Patent Application
20130319004
This application relates to an arrangement of slots in a rotor as utilized in a gas turbine engine.
Gas turbine engines are known, and typically include a compressor section that compresses air and delivers it downstream into a combustion section. The air is mixed with fuel and ignited, and products of the combustion pass downstream over turbine rotors, driving them to rotate.
Both the compressor and the turbine include rotors that can carry removable blades. In one type of blade arrangement, the blades have a mount portion, or dovetail, which is mounted underneath a ledge in the rotor. So-called “load slots” allow the dovetail to be inserted past the ledge, and the blade is then turned, such that the blade can no longer move outwardly of the ledge. The blades are then moved circumferentially to be aligned with the adjacent blades.
The ledge typically also includes a lock slot. A plurality of locks are inserted into openings in at least some of the blades, and are mechanically loaded radially outward to lock the blade within the ledge. The lock slots and the load slots are each formed in the ledge.
At times, there may be an arrangement of locks and lock slots such that there is a lock slot adjacent to a load slot on one circumferential side, but not the other. This can raise stress concentrations around the load slot which are somewhat undesirable.
In one featured embodiment, a rotor for use in a gas turbine engine has a rotor body for rotation about an axis of rotation. The rotor body extends circumferentially about the axis of rotation, and also has an axial direction along the axis of rotation. A ledge provides a holding structure for holding blades radially inwardly of the ledge. A plurality of blades have mount structure positioned beneath the ledge. The blades have an airfoil extending upwardly from a platform. The mount structure extends inwardly from the platform. A load slot in the ledge is sized to allow the mount structure of the blades to be moved radially inwardly of the ledge by positioning the mounting structure to move through the load slot. The blades then are moved circumferentially to have the mount structure radially inwardly of the ledge. A lock slot in the ledge is on one circumferential side of the load slot. The lock slot receives a lock. The lock is being partially received within a portion of at least one of the blades, and a shield slot in the ledge is on a second circumferential side of the load slot. The shield slot is sized to be different from the lock slot such that a lock cannot be inadvertently positioned within the shield slot.
In another embodiment according to the previous embodiment, the shield slot and lock slot each extend axially into the ledge for a depth, with a depth of the shield slot being less than a depth of the lock slot.
In another embodiment according to any of the previous embodiments, each of the lock slot and shield slot are curved portions each formed at at least one radius.
In another embodiment according to any of the previous embodiments, the curved portions of both the lock slot and shield slot are part circular portions.
In another embodiment according to any of the previous embodiments, a radius of the lock slot is greater than a radius of the shield slot.
In another embodiment according to any of the previous embodiments, a circumferential distance from a circumferential edge of the load slot most adjacent the lock slot to an edge of the lock slot most adjacent the load slot is defined as a first distance, and a second distance is defined from a circumferential edge of the load slot closest to the shield slot, to an edge of the shield slot most adjacent to the load slot, with the second distance being less than the first distance.
In another embodiment according to any of the previous embodiments, each of the lock slot and shield slot are curved portions each formed at at least one radius.
In another embodiment according to any of the previous embodiments, the curved portions of both the lock slot and shield slot are part circular portions.
In another embodiment according to any of the previous embodiments, a radius of the lock slot is greater than a radius of the shield slot.
In another embodiment according to any of the previous embodiments, a circumferential distance from a circumferential edge of the load slot most adjacent the lock slot to an edge of the lock slot most adjacent the load slot is defined as a first distance, and a second distance is defined from a circumferential edge of the load slot closest to the shield slot, to an edge of the shield slot most adjacent to the load slot, with the second distance being less than the first distance.
In another featured embodiment, a gas turbine engine has a compressor, a combustion section, and a turbine section. The compressor section includes at least a first compressor rotor and a rotor body for rotation about an axis of rotation. The rotor body extends circumferentially about the axis of rotation, and also has an axial direction along the axis of rotation. A ledge provides a holding structure for holding blades radially inwardly of the ledge. A plurality of blades have mount structure positioned beneath the ledge. The blades have an airfoil extending upwardly from a platform. The mount structure extends inwardly from the platform. A load slot in the ledge is sized to allow the mount structure of the blades to be moved radially inwardly of the ledge by positioning the mounting structure to move through the load slot. The blades are then moved circumferentially to have the mount structure radially inwardly of the ledge. A lock slot in the ledge is on one circumferential side of the load slot. The lock slot receives a lock, and is also partially received within a portion of at least one of the blades. A shield slot in the ledge is on a second circumferential side of the load slot and is sized to be different from the lock slot such that a lock cannot be inadvertently positioned within the shield slot.
In another embodiment according to the previous embodiment, the shield slot and lock slot each extend axially into the ledge for a depth. The depth of the shield slot is less than a depth of the lock slot.
In another embodiment according to any of the previous embodiments, each of the lock slot and shield slot are curved portions each formed at at least one radius.
In another embodiment according to any of the previous embodiments, the curved portions of both the lock slot and shield slot are part circular portions.
In another embodiment according to any of the previous embodiments, a radius of the lock slot is greater than a radius of the shield slot.
In another embodiment according to any of the previous embodiments, a circumferential distance from a circumferential edge of the load slot most adjacent the lock slot to an edge of the lock slot most adjacent the load slot is defined as a first distance. A second distance is defined from a circumferential edge of the load slot closest to the shield slot, to an edge of the shield slot most adjacent to the load slot, with the second distance being less than the first distance.
In another embodiment according to any of the previous embodiments, each of the lock slot and shield slot are curved portions each formed at at least one radius.
In another embodiment according to any of the previous embodiments, the curved portions of both the lock slot and shield slot are part circular portions.
In another embodiment according to any of the previous embodiments, a radius of the lock slot is greater than a radius of the shield slot.
In another embodiment according to any of the previous embodiments, a circumferential distance from a circumferential edge of the load slot most adjacent the lock slot to an edge of the lock slot most adjacent the load slot is defined as a first distance, and a second distance is defined from a circumferential edge of the load slot closest to the shield slot, to an edge of the shield slot most adjacent to the load slot, with the second distance being less than the first distance.
These and other features of this application will be best understood from the following specification and drawings, the following of which is a brief description.
The engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A 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.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. The inner shaft 40 is connected to the fan 42 through 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 high pressure compressor 52 and high pressure turbine 54. A combustor 56 is arranged 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 A 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. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion.
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 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 5. 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 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 2.5:1. 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. The flight condition of 0.8 Mach and 35,000 ft, with the engine at its best fuel consumption—also known as “bucket cruise Thrust Specific Fuel Consumption (‘TSFC’)”—is the industry standard parameter of 1 bm of fuel being burned divided by 1 bf 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 [(Tambient deg R)/518.7)̂0.5]. The “Low corrected fan tip speed” as disclosed herein according to one non-limiting embodiment is less than about 1150 ft/second.
Details of a structure which may include the load slots and lock slots are illustrated in Published Patent Application U.S. 2011-0116933 A1, filed by the inventor of the present application. The operation and structure of the load and lock slots, along with the blades and locks as detailed in that application are incorporated herein by reference, but other load slot and lock slot structures may also apply.
A plurality of locks 128 are inserted into an opening space 170 in the platform 161 in at least some of the blades. There are typically many more blades than there are locks, thus, not all of the blades have a platform opening 170. In addition, the ledge 121 includes a lock slot 132. At times, the lock slots may be mounted circumferentially symmetrically about a load slot 126. However, at other times there may be a lock slot on one circumferential side of a load slot 126, but not the other.
As shown in
The depth is defined as the greatest distance within the slot measured away from an outer edge 200. As can be appreciated, the slots 132 and 130 are formed along a curve. In the disclosed embodiment, the slots are part-circular, and thus form at a single radius, but may be other single or multiple curved shapes with or without non-curved sections.
The lock slot 132 has a circumferential edge 100 spaced from the closest circumferential edge 101 of the load slot 126 by a distance d1. An opposed edge 102 of the load slot is spaced from a most adjacent circumferential edge 103 of the shield slot 130 by a distance d2. The shield slot 130 extends for a depth D2, and is formed at a radius R2. In embodiments, the depth D2 is less than the depth D1. This will make it less likely that a lock would inadvertently be inserted into a shield slot 130. In addition, some means of shifting the effect of the shield slot 130 may be incorporated. One method may be increasing the distance d2 relative to the distance d1. Another method may be making the radius R2 smaller than the radius R1. Of course, shield slot 130 could be made larger than the lock slot in any of these dimensions.
Although an embodiment of this invention has been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.
