Abstract:
A method for producing a pot for a pot volute casing for a turbo-motor, particularly for a compressor, and a pot volute casing for a turbo-motor is provided. According to the method for producing a pot for a pot volute casing, the pot is produced from a blank using a chip-removing machining method. The pot volute casing has a pot produced in accordance with the method for producing a pot for a pot volute casing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority to PCT Application No. PCT/EP2013/069171, having a filing date of Sep. 16, 2013, based on DE 101012218800.2 having a filing date of Oct. 16, 2012, the entire contents of which are hereby incorporated by reference. 
     
    
     FIELD OF TECHNOLOGY 
       [0002]    The following relates to a method for producing a pot for a pot-type volute casing for a geared turbocompressor, and to a pot-type volute casing for a geared turbocompressor. 
       BACKGROUND 
       [0003]    Compressors or fluid-compressing apparatuses are used in various industrial sectors for various uses which involve a compression of fluids, specifically (process) gases. Known examples of these are turbocompressors in mobile industrial applications, for example in exhaust-gas turbochargers or in jet engines, or in static industrial applications, such as geared compressors or geared turbocompressors for air separation. 
         [0004]    In the case of a turbocompressor of said type—which operates continuously—the increase in pressure (compression) of the fluid is effected in that a rotary momentum of the fluid is increased from the inlet to the outlet by a rotating impeller, which has radially extending blades, of the turbocompressor by way of the rotation of the blades. In this case, that is to say in a compressor stage of said type, the pressure and temperature of the fluid increase, while the relative (flow) speed of the fluid decreases in the impeller or turbo impeller. 
         [0005]    To achieve the greatest possible pressure increase or compression of the fluid, it is possible for multiple such compressor stages to be connected in series. 
         [0006]    With regard to types of construction of turbocompressors, a distinction is made between radial compressors and axial compressors. 
         [0007]    In the case of the axial compressor, the fluid to be compressed, for example a process gas, flows through the compressor in a direction parallel to the axis (axial direction). In the case of the radial compressor, the gas flows into the impeller of the compressor stage axially and is then diverted outward (radially, radial direction). In the case of multi-stage radial compressors, a flow diversion is thus required downstream of every stage. 
         [0008]    Combined types of construction of axial and radial compressors draw in large volume flows by way of their axial stages, which volume flows are compressed to high pressures in the subsequent radial stages. 
         [0009]    While use is normally made of single-shaft machines, it is the case in (multi-stage) geared turbocompressors (hereinafter also referred to for short as simply geared compressors) that the individual compressor stages are grouped around one large gear, wherein multiple parallel (pinion) shafts which each bear one or two impellers (turbo impellers arranged on free shaft ends of the pinion shafts)—said impellers being accommodated in volute casings which are implemented as casing fixtures and which effect the inflow to and outflow from the compressor stages—are driven by one large drive gearwheel, a large gear, mounted in the casing. 
         [0010]    In the volute casing (also referred to as pot-type volute casing in the case of a pot-shaped design), that is to say in a cylindrical bore in the volute casing, there is inserted—aside from the impeller—a volute insert, in such a way that, in the cylindrical bore axially at the face side of the volute insert, there remains a chamber, a so-called annular chamber, which is enclosed by the volute casing and by the volute insert and via which the fluid—passing from the impeller—flows out radially via a widening cross section. Via a plant pipework, such as a pressure connector pipe which is arranged on the volute casing and which has a pressure connector flange arranged thereon, the fluid then flows onward from the annular chamber out of the compressor stage. 
         [0011]    A geared compressor of said type, a geared compressor from the company Siemens with the designation STC-GC, used for air separation, is known from http://www.energy.siemens.com/hq/de/verdichtung-expansion-ventilation/turboverdichter/getriebeturboverdichter/stc-gc.htm (available on Oct. 5, 2012). 
         [0012]    DE 10 2008 025249 A1, EP 0 101 915 A2, DE 44 16 497 C1 and DE 10 2007 042529 A1 have each disclosed methods for producing a pot for a pot-type volute casing of the type mentioned in the introduction or corresponding pot-type volute casings. 
         [0013]    The volute casing which accommodates the impeller and which effects the inflow and outflow of the fluid to and from the compressor stage or the impeller is normally, in particular for small impellers, designed as a welded or cast structure, the advantages of which lie in a short delivery time and simplified usability for high pressures in the case of the welded structure, and in high efficiency in the case of the cast structure. 
         [0014]    In the case of a welded (pot-type) volute casing, the components thereof, specifically pot, pressure connector pipe, pressure connector flange and collar, are welded to form the volute casing or to form the pot-type volute casing. 
         [0015]    In particular for the connection of the pressure connector pipe to the pot, it is however the case in the welded pot-type volute casing that cumbersome weld seam preparation is necessary, and also, said welded connection constitutes a weak point of the pot-type volute casing. After the seam welding process, the pot-type volute casing must then be annealed into a low-stress state and then sandblasted, which further increases the manufacturing outlay and increases manufacturing costs. 
         [0016]    Embodiments of the invention are based on the object of specifying a pot-type volute casing for a turbomachine which is simple and inexpensive to produce and/or assemble. 
       SUMMARY 
       [0017]    An aspect relates to a method for producing a pot for a pot-type volute casing for a turbomachine and by means of a pot-type volute casing for a turbomachine. In the method for producing a pot for a pot-type volute casing, it is provided that the pot is produced from a blank by way of a cutting manufacturing process. 
         [0018]    In this case, a “blank” refers to a workpiece, for example a solid material body substantially in block form, which—comprising the fully produced pot—is substantially unmachined with regard to the shape and design of the fully produced pot. Only by way of the cutting manufacturing process does the pot then have its substantially final shape and design imparted to it. 
         [0019]    The expression “produced from a blank by way of a cutting manufacturing process” is to be understood to mean that the blank—for example placed into or clamped into a processing machine or processing station—is machined therein in a machining process by way of the cutting method, for example by turning, milling and/or drilling in the processing machine or in the processing station, and, after the cutting machining process, is removed in the form of the substantially finished pot from the processing machine or station. 
         [0020]    That is to say, the cutting machining process carried out on the blank may be a single cutting process technique performed on the blank, such as turning, milling or drilling. It is also possible for the blank to be machined—in one machining process—by way of two or more different cutting process techniques, for example by turning and milling or by turning and drilling or by milling and drilling or by turning, milling and drilling. 
         [0021]    Irrespective of this cutting machining process that produces the pot from the blank, the blank may be subjected to pre-processing, for example forging, in particular forging by virtue of a body part being forged on a main body. Also, irrespective of this cutting machining process that produces the pot from the blank, the pot may be subjected to post-processing, for example by local machining of external and/or internal contour surfaces in the pot, such as the formation of screw-connection and/or contact surfaces for additional components into a pot surface, or post-treatment of screw-connection and/or contact surfaces already produced during the cutting machining process. 
         [0022]    In other words, or put more simply, it is the case according to embodiments of the invention that the pot is produced by cutting in one machining process from one blank. 
         [0023]    The pot-type volute casing has a pot produced in accordance with the method for producing a pot for a pot-type volute casing. 
         [0024]    Further parts or components of the pot-type volute casing, for example a plant pipework or a pressure connector pipe, may then be screwed, in particular directly, to the pot. 
         [0025]    By means of embodiments of the invention, it is thus possible to produce a weld seam-free pot (from one blank in one machining process by purely cutting processes) or a weld seam-free pot-type volute casing. 
         [0026]    By virtue of the fact that, according to embodiments of the invention, the pot or the pot-type volute casing can be or is implemented without a weld seam, the pre-processing and/or interim processing and post-processing steps that are otherwise required in the case of volute casing welded structures, such as weld seam preparation, welding, annealing, sandblasting and weld seam inspection, can be omitted. 
         [0027]    Since, according to embodiments of the invention, the pressure-bearing pot of the volute casing or the pressure-bearing volute casing is free from welded components, the production thereof is simplified and is also reliable in terms of a process, and the pot or the pot-type volute casing that is produced is highly pressure-resistant. 
         [0028]    Also, production times and/or possibilities for the introduction of errors in the production of the pot and in the produced pot or pot-type volute casing can be minimized by means of embodiments of the invention, and pre-processing and/or interim processing and post-processing steps that are otherwise required are eliminated by means of embodiments of the invention. 
         [0029]    The pot, and also the pot-type volute casing, can according to embodiments of the invention also be produced extremely quickly and inexpensively, and in particular, in the case of embodiments of the invention, it is only necessary for a single component, that is to say the blank, to be machined on the processing machine or in the processing station in one machining process. 
         [0030]    It is also possible for common normal steels and/or high-alloy steels to be used for the pot or pot-type volute casing according to embodiments of the invention. Such steels can be procured inexpensively. 
         [0031]    Owing to the compact design of the pot or of the pot-type volute casing that is possible with embodiments of the invention from a manufacturing aspect, the pot can be produced on a small and also inexpensive processing machine/station—consequently also in an inexpensive manner. 
         [0032]    Embodiments of the invention also makes it possible—with the realization of embodiments of the invention in a turbomachine, such as a (geared) compressor, an expander or a turbine—for the impeller/impellers and/or fluid flow/fluid flows therein to remain unchanged. That is to say, previous components of such turbomachines can continue to be used in combination with embodiments of the invention. 
         [0033]    In particular, the previous weak point in welded pot-type volute casings, that is to say the connection between the plant pipework or the pressure connector pipe and the pot, and also other weld seam-induced weak points in welded pot-type volute casings, are eliminated with embodiments of the invention, and in particular, it is possible by means of embodiments of the invention for the “pot/plant pipework” connection to be realized by means of a screw connection between the plant pipework or pressure connector pipe and the pot, and for the other connections to be realized by means of corresponding screw connections. 
         [0034]    A required cross-sectional widening for the build-up of pressure and flow deceleration in the case of a turbomachine or of a compressor stage can then be implemented in the plant pipework or in the pressure connector pipe. 
         [0035]    A “pot/plant pipework” screw connection that is possible by means of embodiments of the invention is then situated upstream of a build-up of pressure (and flow deceleration) in the pressure connector pipe—which may be designed as a diffuser—and said screw connection is thus subjected to a lower load. 
         [0036]    Also, by means of embodiments of the invention, the number of components in the volute casing can be reduced, and it is thus possible according to embodiments of the invention for otherwise welded(-on) further (attachment) parts of the volute casing, for example the collar, to be produced together or integrally with the pot from the blank during the cutting machining process. 
         [0037]    Preferred refinements of embodiments of the invention will also emerge from the dependent claims. 
         [0038]    In a preferred refinement, the cutting manufacturing process is a turning, milling and/or drilling process. That is to say, the cutting machining process carried out on the blank may be a single cutting process technique performed on the blank, such as turning, milling or drilling, and it is also possible for the blank to be machined—in the machining process—by way of two or more different cutting process techniques, for example by turning and milling or by turning and drilling or by milling and drilling or by turning, milling and drilling. 
         [0039]    It is furthermore expedient if the blank is of the most material-saving configuration possible with regard to its shape and/or dimensions. That is to say, the blank should, with regard to its shape and/or dimensions, be configured such that as little material as possible is removed from the blank during the cutting machining process. 
         [0040]    According to embodiments of the invention, the blank has a substantially droplet-shaped external contour as viewed in cross section. In other words, the contour of the blank is a ¾ circle with adjoining rectangle. Taking such a blank shape as a starting point, little material is removed during the cutting machining process. 
         [0041]    Such a blank which is substantially droplet-shaped in cross section can be produced by forging of a body on a substantially cylindrical main body in a die. 
         [0042]    In a further preferred refinement, the pot is subjected to post-processing, for example by way of local (post-) processing of an external and/or an internal contour surface on the pot. 
         [0043]    Accordingly, for example with such post-processing for screw-connection and/or contact surfaces already produced on the pot in the cutting manufacturing process, such as surfaces for additional components, such as the plant pipework or the pressure connector pipe, which can be connected by way of said surfaces to the pot, it is possible to realize special surface characteristics, surface conditions and/or surface configurations. 
         [0044]    It is also possible for special screw-connection and/or contact surfaces—with special surface characteristics, surface conditions and/or surface configurations—for additional components, such as the plant pipework or the pressure connector pipe, which can be connected by way of said surfaces to the pot to be formed on the surface on the pot in the first place by means of such post-processing of the pot. 
         [0045]    In a preferred refinement, the pot-type volute casing has a plant pipework which is screwed to the pot, in particular a pressure connector pipe which is screwed to the pot, via which the supply or discharge of the fluid to or from the turbomachine can be realized. Said plant pipework or said pressure connector pipe may be in the form of a diffuser in order—in the case of a compressor as turbomachine—to effect a flow deceleration and pressure increase there or—in the case of an expander or a turbine as turbomachine—to effect a flow acceleration and pressure decrease there. 
         [0046]    In a further preferred refinement, the pot-type volute casing according to embodiments of the invention is—as a receptacle for an impeller of a compressor stage and as a flow guide for a fluid in the compressor stage—installed in a geared turbocompressor. 
         [0047]    Furthermore, it is possible here for a gearbox connection, for example a collar, for a gear mechanism or pinion shaft which drives the impeller to be screwed to the pot of the pot-type volute casing. Said joint realizes an additional facility for adjustment of the pot-type volute casing relative to the pinion shaft axis on the gearbox. This adjustment facility may if appropriate replace the adjustment facility hitherto provided in this regard by way of lock and support blocks, which is an advantage in particular in the case of turbomachines without a parting joint (stretched pinion shaft). 
         [0048]    The above description of advantageous refinements of embodiments of the invention encompasses numerous features which, in the individual subclaims, have in part been presented in combination. A person skilled in the art will however expediently also consider said features individually and combine them to form further meaningful combinations. 
     
    
     
       BRIEF DESCRIPTION 
         [0049]    Some of the embodiments will be described in detail, with reference to the following figures, wherein like designations denote like members, wherein: 
           [0050]      FIG. 1  shows a longitudinal section through a part of a compressor stage of a geared compressor having an embodiment of a weld seam-free pot-type volute casing of block type of construction; 
           [0051]      FIG. 2  shows a side view of an embodiment of the pot for a weld seam-free pot-type volute casing of block type of construction; 
           [0052]      FIG. 3  shows a plan view of an embodiment of the pot of the weld seam-free pot-type volute casing of block type of construction; 
           [0053]      FIG. 4  shows a longitudinal section through an embodiment of the pot of the weld seam-free pot-type volute casing of block type of construction along the section line IV-IV from  FIG. 3 ; 
           [0054]      FIG. 5  is a sectional illustration of an embodiment of the pot of the weld seam-free pot-type volute casing of block type of construction along the section line V-V from  FIG. 2 ; 
           [0055]      FIG. 6  is a sectional illustration of an embodiment of the pot of the weld seam-free pot-type volute casing of block type of construction along the section line VI-VI from  FIG. 3 ; 
           [0056]      FIG. 7  is a sectional illustration of an embodiment of the pot of the weld seam-free pot-type volute casing of block type of construction along the section line VII-VII from  FIG. 2 ; 
           [0057]      FIG. 8  is a schematic illustration of a blank  3  for the pot  2  for the weld seam-free pot-type volute casing  1  of block type of construction; 
           [0058]      FIG. 9  is a schematic illustration of an embodiment of a blank for a pot for a weld seam-free pot-type volute casing of block type of construction; 
           [0059]      FIG. 10  is a schematic illustration of an embodiment of a blank for a pot for a weld seam-free pot-type volute casing of block type of construction, and 
           [0060]      FIG. 11  is a perspective illustration of the blank as per  FIG. 10  with pot  2  “fitted” therein. 
       
    
    
     DETAILED DESCRIPTION 
       [0061]    Weld seam-free pot-type volute casing of block type of construction for a compressor stage in a geared compressor 
         [0062]      FIG. 1  shows a longitudinal section through a part, illustrated in simplified form, of a compressor stage  18  of a geared compressor  10  having a weld seam-free pot-type volute casing  1  according to embodiments of the invention with a pot  2  produced from a blank  3  by a cutting machining process. 
         [0063]    The compressor stage  18  has a rotor or pinion shaft  19  which rotates about an axis of rotation  22  and which is received in an axial bore  15  in the pot  2  and to one end of which, as illustrated, there is attached an impeller  20 . 
         [0064]    In the region in which the pinion shaft  19  enters the pot  2 , on an axial face surface of the pot  2  at that location, there is arranged a gearbox connection  8 , in the form of a collar  8 , which is screwed (cf. screws  21 ) to the pot  2 . 
         [0065]    The impeller  20  is impinged on (axially) by a fluid  11  by way of an axial inflow  12 , and said impeller delivers the compressed fluid  11  radially outward into an annular chamber  23 . 
         [0066]    After a further diversion  24 , the fluid  11  flows out of the annular chamber  23  into a collecting chamber  25 , collects there and enters via a flow opening  16  or a diffuser opening  16  in the pot  2  into a plant pipework  4 . 
         [0067]    The plant pipework  4  has a pressure connector pipe  5  (illustrated offset in a circumferential direction) which is in the form of a diffuser and which is screwed to the pot  2  at a screw-connection surface  17  on the pot  2  and which has, adjoining it, a pressure connector flange  6  via which the fluid  11  which is compressed further there exits the compressor stage  18 . 
         [0068]    The collecting chamber  25  which extends in a circumferential direction about the axis of rotation  22  is formed by means of the pot  2  and a volute insert  7  which is inserted into a recess  9  or cylindrical bore  9  of the pot  2 . 
         [0069]    The pot  2 , which is composed of a high-alloy steel, is produced from a forged blank  3  purely by cutting in a single machining process in one processing station. 
         [0070]    The outer surface of the blank  3  is, in the cutting machining process—in a manner dependent on the shape of the blank  3 —turned, milled and/or drilled so as to yield the outer contour of the pot  2 . 
         [0071]    The recess  9  in the pot  2  for the volute insert  7  is drilled during the cutting machining process. The slightly conical diffuser opening  16  is likewise drilled. The bore  15  for receiving the pinion shaft  19  is also drilled. The screw-connection surface  17  for the screw connection of the pressure connector pipe  5  to the pot  2  is milled. 
         [0072]    As shown in  FIG. 1 , the volute insert  7  is fitted into the pot  2  such that, axially at the face side of the volute insert  7 , there remains an enclosed chamber which forms the annular chamber  23 . 
         [0073]      FIG. 2  and  FIG. 3  show a side view ( FIG. 2 ) and a plan view ( FIG. 3 ) of the pot  2  according to embodiments of the invention produced from a blank  3  by cutting in one machining process. 
         [0074]    In the illustrations of the pot  2  in  FIG. 2  and  FIG. 3  there are labeled sections IV-IV ( FIG. 3 ), V-V ( FIG. 2 ), VI-VI ( FIG. 3 ) and VII-VII ( FIG. 2 ), the sectional illustrations of which are shown in  FIG. 4 ,  FIG. 5 ,  FIG. 6  and  FIG. 7 . 
         [0075]    As shown in  FIGS. 2 to 7 , the pot  2  has, in radial cross section, a droplet-shaped external contour which extends in an axial direction to realize the three-dimensional form of the pot  2 . In this case, the droplet-shaped external contour is formed by a ¾ circle with an adjoining rectangle. 
         [0076]    The recess  9  for receiving the volute insert  7  is formed on one axial end of the pot  2 , whereby the pot  2  has its pot-shaped form imparted to it; at the other axial end, the bore  15  for receiving the pinion shaft  19  is formed into the pot  2 . 
         [0077]    The screw-connection surface  17  for plant pipework  4  or the pressure connector pipe  5  is formed in the region of one of the two rectangle sides of the rectangle part of the external contour of the pot  2 . The screw-connection surface  17  is of substantially rectangular form, with one corner of the rectangle being rounded. 
         [0078]    Situated in the central region of the screw-connection surface  17  is a radial, substantially conical bore which opens out into the recess  9  in the pot  2  and forms the diffuser opening  16 . 
         [0079]    Threaded bores  27  for screws  21  for the screw connection of the pressure connector pipe  5  to the pot  2  are formed in the screw-connection surface  17  concentrically around the diffuser opening  16 . 
         [0080]      FIG. 8  is a schematic illustration of a blank  3  for the pot  2  according to embodiments of the invention for the weld seam-free pot-type volute casing  1  of block type of construction. 
         [0081]    Like the pot  2 , the blank  3  shown in  FIG. 8  has, in terms of its external contour, a droplet-shaped form or design, which is realized by a ¾ circle with an adjoining square. 
         [0082]    Said droplet-shaped blank  3  is produced by forging of a body  14  on a cylindrical main body  13  in the die. 
         [0083]    During the cutting machining of the blank  3  to form the finished pot  2 , the external contour of the blank  3  is, to a small extent, subjected to turning (cf. material removal  26 ) in order to remove unevennesses from the blank  3 . 
         [0084]    The screw-connection surface  17  for plant pipework  4  or the pressure connector pipe  5  is milled on the blank  3  and, if necessary, subjected to post-processing by smoothing; threaded bores  27  for the screws  21  of the screw connection of pressure connector pipe  5  and pot  2  are formed into the screw-connection surface  17 . 
         [0085]    The cylindrical bore  9  or the recess  9  for receiving the volute insert  7  in the pot  2  is drilled; the drilled-hole walls of the recess  9  are, if necessary, subjected to follow-up turning or smoothing. 
         [0086]    The bore  15  for receiving the pinion shaft  19  is likewise drilled; the drilled-hole wall of the bore  15  is, if necessary, subjected to follow-up turning or smoothing. 
         [0087]    The diffuser opening  16  for the discharge of the fluid  11  from the pot  2  into the pressure connector pipe  5  is also drilled; the drilled-hole walls of the diffuser opening  16  are, if necessary, subjected to follow-up turning or smoothing. 
         [0088]      FIG. 9  and  FIG. 10  show further different schematic illustrations of a blank  3  for the pot  2  according to embodiments of the invention for the weld seam-free pot-type volute casing  1  of block type of construction. 
         [0089]    The blank  3  for the pot  2  as illustrated in  FIG. 9  is a cuboidal, forged solid material body or block with an approximately rectangular cross section. 
         [0090]    The blank  3  for the pot  2  illustrated in  FIG. 10  is a cylindrical solid material body. The latter may be forged or may be obtained from bar stock. 
         [0091]      FIG. 11  is a perspective illustration of the cylindrical blank  3  as per  FIG. 10  with, as indicated, the finished pot  2  prospectively “fitted therein”. 
         [0092]    Here, too, that is to say in the case of the cuboidal or cylindrical blank  3 , it is the case—as with the droplet-shaped blank  3 —that the blank external contour is turned to form the finished pot  2  during the cutting machining process. The cylindrical bore  9  or the recess  9 , the bore  15  for receiving the pinion shaft  19  and the diffuser opening  16  are likewise drilled and subjected to post-processing; the screw-connection surface  17  is milled and subjected to post-processing. 
         [0093]    As can be seen from a comparison of the various blanks  3  (droplet-shaped, cuboidal, cylindrical) in  FIGS. 8 ,  9  and  10 , the amount of material  26  removed during the cutting machining of the blank  3  is least in the case of the droplet-shaped blank  3  ( FIG. 8 ), whereas the amount of material  26  removed during the cutting machining of the blank  3  is greatest in the case of the cylindrical blank  3  ( FIG. 10 ). Correspondingly, the cylindrical blank  3  also has the highest blank weight, whereas the droplet-shaped blank  3  has the lowest blank weight. 
         [0094]    Although the present invention has been disclosed in the form of preferred embodiments and variations thereon, it will be understood that numerous additional modifications and variations could be made thereto without departing from the scope of the invention. 
         [0095]    For the sake of clarity, it is to be understood that the use of “a” or “an” throughout this application does not exclude a plurality, and “comprising” does not exclude other steps or elements. The mention of a “unit” or a “module” does not preclude the use of more than one unit or module.