ENGINE MODULARITY

Abstract: The low pressure compressor (11) and fan (2) together with the intermediate case (10) are removable as a unit from the core engine by removal of the nose cone (62,58) and a stub shaft (40) at the front of the low pressure turbine shaft (38) and at the internal dia­ meter of the fan hub (50) to provide access to attach­ ment bolts (53) at the inner portion of the intermediate case (10) which holds the bearing (34) for the high pressure rotor (35) in position within the intermediate case (10) after assembly of the engine.

Description: The invention relates to a turbine engine comprising a low pressure compressor case, a low pressure rotor within the case, a high pressure compressor case, a high pressure compressor rotor, a through strut and intermediate case assembly between the low pressure compressor case and the high pressure compressor case, a bearing support extending forwardly from the strut and case assembly within the low pressure rotor, a bearing on said support for said low pressure rotor, and a low pressure shaft within the high pressure compressor rotor and extending forwardly therefrom. A turbine engine of this type is disclosed in GB-A-2158161. It is desirable to separate the engine into modules for ease of repair and for shipment. If the modules are readily separable there is significant saving of time and expense for handling, installation and disassembly for shipment or repair. Modularity of engines is not in itself a new concept but extensive disassembly required to separate the modules prevented realizing full advantage and benefits from the modularity. Further, the through strut concept for the intermediate case in the multirotor engine has produced a simpler and lower cost engine but the difficulty of separating the modules between the intermediate case and the high pressure case has discouraged the use of this construction. In GB-A-2158161 referred to modular disassembly of the turbine section of a gas turbine engine is disclosed. The low pressure shaft is detachable from the low pressure compressor rotor and can be removed. The low pressure compressor rotor is directly mounted on the low pressure shaft. No provisions are made for the modular assembly and disassembly of the engine compressor section. A prior gas turbine engine of a similar type is disclosed in EP-A-0203881. This known gas turbine engine has a strut assembly between the low and high pressure compressors supporting bearings for the high pressure shaft and the low pressure rotor. The low pressure rotor is directly splined to the low pressure shaft. Again, no provisions are made for the modular assembly and disassembly of the engine compressor section. The object of the invention is to provide an turbine engine of the through strut intermediate case concept that can be split between low and high pressure compressors into two large modules without extensive disassembly. To achieve this, the turbine engine of the invention is characterized by said strut and case assembly being attached to the downstream end of the low pressure compressor case, a bearing structure at the inner portion of the strut and case assembly to support the high pressure rotor within the strut and case assembly, said bearing structure having an axially slidable connection with the strut and case assembly, a stub shaft having a splined connection to the low pressure shaft and to the low pressure rotor adjacent to its forward end to provide for axial assembly of the stub shaft within the engine, means for removably securing said stub shaft to said low pressure shaft at the forward end of said low pressure shaft said securing means being accessible within the stub shaft, and securing bolts to hold said bearing structure axially within the strut, said bolts being accessible through the low pressure rotor when the stub shaft is removed from within the compressor. In a turbine engine according to the invention a clamping ring permits removal of the stub shaft at the front end of the engine. Access is then possible to the bolts holding the bearing structure within the intermediate case. When these bolts are undone, the front module consisting of the low pressure compressor and the through strut and intermediate case assembly is separable as a unit from the core engine at the front of the high pressure compressor. Access to the attaching elements that hold the engine module together permits the separation with a minimum of disassembly of either module. The nose cone is built so that it can be removed from its supports on the low pressure rotor for access to the stub shaft. When the stub shaft is removed, the low pressure compressor rotor remains properly supported within the surrounding low pressure compressor case. The bearing remains on the end of the high pressure rotor shaft and stays in place when the front module is removed. The bearing structure is so arranged that the front module can be replaced over the bearing and then be attached thereto in reassembly. In a fan engine the fan rotor is attached to the low pressure rotor. The fan rotor and fan case are removable with the front module. Another clamping ring can be provided to secure the low pressure rotor to the stub shaft. Other features and advantages will be apparent from the specification and claims and from the accompanying drawings which illustrate an embodiment of the invention, wherein: Fig. 1 is a sectional view of the low pressure compressor and fan. Fig. 2 is a sectional view similar to Fig. 1 but with the parts disassembled to show the separation of the modules. The invention is shown in a two-rotor fan engine in which the fan 2 is mounted at the forward end of the multistage low pressure compressor 11 having a low pressure rotor 4. They are both supported by a bearing 6 mounted in the forward end of a support 8 bolted to and extending forwardly from the through strut intermediate case assembly 10. This strut and case assembly 10 has an outer ring 12 with inwardly extending vanes 14 crossing the fan duct 16. The inner end of the vanes 14 engage an inner ring 18 forming a part of the inner wall of the fan duct. Inwardly of ring 18, the strut and case assembly 10 has radial legs 22 terminating in an outer ring 23 forming a part of the outer wall of the airflow duct for the turbine engine. Vane shaped struts 24 extend inwardly across the gas path from the outer ring 23 to an inner ring 26 forming a part of the inner wall of the gas path. At the forward end of the ring 26 is a flange 28 to which the support 8 is secured. Near the rearward edge of the ring 26 is another annular flange 30, the inner surface of which is cylindrical to fit over an outer ring 32 on the bearing 34 that supports the forward end of the high pressure rotor shaft 35 on which the high pressure compressor rotor disks and blades 36 are mounted. Bolts 53 are received through the flange 30 and threaded in a cooperating flange of the ring 32 of bearing 34 to secure the flange 30 to the bearing ring 32. The low pressure rotor shaft 38 extends forwardly from the low pressure turbine, not shown, and is connected to the low pressure compressor rotor and fan by a stub shaft 40. This shaft has internal splines 42 near its rearward end to engage with external splines 44 on the shaft 38. At its forward end, the stub shaft 40 has external splines 46 to engage with internal splines 48 on the fan disk 50 on which the fan blades 52 are mounted and to which the low pressure compressor rotor 4 is secured. A threaded clamping ring 77 on the end of the fan disk 50 engages the end of the stub shaft and secures it in position within the fan disk. This threaded ring is removable from the end of the engine as will be pointed out later. The fan disk forms a part of the low pressure compressor rotor as will be apparent. When the low pressure module which includes the fan, the low pressure compressor and the intermediate case 10 are assembled in the position of Fig. 1 and the bolts 53 which secure the outer ring 32 within the flange 30 have been placed in position from the front end of the engine, the stub shaft 40 is then placed in assembled position with the splines 42 and 46 on the stub shaft 40 engaging the splines 44 and 48, respectively. The stub shaft is capable of being inserted from the front of the engine as will be apparent. The stub shaft is then locked in position by a threaded clamping ring 54, the clamping ring engaging threads 55 on the end of the low pressure shaft 38. The clamping ring has a shoulder engaging a flange 56 on the stub shaft 40 to hold the shaft 40 in engagement with the end of the low pressure shaft 38. The low pressure compressor rotor 2 is then locked to stub shaft 40 by a threaded clamping ring 77, the clamping ring engaging threads 78 on the fan disk 50. The clamping ring 77 holds a shoulder 79 on the fan disk 50 against a shoulder 80 on the stub shaft 40. When assembly of the low pressure compressor 2, stub shaft 40, and the low pressure turbine shaft 38 is complete, the rearward ring 58 of the nose cone is bolted to the fan disk 50 by bolts 60 and a cone element 62 is then bolted to the ring 58 by bolts 61. Access to these bolts is possible by recesses 65 and 66 as shown. The assembly is completed by a ring of bolts 67 that hold a flange 68 on the high pressure compressor case 70 against the strut and case assembly 10. Additional rings of bolts not shown by which the inner and outer duct walls, not shown, of the fan air duct are also attached. These rings of bolts are clearly accessible from external of the core engine which begins with the high pressure compressor case and extends rearwardly therefrom. When separating the modules in preparation for overhaul or for shipment a reverse procedure is followed. After removing the rows of bolts 60 and 64 the nose cone elements 62 and 58 are removed for access to the stub shaft 40. The clamping rings 77 and 54 are undone and removed, and the stub shaft 40 is removed by pulling forward from within the fan disk 50. This is easily done once the nose cone has been removed. The bolts 53 are now accessible from the front of the engine through the space opened up by removal of the stub shaft and inwardly of the support 8. Once the bolts 53 and bolts 67 joining intermediate case 10 to the high pressure case 70 are removed, the front module is removable by pulling the front module forward from the core engine. The ring 30 slips forward from the outer ring 32 and once the module clears the end of the shaft 38 it can be moved wherever desired. It will be obvious that the bevel gear 72 disengages from the ring gear 76 on the end of the high pressure rotor 35. This gear 72 is on the inner end of a power takeoff device, the shaft of which is not shown, extends outwardly through the strut and case assembly 10.

Claims: 1. Turbine engine comprising: a low pressure compressor case, a low pressure rotor (4) within the case, a high pressure compressor case (70), a high pressure compressor rotor (36), a through strut and intermediate case assembly (10) between the low pressure compressor case and the high pressure compressor case (70), a bearing support (8) extending forwardly from the strut and case assembly (10) within the low pressure rotor (4), a bearing (6) on said support (8) for said low pressure rotor (4), and a low pressure shaft (38) within the high pressure compressor rotor (36) and extending forwardly therefrom, characterized by: said strut and case assembly (10) being attached to the downstream end of the low pressure compressor case, a bearing structure (34) at the inner portion of the strut and case assembly (10) to support the high pressure rotor (36) within the strut and case assembly (10), said bearing structure (34) having an axially slidable connection with the strut and case assembly (10), a stub shaft (40) having a splined connection (42, 44; 46, 48) to the low pressure shaft (38) and to the low pressure rotor (4) adjacent to its forward end to provide for axial assembly of the stub shaft (40) within the engine, means (54) for removably securing said stub shaft (40) to said low pressure shaft (38) at the forward end of said low pressure shaft (38), said securing means (54) being accessible within the stub shaft (40), and securing bolts (53) to hold said bearing structure (34) axially within the strut and case assembly (10), said bolts (53) being accessible through the low pressure rotor (4) when the stub shaft (40) is removed from within the compressor. 2. Turbine engine according to claim 1, characterized in that said bearing structure (34) has a cylindrical outer surface and said strut and case assembly (10) has an inner cylindrical surface cooperating therewith for axial sliding movement of the strut and case assembly (10) over the bearing structure (34) and cooperating flanges on said bearing structure (34) and said strut and case assembly (10) to receive the bolts (53) for securing the bearing structure (34) within the strut and case assembly (10). 3. Turbine engine according to claim 1, characterized in that the securing means (54) is a threaded ring engaging with threads on the inner low pressure shaft (38) with said ring being shouldered to hold the stub shaft (40) against the end of the low pressure shaft (38). 4. Turbine engine according to claim 1, characterized in that the low pressure compressor rotor (4) includes a fan (2) at its forward end and this fan (2) has a supporting disk (50) to which the rest of the low compressor rotor (4) is secured and this disk (50) has internal splines (48) thereon to engage with the splines (46) on the stub shaft (40). 5. Turbine engine according to claim 4, characterized in that there is a threaded ring (77) on the forward end of the fan disk (50) to hold the stub shaft (40) in position therein. 6. Turbine engine according to claim 4, characterized in that the cooperating splines (42, 44) on the stub shaft (40) and the low pressure shaft (38) are internal splines (42) on the stub shaft (40) and external splines (44) on the low pressure shaft (38) and the cooperating splines (46, 48) at the forward end of the stub shaft (40) are external on the stub shaft (40) and internal on the low pressure compressor rotor (4). 7. Turbine engine according to claim 1, characterized in that the cooperating splines (46, 48) on the stub shaft (40) and the low pressure compressor rotor (8) are internal on the rotor (8) and external on the stub shaft (40). 8. Turbine engine according to claim 7, characterized in that there is a threaded ring (77) at the end of the low pressure rotor (4) and engaging the end of the stub shaft (40) to hold the low pressure rotor (8) on the stub shaft (40). 9. Turbine engine according to claim 1, characterized by a row of bolts (67) holding the high pressure compressor case (70) against the strut and case assembly (10).

Inventors: BRODELL, ROBERT F., MONSARRAT, WILLIAM GRAVES
Applicants: UNITED TECHNOLOGIES CORPORATION
Application year: 1988
Main classification: F02C7
IPC codes: F02C7, F01D5, F02K3