Patent Publication Number: US-2015082805-A1

Title: Air turbine starter including a lightweight, low differential pressure check valve

Description:
TECHNICAL FIELD 
     The present invention generally relates to air turbine starters, and more particularly relates to an air turbine starter with a lightweight, low differential pressure check valve. 
     BACKGROUND 
     An air turbine starter (ATS) is typically used to start the rotation of an aircraft turbine engine, such as a gas turbine jet engine. The ATS is typically mounted to the jet engine through a gearbox or other transmission assembly, and a cover plate or wall is located between the starter and gearbox housings. To start the engine, pressurized air is supplied to the ATS by, for example, opening a starter air valve (SAV). The pressurized air supplied to the ATS causes it to rotate and generate a torque. The gearbox transfers the torque from the rotating ATS to the engine to drive the engine up to speed and allow engine ignition. Thereafter, the SAV is closed, and a clutch disengages the ATS turbine from the ATS output shaft. Thus, the ATS turbine comes to rest, while the ATS output shaft is driven by the engine. 
     Many air turbine starters rely on a supply of lubricant to run properly. Some air turbine starters use an assisted wet cavity design (AWC) to assist in lubricant supply. With these designs, the ATS housing includes a mounting face or mounting flange that is sealingly engaged with, and coupled to, the gearbox. The ATS and gearbox are each configured with ports that allow lubricant to flow between the gearbox and the ATS. 
     In many AWC designs, the pressure within the gearbox and ATS housing may be about 0.1 to 0.3 psi above ambient pressure. This generally presents no issues. However, it has been postulated that if a breach in the ATS housing were to occur, resulting in the ATS housing pressure equalizing with ambient pressure, then the pressure within the gearbox may cause lubricant to leak from the gearbox to the starter and, consequently, out through the breach. To address such a postulated event, many ATSs include a check valve or reed valve. However, because the pressure differential between the ambient environment and the gearbox is relatively small, it has been found that these valve types may not work consistently. 
     Hence, there is a need for a lightweight, low differential pressure check valve that will consistently operate at relatively low differential pressures to ensure lubricant is not lost from the AGB in the event of an ATS housing breach. The present invention addresses at least this need. 
     BRIEF SUMMARY 
     In one embodiment, an air turbine starter includes a starter housing and a check valve. The starter housing includes a lubricant supply opening and a lubricant discharge opening. The lubricant supply opening is adapted to receive lubricant from a lubricant source, and the lubricant discharge opening is configured to supply lubricant from the starter housing to the lubricant source. The check valve is disposed within the starter housing proximate the lubricant discharge opening. The check valve is configured, in response to a pressure differential across the check valve, to selectively allow and prevent lubricant to flow from the starter housing and through the discharge opening. The check valve includes a valve includes a valve body, a valve seat, a valve bore, a valve element, and a plurality of rounded grooves. The valve body includes a lubricant inlet port and a lubricant outlet port. The lubricant inlet port is adapted to receive a flow of lubricant, and the lubricant outlet port is in fluid communication with the lubricant discharge opening. The valve seat is formed in the valve body and is disposed between the lubricant inlet port and the lubricant outlet port, and has an opening formed therein. The valve bore is formed in the valve body between the valve seat and the lubricant outlet port. The valve element is disposed within the valve bore and is movable between a plurality of open positions, in which lubricant may flow between the lubricant inlet port and the lubricant outlet port, and a closed position, in which lubricant may not flow between the lubricant inlet port and the lubricant outlet port. The rounded grooves are formed in the valve body, and are disposed adjacent to, and in fluid communication with, the valve bore to improve lubricant to flow past the valve element when the valve element is in an open position. 
     In another embodiment, a gas turbine engine system includes a gas turbine engine, a gear box, and an air turbine starter. The gear box is coupled to the gas turbine engine and is configured to supply and receive lubricant. The air turbine starter is coupled to the auxiliary gear box and includes a starter housing and a check valve. The starter housing includes a lubricant supply opening and a lubricant discharge opening. The lubricant supply opening is coupled to receive lubricant supplied from the auxiliary gear box, and the lubricant discharge opening is configured to supply lubricant from the starter housing to the auxiliary gear box. The check valve is disposed within the starter housing proximate the lubricant discharge opening. The check valve is configured, in response to a pressure differential between the starter housing and the auxiliary gear box, to selectively allow and prevent lubricant to flow from the starter housing, through the discharge opening, and into the auxiliary gear box. The check valve includes a valve includes a valve body, a valve seat, a valve bore, a valve element, and a plurality of rounded grooves. The valve body includes a lubricant inlet port and a lubricant outlet port. The lubricant inlet port is adapted to receive a flow of lubricant, and the lubricant outlet port is in fluid communication with the lubricant discharge opening. The valve seat is formed in the valve body and is disposed between the lubricant inlet port and the lubricant outlet port, and has an opening formed therein. The valve bore is formed in the valve body between the valve seat and the lubricant outlet port. The valve element is disposed within the valve bore and is movable between a plurality of open positions, in which lubricant may flow between the lubricant inlet port and the lubricant outlet port, and a closed position, in which lubricant may not flow between the lubricant inlet port and the lubricant outlet port. The rounded grooves are formed in the valve body, and are disposed adjacent to, and in fluid communication with, the valve bore to improve lubricant to flow past the valve element when the valve element is in an open position. 
     In yet another embodiment, a check valve includes a valve body, a valve seat, a valve bore, a valve element, and a plurality of rounded grooves. The valve body includes a lubricant inlet port and a lubricant outlet port. The lubricant inlet port is adapted to receive a flow of lubricant, and the lubricant outlet port is in fluid communication with the lubricant discharge opening. The valve seat is formed in the valve body and is disposed between the lubricant inlet port and the lubricant outlet port, and has an opening formed therein. The valve bore is formed in the valve body between the valve seat and the lubricant outlet port. The valve element is disposed within the valve bore and is movable between a plurality of open positions, in which lubricant may flow between the lubricant inlet port and the lubricant outlet port, and a closed position, in which lubricant may not flow between the lubricant inlet port and the lubricant outlet port. The rounded grooves are formed in the valve body, and are disposed adjacent to, and in fluid communication with, the valve bore to improve lubricant to flow past the valve element when the valve element is in an open position. 
     Furthermore, other desirable features and characteristics of the air turbine starter will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements, and wherein: 
         FIG. 1  depicts a simplified functional block diagram of at least a portion of one embodiment of a gas turbine engine system; 
         FIG. 2  depicts a cross section view of one embodiment of an air turbine starter that may be used to implement the system of  FIG. 1 ; 
         FIG. 3  depicts a cross section view of one embodiment of a check valve that may be disposed within the air turbine starter of  FIG. 1  or  FIG. 2 ; and 
         FIG. 4  depicts and end view of the check valve depicted in  FIG. 3 , but with the valve element removed. 
     
    
    
     DETAILED DESCRIPTION 
     The following detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. As used herein, the word “exemplary” means “serving as an example, instance, or illustration.” Thus, any embodiment described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other embodiments. All of the embodiments described herein are exemplary embodiments provided to enable persons skilled in the art to make or use the invention and not to limit the scope of the invention which is defined by the claims. Furthermore, there is no intention to be bound by any expressed or implied theory presented in the preceding technical field, background, brief summary, or the following detailed description. 
     Turning now to the description, and with reference to  FIG. 1 , a simplified functional block diagram of at least a portion of a gas turbine engine system  100  is depicted. The depicted system  100  includes a gas turbine engine  102 , a gear box  104 , and an air turbine starter (ATS)  106 . The gas turbine engine  102  may be implemented as any one of numerous types of gas turbine engines. For example, the gas turbine engine  102  may be implemented as a propulsion engine or an auxiliary power unit (APU). In this regard, it may be implemented using any one of numerous multi-spool turbofan gas turbine propulsion engines, or as a single or multi-spool APU. 
     Regardless of its specific implementation, the gas turbine engine  102  is coupled to the gear box  104 . The gear box  104 , which may be configured as an auxiliary gear box (AGB), houses a plurality of non-illustrated gears. These non-illustrated gears are configured to transfer torque from the ATS  106  to the gas turbine engine  102  during the start cycle of the gas turbine engine  102 . The gear box  104  is additionally configured to supply and receive lubricant. In particular, it is configured to at least supply lubricant to, and to receive lubricant from, the ATS  106 . To do so, the gear box  104  includes a lubricant supply passage  108  and a lubricant return passage  112 . Lubricant is supplied from the gear box  104  to the ATS  106  via the lubricant supply passage  108 , and is returned from the ATS  106  to the gear box  104  via the lubricant return passage  112 . 
     The ATS  106  includes a turbine section  114  and an output section  116 , which are housed within a starter housing  118 . The turbine section  114  is coupled to selectively receive a flow of compressed air from a non-illustrated pressurized air source via, for example, a starter air valve (SAV)  122 . When the SAV  122  is opened, and pressurized air is supplied from the non-illustrated pressurized air source to the turbine section  114 , the turbine section  114  rotates and generates a torque. This torque is transferred, via the output section  116  and the gear box  104 , to the gas turbine engine  102 . When the gas turbine engine  102  is driven to speed ignited, the SAV  122  is closed, and clutch (not depicted in  FIG. 1 ) disengages the turbine section  114  from the output section  116 . Thus, the turbine section  114  comes to rest, while the output section  116  is driven by the gas turbine engine  102 . 
     Because at least a portion of the ATS  106  continuously rotates during both the start and run phases of the gas turbine engine  102 , the ATS  106  relies on a continuous flow of lubricant into and through it to ensure proper and continued operation. Thus, as  FIG. 1  further depicts, the starter housing  118  includes a lubricant supply opening  124  and a lubricant discharge opening  126 . The lubricant supply opening  124  is coupled to receive lubricant from a lubricant source, and the lubricant discharge opening  126  is configured to supply lubricant from the starter housing  118  to the lubricant source. In the depicted embodiment the lubricant source is the gear box  104 . As such, the lubricant supply opening  124  and the lubricant discharge opening  126  are in fluid communication with the lubricant supply passage  108  and the lubricant return passage  112 , respectively. 
     In addition to the above, a reservoir  128  and a check valve  132  are also disposed within the starter housing  118 . The reservoir  128 , which may be defined by the starter housing  118  and may be configured as a sump, is sized to hold a predetermined volume of the lubricant that is supplied to the ATS  106  via the lubricant supply opening  124 . The check valve  132  is disposed within the starter housing  118  proximate the lubricant discharge opening  126 , and receives lubricant from the reservoir  128  when the lubricant therein exceeds the predetermined volume. The check valve  132  is configured, in response to a pressure differential across the check valve  132 , to selectively allow and prevent lubricant to flow from the starter housing  118  and through the lubricant discharge opening  126 . The pressure differential across the check valve  132  exists when there is a pressure differential between the interior portion of the gear box  104  and the interior of the starter housing  118 . A particular preferred embodiment of the check valve  132  will be described further below. Before doing so, however, and for completeness, a slightly more detailed description of an embodiment of the ATS  106  will be provided. 
     Referring now to  FIG. 2 , a cross sectional view of an exemplary ATS  106  that may be used to implement the gas turbine engine system  100  of  FIG. 1  is depicted. The ATS  106 , as already noted, is coupled to the gear box  104  and is housed within the starter housing  118 . The starter housing  118  may be made up of two or more parts that are combined together or may be integrally formed as a single piece, but in the depicted embodiment it includes at least a starter housing turbine section  202  and a starter housing output section  204 . The starter housing  118  additionally includes an inlet plenum  206 , which directs pressurized air into the starter housing  118 . The pressurized air supplied to the plenum  206  flows through an annular flow channel  208  and out a radial outlet port  212 . The annular flow channel  208  includes an axial flow portion  214  and a exhaust diffuser  216 . The axial flow portion  214  is formed through a stator assembly  218  that is mounted within the stator housing turbine section  202  proximate the inlet plenum  206 . The exhaust diffuser  216  is formed between a portion of the stator housing turbine section  202  and an exhaust housing  219  that is mounted between the starter housing  118  and the starter housing output section  204 . 
     A turbine wheel  222  is rotationally mounted within the stator housing turbine section  202 . In particular, the turbine wheel  222  has an output shaft  224  that extends from a hub  226 , through the exhaust housing  219 , and into the stator housing output section  204 . The turbine wheel output shaft  224  is rotationally mounted in the stator housing output section  204  by bearing assemblies  228 . A gear  232  is coupled to the turbine wheel output shaft  224 , and meshes with a compound planetary gear train  234 . The compound planetary gear train  234  engages a ring gear  238  and a hub gear  242 , which is in turn coupled to an overrunning clutch  244 . During operation of the ATS  106 , this gearing configuration converts the high speed, low torque output of the turbine wheel output shaft  224  into low speed, high torque input for the overrunning clutch  244 . The overrunning clutch  244 , as just noted, is coupled to the hub gear  242 , which is supported by another bearing assembly  246 . A drive shaft  248  extends from the overrunning clutch  244 , through the starter housing output section  204 , and is coupled to a starter output shaft  252 . The starter output shaft  252  is, in turn, coupled to non-illustrated gearing within the gear box  104 . 
     The check valve  132  is also depicted in  FIG. 2  and, as was previously noted, is disposed within the starter housing  118  proximate the lubricant discharge opening  126 . The check valve  132  is also disposed adjacent the reservoir  132  and receives lubricant therefrom when the lubricant in the reservoir exceeds the predetermined volume. With reference now to  FIG. 3 , an embodiment of the check valve  132  will be described. 
     The check valve  132  includes a valve body  302  and a valve element  304 . The valve body  302  includes a lubricant inlet port  306  and a lubricant outlet port  308 . The lubricant inlet port  306  is adapted to receive a flow of lubricant from, for example, the reservoir  128 , and the lubricant outlet port  308  is in fluid communication with the lubricant discharge opening  126 . It will be appreciated that the valve body  302  may be formed as an integral part of the starter housing  118 , and thus be defined by the lubricant discharge opening  126 , or the valve body  302  may be separately formed and disposed adjacent to or within the discharge opening  126 . 
     The valve body  302  has a valve seat  312  and a valve bore  314  formed therein. The valve seat  312  is disposed between the lubricant inlet port  306  and the lubricant outlet port  308  and has an opening  316  formed therein. The opening  316 , as will be described momentarily, is selectively sealed and unsealed by the valve element  304 , and thus selectively prevents and allows, respectively, lubricant flow between the lubricant inlet  306  and outlet  308  ports. The valve bore  314  is formed in the valve body  302  between the valve seat  312  and the lubricant outlet port  308 , and has the valve element  304  disposed therein. 
     The valve element  304  is movably disposed within the valve bore  314  and is movable between a closed position and a plurality of open positions. In the closed position, the valve element  304  sealingly engages the valve seat  312  and thus lubricant may not flow between the lubricant inlet port  306  and the lubricant outlet port  308 . Conversely, in an open position, the valve element  304  is spaced apart from the valve seat  312  and thus lubricant may flow between the lubricant inlet port  306  and the lubricant outlet port  308 . 
     As  FIG. 3  also depicts, a perforated screen  318  is coupled to the valve body  302  and is disposed adjacent the lubricant outlet port  308 . The perforated screen  318 , which may be implemented with any one of numerous suitably sized perforations, prevents any debris that may be present in the lubricant in the starter housing  118  from entering the gear box  104 . The perforated screen  318  additionally retains the valve element  304  within the valve bore  314 . 
     It will be appreciated that the valve element  304  may be variously shaped, and may comprise various materials. In the depicted embodiment, the valve element  304  is solid and spherically shaped, and is comprised of a relatively lightweight, non-buoyant thermoplastic such as, for example, PEEK (polyetheretherketone). Regardless of the specific shape of the valve element  302 , it will additionally be appreciated that the valve seat  312  is preferably conformed to the shape of the valve element  304  in order to provide a sufficiently fluid-tight seal when the valve element  304  is in the closed position. 
     The valve element  304  and valve bore  314  are dimensioned to accommodate the maximum lubricant flow rate that is needed between the gear box  104  and ATS  106 . Moreover, the valve element  304  is preferably sized as large as possible to respond quickly to a pressure differential between the gear box  104  and starter housing  118 . To balance these flow and size needs, the valve body  302 , as depicted more clearly in  FIG. 4 , has a plurality of rounded grooves  402  formed therein. The rounded grooves  402  are disposed adjacent to, and are in fluid communication with, the valve bore  314  and are configured to improve lubricant flow past the valve element  304  when the valve element  304  is in an open position. Although the number and location of the grooves  402  may vary, in the depicted embodiment the valve bore  314  has two grooves  402  formed therein, which are radially spaced apart by about 120-degrees. It is additionally noted that remainder of the valve bore  314  between the grooves  402  is shaped and dimensioned to provide proper positioning and centering of the valve element  304 . 
     During normal operations of the gas turbine engine system  100 , there is no pressure differential between the gear box  104  and ATS  106 , and thus no pressure differential between the gear box lubricant return passage  112  and the ATS lubricant discharge opening  126 . As a result, the valve element  304  may freely translate within the valve bore  314  to an open position, allowing lubricant to flow from the reservoir  128 , into and through the lubricant inlet port  306 , into and through the opening  316  in the valve seat  312 , and out the lubricant outlet port  308 . As noted above, the rounded grooves  402  formed in the valve body  302  allow lubricant that flows through the opening  316  in the valve seat to flow past the valve element  304  to the lubricant outlet port. 
     Now, in the highly unlikely, yet postulated event of a breach in the starter housing  118 , the pressure in the ATS  106  equalizes with ambient pressure and drops below the pressure within the gear box  104 . This pressure differential will generally be relatively small and can be, for example, about 0.1 to 0.3 psid. Regardless of the specific magnitude, the check valve  132 , in response to the differential pressure, moves to the closed position. More specifically, the valve element  304  sealingly engages the valve seat  312 , and thus prevents lubricant flow from the gear box lubricant return passage  112  into the ATS lubricant discharge opening  126 , and out the breach in the starter housing  118 . 
     The check valve  132  disclosed herein is a lightweight, low differential pressure valve that consistently operates at relatively low differential pressures to ensure lubricant is not lost from the gear box in the highly unlikely, yet postulated event of a starter housing breach. 
     In this document, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Numerical ordinals such as “first,” “second,” “third,” etc. simply denote different singles of a plurality and do not imply any order or sequence unless specifically defined by the claim language. The sequence of the text in any of the claims does not imply that process steps must be performed in a temporal or logical order according to such sequence unless it is specifically defined by the language of the claim. The process steps may be interchanged in any order without departing from the scope of the invention as long as such an interchange does not contradict the claim language and is not logically nonsensical. 
     Furthermore, depending on the context, words such as “connect” or “coupled to” used in describing a relationship between different elements do not imply that a direct physical connection must be made between these elements. For example, two elements may be connected to each other physically or in any other manner, through one or more additional elements. 
     While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention. It being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.