AIR TURBINE STARTER INCLUDING A LIGHTWEIGHT, LOW DIFFERENTIAL PRESSURE CHECK VALVE

An air turbine starter includes a starter housing and a check valve. The check valve is disposed within the starter housing and is configured, in response to a pressure differential across the check valve, to selectively allow and prevent lubricant to flow therefrom. 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 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 and a closed position. 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.

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.

DETAILED DESCRIPTION

Turning now to the description, and with reference toFIG. 1, a simplified functional block diagram of at least a portion of a gas turbine engine system100is depicted. The depicted system100includes a gas turbine engine102, a gear box104, and an air turbine starter (ATS)106. The gas turbine engine102may be implemented as any one of numerous types of gas turbine engines. For example, the gas turbine engine102may 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 engine102is coupled to the gear box104. The gear box104, 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 ATS106to the gas turbine engine102during the start cycle of the gas turbine engine102. The gear box104is additionally configured to supply and receive lubricant. In particular, it is configured to at least supply lubricant to, and to receive lubricant from, the ATS106. To do so, the gear box104includes a lubricant supply passage108and a lubricant return passage112. Lubricant is supplied from the gear box104to the ATS106via the lubricant supply passage108, and is returned from the ATS106to the gear box104via the lubricant return passage112.

The ATS106includes a turbine section114and an output section116, which are housed within a starter housing118. The turbine section114is 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 SAV122is opened, and pressurized air is supplied from the non-illustrated pressurized air source to the turbine section114, the turbine section114rotates and generates a torque. This torque is transferred, via the output section116and the gear box104, to the gas turbine engine102. When the gas turbine engine102is driven to speed ignited, the SAV122is closed, and clutch (not depicted inFIG. 1) disengages the turbine section114from the output section116. Thus, the turbine section114comes to rest, while the output section116is driven by the gas turbine engine102.

Because at least a portion of the ATS106continuously rotates during both the start and run phases of the gas turbine engine102, the ATS106relies on a continuous flow of lubricant into and through it to ensure proper and continued operation. Thus, asFIG. 1further depicts, the starter housing118includes a lubricant supply opening124and a lubricant discharge opening126. The lubricant supply opening124is coupled to receive lubricant from a lubricant source, and the lubricant discharge opening126is configured to supply lubricant from the starter housing118to the lubricant source. In the depicted embodiment the lubricant source is the gear box104. As such, the lubricant supply opening124and the lubricant discharge opening126are in fluid communication with the lubricant supply passage108and the lubricant return passage112, respectively.

In addition to the above, a reservoir128and a check valve132are also disposed within the starter housing118. The reservoir128, which may be defined by the starter housing118and may be configured as a sump, is sized to hold a predetermined volume of the lubricant that is supplied to the ATS106via the lubricant supply opening124. The check valve132is disposed within the starter housing118proximate the lubricant discharge opening126, and receives lubricant from the reservoir128when the lubricant therein exceeds the predetermined volume. The check valve132is configured, in response to a pressure differential across the check valve132, to selectively allow and prevent lubricant to flow from the starter housing118and through the lubricant discharge opening126. The pressure differential across the check valve132exists when there is a pressure differential between the interior portion of the gear box104and the interior of the starter housing118. A particular preferred embodiment of the check valve132will be described further below. Before doing so, however, and for completeness, a slightly more detailed description of an embodiment of the ATS106will be provided.

Referring now toFIG. 2, a cross sectional view of an exemplary ATS106that may be used to implement the gas turbine engine system100ofFIG. 1is depicted. The ATS106, as already noted, is coupled to the gear box104and is housed within the starter housing118. The starter housing118may 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 section202and a starter housing output section204. The starter housing118additionally includes an inlet plenum206, which directs pressurized air into the starter housing118. The pressurized air supplied to the plenum206flows through an annular flow channel208and out a radial outlet port212. The annular flow channel208includes an axial flow portion214and a exhaust diffuser216. The axial flow portion214is formed through a stator assembly218that is mounted within the stator housing turbine section202proximate the inlet plenum206. The exhaust diffuser216is formed between a portion of the stator housing turbine section202and an exhaust housing219that is mounted between the starter housing118and the starter housing output section204.

A turbine wheel222is rotationally mounted within the stator housing turbine section202. In particular, the turbine wheel222has an output shaft224that extends from a hub226, through the exhaust housing219, and into the stator housing output section204. The turbine wheel output shaft224is rotationally mounted in the stator housing output section204by bearing assemblies228. A gear232is coupled to the turbine wheel output shaft224, and meshes with a compound planetary gear train234. The compound planetary gear train234engages a ring gear238and a hub gear242, which is in turn coupled to an overrunning clutch244. During operation of the ATS106, this gearing configuration converts the high speed, low torque output of the turbine wheel output shaft224into low speed, high torque input for the overrunning clutch244. The overrunning clutch244, as just noted, is coupled to the hub gear242, which is supported by another bearing assembly246. A drive shaft248extends from the overrunning clutch244, through the starter housing output section204, and is coupled to a starter output shaft252. The starter output shaft252is, in turn, coupled to non-illustrated gearing within the gear box104.

The check valve132is also depicted inFIG. 2and, as was previously noted, is disposed within the starter housing118proximate the lubricant discharge opening126. The check valve132is also disposed adjacent the reservoir132and receives lubricant therefrom when the lubricant in the reservoir exceeds the predetermined volume. With reference now toFIG. 3, an embodiment of the check valve132will be described.

The check valve132includes a valve body302and a valve element304. The valve body302includes a lubricant inlet port306and a lubricant outlet port308. The lubricant inlet port306is adapted to receive a flow of lubricant from, for example, the reservoir128, and the lubricant outlet port308is in fluid communication with the lubricant discharge opening126. It will be appreciated that the valve body302may be formed as an integral part of the starter housing118, and thus be defined by the lubricant discharge opening126, or the valve body302may be separately formed and disposed adjacent to or within the discharge opening126.

The valve body302has a valve seat312and a valve bore314formed therein. The valve seat312is disposed between the lubricant inlet port306and the lubricant outlet port308and has an opening316formed therein. The opening316, as will be described momentarily, is selectively sealed and unsealed by the valve element304, and thus selectively prevents and allows, respectively, lubricant flow between the lubricant inlet306and outlet308ports. The valve bore314is formed in the valve body302between the valve seat312and the lubricant outlet port308, and has the valve element304disposed therein.

The valve element304is movably disposed within the valve bore314and is movable between a closed position and a plurality of open positions. In the closed position, the valve element304sealingly engages the valve seat312and thus lubricant may not flow between the lubricant inlet port306and the lubricant outlet port308. Conversely, in an open position, the valve element304is spaced apart from the valve seat312and thus lubricant may flow between the lubricant inlet port306and the lubricant outlet port308.

AsFIG. 3also depicts, a perforated screen318is coupled to the valve body302and is disposed adjacent the lubricant outlet port308. The perforated screen318, 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 housing118from entering the gear box104. The perforated screen318additionally retains the valve element304within the valve bore314.

It will be appreciated that the valve element304may be variously shaped, and may comprise various materials. In the depicted embodiment, the valve element304is 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 element302, it will additionally be appreciated that the valve seat312is preferably conformed to the shape of the valve element304in order to provide a sufficiently fluid-tight seal when the valve element304is in the closed position.

The valve element304and valve bore314are dimensioned to accommodate the maximum lubricant flow rate that is needed between the gear box104and ATS106. Moreover, the valve element304is preferably sized as large as possible to respond quickly to a pressure differential between the gear box104and starter housing118. To balance these flow and size needs, the valve body302, as depicted more clearly inFIG. 4, has a plurality of rounded grooves402formed therein. The rounded grooves402are disposed adjacent to, and are in fluid communication with, the valve bore314and are configured to improve lubricant flow past the valve element304when the valve element304is in an open position. Although the number and location of the grooves402may vary, in the depicted embodiment the valve bore314has two grooves402formed therein, which are radially spaced apart by about 120-degrees. It is additionally noted that remainder of the valve bore314between the grooves402is shaped and dimensioned to provide proper positioning and centering of the valve element304.

During normal operations of the gas turbine engine system100, there is no pressure differential between the gear box104and ATS106, and thus no pressure differential between the gear box lubricant return passage112and the ATS lubricant discharge opening126. As a result, the valve element304may freely translate within the valve bore314to an open position, allowing lubricant to flow from the reservoir128, into and through the lubricant inlet port306, into and through the opening316in the valve seat312, and out the lubricant outlet port308. As noted above, the rounded grooves402formed in the valve body302allow lubricant that flows through the opening316in the valve seat to flow past the valve element304to the lubricant outlet port.

Now, in the highly unlikely, yet postulated event of a breach in the starter housing118, the pressure in the ATS106equalizes with ambient pressure and drops below the pressure within the gear box104. 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 valve132, in response to the differential pressure, moves to the closed position. More specifically, the valve element304sealingly engages the valve seat312, and thus prevents lubricant flow from the gear box lubricant return passage112into the ATS lubricant discharge opening126, and out the breach in the starter housing118.

The check valve132disclosed 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.