The application relates generally to gas turbine engines and, more particularly, to accessories mounting arrangement.
Gas turbine engines which power aircraft are often provided with accessories such as electrical generators, pumps and the like, which are required for operation of the engine and an associated aircraft. It is common practice to mechanically connect such accessories to the engine by means of an accessory gearbox, which is itself mechanically connected to the rotational shaft of the engine. The accessories may be mounted either in parallel to the main engine shaft(s) or be mounted serially at one end, or a combination thereof. Accessories must also sometimes be removed and repaired or replaced, ideally without also removing the engine from within the aircraft. A need for improvement in engine accessories exists.
In one aspect, there is provided a gas turbine engine comprising: an air inlet case for receiving air, a compressor, a combustor, a turbine having a shaft rotatable about a turbine shaft centerline, an accessory gear box (AGB) positioned adjacent an axial end of the air inlet case and driven by the turbine, and at least one engine accessory drivingly connected to the AGB and having an input shaft having an input axis which is disposed transverse to the turbine shaft.
In another aspect, there is provided a gas turbine engine comprising: an air inlet case for receiving air, a compressor rotatable about an engine centerline for pressurizing the air from the air inlet case, a combustor in which the air compressed by the compressor is mixed with fuel and ignited for generating a stream of combustion gases, a turbine rotatable about the engine centerline for extracting energy from the combustion gases, an accessory gear box (AGB) centered relative to the engine centerline upstream of the air inlet case, and accessories drivingly connected to the AGB, the accessories being oriented transversally to the engine centerline.
In yet another aspect, there is provided a gas turbine engine comprising an air inlet case for receiving air, a compressor rotatable about an engine centerline for pressurizing the air from the air inlet case, a combustor in which the air compressed by the compressor is mixed with fuel and ignited for generating a stream of combustion gases, a turbine rotatable about the engine centerline for extracting energy from the combustion gases, an accessory gear box (AGB) mounted in-line with the engine centerline, and at least one accessory drivingly connected to the AGB, the at least one accessory being oriented transversally to the engine centerline.
Reference is now made to the accompanying figures in which:
The gas turbine engine 10 (sometimes referred to herein simply as “engine 10”) has a central core 18 defining a gas path through which gases flow as depicted by flow arrows in
It will thus be appreciated that the expressions “forward” and “aft” used herein refer to the relative disposition of components of the engine 10, in correspondence to the “forward” and “aft” directions of the engine 10 and aircraft including the engine 10 as defined with respect to the direction of travel. In the embodiment shown, a component of the engine 10 that is “forward” of another component is arranged within the engine 10 such that it is located closer to the propeller 16. Similarly, a component of the engine 10 that is “aft” of another component is arranged within the engine 10 such that it is further away from the propeller 16.
Still referring to
The LP spool 20 includes at least one component to compress the air that is part of the compressor section 12, and at least one component to extract energy from the combustion gases that is part of the turbine section 14. More particularly, the LP spool 20 has a low pressure turbine 21 which extracts energy from the combustion gases, and which is drivingly engaged (e.g. directly connected) to an LP compressor 22 for pressurizing the air. The LP turbine 21 (also referred to as the power turbine) drives the LP compressor 22, thereby causing the LP compressor 22 to pressurize the air. Both the LP turbine 21 and the LP compressor 22 are disposed along the axis 17. In the depicted embodiment, both the LP turbine 21 and the LP compressor 22 are axial rotatable components having an axis of rotation that is coaxial with the center axis 17. They can include one or more stages, depending upon the desired engine thermodynamic cycle, for example.
In the depicted embodiment, the LP spool 20 has a power shaft 23 which mechanically couples the LP turbine 21 and the LP compressor 22, and extends axially between them. The shaft 23 is coaxial with the central axis 17 of the engine 10. The shaft 23 allows the LP turbine 21 to drive the LP compressor 22 during operation of the engine 10. The shaft 23 is not limited to the configuration depicted in
The LP turbine 21 is forward of the LP compressor 22. The LP turbine 21 is also aft of the exhaust outlet 15. The LP compressor 22 is forward of the air inlet case 11. This arrangement of the LP turbine 21 and the LP compressor 22 provides for a reverse-flow engine 10 that has one or more LP compressors located at the rear of the engine 10, which are driven by one or more LP turbines located at the front of the engine 10.
Still referring to
A rotatable load, which in the embodiment shown includes the propeller 16, is mountable to the engine 10, and when mounted, is drivingly engaged (e.g. directly connected) to the LP turbine 21, and is located forward of the LP turbine 21. In such a configuration, during operation of the engine 10, the LP turbine 21 drives the rotatable load such that a rotational drive produced by the LP turbine 21 is transferred to the rotatable load. The rotatable load can therefore be any suitable component, or any combination of suitable components, that is capable of receiving the rotational drive from the LP turbine 21, as now described.
In the embodiment shown, a reduction gearbox 31 (sometimes referred to herein simply as “RGB 31”) is mechanically coupled to a front end of the drive shaft 24, which extends between the RGB 31 and the LP turbine 21. The RGB 31 processes and outputs the rotational drive transferred thereto from the LP turbine 21 via the drive shaft 24 through known gear reduction techniques. The RGB 31 allows for the propeller 16 to be driven at its optimal rotational speed, which is different from the rotational speed of the LP turbine 21.
The propeller 16 is mechanically coupled to the output of the RGB 31 via a propeller shaft 35. The propeller shaft 35 allows the rotational drive outputted by the RGB 31 during operation of the engine 10 to be transferred to the propeller 16 to provide propulsion during flight. In an alternate embodiment where the engine 10 is a turboshaft, the propeller 16 is omitted and the rotational load (which may include, but is not limited to, helicopter main rotor(s) and/or tail rotor(s), propeller(s) for a tilt-rotor aircraft, pump(s), generator(s), gas compressor(s), marine propeller(s), etc.) is driven by the LP turbine 21 via the RGB 31, or the propeller 16 and RGB 31 are omitted such that the output of the engine 10 is provided by the output drive shaft 24.
The drive shaft 24 extending forward of the LP turbine 21 and the power shaft 23 extending aft of the LP turbine 21 provide the engine 10 with bidirectional drive. Modularity criteria for gas turbine engines may require the use of distinct shafts 23, 24 that are directly or indirectly connected together. Alternately, the power shaft 23 and the drive shaft 24 can be integral with one another, with a first segment of the integral output shaft extending between the LP compressor 22 and the LP turbine 21, and a second segment extending between the rotatable load and the LP turbine 21. Whether the power shaft 23 is integral with the drive shaft 24 or distinct therefrom, the LP turbine 21 provides rotational drive outputted at each end of the power shaft 23.
In light of the preceding, it can be appreciated that the LP turbine 21 drives both the rotatable load and the LP compressor 22. Furthermore, the rotatable load, when mounted to the engine 10 and the LP compressor 22 are disposed axially on opposite ends of the LP turbine 21. It can thus be appreciated that one or more low pressure turbines are used to drive elements in front of the low pressure turbines (e.g. propeller 16, RGB 31, etc.) as well as to drive elements to the rear of the low pressure turbines (e.g. LP compressor 22). This configuration of the LP turbine 21 allows it to simultaneously drive the rotatable load and the LP compressor 22, if desired. As will be discussed in greater detail below, this arrangement of the rotatable load, the LP turbine 21, and the LP compressor 22 can contribute to improving the thermodynamic efficiency of the engine 10.
Still referring to
The HP turbine 41 is aft of the LP turbine 21, and forward of the combustor 13. The HP compressor 42 is aft of the combustor 13, and forward of the LP compressor 22. From this arrangement of the HP turbine 41 and the HP compressor 42, it can be appreciated that during operation of the engine 10, the LP compressor 22 driven by the LP turbine 21 feeds pressurized air to the HP compressor 42. Therefore, the pressurized air flow produced by the LP compressor 22 is provided to the HP compressor 42 and contributes to the work of both the LP turbine 21 and the HP turbine 41.
It can thus be appreciated that the presence of the above-described LP and HP spools 20, 40 provides the engine 10 with a “split compressor” arrangement. More particularly, some of the work required to compress the incoming air is transferred from the HP compressor 42 to the LP compressor 22. In other words, some of the compression work is transferred from the HP turbine 41 to the more efficient LP turbine 21. This transfer of work may contribute to higher pressure ratios while maintaining a relatively small number of rotors. In a particular embodiment, higher pressure ratios allow for higher power density, better engine specific fuel consumption (SFC), and a lower turbine inlet temperature (sometimes referred to as “T4”) for a given power. These factors can contribute to a lower overall weight for the engine 10. The transfer of compression work from the HP compressor 42 to the LP compressor 22 contrasts with some conventional reverse-flow engines, in which the high pressure compressor (and thus the high pressure turbine) perform all of the compression work.
In light of the preceding, it can be appreciated that the LP turbine 21 is the “low-speed” and “low pressure” turbine when compared to the HP turbine 41. The LP turbine 21 is sometimes referred to as a “power turbine”. The turbine rotors of the HP turbine 41 spin at a higher rotational speed than the turbine rotors of the LP turbine 21 given the closer proximity of the HP turbine 41 to the outlet of the combustor 13. Consequently, the compressor rotors of the HP compressor 42 may rotate at a higher rotational speed than the compressor rotors of the LP compressor 22. The engine 10 shown in
The HP turbine 41 and the HP compressor 42 can have any suitable mechanical arrangement to achieve the above-described split compressor functionality. For example, and as shown in
The split compressor arrangement also allows bleed air to be drawn from between the HP compressor 42 and the LP compressor 22. More particularly, in the embodiment of
Still referring to the embodiment shown in
The AGB 50 is mounted in-line with the LP spool and the HP pressure spool on an axially facing surface of the air inlet case 11. According to the embodiment illustrated in
It is understood that the in-line mounting of the AGB 50 is not strictly limited to a coaxial or centralized mounting of the AGB 50 as shown in
According to the illustrated embodiment, the AGB 50 is drivingly connected to the HP spool 40. To get around the LP compressor 22, which is physically disposed between the HP compressor and the AGB, an HP offset drive may be used. The HP offset drive may include a tower shaft 51 that is mechanically coupled to a rear of the HP shaft 43 and driven thereby. The tower shaft extends from the HP spool 40 in a direction away from the engine axis 17 for connection with an accessory gear box drive shaft 52 having a first geared end 52A mechanically coupled to the tower shaft 51, and a second geared end 52B mechanically coupled to the AGB 50. As can be appreciated from
In the depicted embodiment, the accessory gearbox drive shaft 52 extends across the air inlet case 11. This configuration of the accessory gearbox drive shaft 52 can take different forms. For example, it can be located outside the air inlet case 11, or may be placed within the air inlet case 11 along a strut of the air inlet case 11. It can thus be appreciated that the second end 52B of the accessory gearbox drive shaft 52 meshes with an input gear of the AGB 50 to drive the AGB 50 across the air inlet case 11.
During operation of the engine 10, the high pressure shaft 43 transmits a rotational drive to the tower shaft 51, which, in turn, drives the accessory gearbox drive shaft 52 to thereby drive the accessories A (
As shown in
As shown in
As shown in
For instance, according to the embodiment shown in
Referring to
The above description is meant to be exemplary only, and one skilled in the art will recognize that changes may be made to the embodiments described without departing from the scope of the invention disclosed. For instance, while some aspects of the present invention have been described in the context of a reverse flow engine, it is understood that they are equally applicable to straight flow engines and to various types of gas turbine engines, including turboprop, turboshaft and turbofan engines. For instance, the AGB could be mounted in-line at the front of the engine. It is also understood that not all of the accessories need to have the same orientation. For instance, some accessories could be perpendicular to the engine axis while others are parallel thereto. Other modifications which fall within the scope of the present invention will be apparent to those skilled in the art, in light of a review of this disclosure, and such modifications are intended to fall within the appended claims.
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