Patent Application
20120020770
The present invention relates to a gas turbine engine, and more particularly, to an energy absorbing apparatus used with a vane segment in a gas turbine engine.
A turbine engine includes a compressor typically comprising a plurality of axial stages, which compress airflow in turn. A typical axial compressor includes a split outer casing having two 180 degree halves, which are suitably bolted together. The casing includes rows of axially spaced apart casing slots which extend circumferentially for mounting respective vane segments.
A typical vane segment includes a pair of 180 degree diaphragm assemblies, each diaphragm assembly comprising radially outer and inner shrouds between which are attached a plurality of circumferentially spaced apart airfoils. The outer shroud includes a pair of axially spaced apart hook elements. The casing includes complementary first and second axially spaced apart grooves, which extend circumferentially within each of the casing slots for receiving the corresponding hook elements in a tongue-and-groove mounting arrangement.
During assembly, the individual diaphragm assemblies are circumferentially inserted into respective ones of the casing halves by engaging the hook elements with the corresponding grooves. Each diaphragm assembly is slid circumferentially in turn into its casing slot. The two casing halves are then assembled together so that the diaphragm assemblies in each casing slot define a respective annular vane segment for each compression stage. In this configuration, the individual diaphragm assemblies are mounted to the outer casing solely by their outer shrouds, with the airfoils and inner shrouds being suspended therefrom.
During operation of the compressor, each vane segment experiences stage differential pressure and airflow impingement, resulting in longitudinal, circumferential, and radial loads being transferred to and through the hook elements of the diaphragm assembly. Those steady loads are combined with pulsating blade-passing aerodynamic excitation loads, which cause the airfoils and outer shrouds of the diaphragm assemblies to vibrate. The vibrations in the outer shrouds cause the hook members to move within the corresponding grooves. Such movement results in frictional wear between the outer shrouds and the engine casing, which wear reduces part life.
In accordance with a first aspect of the present invention, a gas turbine is provided comprising a casing, a first diaphragm assembly, a second diaphragm assembly, and first energy absorbing apparatus. The casing has a radially outer surface and a radially inner surface comprising an annular slot extending circumferentially therein. The first diaphragm assembly comprises a first inner structure, a first outer structure and a plurality of airfoils extending between the first inner and outer structures. The second diaphragm assembly comprises a second inner structure, a second outer structure and a plurality of airfoils extending between the second inner and outer structures. The first energy absorbing apparatus engages a first end portion of the first outer structure so as to absorb at least portions of unsteady aerodynamic loads and steady rotational loads generated by the first diaphragm assembly.
The first energy absorbing apparatus may comprise a first spring support coupled to the first end portion of the first outer structure of the first diaphragm assembly, a second spring support coupled to a second end portion of the second outer structure of the second diaphragm assembly, and first spring structure positioned between the first and second spring supports.
The gas turbine may further comprise a second energy absorbing apparatus comprising a third spring support coupled to a second end portion of the first outer structure of the second diaphragm assembly, a fourth spring support coupled to a first end portion of the second outer structure of the second diaphragm assembly, and second spring structure positioned between the third and fourth spring supports.
The first energy absorbing apparatus may further comprise a spring support plate coupled to the second spring support of the first energy absorbing apparatus, the spring support plate abutting the casing to prevent rotation of the first energy absorbing apparatus within the annular slot.
The casing may comprise first and second casing halves, the spring support plate abutting a first end portion of the second casing half.
The first energy absorbing apparatus may be disposed within the slot in the compressor casing.
The first energy absorbing apparatus may substantially prevent the first end portion of the first outer structure of the first diaphragm assembly from contacting the second end portion of the second outer structure of the second diaphragm assembly.
In accordance with a second aspect of the present invention, a gas turbine is provided comprising a casing, a first diaphragm assembly, a second diaphragm assembly, first energy absorbing apparatus, and second energy absorbing apparatus. The casing has a radially outer surface and a radially inner surface comprising an annular slot extending circumferentially therein. The first diaphragm assembly comprises a first inner structure, a first outer structure and a plurality of airfoils extending between the first inner and outer structures. The second diaphragm assembly comprises a second inner structure, a second outer structure and a plurality of airfoils extending between the second inner and outer structures. The first energy absorbing apparatus engages a first end portion of the first outer structure so as to absorb at least portions of unsteady aerodynamic loads and steady rotational loads generated by the first diaphragm assembly. The second energy absorbing apparatus engages a first end portion of the second outer structure so as to absorb at least portions of unsteady aerodynamic loads and steady rotational loads generated by the second diaphragm assembly.
The gas turbine may further comprise a first spring support plate coupled to the second spring support of the first energy absorbing apparatus, the spring support plate abutting the casing to prevent rotation of the first energy absorbing apparatus within the annular slot.
The gas turbine may yet further comprise a second spring support plate coupled to the first spring support of the second energy absorbing apparatus, the second spring support plate abutting the casing to prevent rotation of the second energy absorbing apparatus within the annular slot.
In accordance with a third aspect of the present invention, a gas turbine is provided comprising a casing, a first diaphragm assembly, a second diaphragm assembly, and first energy absorbing apparatus. The casing has a radially outer surface and a radially inner surface comprising an annular slot extending circumferentially therein. The first diaphragm assembly comprises a first inner structure, a first outer structure and a plurality of airfoils extending between the first inner and outer structures. The second diaphragm assembly comprises a second inner structure, a second outer structure and a plurality of airfoils extending between the second inner and outer structures. The first energy absorbing apparatus engages a first end portion of the first outer structure so as to absorb at least portions of unsteady aerodynamic loads and steady rotational loads generated by the first diaphragm assembly. The first energy absorbing apparatus comprises a first spring support coupled to the first end portion of the first outer structure of the first diaphragm assembly, a second spring support coupled to a second end portion of the second outer structure of the second diaphragm assembly, and first spring structure positioned between the first and second spring supports.
While the specification concludes with claims particularly pointing out and distinctly claiming the present invention, it is believed that the present invention will be better understood from the following description in conjunction with the accompanying Drawing Figures, in which like reference numerals identify like elements, and wherein:
In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration, and not by way of limitation, specific preferred embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and that changes may be made without departing from the spirit and scope of the present invention.
Only the first vane segment 20 is illustrated in
The first vane segment 20 will now be described, it being understood that the remaining vane segments 20 may be substantially similar to the first vane segment 20 described herein. In the illustrated embodiment, the first vane segment 20 comprises a first diaphragm assembly 20A mounted within the first casing half WA and a second diaphragm assembly 20B mounted within the second casing half 10B.
Each diaphragm assembly 20A and 20B comprises a respective arcuate-shaped inner structure or shroud 24A, 24B, a respective arcuate-shaped outer structure or shroud 26A, 26B, and a plurality of airfoils 28A, 28B extending between the respective inner and outer shrouds 24A, 24B and 26A, 26B. It is noted that each diaphragm assembly 20A and 20B may comprise a single unitary structure, as illustrated in
The casing slot 14A is configured for mounting the first diaphragm assembly 20A, as well as the second diaphragm assembly 20B, via the respective outer shrouds 26A, 26B thereof in a tongue-and-groove manner for allowing ready assembly and disassembly thereof. As shown in
It is noted that first and second splitlines or lines of separation 40A and 40B (see
Referring to
According to this embodiment, the first energy absorbing apparatus 50 comprises a first spring support 52 coupled to the first end portion 26A1 of the first outer shroud 26A, and a second spring support 54 coupled to the second end portion 26B2 of the second outer shroud 26B, see
The first energy absorbing apparatus 50 also comprises first spring structure 56 positioned between the first and second spring supports 52 and 54. The first spring structure 56 in the embodiment shown comprises first, second, and third springs 58A, 58B, and 58C, see
In the embodiment shown, the springs 58A-58C are held in position between the first and second spring supports 52 and 54 via a casing wall 10E defining the casing slot 14A. Moreover, in the embodiment shown, first and second plate members 59A and 59B (see
Referring to
A second energy absorbing apparatus 70 according to an embodiment of the invention is shown in
The second energy absorbing apparatus 70 comprises a third spring support 72 coupled to the second end portion 26A2 of the first outer shroud 26A, and a fourth spring support 74 coupled to the first end portion 26B1 of the second outer shroud 26B, see
Similar to the first energy absorbing apparatus 50, the second energy absorbing apparatus 70 further comprises a second spring support plate 80, see
The remaining structure of the second energy absorbing apparatus 70 is substantially similar to that of the first energy absorbing apparatus 50 and, thus, will not be described in detail herein.
It is noted that, the end portions 26A1 and 26B1 of the outer shrouds 26A and 26B that do not include a spring support plate 60 or 80 affixed to their respective spring supports 52 and 74 are referred to herein as the “free ends” of the respective diaphragm assemblies 20A and 20B, and the end portions 26A2 and 26B2 of the outer shrouds 26A and 26B that include a spring support plate 60 or 80 affixed to their respective spring supports 54 and 72 are referred to herein as the “fixed ends” of the respective diaphragm assemblies 20A and 20B.
During assembly of the compressor, the first, second, third and fourth spring supports 52, 54, 72, 74 are affixed to the respective diaphragm assemblies 20A and 20B. The first vane segment 20 is then circumferentially inserted into the casing 10 by inserting the free ends of the diaphragm assemblies 20A and 20B into the corresponding casing halves 10A and 10B, i.e., the first and second hook elements 32A, 32B and 34A, 34B are slid into the respective first and second grooves 36 and 38 in the casing halves 10A and 10B. The diaphragm assemblies 20A and 20B are circumferentially inserted into the casing halves 10A and 10B until the spring support plates 60 and 80 contact the respective wall portions 62A and 82A. The second and third vane segments 20 are assembled in a similar manner into the slots 14B and 14C of the casing 10, and any other static airfoil stages in the compressor may be similarly assembled.
After the first, second, and third vane segments 20, e.g., the first and second diaphragm assemblies 20A and 20B of the first vane segment 20, and any other static airfoil stages in the compressor have been installed into the casing 10, the spring structures 56 and 76 for each of the first, second, and third vane segments 20 (and any other static airfoil stages in the compressor) are installed into the lower casing half, i.e., the second casing half 10B in the embodiment shown, by placing the spring structures 56 and 76 onto the second and fourth spring supports 54 and 74 of the respective energy absorbing apparatuses 50 and 70. The upper casing half, i.e., the first casing half 10A in the embodiment shown, is then installed onto the lower casing half 10B. The weight of the upper casing half 10A compresses the springs 58A-58C of the spring structures 56 and 76, thus producing a separational force between the first and second diaphragm assemblies 20A and 20B. The casing halves 10A and 10B are then suitably fastened together, such as by bolting.
During operation, air travels through the compressor in the direction of arrow A, as shown in
As the air flows through the airfoils 28A, 28B of the first, second, and third vane segments 20 (and any other static airfoil stages in the compressor), each diaphragm assembly 20A, 20B experiences axial and tangential loads of a steady nature caused by a difference in pressure across the each vane segment 20 and the airflow impinging on the corresponding airfoils 28A and 28B. Additionally, there are airfoil-passing aerodynamic excitation loads of a pulsating nature. Together, these loads cause the rows of airfoils 28A and 28B and, thus, correspondingly, the outer shroud 26A, 26B of each diaphragm assembly 20A, 20B, to vibrate.
The energy absorbing apparatuses 50 and 70 in each of the first, second, and third vane segments 20 (and any other static airfoil stages in the compressor) dampen these vibrations and, hence, absorb at least a portion of the unsteady aerodynamic excitation loads, i.e., via the separational force provided by the spring structures 56 and 76. Hence, very little frictional movement occurs between the diaphragm assemblies 20A and 20B and the engine casing 10, which is believed to reduce the amount of wear between diaphragm assemblies 20A and 20B and the engine casing 10. Specifically, in prior art designs, it has been found that a large amount of frictional wear occurs at locations L1, L2, L3, L4, and L5 illustrated in
The energy absorbing apparatuses 50 and 70 also effectively tie the first and second diaphragm assemblies 20A and 20B together, which is believed to improve load distribution on the first and second hook elements 32A, 32B and 34A, 34B and reduce movement of the end portions 26A1, 26A2, 26B1, 26B2 of the first and second outer shrouds 26A and 26B. The improved load distribution and reduction of movement of the end portions 26A1, 26A2, 26B1, 26B2 are believed to further reduce wear between the diaphragm assemblies 20A and 20B and the engine casing 10 at the locations L1, L2, L3, L4, and L5 by limiting the movement between these components, which reduces frictional contact therebetween.
Moreover, the spring structures 56 and 76 of the energy absorbing apparatuses 50 and 70 are compressed during operation of the engine so as to absorb steady rotational loads of the first and second diaphragm assemblies 20A and 20B. That is, as the air flows through the compressor, the air imparts a steady rotational force on the airfoils 28A and 28B of the respective first and second diaphragm assemblies 20A and 20B of the first, second, and third vane segments 20, (and any other static airfoil stages in the compressor), in the direction of the arrow ROT in
Further, the spring structures 56 and 76 of the energy absorbing apparatuses 50 and 70 provide a separational force between the first and second diaphragm assemblies 20A and 20B to prevent or reduce contact therebetween. Hence, very little or no wear occurs between the first and second diaphragm assemblies 20A and 20B.
The reduction in the wear of the components discussed herein is believed to increase component life, and, thus prevent or reduce the need for repairs of these components.
While particular embodiments of the present invention have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the invention. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this invention.
