Patent Document

CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present application claims priority to European Patent Application No. 15176912.2, filed Jul. 15, 2015, the contents of which are incorporated herein by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to an adaptor for connecting a generator to a prime mover in a power generation system, and in particular an adaptor which can facilitate servicing of parts of the system. 
         [0003]    Power generation systems typically comprise a prime mover which drives an electrical generator in order to produce output electrical power. For example, a power generating set may comprise an engine coupled to a generator (alternator). Typically the crankshaft of the engine is mechanically coupled to the shaft of the generator using a coupling. 
         [0004]    In a power generation system it is necessary for the prime mover and the generator to be precisely aligned, to ensure concentricity of the rotating parts. In a generating set this is usually achieved by mounting the engine and the generator on a bed frame. In addition, an adaptor may be used to connect non-rotating parts of the generator and the engine. The adaptor provides additional stability and helps to prevent relative movement between the engine and the generator. 
         [0005]    During the lifetime of the power generation system it may become necessary to service some of the moving parts. For example, in certain generating sets, it may become necessary to service parts such as the coupling between the engine and the generator, and/or the engine or generator bearings. 
         [0006]    Existing power generating systems typically require the generator to be moved to provide access for servicing moving parts. In order to move the generator it must first be disconnected. Following servicing, the generator must be reconnected and the engine and generator re-aligned. As a consequence, the servicing of moving parts can be time consuming, complex and costly. For example, the servicing repair time for the coupling on a typical gas generator set installation may be around 14 to 15 hours. 
         [0007]    Existing adaptors are usually cylindrical, and surround the generator shaft and/or the coupling. Such adaptors are typically formed from a single cast piece of metal. Openings or windows may be provided in the adaptor to allow an operator to connect the rotating parts. However these openings do not normally allow servicing of moving parts. 
       SUMMARY OF THE INVENTION 
       [0008]    According to a first aspect of the present invention there is provided an adaptor for connecting a generator to a prime mover, the adaptor comprising two separable parts. 
         [0009]    The present invention may provide the advantage that, by providing an adaptor comprising two (or more) separable parts, it may be possible for one part to be removed in order to allow access to moving parts. Thus the present invention may simplify the process of servicing moving parts, in comparison to previous techniques. 
         [0010]    Preferably one part of the adaptor can be removed while the other part is connected between the generator and prime mover. This may allow access to moving parts to be provided without requiring the generator and/or engine to be moved. This this arrangement may allow the alignment between the generator and the engine to be maintained. 
         [0011]    Preferably each part of the adaptor is connectable between the generator and the prime mover. For example, each part of the adaptor may comprise a first flange for connection to the engine and a second flange for connection to the generator. Thus each part of the adaptor may be structural, which may help to provide rigidity between the engine and the generator. 
         [0012]    Preferably the removal of one part of the adaptor exposes the inside of the adaptor. Thus, in use, the removal of one part of the adaptor may expose parts which are inside or adjacent to the adaptor, such as a coupling or bearing. This may allow servicing of those parts which would otherwise be inaccessible due to the presence of the adaptor. 
         [0013]    Preferably a part of the adaptor which has been removed can be reinstalled, for example, following the servicing of a moving part. In order to facilitate reinstallation, the removable part of the adaptor may comprise at least one fit bolt. The fit bolt may engage, for example, with the generator or the prime mover. This may help to locate the removable part when it is reinstalled. 
         [0014]    Preferably the two separable parts of the adaptor are connectable, for example by means of bolts or clamps. This can help to ensure that the adaptor has the required mechanical stiffness. 
         [0015]    At least one of the two separable parts may comprise a centering pin which engages with the other separable part. This may help to locate a removable part when it is reinstalled. 
         [0016]    Preferably each separable part comprises a flange for interfacing with the other part. This may help to ensure a connection between the two parts with the required mechanical rigidity. The flanges comprise bolt holes for connecting the two parts. Alternatively some other means such as clamps may be used for connecting the two parts. 
         [0017]    The adaptor may be cylindrical in shape, and is preferably in the form of an open cylinder. This can allow rotating components, such as a generator shaft and/or a coupling, to be located inside the adaptor. 
         [0018]    The two parts of the adaptor may be separable along lines which run in an axial direction between one end of the adaptor and the other. Thus, where the adaptor is in the form of an open cylinder, the lines may run between one open end of the cylinder and the other. However other arrangements are also possible, and for example a removable part of the adaptor may extend along only part of the length of the adaptor in an axial direction. 
         [0019]    The lines of separation between the two parts of the adaptor may be straight, or some other shape such as curved, waved, serrated or castellated. In one embodiment, the lines are substantially parallel to an axis of rotation of the electrical machine, and/or parallel to each other. 
         [0020]    If desired, the adaptor may be separable into three or more different parts. In this case, at least one part may be separable from the or each other part, while at least one part remains connected between the prime mover and the generator. 
         [0021]    The adaptor is preferably arranged to surround a coupling between the engine and the generator. By providing by providing an adaptor comprising two separable parts, it may be possible for one part to be removed in order to allow the coupling to be serviced. Furthermore, it may be possible to access other parts such as bearings for servicing and/or replacement. 
         [0022]    The adaptor may be produced using any appropriate technique such as casting, machining, or a combination of the two. In a preferred embodiment the adaptor is at least initially cast. The cast adaptor may subsequently be machined to produce the final adaptor. 
         [0023]    According to another aspect of the present invention there is provided a power generation system comprising a prime mover, a generator and an adaptor in any of the forms described above. 
         [0024]    The power generation system may further comprise a coupling for connecting rotating components of the generator and the prime mover. The coupling may be a flexible coupling, which may help to dampen vibratory torque in the system and/or act as a fuse in the drive line. 
         [0025]    Flexible couplings typically comprise an elastomeric component, in order to provide the desired flexibility. The elastomeric component may be, for example, rubber or any other appropriate material. In use, the elastomeric component may degrade over time, and may require replacement. This is typically a complex operation requiring removal of the generator and/or engine. 
         [0026]    In a preferred embodiment of the invention, the coupling comprises an elastomeric component which is removable radially from the coupling. This may allow the elastomeric component to be removed and replaced by removing a part of the adaptor. 
         [0027]    The elastomeric component is preferably removable without requiring removal of the generator. Preferably one part of the adaptor is removable to leave an opening while the other part of the adaptor remains in place, and the elastomeric component is removable through the opening. 
         [0028]    In one embodiment, the coupling comprises a hub and a coupling flange, and the elastomeric component is located between the hub and the coupling flange. For example, the elastomeric component may be disc-shaped, and may be located inside the coupling flange. This may provide a compact coupling arrangement. 
         [0029]    In order to allow the elastomeric component to be removed, the coupling may be arranged such that the coupling flange can be moved axially in order to disengage with the elastomeric component. A locking assembly may be provided for holding the coupling together during operation of the power generation system. The locking assembly, when disconnected, may be movable in an axial direction, in order to reveal the hub. 
         [0030]    In one embodiment the coupling comprises two elastomeric components, both of which may be located between the hub and a coupling flange, and both of which may be removable. At least one of the elastomeric components may be located around the hub. One or both of the elastomeric components may be located inside the coupling flange. 
         [0031]    Alternatively, other types of flexible coupling may be used. For example, the elastomeric component may be located adjacent to at least one of the hub and the coupling flange in an axial direction. 
         [0032]    The power generation system may further comprise a bed frame on which the prime mover and generator are mounted. Preferably one part of the adaptor can be removed to provide access to serviceable parts without removing the prime mover or the generator from the bed frame. 
         [0033]    The prime mover may be, for example, an internal combustion engine, such as a gas engine, a diesel engine or a petrol engine, or some other type of prime mover such as a wind or wave turbine. The generator may be any type of electrical generator, such as a synchronous generator or a permanent magnet generator. 
         [0034]    Corresponding methods may also be provided. Thus according to another aspect of the invention there is provided a method of servicing a power generation system comprising a prime mover coupled to a generator via an adaptor, the adaptor comprising two separable parts, the method comprising removing one part of the adaptor while the other part of the adaptor remains connected between the prime mover and the generator in order to provide access to serviceable parts. 
         [0035]    The power generation system may further comprise an elastomeric coupling, and the method may further comprise removing the elastomeric component of the coupling through an opening left by the removed part of the adaptor. Preferably the elastomeric component is removed in a radial direction and/or without moving the generator. 
         [0036]    In the present specification terms such as “radial”, “axial”, “circumferential” etc. are generally defined with reference to the axis of a generator and/or engine to which the adaptor is to be connected, and/or the longitudinal axis of the adaptor. 
         [0037]    Features of one aspect of the invention may be provided with any other aspect. Apparatus features may be provided with method aspects and vice versa. 
         [0038]    Preferred features of the present invention will now be described, purely by way of example, with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0039]      FIG. 1  shows an overview of a generating set in an embodiment of the present invention; 
           [0040]      FIG. 2  shows an adaptor in an embodiment of the present invention; 
           [0041]      FIG. 3  shows part of the generating set with the adaptor in place; 
           [0042]      FIG. 4  is an exploded view of a coupling for use in an embodiment of the present invention; and 
           [0043]      FIGS. 5 to 13  illustrate a process for replacement of elastomeric components in the coupling. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Overview 
       [0044]      FIG. 1  shows an overview of a generating set in an embodiment of the present invention. Referring to  FIG. 1 , the generating set comprises an engine  10  coupled to a generator (alternator)  12 . In this embodiment the engine  10  is a gas engine, although any type of internal combustion engine such as a petrol or diesel engine may be used instead. In this embodiment the generator  12  is a synchronous generator, although any other type of electrical generator may be used instead. The engine  10  and generator  12  are both mounted on a bed frame  14 . A coupling  16  is used to connect the engine flywheel to the shaft of the generator. An adaptor  18  surrounds the coupling, and is used to connect the engine to the generator housing. The adaptor  18  helps to prevent relative movement between the engine and the generator, thus ensuring greater stability during operation of the generating set. 
         [0045]    In the embodiment of  FIG. 1 , the coupling  16  is a flexible coupling. Flexible couplings are typically used in high power generating sets. For example, high horse power continuous purpose gas generating sets may require a flexible coupling, in particular where a variety of gases such as low BTU natural gas to pipeline gas are used. The flexible coupling can dampen vibratory torque in the system and acts as fuse in the drive line. 
         [0046]    Flexible couplings typically include an elastomeric material. The elastomeric material may degrade over time, particularly when subject to high stresses. As a consequence, the life time of a flexible coupling varies depending on its application. In some cases the flexible coupling may fail before the end of its target life. In this case servicing of the coupling may be required outside of a scheduled overhaul of the generator set. 
         [0047]    In existing generator set designs, the adaptor is formed from a single piece of cast metal. Windows may be provided in the adaptor, to allow an operator to connect the coupling once the generator and engine have been aligned. However this does not allow replacement or servicing of the coupling. 
         [0048]    In order to service the coupling in existing generator set designs, the generator set is first shut down. All harnesses and other connections are disconnected, and the generator with adaptor is pulled back from the engine. Following replacement or servicing of the coupling, it is necessary for all parts to be reconnected, and the generator to be re-aligned with the engine. 
         [0049]    As a consequence, replacement or servicing of the coupling is a complex and time consuming process, typically taking 14 to 15 hours depending on the installation. This results in high shutdown costs, both in terms of the servicing required and the lost generating capacity. 
       Adaptor Design 
       [0050]    Embodiments of the present invention relate to a new adaptor design and a new flexible coupling which can facilitate servicing without requiring the generator to be moved. 
         [0051]      FIG. 2  shows an adaptor  18  in an embodiment of the present invention. Referring to  FIG. 2 , the adaptor  18  is generally cylindrical, and comprises a first flange  22  for connection to the generator and a second flange  24  for connection to the engine. The first flange and second flange each comprise a number of bolt holes. Bolts  26  pass through the bolt holes in the first flange in order to connect the adaptor to the generator, while bolts  28  pass through the bolt holes in the second flange in order to connect the adaptor to the engine. In this embodiment cross braces  23  are provided on the outside surface of the adaptor, to help provide structural rigidity. Windows  25  are provided in the adaptor, to allow an operator to lock the coupling on generator shaft once the engine, generator and adaptor are in place. 
         [0052]    In the arrangement of  FIG. 2 , the adaptor  18  is divided into a top part  30  and a bottom part  32 . In this embodiment the division occurs in a plane within which the axis of symmetry of the adaptor lies. Thus, in this embodiment the two halves are semi-cylindrical. However the division may occur in different places and the two parts are not necessarily equal. 
         [0053]    Still referring to  FIG. 2 , flanges  34 ,  36  are provided at the interfaces between the top part and the bottom part. Each of the flanges has a number of bolt holes  38 . Bolts  40  pass through the bolt holes to connect the two parts together. Two additional centering pins  42  are provided on each side of the adaptor. The centering pins  42  help to ensure alignment between the two parts of the adaptor. In addition, centering pins  44  are provided in the second flange  24  in the top part  30 . The centering pins  44  help to ensure alignment of the top part  30  with the engine, in particular following removal of the top part in the way described below. 
         [0054]    The adaptor  18  of  FIG. 2  may be made from a cast metal, such as spheroidal graphite cast iron. The adaptor may be machined following casting to provide the appropriate interface surfaces and/or bolt holes. 
         [0055]      FIG. 3  shows part of the generating set with the adaptor  18  in place. Referring to  FIG. 3 , the two parts  30 ,  32  of the adaptor  18  are held together by bolts  40 . The adaptor is bolted to the engine  10  with bolts  26 , and to the generator  12  with bolts  28 . 
       Flexible Coupling 
       [0056]      FIG. 4  is an exploded view of a coupling for use in an embodiment of the present invention. Referring to  FIG. 4 , the coupling comprises a hub  50 , two elastomeric components  52 ,  54 , a coupling flange  56 , and a locking assembly  58 . The hub  50  is arranged to be connected to the generator shaft, while the coupling flange  56  is arranged to be connected to the engine fly wheel. 
         [0057]    In the arrangement of  FIG. 4 , each of the elastomeric components  52 ,  54  is disc-shaped. The elastomeric components may be made from any suitable material having the required degree of flexibility, such as rubber. A sleeve  53 ,  55  is provided on the inside of each of the elastomeric components  52 ,  54 . The sleeves are made from a rigid material such as a metal or a high density plastic. Each of the sleeves  53 ,  55  includes bolt holes  57 ,  59  for connecting the elastomeric components  52 ,  54  to the hub  50 . 
         [0058]    The hub  50  includes a hub flange  60  with bolt holes  62 . Hub bolts  64  pass through the bolt holes  62  and the bolt holes  57 ,  59  in the sleeves  53 ,  55 , in order to bolt the hub  50  to the elastomeric components  52 ,  54 . When connected, part of the hub  50  passes through the inside of the second elastomeric component  54 , while the end of the hub  50  engages with the sleeve  53  in the first elastomeric component  52 . 
         [0059]    The outside circumferences of the elastomeric components include castellations  66 . The coupling flange  56  is generally cylindrical, and fits around the elastomeric components  52 ,  54 . The inside surface of the coupling flange includes castellations  68 , which engage with the castellations  66  on the outside of the elastomeric components  52 ,  54 . 
         [0060]    The coupling flange  56  includes a flange  70  with bolt holes  72 . Flange bolts  74  are used to bolt the coupling flange to the engine fly wheel through the bolt holes  72 . The external locking assembly  58  comprises bolts  76  which are used to hold the coupling together. 
         [0061]    The coupling shown in  FIG. 4  provides a torsionally soft connection between the engine and the generator. A flexible torque transmission characteristic is achieved by means of the elastomeric components  52 ,  54  between the hub  50  and the coupling flange  56 . This can allow the absorption of torsional vibrations and may help to compensate for misalignments. 
       Servicing 
       [0062]    In use the elastomeric components  52 ,  54  shown in  FIG. 4  may degrade and require replacement.  FIGS. 5 to 13  illustrate a process for replacement of the elastomeric components  52 ,  54  without requiring removal of the generator  12 . 
         [0063]    Referring to  FIG. 5 , in step  1  the adaptor bolts  26  connecting the top part of the adaptor  30  to the engine  10 , and the adaptor bolts  28  connecting the top part of the adaptor  30  to the generator  12 , are undone. In addition, the bolts  40  connecting the two parts of the adaptor together are undone. 
         [0064]    Referring to  FIG. 6 , in step  2  the top part  30  of the adaptor is removed from the generator set in a radial direction. Removal of the top part of the adaptor exposes the coupling  16 . 
         [0065]    Referring to  FIG. 7 , in step  3  the bolts  76  of the external locking assembly  58  are undone. The locking assembly  58  is then slid axially along the shaft towards the generator  12 . This exposes the hub bolts  64 . 
         [0066]    Referring to  FIG. 8 , in step  4  the hub bolts  64  are undone and removed. This disconnects the elastomeric components  52 ,  54  from the hub  50 . 
         [0067]    Referring to  FIG. 9 , in step  5  the coupling flange bolts  74  are undone and removed. This disconnects the coupling flange  56  from the engine  10 . 
         [0068]    Referring to  FIG. 10 , in step  6  the coupling flange  56  is slid axially along the shaft towards the generator  12 . This reveals the first elastomeric component  52  and part of the second elastomeric component  54 . In this position the coupling flange  56  is held in place, for example, with a lifting device (not shown). 
         [0069]    Referring to  FIG. 11 , in step  7  the first elastomeric component  52  is then removed in a radial direction. Removal of the elastomeric component  52  is possible due to the fact that the hub bolts  64  have been removed and the coupling flange  56  has been pulled back. 
         [0070]    Referring to  FIG. 12 , in step  8  the second elastomeric component  54  is then slid axially along the hub  50  in the direction of the engine  10 . This releases the elastomeric component  54  from the hub. 
         [0071]    Referring to  FIG. 13 , in step  9  the second elastomeric component  54  is then removed in a radial direction. 
         [0072]    The elastomeric components  52 ,  54  can then be replaced. Steps  1  to  9  are then repeated in reverse, in order to reassemble the coupling with the new elastomeric components. 
         [0073]    Some of the advantages which may be provided by the techniques described above are as follows:
       No need to move the generator back when servicing the coupling   Fewer steps for disassembly/assembly   Servicing time reduced by 80% compared to previous techniques   Less facility space required   No need to disassemble other subsystems of the generator set, such as wires from the generator   Lower cost of ownership to the end user.       
 
         [0080]    In the above, embodiments of the invention have been described by way of example only, and variations in the design are possible. For example, the division between the two parts of the adaptor may be in different places and the two parts are not necessarily equal. It is not necessary for the adaptor to be divided along the whole of its length, and the removable part may extend along only part of the length of the adaptor. If desired, castellations may be provided on the interfaces between the two parts of the adaptor. Furthermore, if desired, the adaptor may comprise three or more parts, the only requirement being that at least one part of the adaptor is separable from the or each other part. Many other variations in detail will be apparent to the skilled person within the scope of the appended claims. 
         [0081]    Although embodiments of the invention have been described with reference to a generator set, the present invention may be used with any type of power generation system where an adaptor is used to connect a prime mover to a generator.

Technology Category: 2