BACKGROUND 1. Field

[0001] The present invention relates to a gas turbine engine, and specifically, pre- swirler having pre-swirler plug configured for cooling downstream components of the gas turbine engine.

2. Description of the Related Art

[0002] A gas turbine engine produces mechanical work used to drive an electric generator for power production. The gas turbine engine generally includes multiple stages of stator vanes and rotor blades to convert the energy from the hot gas flow into mechanical energy that drives the rotor shaft of the engine.

[0003] Gas turbines engines are becoming larger, more efficient, and more robust. Large blades and vanes are being utilized, especially in the hot section of the engine system. In view of high pressure ratios and high engine firing temperatures implemented in modern engines, certain components, such as airfoils, e.g., stationary vanes and rotating blades, require more efficient cooling. The blades, therefore, require significant cooling to maintain an adequate component life. Blade cooling is accomplished by extracting a portion of the cooler compressed air from the compressor and directing it to the turbine section, thereby bypassing combustors. After introduction into the turbine section, this cooling air flows through passages or channels formed in the airfoil portions of the blades.

[0004] Pre-swirlers are commonly used in gas turbine engines. Using of pre- swirlers may reduce blade cooling flow requirements. There are several mechanical arrangements for pre-swirlers, such as airfoil pre-swirlers and drilled hole pre- swirlers. Airfoil pre-swirlers, if used are typically undersized and open as required by cutting back a trailing edge. Using drilled hole pre-swirlers, manufacturing limitations may prevent the drilled hole pre-swirlers alone to have high precision shapes to achieve design requirements.

SUMMARY OF THE INVENTION

[0005] Briefly described, aspects of the present invention relate to a gas turbine engine, a pre-swirler for a gas turbine engine and a method for arranging a pre-swirler for a gas turbine engine.

[0006] In an aspect of the present invention, a gas turbine engine is presented. The gas turbine engine comprises a component. The gas turbine engine comprises at least one pre-swirler arranged on the component. The at least one pre-swirler comprises a hole drilled through the component. The at least one pre-swirler comprises a pre- swirler plug positioned in the drilled hole. The pre-swirler plug comprises a profiled shape. The pre-swirler plug is configured to be replaceable in the drilled hole.

[0007] In an aspect of the present invention, a pre-swirler for a gas turbine engine is presented. The pre-swirler comprises a hole drilled through a component of the gas turbine engine. The pre-swirler comprises a pre-swirler plug positioned in the drilled hole. The pre-swirler plug comprises a profiled shape. The pre-swirler plug is configured to be replaceable in the drilled hole.

[0008] In an aspect of the present invention, a method for arranging a pre-swirler for a gas turbine engine is presented. The method comprises drilling a hole through a component of the gas turbine engine. The method comprises arranging the pre-swirler by positioning a pre-swirler plug in the drilled hole. The pre-swirler plug comprises a profiled shape. The pre-swirler plug is configured to be replaceable in the drilled hole.

[0009] Various aspects and embodiments of the application as described above and hereinafter may not only be used in the combinations explicitly described, but also in other combinations. Modifications will occur to the skilled person upon reading and understanding of the description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Exemplary embodiments of the application are explained in further detail with respect to the accompanying drawings. In the drawings. [0011] FIG. 1 is a schematic cross section of a side view of a mid-frame of a gas turbine engine, with several potential locations of a pre-swirler according to an exemplary embodiment of the present invention;

[0012] FIG. 2 is a perspective view of a chamfered pre-swirler plug according to an exemplary embodiment of the present invention; [0013] FIG. 3 is a perspective view of an angled pre-swirler plug according to an exemplary embodiment of the present invention; and

[0014] FIG. 4 is a perspective view of a flow accelerating pre-swirler plug according to an exemplary embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION [0015] In the following detailed description of the preferred embodiment, 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, a specific embodiment 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.

[0016] Broadly, an embodiment of the present invention provides a gas turbine engine that includes at least one pre-swirler. Each pre-swirler includes a hole drilled through a component of the gas turbine engine. The pre-swirler also includes a pre- swirler plug that is positioned in the drilled hole. The pre-swirler plug is removable and replaceable in the drilled hole.

[0017] A gas turbine engine may comprise a compressor section, a combustor and a turbine section. The compressor section compresses ambient air. The combustor combines the compressed air with a fuel and ignites the mixture creating combustion products comprising hot gases that form a working fluid. The working fluid travels to the turbine section. Within the turbine section are circumferential alternating rows of vanes and blades, the blades being coupled to a rotor. Each pair of rows of vanes and blades forms a stage in the turbine section. The turbine section comprises a fixed turbine casing, which houses the vanes, blades and rotor.

[0018] In certain embodiments, air for cooling the rotor and rotating blades may be extracted from the axial compressor discharge at a combustor shell. The compressor discharge air may pass through an air-to-air cooler and may be filtered for rotor cooling. Direct cooling may occur at the turbine spindle blade root end along one or more stages. The turbine stationary vanes may be cooled by both internal bypassing and external bleeding lines.

[0019] An effective step that can be taken to increase the power output and improve the efficiency of a gas turbine engine may be to increase the temperature at which heat is added to the system, that is, to raise the turbine inlet temperature of the combustion gases directed to the turbine. Increases in efficient turbines have led to an increase in the temperature that must be withstood by the turbine blades and rotor.

The result is that to use the highest desirable temperatures, some form of forced cooling may be desirable. This cooling may be in the form of air bled from the compressor at various stages and ducted to critical elements in the turbine. Although emphasis is placed on cooling the initial stages of vanes and blades, air may be also directed to other vanes, blade rings and discs.

[0020] Secondary Air System (SAS) main functions include providing cooling flow to engine components, seal bearing chambers, and control seal axial loads. SAS includes the airflow that is not part of the primary flow path. SAS requires fine tuning that is an intricate process. Often, air system circuits in turbines are affected by variations negatively, such as with pressure loss, flow reversal, and other technical issues.

[0021] Because the airfoil is subjected to these high temperatures and pressures, it is very difficult to maintain an acceptable metal temperature. Adjustments in pressure loss and fluid separation through a more effective cooling system is desirable. Embodiments of the present invention provide a turbine engine pre-swirler with pre- swirler plugs.

[0022] FIG. 1 shows a schematic view of a mid-frame area that may be included in turbomachinery, such as a gas turbine engine 10. The gas turbine engine 10 has various components. As shown in FIG. 1, the various components include inner casings, such as, an inner compressor exit diffuser 11, a shaft cover 12, etc. The shaft cover 12 is enclosed by the inner compressor exit diffusor 11. Holes 26 are drilled through the inner compressor exit diffuser 11 and the shaft cover 12 of the gas turbine engine 10. A pre-swirler plug 16 is positioned in the drilled hole 26 to function as a pre-swirler 14. The pre-swirler plug 16 is hollow inside. The pre-swirler plug 16 has a profiled shape. The profiled shape may be designed to have a flow area to achieve the design requirements of the gas turbine engine 10, such as to help throttle the flow to a required flow rate, to allow the flow to accelerate as required for high speeds, to significantly reduce pressure drop across the drilled hole 26. According to various embodiments of the present invention, different pre-swirler plugs 16 may have different profiled shapes to achieve various design requirements. The different pre- swirler plugs 16 having different profiled shapes are replaceable in the same drilled hole 26. FIG. 1 is for illustration purpose only. It is understood that holes 26 may be drilled through other components of the gas turbine engine 10, such as rotor disk, combustion, etc. The different pre-swirler plugs 16 having different profiled shapes are replaceable in the same drilled hole 26 of the other components. [0023] FIG. 2 shows an embodiment of a pre-swirl er plug 16. In this embodiment, the pre-swirl er plug 16 has an inlet treatment. Here, the inlet treatment is a chamfered shape 18 at an inlet 32. As shown in FIG. 3, the chamfered shape 18 at the inlet 32 provides a chamfer angle 19 at the inlet 32 of the pre- swirl er plug 16. Diameter of the pre-swirl er plug 16 is stepped by the chamfered shape 18. The diameter of the pre swirl er plug 16 is measured in an axis that is perpendicular to a flow of fluid 28. There are limitations on an angle that can be chamfered on a drilled hole 26. With the pre-swirl er plug 16 having a chamfered shape 18 positioned in the drilled hole 26, the chamfer angle 19 can be reduced to under 10 degrees. The chamfer angle 19 provided by the chamfered shape 18 can be much lower than a limitation of 30 degrees from an angle of a manufactured hole. The smaller chamfer angle 19 of the pre-swirler plug 16 may significantly reduce pressure drop across the pre-swirler plug 16. In other embodiments, the inlet treatment can include fillets, conical sections, step down in lengths, internal curvature, surface smoothness, and the like.

[0024] FIG. 3 shows another embodiment of a pre-swirler plug 16. In this embodiment, the pre-swirler plug 16 has an angled portion 22. The pre-swirler plug 16 having the angled portion 22 allows the pre-swirler 14 to be placed where access may be obstructed by proximity and/or curvature. Proximity may prevent the drilled hole 26 alone to provide space, when a component or the like may be in the way. With curvature, a hole cannot be drilled to turn flow at a desired angle. This lack of turning results in a swirl ratio of 0. The swirl ratio is the ratio of a rotor speed to air speed in a particular direction. FIG. 4 shows a portion of a pre-swirler plug 16, where the flow of fluid 28 enters in one direction, and then takes a roughly 90-degree turn. The degree of the turn can have a wide range, as long as there is a turn, and therefore an increase in the swirl ratio.

[0025] FIG. 4 shows a further embodiment of the pre-swirler plug 16. In this embodiment, the pre-swirler plug 16 has a flow accelerating portion 24. The pre- swirler plug 16 having at least one flow accelerating portion 24 can be used to achieve higher air speeds. Sometimes in applications, there is more importance attributed to air speed than to pressure deficit. An example of such an application would be cooling dense air flow for thermal conditioning of hardware, or the like. The flow accelerating portion 24 may include a shape that provides a venturi effect causing pressure drop and velocity rise. As shown in FIG. 5, the flow accelerating portion 24 may be a restricted section of the pre-swirler plug 16, such as a nozzle.

[0026] By using the pre-swirler 14 having the pre-swirler plug 16 positioned in a drilled hole 26 of a component of the gas turbine engine 10, such as the inner compressor exit diffusor 11, the shaft cover 12, rotor disk, or combustion, etc., the same component can be used with the ability to tune the design of the gas turbine engine 10 as needed. The design of the gas turbine engine 10 can also be tuned during the testing phase as well. A suite of the gas turbine engines 10 can share a common component and designated drilled holes 26 with different pre-swirler plugs 16 having different profiled shapes. This allows for a common casting with different pre-swirler plugs 16 that can be interchangeable. Additionally, manufacturing limitations can be overcome using the pre-swirler plugs 16.

[0027] The pre-swirler plugs 16 can be threaded, welded, staked, bolted or press fit into the drilled holes 26 of the component of the gas turbine engine 10. Efficiency of the engine 10 can be improved by using the pre-swirler plugs 16 having profiled shapes to recover pressure deficit on drilled holes alone. Bypass hole air can be turned to achieve a high swirl ratio, such as ratio of 1 and higher, to allow for more effective cooling of rotating components, such as rotor, and potentially lead to the ability to use lower grades of material to manufacture rotor disks. The pre-swirler plugs 16 having profiled shapes allow for accelerating dense air. The acceleration of the dense air can increase the heat transfer coefficient of the surface to be thermally heated/cooled by a significant factor which also increases the rate of cooling/heating of components, reducing thermal stress spiking during transient operation and therefore, eliminating the need to service bolts and the like less often and opens the material selection to lower grades per application. [0028] Machining of features that are applied to the pre-swirl er plugs 16 can be made with precision. For example, a feature of a size less than 10 mm in total size envelope can be made to support parts with total size envelopes of 2000 mm and above. The ability to produce these pre-swirl er plugs 16 reduces variation below levels where flow reversal, pressure losses and the like can occur. Using pre-swirler plugs 16 provide additional ability to control and shape the flow of fluid 28 at precision levels otherwise not available/possible with standard manufacturing methods.

[0029] Additionally, the pre-swirler plugs 16 allow for rebalancing and adjustments of the air circuitry in the gas turbine engine 10 during operation by replacing the pre-swirler plugs 16 and not having to replace the major components, such as inner casings. Using pre-swirler plugs 16 can also eliminate standard service or maintenance otherwise required and reduction or elimination of clearance variation due to manufacturing tolerance that potentially lead to field issues. Engine upgrades can be performed by simply replacing the pre-swirler plugs 16 without the need to replace expensive large components or even without the necessity of opening the engine.

[0030] While specific embodiments have been described in detail, those with ordinary skill in the art will appreciate that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only, and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims, and any and all equivalents thereof.