Patent Application
20160169118
This disclosure relates to an accessory drive gearbox for a gas turbine engine.
A gas turbine engine typically includes a fan section, a compressor section, a combustor section and a turbine section. Air entering the compressor section is compressed and delivered into the combustor section where it is mixed with fuel and ignited to generate a high-speed exhaust gas flow. The high-speed exhaust gas flow expands through the turbine section to drive the compressor and the fan section. The compressor section typically includes low and high pressure compressors, and the turbine section includes low and high pressure turbines.
A typical gas turbine engine utilizes one or more gearboxes to drive accessory components, such as generators, fuel pumps and oil pumps. Each of the accessory drive components must be driven at a desired rotational speed. As a result, the accessory is coupled to either the low or high speed spool and geared accordingly to obtain the speed at which the accessory operates more efficiently. Thus, it is not uncommon to use one gearbox coupled to the low spool to drive lower speed accessory drive components, and use a separate gearbox coupled to the high spool to drive the other accessory drive components at a higher speed.
One gearbox has been proposed in which both high and low speed accessory drive components are driven by a single tower shaft. Gearing within the gearbox obtains a desired rotational speed and direction for each of the accessory drive components.
In one exemplary embodiment, a gas turbine engine includes a turbine section that has first and second turbines mounted for rotation about a common rotational axis within an engine static structure. First and second turbine shafts coaxial with one another and to which the first and second turbines are respectively operatively mounted. First and second tower shafts respectively coupled to the first and second turbine shafts. An accessory drive gearbox is mounted to the engine static structure. The accessory drive gearbox includes gears arranged within a common housing. The first and second tower shafts extend into the common housing and are coupled to the gears.
In a further embodiment of the above, the first and second turbine shafts are inner and outer shafts, respectively. The first and second turbines are low and high pressure turbines, respectively.
In a further embodiment of any of the above, the second tower shaft is configured to rotate at a higher speed than the first tower shaft.
In a further embodiment of any of the above, a first set of accessories are configured to be rotationally driven by the first tower shaft. A second set of accessories are configured to be rotationally driven by the second tower shaft.
In a further embodiment of any of the above, the first set of accessories includes at least one of a generator, a deoiler and a hydraulic pump.
In a further embodiment of any of the above, the second set of accessories includes at least one of a generator, a fuel pump, an oil pump and a permanent magnet alternator.
In a further embodiment of any of the above, the first and second tower shafts extend in a generally radial direction from the rotational axis. The first and second tower shafts are arranged at an angle circumferentially relative to one another.
In a further embodiment of any of the above, the angle is less than 90°.
In a further embodiment of any of the above, the gears include first and second sets of gears respectively coupled to the first and second tower shafts. The the first set of gears is not in meshing engagement with the second set of gears.
In a further embodiment of any of the above, at least a portion of the first and second sets of gears circumferentially overlap one another.
In a further embodiment of any of the above, the housing includes a locating feature that is configured to circumferentially locate and align at least one of the first and second tower shafts relative to at least one of the first and second turbine shafts.
In a further embodiment of any of the above, the locating feature includes a bore and a first cover that has an eccentric pilot received in the bore. The first cover includes a hole and is rotatable within the bore to reposition the hole relative to the housing. The hole supports one of the first and second tower shafts.
In a further embodiment of any of the above, the housing includes a second cover opposite the first cover and is configured to facilitate insertion of one of the first and second tower shafts into the housing during assembly.
In another exemplary embodiment, there is a method of installing an accessory gearbox onto a gas turbine engine. The method includes the steps of mounting a gearbox housing onto an engine static structure. The gearbox housing has first and second opposing sides. A first tower shaft is inserted into the first side of the housing, through the second side, and into the engine static structure to couple the first tower shaft with a first turbine shaft in the static structure and a first gear set in the gearbox housing. A second tower shaft is inserted into the first side of the housing, through the second side, and into the engine static structure to couple the second tower shaft with a second turbine shaft in the static structure and a second gear set in the gearbox housing.
In a further embodiment of any of the above, the first set of gears is not in meshing engagement with the second set of gears.
In a further embodiment of any of the above, the method includes the step of adjusting a position of a locating feature to circumferentially locate and align at least one of the first and second tower shafts relative to at least one of the first and second turbine shafts.
In a further embodiment of any of the above, a turbine section has first and second turbines mounted for rotation about a common rotational axis within the engine static structure. The first and second turbine shafts coaxial with one another and to which the first and second turbines are respectively operatively mounted. The first and second turbine shafts are inner and outer shafts, respectively. The first and second turbines are low and high pressure turbines, respectively. The second tower shaft is configured to rotate at a higher speed than the first tower shaft.
In a further embodiment of any of the above, the inserting steps include installing the first and second tower shafts in a generally radial direction relative to the rotational axis. The first and second tower shafts are at an acute angle circumferentially relative to one another.
In a further embodiment of any of the above, the method includes the step of mounting first and second sets of accessories to the gearbox. The first set of accessories includes at least one of a generator, a deoiler and a hydraulic pump. The second set of accessories includes at least one of a generator, a fuel pump, an oil pump and a permanent magnet alternator.
The disclosure can be further understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:
The embodiments, examples and alternatives of the preceding paragraphs, the claims, or the following description and drawings, including any of their various aspects or respective individual features, may be taken independently or in any combination. Features described in connection with one embodiment are applicable to all embodiments, unless such features are incompatible.
The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis X relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided, and the location of bearing systems 38 may be varied as appropriate to the application.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a first (or low) pressure compressor 44 and a first (or low) pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism, which in exemplary gas turbine engine 20 is illustrated as a geared architecture 48 to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a second (or high) pressure compressor 52 and a second (or high) pressure turbine 54. A combustor 56 is arranged in exemplary gas turbine 20 between the high pressure compressor 52 and the high pressure turbine 54. A mid-turbine frame 57 of the engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The mid-turbine frame 57 further supports bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis X which is collinear with their longitudinal axes.
The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The mid-turbine frame 57 includes airfoils 59 which are in the core airflow path C. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion. It will be appreciated that each of the positions of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may be varied. For example, gear system 48 may be located aft of combustor section 26 or even aft of turbine section 28, and fan section 22 may be positioned forward or aft of the location of gear system 48.
The engine 20 in one example is a high-bypass geared aircraft engine. In a further example, the engine 20 bypass ratio is greater than about six (6), with an example embodiment being greater than about ten (10), the geared architecture 48 is an epicyclic gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3 and the low pressure turbine 46 has a pressure ratio that is greater than about five. In one disclosed embodiment, the engine 20 bypass ratio is greater than about ten (10:1), the fan diameter is significantly larger than that of the low pressure compressor 44, and the low pressure turbine 46 has a pressure ratio that is greater than about five 5:1. Low pressure turbine 46 pressure ratio is pressure measured prior to inlet of low pressure turbine 46 as related to the pressure at the outlet of the low pressure turbine 46 prior to an exhaust nozzle. The geared architecture 48 may be an epicycle gear train, such as a planetary gear system or other gear system, with a gear reduction ratio of greater than about 2.3:1. It should be understood, however, that the above parameters are only exemplary of one embodiment of a geared architecture engine and that the present invention is applicable to other gas turbine engines including direct drive turbofans.
A significant amount of thrust is provided by the bypass flow B due to the high bypass ratio. The fan section 22 of the engine 20 is designed for a particular flight condition—typically cruise at about 0.8 Mach and about 35,000 feet (10,668 meters). The flight condition of 0.8 Mach and 35,000 ft (10,668 meters), with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of lbm of fuel being burned divided by lbf of thrust the engine produces at that minimum point. “Low fan pressure ratio” is the pressure ratio across the fan blade alone, without a Fan Exit Guide Vane (“FEGV”) system. The low fan pressure ratio as disclosed herein according to one non-limiting embodiment is less than about 1.45. “Low corrected fan tip speed” is the actual fan tip speed in ft/sec divided by an industry standard temperature correction of [(Tram ° R)/(518.7° R)]0.5. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second (350.5 meters/second).
Referring to
Referring to
The gearbox 60 includes first and second opposing sides 80, 82. In one example, the first and second tower shafts 68, 70 are inserted (shown in
Referring to
Referring to
The first tower shaft 68 is inserted through a first stub shaft 106, which is coupled to a first bevel gear 110. The first stub shaft 106 includes a first splined hole 114 that meshes with an end of the first tower shaft 68 once inserted into the gearbox 60. Similarly, the gearbox 60 includes a second stub shaft 108 coupled to a second bevel gear 112. The second stub shaft 108 includes a second splined hole 116, which is interconnected to the second tower shaft 70 once installed. The tower shafts 68, 70 extend through first covers 118 mounted on the first side 80, shown in
Since there are two tower shafts extending from the same gearbox 60, it may be desirable to incorporate a locating feature to reposition at least one of the tower shafts and align it with features in the gas turbine engine, such as the inner and outer shafts 40, 52. In one example shown in
It should also be understood that although a particular component arrangement is disclosed in the illustrated embodiment, other arrangements will benefit herefrom. Although particular step sequences are shown, described, and claimed, it should be understood that steps may be performed in any order, separated or combined unless otherwise indicated and will still benefit from the present invention.
Although the different examples have specific components shown in the illustrations, embodiments of this invention are not limited to those particular combinations. It is possible to use some of the components or features from one of the examples in combination with features or components from another one of the examples.
Although an example embodiment has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of the claims. For that reason, the following claims should be studied to determine their true scope and content.
This application claims priority to U.S. Provisional Application No. 62/091,054, which was filed on Dec. 12, 2014 and is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 62091054 | Dec 2014 | US |
