Patent Publication Number: US-2018050422-A1

Title: Method for manufacturing compressor components

Description:
TECHNICAL FIELD 
     The present disclosure generally pertains to fabrication of certain engine or compressor components. More particularly, this disclosure to forming certain components, for example, a labyrinth seal, for use within a centrifugal gas compressor. 
     BACKGROUND 
     Gas compressors exist in various forms and can have separated drive and compressor coupled by a drive shaft. Some related examples include, integrated hydroelectric generators, wind turbines with hub generators, etc. For pressurized devices such as compressors, several seals can be used to seal the shaft and various compressor stages from each other and from the atmosphere. Magnetic bearings may support moving machinery without physical contact. For example, they can levitate a rotating shaft, providing for rotation with very low friction and no mechanical wear. However in order to provide compression of a working fluid (e.g., air or other gaseous compounds) multiple seals may be needed between compressor stages and between the compressor and the atmosphere. Such seals can be low friction mechanical seals with a tortious path from inlet to outlet to prevent leakages. An example of such a tortious mechanical seal is a labyrinth seal. 
     A labyrinth seal may be comprised of many grooves that press tightly inside another axle, or inside a hole, so that the working fluid has to pass through a long and difficult path to escape. The grooves interlock, to produce the long characteristic path which slows leakage. For labyrinth seals on a rotating shaft such as in a compressor, a very small clearance must exist between the tips of the labyrinth threads and the running surface. 
     Labyrinth seals on rotating shafts provide non-contact sealing action by controlling the passage of fluid through a variety of chambers by centrifugal motion, as well as by the formation of controlled fluid vortices. At higher speeds, centrifugal motion forces the liquid towards the outside and therefore away from any passages. Similarly, if the labyrinth chambers are correctly designed, any working fluid that has escaped the main chamber becomes entrapped in a labyrinth chamber, where it is forced into a vortex-like motion. This acts to prevent its escape, and also acts to repel any other fluid. 
     Labyrinth seals can be difficult to manufacture, given the nature of the materials and the construction of their various surfaces. The present disclosure is directed toward overcoming one or more of the problems discovered by the inventors or that is known in the art. 
     SUMMARY 
     An aspect of the disclosure provides a method for forming a metallic structure having two or more portions. The method can include providing a first layer of metal-forming material. The method can also include applying energy of a first power level to a first area of the first layer of metal-forming material to form a first portion of the metallic structure having a first density. The method can also include applying energy of a second power level to a second area of the first layer of metal-forming material to form a second portion of the metallic structure having a second density. The method can also include providing a second layer of the metal-forming material on top of the first portion and the second portion of the metallic structure. The method can also include applying the energy of the first power level to a first area of the second layer of metal-forming material. The method can also include applying the energy of the second power level to a second area of the second layer of metal-forming material. 
     Another aspect of the disclosure provides a method for making a labyrinth seal for use in an internal-driven compressor, the labyrinth seal having a cylindrical body, an integral open cell structure, and a filler media within the open cell structure. The method can include providing a first layer of metallic powder. The method can also include applying laser energy of a first power level to a first area of the first layer of metallic powder to form a first portion of the cylindrical body having a first weld strength. The method can also include applying laser energy of a second power level to a second area of the first layer of metallic powder to form a first portion of the open cell structure having a second weld strength. The method can also include applying laser energy of a third power level to a third area of the first layer of metallic powder to form a first portion of the filler material having a third weld strength. The method can also include providing a second layer of metallic powder on top of the first portions of the cylindrical body, the open cell structure, and the filler media. The method can also include applying laser energy of the first power level to a first area of the second layer of metallic powder to form a second portion of the cylindrical body. The method can also include applying laser energy of the second power level to a second area of the second layer of metallic powder to form a second portion of the open cell structure. The method can also include applying laser energy of the third power level to a third area of the second layer of metallic powder to form a second portion of the filler material. 
     Another aspect of the disclosure provides a labyrinth seal prepared by a process. The process can include providing a first layer of metal-forming material. The process can also include applying energy of a first power level to a first area of the first layer of metal-forming material to form a first portion of the metallic structure having a first density. The process can also include applying energy of a second power level to a second area of the first layer of metal-forming material to form a second portion of the metallic structure having a second density. The process can also include providing a second layer of the metal-forming material on top of the first portion and the second portion of the metallic structure. The process can also include applying the energy of the first power level to a first area of the second layer of metal-forming material. The process can also include applying the energy of the second power level to a second area of the second layer of metal-forming material. 
     Other features and advantages will become clear with a review of the following description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an exemplary internal-driven compressor. 
         FIG. 2  is a cross sectional side view of a portion of the internal-driven compressor of  FIG. 1 . 
         FIG. 3  is a perspective view of a labyrinth seal of the internal-driven compressor of  FIG. 1 . 
         FIG. 4  is a cross sectional side view of the labyrinth seal of  FIG. 3 . 
         FIG. 5  is a detailed side view of a portion of an embodiment of the labyrinth seal of  FIG. 4 . 
         FIG. 6  is a detailed side view of a portion of another embodiment of the labyrinth seal of  FIG. 4 . 
         FIG. 7  is a flowchart of a method for manufacturing the labyrinth seal of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure relates to a centrifugal gas compressor. Embodiments provide an internal-driven compressor that integrates the motor (e.g., electric motor) within the compressor itself. Other embodiments can have a separated compressor and driver or motor. While a gas compressor with an integrated motor may be used as a primary example herein, the disclosure is also applicable to systems with a separated compressor and motor or drive system. Other embodiments can include other types of mechanical systems and associated components. The compressor rotor can be rotatably mounted on a fixed central axle of a compressor bearing system. The impeller is driven by an electric motor rotor imbedded in the impeller bore surface. In addition, the electric motor is axially located between radial bearings. 
       FIG. 1  is a perspective view of an exemplary internal-driven compressor. In particular, the illustrated internal-driven compressor  100  is embodied as an axially-fed, industrial centrifugal gas compressor having a side discharge. However, this particular configuration is merely for illustration purposes, as the illustrated internal-driven compressor  100  can include any combination of singular or plural, axial, linear, and radial feeds and discharges. Likewise, the present disclosure may be applied to other types of pumps, compressors, and the like. Here and in other figures, various components and surfaces have been left out or simplified for clarity purposes and ease of explanation. 
     For reference, the internal-driven compressor  100  generally includes a center axis  95  about which its primary rotating components rotate. The center axis  95  may be common to or shared with various other components of the internal-driven compressor  100 . All references to radial, axial, and circumferential directions and measures refer to center axis  95 , unless specified otherwise, and terms such as “inner” and “outer” or “inward” and “outward” generally indicate a lesser or greater radial distance from the center axis  95 , wherein a radial  96  may be in any direction perpendicular and radiating outward from center axis  95 . 
     In addition, this disclosure may reference a forward and an aft direction. Generally, all references to “forward” and “aft” are associated with a flow direction, relative to the center axis  95 , of the compressed gas. In particular, the suction end  97  (inlet) of the internal-driven compressor  100 , relative to the center axis  95  is referred to as the forward end or forward direction. Accordingly, the opposite end or discharge end  98  is referred to as the aft end or direction, unless specified otherwise. 
     Externally, the internal-driven compressor  100  includes a compressor housing  110  and an external power supply interface  105  and a communication interface  106 . Here, the communication interface  106  is illustrated as combined with the external power supply interface  105  for convenience; however, the communication interface  106  may be embodied as separate from the external power supply interface  105 . 
     Generally, the compressor housing  110  encloses and supports internal components of the internal-driven compressor  100 . Also, unlike a conventional shaft-driven compressor (requiring a dynamic seal), the external power supply interface  105  and the communication interface  106  may be statically sealed to compressor housing  110 . 
     Additional controls for the internal-driven compressor  100  may be integrated into the internal-driven compressor  100  and/or located remotely. Moreover, communications, feedback, and control for the internal-driven compressor  100  may be interfaced independently, as discussed above. Alternately, communications, feedback, and control for the internal-driven compressor  100  may be interfaced via the external power supply interface  105 . 
     The compressor housing  110  can have a suction port  111  and a discharge port  112 . The suction port  111  interfaces with a fluid supply (not shown), and is configured to supply a fluid (e.g. working gas, working fluid, process gas, pumped fluid, etc.) to the internal-driven compressor  100 . Here, the fluid is a gas  15 . Similarly, the discharge port  112  interfaces with a fluid discharge (not shown), and is configured to discharge the gas  15  from the internal-driven compressor  100 . The compressor housing  110  may also include support legs  113 , or other features to secure or physically ground the internal-driven compressor  100 . 
     The external power supply interface  105  may include power conduit and associated power control devices configured to provide power from an external supply (not shown) into the internal-driven compressor  100 . For example, the external power supply interface  105  may include electrical conduit and accessories conventionally associated with an electrical supply. Alternately, the external power source may be hydraulically or pneumatically based. 
       FIG. 2  is a cross sectional view of an embodiment of the internally driven compressor of  FIG. 1 . The compressor  100  can have multiple compressor stages, however only a single compressor stage is shown for illustrative purposes. As above, various components and surfaces may have been left out, cut away, and/or simplified for clarity purposes and ease of description. As shown, the gas  15  enters the internal-driven compressor  100  axially, is compressed in a single stage, and is subsequently collected and discharged. 
     Internally, the internal-driven compressor  100  includes a central axle  115 , a compressor inlet  120 , a compressor outlet  125 , a powered compressor rotor  130 , an internal driver  140 , and a compressor bearing system  150 . The internal driver  140  and the compressor bearing system  150  are configured to drive and support the powered compressor rotor  130  about the center axis  95 , respectively. The powered compressor rotor  130  rides in a cavity within the compressor housing  110 . In addition, the internal driver  140 , and the compressor bearing system  150  are enclosed within the compressor housing  110 . According to an embodiment, the internal-driven compressor  100  may include a powered compressor rotor assembly including portions of the powered compressor rotor  130  and the internal driver  140  coupled to the central axle  115 . Moreover, the powered compressor rotor assembly may contain portions of the compressor bearing system  150 . 
     The powered compressor rotor  130  makes up a single compression stage (as discussed below, additional stages may be used). The internal-driven compressor  100  may further include a diffuser  160  downstream of the powered compressor rotor  130 . Thus, the gas  15  compressed by the powered compressor rotor  130  may then be diffused by the diffuser  160 . 
     The compressor inlet  120  includes an upstream opening in the compressor housing  110  configured to introduce the gas  15  into the compressor flow path within the compressor housing  110 . The compressor flow path may be bound in part by the compressor housing  110  (or additional structures within the compressor housing  110 ), and in part by the powered compressor rotor  130 . Here the compressor inlet  120  is configured as an axial inlet; however, as illustrated below, in other embodiments the compressor inlet  120  may be configured as a radial or side inlet. 
     The compressor inlet  120  may generally include the suction port  111  and any flow distributing/shaping features downstream of the suction port  111  and upstream of the powered compressor rotor  130 . For example, these features may include struts, vanes, ducting, in-line filters, etc. Also for example, the compressor inlet  120  may include a nose cover  121 . The nose cover  121  is an aero structure at the upstream end of the powered compressor rotor  130  configured to direct and condition flow entering the compression flow path. The nose cover  121  may also be configured to seal internal components from the gas, particularly where the powered compressor rotor  130  is supported by a cantilever and the compressor inlet  120  is configured as an axial inlet. The nose cover  121  may be fixed to the powered compressor rotor  130 , as illustrated. Alternately, the nose cover  121  may be fixed to a structure inside the powered compressor rotor  130  (e.g., the central axle  115 ) or to a portion of the compressor housing  110 . 
     The compressor outlet  125  includes a downstream opening (not shown in this view) in the compressor housing  110  configured to discharge the gas  15  from the compressor housing  110 . For example, the downstream opening may be defined by the interface between the compressor housing  110  and the discharge port  112  ( FIG. 1 ). Moreover, the compressor outlet  125  may generally include the discharge port  112  and any upstream flow distributing/shaping features. These upstream flow distributing/shaping features may include struts, vanes, ducting, etc. upstream of the discharge port  112  and downstream of the powered compressor rotor  130  or the diffuser  160 . According to an embodiment, the compressor outlet  125  may include a plurality of outlet vanes  126  radially distributed about the center axis  95 , downstream of the powered compressor rotor  130 . The plurality of outlet vanes  126  may be configured to reduce swirl in the gas  15  imparted by the powered compressor rotor  130 . 
     Here, the compressor outlet  125  is configured as a radial or side outlet. Thus, the compressor outlet  125  may also include a collector  127  at its upstream end. The collector may be integrated into the compressor housing  110 , or may be joined to it as discrete unit. The collector  127  forms part of the compressor flow path, receiving the gas  15  in a radial flow and discharging the gas  15  in a linear direction. In addition, the plurality of outlet vanes  126  may be positioned and distributed at an upstream end of the collector. According to one embodiment, the collector  127  may be embodied as a discharge volute. The discharge volute is a curved funnel that increases in area as it approaches with the discharge port  112 . 
     According to one embodiment, the powered compressor rotor  130  may be a powered impeller, having portions of the internal driver  140  embedded into or otherwise fixed to the powered impeller. In particular, the powered impeller may include a rotor  141  of the internal driver  140  embedded or otherwise fixed to the powered impeller. Thus, no drive shaft, or the like, is between the powered impeller and rotor  141  of the internal driver  140 . 
     The powered impeller may include an annular body  131  having an impeller bore surface  132 , and a series of impeller vanes  133  about an impeller axis. The annular body  131  includes an opening or impeller bore about the impeller axis. The center axis  95  may be shared or common to the impeller axis (hereinafter center axis  95 ) when installed. Additional features of the powered impeller may be integrated in or otherwise extend from the annular body. In some embodiments the bore of annular body may be closed at one or more locations along the center axis  95 . 
     The impeller bore surface  132  is an inner surface of the powered impeller, circumscribing the center axis  95 . Moreover, the impeller bore surface  132  may include one or more grooves, notches, slots, or other departures from a regular (e.g., cylindrical) surface, such that one or more components may be fixed to, or features may be added to the powered compressor rotor  130 . For example, the impeller bore surface  132  may include a departure from a regular surface of rotation (e.g., cutout, cavity, groove, etc.), such that it is configured to engage the rotor  141 . Likewise, portions of the rotor  141  may be embedded in the departure from the regular surface of rotation. 
     Where the internal driver  140  is an electric motor rotor, the rotor  141  may be engaged (or fixed to and located) to the impeller bore surface  132 , or another portion of the annular body  131 . Being fixed directly to the annular body  131 , the rotor  141  is thus configured to rotate its impeller vanes  133  about the center axis  95  in direct response to an electromotive force imparted by the stator  142  of the internal driver  140 . In this case, the stator  142  of the internal driver  140  is located radially inward of the rotor  141 , and may be embedded or otherwise fixed to a central axle  115 . 
     Additionally, the series of impeller vanes  133  may include flow motion transmission surfaces extending from the annular body  131 . The series of impeller vanes  133  may be configured to compress and/or redirect the gas  15  along the compression flow path. For example, here, the series of impeller vanes  133  are configured to compress an axial flow of gas while redirecting it into a radial flow. 
     Furthermore, and as illustrated, the powered impeller may be a covered or enclosed impeller. Thus, the series of impeller vanes  133  may be part of a series of ducted vanes. The series of ducted vanes includes a shroud  134  around the series of impeller vanes  133  underneath. Accordingly, a portion of the compression flow path will be bounded by the ducted vanes and the surface of the annular body  131  between each impeller vanes  133 . The shroud  134  and the series of impeller vanes  133  may be integrated as a single unit along with the annular body  131 , extending inward to the impeller bore surface  132 . 
     In this embodiment, the powered compressor rotor  130  may also include one or more seals between the compressor housing  110  and the powered impeller. The one or more seals are configured to impede the gas  15  from bypassing or flowing other than through the compressor flow path of the ducted vanes. For example, the powered compressor rotor  130  may include one or more dry seals, such as, for example, a labyrinth seal  300 . The labyrinth seal  300  can interact with labyrinth teeth  135  located on an outer circumference of the powered compressor rotor  130  proximate its upstream end. The labyrinth teeth  135  and labyrinth seal  300  can be a dry seal, formed by the interaction between the labyrinth teeth  135  and the labyrinth seal  300 . The labyrinth teeth  135  can be machined, formed into, or otherwise fixed to the shroud  134 . Alternately, one or more similar labyrinth seals may be machined, formed into, or otherwise fixed to the compressor housing  110 . The labyrinth seal  300  can be machined or otherwise formed as a user-replaceable component that surrounds or encompasses the labyrinth teeth  135 . In some examples, the labyrinth seal  300  can also be referred to as a shroud seal, depending on the location of the seal within the internal-driven compressor  100 . 
     Also in this embodiment, the powered compressor rotor  130  may further include an impeller hub  136 . The impeller hub  136  may be located at a downstream end of the powered compressor rotor  130  (i.e., axially towards the discharge end  98 ). The impeller hub  136  may include hub teeth and be positioned proximate a piston head  138  having head teeth  137 . The hub teeth and the head teeth  137  can also be similar to the labyrinth teeth  135  and interact with a shrouded structure similar to the labyrinth seal  300  to complete the dry seal. For example, a balance piston seal  139  can interact with the head teeth  137  to form a labyrinth seal or shroud seal. 
     The head teeth  137  can have a similar configuration to the labyrinth teeth  135  and have a seal housing similar to the labyrinth seal  300 . The piston head  138  may have an effective area generally defined by the annular region between its diameter and the diameter of the impeller bore surface  132  at the downstream end of the powered impeller. 
     The balance piston cavity  117  is ported to a lower pressure supply (e.g., upstream the powered impeller, ambient, etc.). In particular, due to the pressure rise developed through the powered impeller, a pressure difference exists such that a net thrust is created in the upstream direction. By subjecting the piston head  138  to the lower pressure supply, a pressure differential opposite to the direction of the net thrust is created. For example, the balance piston cavity  117  may be ported via a series of openings  122  (e.g., through the nose cover  121  and portions of the central axle  115 ) that create a flow path between a low pressure area (inlet pressure) and the balance piston cavity  117 . 
     According to an embodiment, the internal-driven compressor  100  may support the internal driver  140  and the compressor bearing system  150  via the central axle  115 . Moreover the powered compressor rotor  130  may be rotatably mounted to the central axle  115 , such that the powered compressor rotor  130  may rotate about the center axis  95 . The central axle  115  is then supported by the compressor housing  110 . For example, here, the central axle  115  is nonrotatably fixed to the compressor housing  110  and is cantilevered from an endcap  118  located its aft end. Alternately, the central axle  115  may be supported from both its forward and aft ends (e.g., where the internal-driven compressor  100  includes radial feed and discharge, and two endcaps). Also for example and as illustrated, the central axle  115  may include a cylindrical outer diameter. 
     Generally, the central axle  115  includes a member fixed to the compressor housing  110  at one or more locations. For example, the central axle  115  may include a member concentric with the center axis  95  and fixed to the compressor housing  110  at its aft and/or forward ends. Also for example, the central axle  115  may be solid, hollow, symmetrical, and/or asymmetrical. Accordingly, the central axle  115  may have a cylindrical shape, and be positioned in a location similar to that of a conventional drive shaft. However, unlike a conventional drive shaft, penetrating its respective compressor housing and operating at a high rotation speed, the driver central axle  115  may reside completely within the compressor housing  110 , or at least be substantially sealed within the compressor housing  110 . 
     According to one embodiment, the central axle  115  may be hollow or include hollow portions. In particular, the central axle  115  may include one or more passageways through which power, control, cooling, pressure equalization, etc. may be provided to or within the internal-driven compressor  100 . For example, the central axle  115  may have a generally tubular shape. In addition, the central axle  115  may include an access port  119  at the endcap  118 . As such, the external power supply interface  105  may be statically sealed at the access port  119 , and power and signal cables may be routed through the fixed central axle  115 . Also for example, the central axle  115  may ported such that equalization pressure may reach the balance piston cavity  117 . 
       FIG. 3  is a perspective view of an embodiment of the labyrinth seal of  FIG. 2 . The labyrinth seal  300  can have an overall cylindrical body  302  formed to fit in one or more locations within the internal-driven compressor  100 . For example, the labyrinth teeth  135  can have the labyrinth seal  300 . The balance piston seal  139  ( FIG. 2 ) can also have an embodiment of the labyrinth seal  300  to form a dry seal such as a labyrinth seal. 
     The labyrinth seal  300  can have seal media  310  formed on the interior of the cylindrical body  302 . The seal media  310  can have one or more abradable components or substructures that interact with a plurality of circumferential teeth, e.g., the labyrinth teeth  135 . The labyrinth teeth  135  are shown in the cross section of  FIG. 2  with the labyrinth seal  300  and can form grooves in the seal media  310  with the rotation of the compressor rotor  130 . The labyrinth teeth  135  can abrade the seal media and form grooves on within the seal media  310  that then interlock with the labyrinth teeth  135  to produce a long path or “labyrinth” that slows or prevents leakage. Accordingly, a portion of the seal media  310  is sacrificial as it is worn away by the labyrinth teeth  135  to create the interlocking grooves or labyrinth. For example, on a rotating shaft, a very small clearance exists between the tips of the labyrinth teeth  135  and the running surface of the seal media  310 . 
       FIG. 4  is a cross section of the labyrinth seal  300  of  FIG. 3 . In some embodiments, the seal media  310  can be formed of one or more substructures. In some examples, the cylindrical body  302  can be machined or formed to have a circumferential lip  304  or other features such as a plurality of apertures  306 . The apertures  306  can be present to allow, for example, bleed air to penetrate the cylindrical body  302  to increase the rotational stability of the compressor rotor  130  or other purposes. The seal media  310  can also have an open cell structure  312 . The open cell structure  312  can be formed separately from the cylindrical body  302  and attached thereto via various welding processes, such as brazing, for example. The open cell structure  312  can be a honeycomb, another repeating pattern, or other structure having a plurality of open cells. 
     In some examples, the open cell structure  312  can have a plurality of cavities  314  within the open cells. The cavities  314  be filled with a powdered metal and then baked to solidify and harden the powdered metal within the open cell structure. The open cell structure  312  and the baked and hardened metal powder can then form the seal media  310 . In some embodiments, the cylindrical body  302  and the seal media  310  can also be formed in successive layers by hardening or welding a metal-forming material (e.g., powdered metal) using varying energy levels on specific portions of the layers of powdered metal. For example, a laser can be used to weld specific portions of each layer of the powdered metal for form a given structure, such as the labyrinth seal  300 . In some embodiments, the seal media  310  may have only the open cell structure  312  without filling the cells with the metallic powder. In some other embodiments, the seal media  310  can be a solid material without the open cell structure  312 . In some embodiments, the powdered metal can be, for example, an Incol-based alloy, HastX (e.g., Hastelloy X), 17-4, or 316SS stainless steel. The skilled person will appreciate that other materials are also compatible with such a use. 
       FIG. 5  is a detailed view of a portion of an embodiment of the labyrinth seal of  FIG. 4 . The portion of the labyrinth seal  300  shown has an open cell structure  502 . The open cell structure  502  can be a repeating geometric pattern, such as the pattern shown. The open cell structure  502  can also be other patterns such as a honeycomb pattern, or a mesh pattern comprising a repeating polygon, such as for example, a hexagon or a square. The open cell structure  502  can provide an amount of rigidity to the seal media  310 . 
     In some embodiments, the open cell structure  502  can have a media filler  504  filling the open cells of the open cell structure  502  (e.g., the cavities  314  of  FIG. 4 ). The media filler  504  can have a different consistency, a different hardness, and/or a different density than that of the open cell structure  502 . Similarly, the portion of the cylindrical body  302  shown can have density and hardness that is different from the open cell structure  502  and the media filler  504 . In some examples, the cylindrical body  302  can be the hardest or have the highest weld strength of the three components, followed by the open cell structure  502 , and then the media filler  504 , if present. The skilled person should appreciate that other combinations or structures are also possible having varying characteristics. 
     As noted above, the labyrinth seal  300  can be formed using more than one individual component. In some examples, the cylindrical body  302  can be milled or cast from a first material. The open cell structure  312  ( FIG. 4 ) can be formed from a second material and brazed or otherwise secured to the cylindrical body  302 . The resulting structure is an embodiment of the labyrinth seal  300  usable with the labyrinth teeth  135  as described above. 
     In some other examples, the cavities  314  can be filled with, for example, a powered metallic substance and baked or otherwise processed such that the powder metallic substance solidifies. The powered metal then forms a solid material that fills the cavities  314  of the open cell structure  312 . The resulting structure is another embodiment of the labyrinth seal  300  usable with the labyrinth teeth  135 . 
     In some embodiments of the disclosure, the labyrinth seal  300  can be formed in successive layers. For example, a first layer  510  of a metal-forming material (e.g., metallic powder or powdered metal) can be subjected to different energy levels from, for example, a laser. In a similar way that baking solidifies and hardens the metallic powder packed into the cavities  314 , application of laser energy at different power levels can result in different weld strengths, hardnesses, and/or different densities of the same metallic powder or similar material in a given layer (e.g., the first layer  510 ) of the labyrinth seal  300 , for example. As used herein, weld strength can refer to the strength of the bond between adjacent metallic particles. In some examples, application of higher energy laser will result in adjacent metallic particles melting together to create a solid piece of metal. Lower energy application can result in lower weld strength resulting in a porous or not completely bonded structure. For example, the powder used to form the cylindrical body  302  may be heated to form a very hard structure. The cylindrical body  302  may be the main structural component of the labyrinth seal  300  so it may require the hardest material. The open cell structure  502  may be the same hardness or a different hardness than cylindrical body  302 , for example, as portions of it may be abraded by the labyrinth teeth  135  when installed and in use. The teeth of the labyrinth teeth  135  can cut through open cell structure  502  to create the labyrinth of the labyrinth teeth  135 , as described above. 
     In another embodiment having the filler material  504 , a third energy level can be applied to the layer of filler material  504 . Accordingly, with each successive layer, such as the first layer  510  and a second layer  520 , a structure with multiple hardnesses, densities, or weld strengths within each layer can be formed in successive layers. This can simplify, for example, the casting, brazing, baking, and machining, that is needed to form the labyrinth seal  300 , or another metallic component. This can dramatically decrease the complexity of fabricating certain components. 
       FIG. 6  is a detailed view of a portion of another embodiment of the labyrinth seal of  FIG. 4 . A section  600  can be formed in a similar manner as the portion  500 . The portion  600  has an open cell structure  602 . As shown, a different geometric pattern can be implemented for the open cell structure  602 . The portion  600  can also have a filler media  604 . However, the filler media  604  may not be required for proper functioning of the labyrinth teeth  135  in conjunction with the labyrinth seal  300 . 
     The portion  600  can be formed in layers similar to the portion  500 . Once a first layer  610  is laid down, laser energy can be applied to form the cylindrical body  302  and the open cell structure  602 . As shown, the first layer  610 , denoted by a dashed line, has a portion of the cylindrical body  302  and portions of both the open cell structure  602  and the filler media  604 , each with a different weld strength. The different weld strengths needed for different areas of the portion  600  can be achieved by varying the energy levels applied to those areas. 
     A second layer  620  can be formed on top of the first layer  610  using the metal-forming material. The metal-forming material can be welded in portions corresponding to desired structure (e.g., the labyrinth seal  300 ). Accordingly, the labyrinth seal  300  can be formed using multiple layers of metallic powder or other materials that solidify with application of varying laser power levels. 
       FIG. 7  is a flowchart of a method for using multiple power levels to create a metallic component having multiple densities. A method  700  can be used to form, for example, the labyrinth seal  300  ( FIG. 3 ). The method  700  can begin at block  705  when a first layer of metal-forming material can be provided. In some examples, the metal-forming material can be a layer of powdered metal or similar material. The first layer of metal-forming material (or powdered metal) can be similar to the first layer  510  ( FIG. 5 ) or the first layer  610  ( FIG. 6 ). 
     At block  710 , the method  700  can include applying energy of a first power level to a first area of the first layer of metal-forming material to form a first portion of the metallic structure having a first density. The energy can be imparted by a laser or other heating element than can melt or weld adjacent metallic particles together. Different energy levels can produce different weld strengths between the particles of powdered metal. For example, higher energy can create a more complete weld or a more dense metal form. Accordingly, the amount of energy applied to the metal-forming material can determine how hard the resulting metal structure becomes. In some examples, the first portion of the metallic structure can be the cylindrical body  302 . In some other examples, the first portion of the metallic structure can also be the cylindrical body  302  coupled to the open cell structure  312 . 
     At block  715  the method  700  can include applying energy of a second power level to a second area of the first layer of metal-forming material to form a second portion of the metallic structure having a second density. Similar to the process of block  710 , the energy imparted can be from a laser, welding the adjacent metal particles together to form the second portion of the first layer. Again the first layer in blocks  710 ,  715  can be similar to the first layer  510  or the layer  610 . As described in connection with block  710 , the first portion of the metallic structure can be the cylindrical body  302 . In such an example, the second portion of the metallic structure can be the open cell structure  312 , for example. Accordingly, the cylindrical body  302  and the open cell structure  312  can have different weld strengths, hardnesses, or densities. 
     Also noted above, the cylindrical body  302  and the open cell structure  312  can both be the first portion of the metallic structure. Thus, in such an example, the second portion of the metallic structure (having the second weld strength) can also be the media filler  504  ( FIG. 5 ) within the cavities  314 . In still other examples, all three components (e.g., the cylindrical body  302 , the open cell structure  312 , and the media filler  504 ) can each have different weld strengths, densities, or hardnesses, based on the power level of the energy incident on the particular portion of the metal-forming material. 
     At block  720  the method  700  can include providing a second layer of the metal-forming material on top of the first portion and the second portion of the metallic structure. Once the first layer (e.g., the first layer  510  or the first layer  610 ) is hardened or welded by the laser energy, a second layer of the powdered metal can be laid on top of the first layer of the welded metallic structure (e.g., the labyrinth seal  300 ). The second layer of powdered metal, once welded, can form the second layer (e.g., the second layer  520  or the second layer  620 ) of, for example, the labyrinth seal  300 . 
     At block  725  the method  700  can include applying the energy of the first power level to a first area of the second layer of metal-forming material. In some examples, this can enlarge the first portion of the first layer. 
     At block  730 , the method  700  can include applying the energy of the second power level to a second area of the second layer of metal-forming material. Similar to block  725 , this can also enlarge the second portion of the first layer. 
     The method  700  can be repeated successively until a desired structure is completed. The method  700  can be used to form the labyrinth seal  300  using successive layers of powdered metal. Each layer of powdered metal can be welded to the preceding layer, enlarging the structure (e.g., the labyrinth seal  300 ) and improving the method for producing such a component. 
     One of ordinary skill can appreciate that the method  700  is not confined to creating or forming the shroud seal. Many other components can be formed using a similar process where a composite metallic structure is formed using successive layers of powdered metal. The layers can have specific portions of differently welded material. 
     INDUSTRIAL APPLICABILITY 
     Internal-driven compressors such as those described herein rely on various dry seals to maintain pressurization as the working fluid is compressed. One such dry seal is the labyrinth seal  300  ( FIG. 2 ). The compressor rotor  130  (or other rotating body) can have labyrinth teeth  135  that are a series of circumferential ridges that resemble teeth when viewed from a lateral perspective (see for example,  FIG. 2 ). The labyrinth teeth  135  interact with the open cell structure  312  and/or the media filler  504  within the cavities  314  on the inside of the labyrinth seal  300 . The teeth can score indentations in the inner surface of the labyrinth seal  300  creating channels or grooves that complement the size and shape of the labyrinth teeth. This complementary or interlocking relationship of the labyrinth teeth  135  and the grooves in the seal media  310  can produce the long, circuitous path which slows leakage from a high pressure side of the seal to the low pressure side. 
     One manner of forming such a labyrinth seal  300  (as noted above) is to mill the cylindrical body  302  from a portion of metal, form the open cell structure  312  and braze the open cell structure to the interior of the cylindrical body  302 . From there, if the media filler  504  is required, powdered metal is packed within the cavities  314  and the entire structure is baked to harden or weld the media filler  504 . A final milling of the completed labyrinth seal  300  may then be required to remove imperfections. This process is complex and expensive. 
     The methods and devices as disclosed herein can improve the process by directly forming each complex metallic structure in a single step. Powdered metal or other metal-forming material can be subjected to laser energy to weld the powdered metal together. The power level of the incident laser can determine how hard or how strong the welds are. Successive layers of the powdered metal can be laid down over completed layers to expand the structure and complete a given component. The disclosure presents the labyrinth seal  300  as a primary example of how a component comprising parts having different weld strengths or densities can be formed in a single process. This can lead to higher efficiency, lower unit cost, and even stronger components. The skilled person will appreciate that the concepts and methods disclosed herein are not limited to formation of the labyrinth seal  300  and can be used for any number of different components. 
     Those of skill will appreciate that the various illustrative logical blocks, modules, units, and algorithm steps described in connection with the embodiments disclosed herein can often be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular constraints imposed on the overall system. Skilled persons can implement the described functionality in varying ways for each particular system, but such implementation decisions should not be interpreted as causing a departure from the scope of the invention. In addition, the grouping of functions within a unit, module, block, or step is for ease of description. Specific functions or steps can be moved from one unit, module, or block without departing from the invention. 
     The preceding detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. The described embodiments are not limited to use in conjunction with a particular type of gas turbine engine. It will be appreciated that the gas turbine engine in accordance with this disclosure can be implemented in various other configurations. Furthermore, there is no intention to be bound by any theory presented in the preceding background or detailed description. It is also understood that the illustrations may include exaggerated dimensions to better illustrate the referenced items shown, and are not consider limiting unless expressly stated as such.