUM> of first tube <NUM> (<NUM>). In some examples, first end <NUM> of second tube <NUM> may be slidably translated axially into first tube recess <NUM> until first end <NUM> of second tube <NUM> contacts first tube recess surface <NUM>. In some examples, slidably translating first end <NUM> of second tube <NUM> into first end <NUM> of first tube <NUM> comprises slidably translating at least a part of first portion <NUM> of second tube <NUM>, which may be near and/or include first end <NUM>, into first end <NUM> of first tube <NUM>. In some examples, tail portion <NUM> of first portion <NUM> may extend beyond recess <NUM> of first tube <NUM>. In some examples, first portion <NUM> of second tube <NUM> may define a smaller circumferential outer perimeter P1 than the outer circumferential perimeter P2 of second portion <NUM> of second tube <NUM>.

The technique also includes slidably translating insert <NUM> into position within first portion <NUM> of second tube <NUM> (<NUM>). In some examples, first portion <NUM> may be near first end <NUM> of second tube <NUM>.

In some examples, steps <NUM> and <NUM> may occur in temporal order; first slidably translating second tube <NUM> into first tube <NUM>, and then subsequently slidably translating insert <NUM> into position with first portion <NUM> of second tube <NUM>. In some examples, slidably translating insert <NUM> into position may include hammering or otherwise applying force to insert <NUM> such that first portion <NUM> is mechanically deformed during positioning of insert <NUM>. However, it is also considered that in some examples, insert <NUM> may first be positioned withing second tube <NUM> before second tube <NUM> is slidable translated into first tube <NUM>. In any case, first tube <NUM>, second tube <NUM>, and insert <NUM> may form seal <NUM> at joint <NUM>, and may provide an elegant joint that is robust enough to withstand thermal cycling. In some examples, a coefficient of thermal expansion (CTE) of first tube <NUM> may be similar to a CTE of insert <NUM> and different from a CTE of second tube <NUM>. In some examples, first tube <NUM> and insert <NUM> include a ceramic material. In some examples, second tube <NUM> includes a metal material. Insert <NUM> may define lumen <NUM> which may extend from first end <NUM> of insert <NUM> to second opposite end <NUM> of insert <NUM>.

In some examples the CTE of first tube <NUM> may be lower than the CTE of second tube <NUM>. Performing the described technique to seal tubes having CTEs with this relationship may form an assembly including seal <NUM>, which in some examples may be gas-tight (e.g., gas-tight or nearly gas-tight). In some examples, the CTE of first tube <NUM> may be the same (e.g., the same or nearly the same) as the CTE of insert <NUM>. In some examples, a magnitude of the difference between the CTE of first tube <NUM> and the CTE of second tube <NUM> may be at least <NUM> parts per million per degree Celsius (ppm/°C).

In some examples, slidably translating first end <NUM> of second tube <NUM> into first end <NUM> of first tube <NUM> may include slidably translating first end <NUM> of second tube <NUM> into first tube recess <NUM> defined by first tube <NUM>. In some examples, first tube recess <NUM> may define first tube recess perimeter P3. First tube recess perimeter P3 may, in some examples, matches outer perimeter P1 of second tube <NUM>. In some examples, first tube recess <NUM> may be cylindrical, or may alternatively define another geometric shape. For example, with reference to <FIG>, outer perimeter P1 of second tube <NUM> may define a corrugated shape with a series of ridges <NUM> and grooves <NUM>. Insert <NUM> may define outer perimeter P4, and outer perimeter P4 of insert <NUM> may define a corrugated shape.

Referring to <FIG>, in some examples, first tube recess <NUM> may define a first end at first end <NUM> of first tube <NUM> and a second opposite end at first tube recess surface <NUM>. First tube recess <NUM> may define a non-uniform diameter in an axial direction A, and the diameter may be larger at the first end <NUM> of the first tube recess <NUM> (D2) than at the opposite end (D1) of first tube recess <NUM>.

A seal assembly in accordance with the present disclosure was constructed and tested. Graphite was the ceramic material used to make the first tube and the insert, and Inconel <NUM> was used to make the second tube. The difference between the CTEs of the ceramic graphite and the metallic Inconel <NUM> was about <NUM> ppm/°C. The assembly was thermally cycled under a thermal gradient by exposing a heat source approximately <NUM> away from the joint along the first tube in the axial direction. The heat source was at a temperature of <NUM>. Thermal cycling under a thermal gradient was conducted. During the heating periods, the assembly reached a temperature of <NUM> at the joint, as measured by a thermocouple placed near the seal on the outer surface of the first tube. The joint showed successful sealing and no damage after several cycles of heating and cooling down.

Claim 1:
An assembly comprising:
a first tube (<NUM>, <NUM>, <NUM>);
a second tube (<NUM>, <NUM>, <NUM>), wherein a first end (<NUM>, <NUM>) of the second tube is configured to slidably translate into a first end (<NUM>, <NUM>) of the first tube; and
an insert (<NUM>, <NUM>, <NUM>) configured to be disposed within a first portion (<NUM>, <NUM>, <NUM>) of the second tube, wherein the first portion of the second tube is near the first end of the second tube,
wherein the first tube, the second tube, and the insert are configured to form a seal,
wherein the insert defines a lumen (<NUM>) from a first end (<NUM>) of the insert to a second opposite end (<NUM>) of the insert, the length of the insert between the first end and the second opposite end being less than the length defined by the first portion of the second tube;
wherein a coefficient of thermal expansion, called CTE, of the first tube is substantially similar to a CTE of the insert and substantially different from a CTE of the second tube; and
wherein the CTE of the first tube is lower than the CTE of the second tube.