Patent Description:
Turbine engines typically include one or more components that compress an incoming flow of air and deliver the compressed flow of air to a combustor that mixes the compressed flow of air with a pressurized flow of fuel and ignites the mixture to create a flow of combustion gases. Combustors of turbine systems often include a micromixer assembly that typically includes a base nozzle structure in communication with a fuel plenum, an air intake, and numerous mixing tubes forming one or more segmented mixing tube bundles. The base nozzle structure supplies a fuel to the fuel plenum. The fuel exits the fuel plenum and enters the mixing tubes. Air is directed into the mixing tubes through the air intake and mixes with the fuel to create an air/fuel mixture. The air/fuel mixture exits the mixing tubes and enters into a downstream combustion chamber. This flow of combustion gases drives the turbine to produce mechanical work for electrical power generation and the like. A turbine engine may use any of a variety of fuels and may be selected from any of a number of different turbine engines, such as those offered by General Electric Company of Schenectady, N. In some particular embodiments, the micromixer assembly includes a plurality of tubes and at least a first end plate that has a plurality of holes drilled or otherwise cut into it in which a first end of each of the tubes terminates, the plurality of holes in the end plate corresponding in number to the plurality of tubes that are disposed within the apertures thereof.

According to various methods, assembly of micromixer tubes within the plate apertures involves a process for fixing them therein in order to stabilize the assembly and minimize vibration of the tubes within the plate. In some instances, this fixation is achieved by friction welding, and in other instances, by use of a relatively expensive brazing filler, which may include gold and/or nickel. Such processes can be time consuming and expensive, and may not always achieve the desired result. Thus, during operation, vibration of the tube within the plate aperture can lead to wear that can ultimately contribute to metal loss and tube tip failure, which can in turn lead to combustor inefficiency and possible failure. <CIT> discloses bundled tube fuel injectors provided with wear resistant coatings to the tube tips. <CIT> discloses braze material compositions and processes for the coating of gas turbine components. <CIT> discloses a method of repair of bundled tube injector. <CIT> discloses a method for providing wear-resistant coatings.

According to the invention, a method of assembling a wear resistant micromixer assembly of a turbine system is provided according to claim <NUM>.

Other features and advantages of the present invention will be apparent from the following more detailed description of the preferred embodiment, taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.

Provided are manufacturing methods, and articles for combustion micromixer tube wear management including micromixer tubes and assemblies. Embodiments of the present disclosure, in comparison to articles and methods that do not include one or more of the features disclosed herein, provide additional wear protection features to extend the operating lifetime of the parts, minimize the need for use of costlier materials and processes for assembly and fixation of combustor parts, permit the useful life of turbine components to be extended, permit gas turbine systems using embodiments of the turbine components to be more efficient, permit use of less costly underlying parts materials, or a combination thereof. In particular, embodiments of the present disclosure, in comparison to processes and articles that do not include one or more of the features disclosed herein, enable a significant wear reduction benefit, thereby allowing metal loss and tube tip failure, and thereby enhancing part life and continued operation of the turbine.

Referring now to <FIG>, illustrated is a representative embodiment of a combustion component of a turbine system <NUM> having a combustor section <NUM> and a head end <NUM>. The head end <NUM> is disposed at an adjacent upstream location of the combustor section <NUM> and includes a micromixer assembly <NUM>. The micromixer assembly <NUM> includes a plate <NUM> that extends generally radially and circumferentially and has, in some embodiments, a plurality of sectors <NUM>, each of which comprises a plurality of tubes <NUM>. The combustor section <NUM> is defined by an outer liner <NUM> that extends to an upstream end <NUM>. Spaced radially outwardly of the outer liner <NUM>, and surrounding and enclosing the outer liner <NUM>, is a flow sleeve <NUM>. A flow of air passes upstream within an air passage defined by the outer liner <NUM> and the flow sleeve <NUM> to the upstream end <NUM> of the outer liner <NUM>. It will be appreciated that the embodiment shown is merely representative, and that other examples of combustion components are known in the art, including those with alternate features of micromixer assemblies, thus, the embodiments as shown is not limiting.

In operation of the combustor, a working fluid can flow through the passage of the flow sleeve <NUM> along the outside of the outer liner <NUM> to provide convective cooling to the outer liner <NUM>. When the fluid reaches the end cover of the combustor, the fluid reverses direction and flows through at least a portion of the tubes <NUM> where it mixes with fuel before it is injected into the combustor section <NUM>. The tubes <NUM> generally include an upstream end that is axially separated from a downstream end, and according to the invention, as described herein below, each of the tubes <NUM> is brazed at least at an end that inserts into one or more plates <NUM>.

Referring to <FIG>, a top, cross-sectional view of the plate <NUM> and a tube <NUM> of the plurality of tubes is illustrated, showing the tube <NUM> disposed within a receiving aperture <NUM> of the plate <NUM>. The plate <NUM> includes a plurality of receiving apertures that extend relatively axially through the plate <NUM> and are each configured to have a receiving diameter <NUM> that is dimensioned to allow the tube <NUM> to be inserted therein. Specifically, the tube <NUM> comprises an inner diameter <NUM>, an outer diameter <NUM>, an inlet <NUM> and an outlet <NUM>. It is the outer diameter <NUM> of the tube <NUM> that is dimensioned to be inserted within the receiving diameter <NUM> of the receiving aperture <NUM>.

According to the invention, the tube <NUM> is dimensioned and adapted to facilitate the formation of a friction weld between an outer wall portion of the tube <NUM> and the receiving aperture <NUM> of the plate. According to such embodiments, as is shown in <FIG>, a micromixer tube <NUM> is adapted to receive an expander that may include at least one expander head <NUM> having an outer diameter <NUM> that is closely dimensioned with that of the inner diameter <NUM> of the tube <NUM>. The expander comprises a shaft portion <NUM> that extends in a longitudinal direction <NUM> that relatively coincides with an axial direction of the turbine system <NUM>, with the at least one expander head <NUM> disposed along the length thereof. The function of the expander head <NUM> is to be controllably disposed at a position within the tube <NUM> that is desired to form a friction weld with the receiving aperture <NUM> of the plate <NUM>. It will be appreciated that there are alternate means by which a tube may be affixed into engagement within a plate aperture, such alternatives not being according to the claims.

Each of the plurality of tubes and the plate are typically formed of a durable material that is suitable for functioning in a region having a temperature that may exceed <NUM>,<NUM>° F. Such a material may comprise stainless steel and/or a nickel-based alloy, such as Hastelloy® X, the aforementioned material being discussed herein as merely illustrative and non-limiting. In various non-limiting examples, the tubes and plates may include any suitable material, for example, stainless steel, a nickel-based alloy, an iron-based alloy, or any other suitable metal or metallic material.

In accordance with the invention, methods are provided for improving the wear resistance of micromixer tubes, in particular the tube ends that are engaged with one or more micromixer plates. Referring now to <FIG>, a representative flow diagram of the methods according to the disclosure is provided. Brazing may be accomplished by any suitable brazing technique. And it will be appreciated that the term brazing as used herein is with reference to surface treatment of a micromixer tube as substrate wherein the process does not include joining workpieces, but rather is performed to affix a braze filler material directly to the surface of the micromixer tube to achieve benefits. In some embodiments according to the invention, the techniques of vacuum brazing are used. As used herein, vacuum brazing means and refers to a process that offers the advantages of providing clean, superior, flux-free braze joints and surfaces of high integrity and strength. The process is performed inside a vacuum chamber vessel at a pressure of about <NUM> Pa (<NUM> x <NUM>-<NUM> torr), and in some embodiments, not more than <NUM> Pa (<NUM> x <NUM>-<NUM> torr), wherein temperature uniformity typically in the range from about <NUM> (<NUM>° F. ) to about <NUM> (<NUM>° F. ) is maintained on the work piece under continuous heat to thereby reduce or eliminate the stress that can be introduced by other methods where heating and cooling cycles can occur.

Thus, in one embodiment, the brazing is accomplished as a single-step vacuum brazing, at about <NUM> Pa (<NUM> x <NUM>-<NUM> torr) and the brazing temperature is between about <NUM> (<NUM>° F. ) and about <NUM> (<NUM>° F. ), between about <NUM> (<NUM>° F. ) and about <NUM> (<NUM>° F. ), between about <NUM> (<NUM>° F. ) and about <NUM> (<NUM>° F. ), between about <NUM> (<NUM>° F. ) and about <NUM> (<NUM>° F. ), between about <NUM> (<NUM>° F. ) and about <NUM> (<NUM>° F. ), or any suitable combination, sub-combination, range, or sub-range therein. In one embodiment, the brazing duration is between about <NUM> minute and about <NUM> minutes, between about <NUM> minutes and about <NUM> minutes, between about <NUM> minutes and about <NUM> minutes, between about <NUM> minutes and about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, about <NUM> minutes, or any suitable combination, sub-combination, range, or sub-range therein.

According to the invention, the methods include applying a surface treatment to at least a portion of at least one micromixer tube, the treatment comprising a wear resistant brazed coating by application of one or a mix of powdered braze materials to all or a portion of a micromixer tube followed by vacuum brazing. In accordance with such methods, the powdered braze material comprises known or novel low melt materials, and in particular, for use with tubes formed of stainless steel, the braze powders are particularly compatible with such tube base material. It will be appreciated, of course, that other tube base materials may be used, and as such, other braze materials may be selected, which may be low melt or other than low melt. Beyond the claimed method, the method of brazing may be other than vacuum brazing.

Thus, in accordance with various embodiments, the material for the braze powders selected for the braze coat surface treatment may be any suitable brazing material, including, but not limited to, metal alloys and superalloys, including nickel and cobalt-based superalloys, alloys and combinations thereof. Suitable examples of a nickel-based alloy may have a formula (by mass) of Ni<NUM>Cr<NUM>B<NUM>C<NUM>Al<NUM>Ta<NUM>Y<NUM> (commercially available as Amdry DF4B from Sulzer Metco, located in Westbury, New York) or a formula (by mass) of Ni<NUM>Cr<NUM>. <NUM>Si<NUM> (commercially available as BNi-<NUM> from many providers, including Wall Colmonoy, located in Madison Heights, Michigan). The braze layer may enable a fit tolerance between the surface of the micromixer tube and the inner surface of the plate aperture of between about <NUM> (<NUM> inches) to about <NUM> (<NUM> inches). The braze surface treatment may fill minor gaps and surface imperfections on the tubes, and in various embodiments, the braze coat provides enhanced surface hardness imparting greater wear resistance as compared to conventional micromixer tubes that are not braze treated.

In one example according to the disclosure, a selection of micromixer tubes were surface treated with a braze material to confer wear resistance. In such representative embodiment, a low-melt material (MM509B) suitable for brazing the micromixer tube components may be selected, having a composition, by weight, of between about <NUM>% and about <NUM>% Cr, up to about <NUM>% Ti (for example, between about <NUM>% and about <NUM>%), between about <NUM>% and about <NUM>% W, between about <NUM>% and about <NUM>% Ni, between about <NUM>% and about <NUM>% Ta, up to about <NUM>% C (for example, between about <NUM>% and about <NUM>%), between about <NUM>% and about <NUM>% B (for example, between about <NUM>% and about <NUM>%), about <NUM>% Fe, up to about <NUM>% Si, up to about <NUM>% Mn, up to about <NUM>% S, and a balance of cobalt. Another suitable low-melt material has a composition, by weight, of about <NUM>% Cr, about <NUM>% Co, about <NUM>% Al, about <NUM>% B, and a balance of nickel. Another suitable low-melt material has a composition, by weight, of about <NUM>% Cr, about <NUM>% Co, about <NUM>% Ta, about <NUM>% Al, about <NUM>% B, and a balance of nickel. In yet other examples, alloys suitable for brazing according to the instant disclosure include materials selected from BN12, and BN19.

According to such embodiments, surface treated micromixer tubes are provided with a braze surface treatment in the range from about <NUM> to <NUM> coat thickness, using the low-melt braze coating material as described above. The braze treatment confers visibly altered surface properties and provides enhanced surface hardness. In accordance with the disclosure, surface treatment of the micromixer tubes may range from about <NUM> to about <NUM> thickness, and in various embodiments, the thickness may be <NUM>, <NUM>, <NUM>, <NUM>, and <NUM>, and fractions there between in the amount of from <NUM> to <NUM>.

It will be appreciated that the braze materials may be used alone, or in combinations. Accordingly, in some embodiments, the braze powders used herein may include a combination of MM509B with BN12, or the combination of MM509B with BN19.

The method optionally further includes applying at least one bonding coat layer directly adjacent the micromixer tube, over which layer the brazed wear layer is applied. The method optionally further includes applying at least one heat resistant coat, such as a thermal barrier coating, either or both between the material of the micromixer tube and the brazed wear layer or over the brazed wear layer. According to the invention, the method further comprises the step of inserting the tube into a receiving aperture of a plate. Further included is applying a fixation means for securing engagement between the tube and the plate, the means including exerting a radial force on an inner wall of the tube with an expander to form at least one operable connection between an outer diameter of the tube and the receiving aperture of the plate.

A technical advantage of the present surface treatment for micromixer tubes includes greater longevity for the mixing tubes, and reduced failure rate of the tubes and the combustor. Another advantage is reduction of cost associated with repairs.

Claim 1:
A method of assembling a micromixer assembly (<NUM>) of a turbine system (<NUM>) comprising: applying a surface treatment wear layer to at least a portion of at least one micromixer tube (<NUM>), the treatment consisting of application of a braze alloy powder followed by vacuum braze processing to form a wear resistant brazed coating, inserting the surface treated at least one micromixer tube (<NUM>) into a receiving aperture (<NUM>) of a plate (<NUM>), and optionally securing the micromixer tube (<NUM>) and the plate (<NUM>),
wherein the at least one micromixer tube (<NUM>) is operably coupled to the plate by friction welding, and
wherein friction welding is achieved by exerting a radial force on an inner wall (<NUM>) of the tube (<NUM>) with an expander to form at least one operable connection between the outer surface (<NUM>) of the at least one micromixer tube (<NUM>) and the receiving aperture (<NUM>) of the plate (<NUM>).