Gas turbine engine preswirler with angled holes

A gas turbine engine preswirler (470) includes an outer ring (471) and an inner ring (472). The inner ring (472) includes a plurality of angled holes (490). Each angled hole (490) follows a vector which is angled in at least one plane. A component of the vector is located on a plane perpendicular a radial from an axis of the preswirler (470). The component of the angle is angled relative to an axial direction of the preswirler (470).

TECHNICAL FIELD

The present disclosure generally pertains to as turbine engines, and is more particularly directed toward a preswirler with angled holes configured for cooling downstream components.

BACKGROUND

Gas turbine engines include compressor, combustor, and turbine sections. Portions of a gas turbine engine are subject to high temperatures. In particular, the first stage of the turbine section is subject to such high temperatures that the first stage is cooled by an directed through internal cooling passages from the compressor. In one such passage, air is directed through the diaphragm of a gas turbine engine and into the preswirler. Uncontrolled cooling air may lead to a loss of efficiency and improper cooling.

U.S. Pat. No. 7,341,429 to J. Montgomery, discloses a method of manufacturing a gas turbine engine includes providing a turbine mid-frame, coupling a plurality of rotor blades to a rotor disk, the rotor disk is coupled axially aft from the turbine mid-frame such that a cavity is defined between the rotor disk and the turbine mid-frame, and forming at least one opening extending through the turbine mid-frame to facilitate channeling cooling air into the gap, the opening configured to impart a high relative tangential velocity into the cooling air discharged from the opening.

The present disclosure is directed toward overcoming one or more of the problems discovered by the inventors.

SUMMARY OF THE DISCLOSURE

A gas turbine engine preswirler includes an outer ring and an inner ring. The inner ring includes a plurality of angled holes. Each angled hole follows a vector which is angled in at least one plane. A component of the vector is located on a plane perpendicular a radial from an axis of the preswirler. The component of the angle is angled relative to the axial direction of the preswirler.

A method for forming a preswirler is also provided. The method includes forming an angled hole through the preswirler at an angle from twenty to eighty-five degrees relative to an axial direction of the preswirler. The method also includes forming a first stress relief region contiguous the angled hole. The first stress relief region is configured to be in flow communication with the angled hole.

DETAILED DESCRIPTION

The systems and methods disclosed herein include a gas turbine engine preswirler with angled holes. In embodiments, the preswirler may be configured to provide a predictable amount of cooling air to the next stage turbine rotor disk and dampers aft of the preswirler. The angled holes can be configured to swirl the cooling air such that the angular velocity of the cooling air matches the angular velocity of the next stage turbine rotor disk. Matching the angular velocity of the cooling air with the angular velocity of the turbine rotor disk can reduce any temperature increases or pressure drops in the cooling air, which can result in an increase in efficiency.

FIG. 1is a schematic illustration of an exemplary gas turbine engine. A gas turbine engine100typically includes a compressor200, a combustor300, a turbine400, and a shaft120. The gas turbine engine100may have a single shaft or a dual shaft configuration. For convention in this disclosure all references to radial, axial, and circumferential directions and measures refer to center axis95unless otherwise specified. Center axis95may generally be defined by the longitudinal axis of shaft120. Center axis95may be common to or shared with other gas turbine engine concentric components.

Air10enters an inlet15as a “working fluid” and is compressed by the compressor200. Fuel35is added to the compressed air in the combustor300and then ignited to produce a high energy combustion gas. Energy is extracted from the combusted fuel/air mixture via the turbine400and is typically made usable via a power output coupling5. The power output coupling5is shown as being on the forward side of the gas turbine engine100, but in other configurations it may be provided at the aft end of gas turbine engine100. Exhaust90may exit the system or be further processed (e.g., to reduce harmful emissions or to recover heat from the exhaust90).

The compressor200includes a compressor rotor assembly210and compressor stationary vanes (“stators”)250. The compressor rotor assembly210mechanically couples to shaft120. As illustrated, the compressor rotor assembly210is an axial flow rotor assembly. The compressor rotor assembly210includes one or more compressor disk assemblies220. Each compressor disk assembly220includes a compressor rotor disk that is circumferentially populated with compressor rotor blades. Stators250axially precede each of the compressor disk assemblies220.

The turbine400includes a turbine rotor assembly410and turbine nozzle assemblies450. The turbine rotor assembly410mechanically couples to the shaft120. As illustrated, the turbine rotor assembly410is an axial flow rotor assembly. The turbine rotor assembly410includes one or more turbine disk assemblies420. Each turbine disk assembly420includes a turbine rotor disk that is circumferentially populated with turbine rotor blades425(shown inFIG. 2). Turbine nozzle assemblies450axially precede each of the turbine disk assemblies420. The turbine nozzle assemblies450have circumferentially distributed turbine nozzle vanes. The turbine nozzle vanes helically reorient the combustion gas that is delivered to the turbine rotor blades425where the energy in the combustion gas is converted to mechanical energy and rotates the shaft120.

A turbine nozzle assembly450paired with a turbine disk assembly420it precedes is considered a turbine stage of the gas turbine engine100. A turbine first stage415is a stage axially adjacent to the combustor300. The turbine first stage415includes a first stage turbine nozzle assembly451and a first stage turbine disk assembly421. The first stage turbine nozzle assembly451includes diaphragm460, preswirler470, and turbine nozzles455(shown inFIG. 2).

The various components of the compressor200are housed in a compressor case201that may be generally cylindrical. The various components of the combustor300and the turbine400are housed, respectively, in a combustor case301and a turbine case401.

FIG. 2is a cross-sectional view of a portion of the turbine first stage415ofFIG. 1. All references to radial, axial, and circumferential directions and measures for elements of preswirler470refer to the axis of preswirler470, which is concentric to center axis95. The axial direction99(illustrated inFIG. 4) of the preswirler470being the direction traveling from the forward or upstream side of the preswirler470to the aft or downstream side of the preswirler470along a path concentric or parallel to the axis of the preswirler470. The first stage turbine nozzle assembly451is adjacent to the combustion chamber310. Cooling air from the compressor200travels along path for cooling air50to the first stage turbine nozzle assembly451, passes through the diaphragm460, and into the preswirler470. The preswirler470redirects the cooling air and imparts a tangential component to the velocity of the cooling air. The tangential component to the velocity of the cooling air may match the angular velocity of the first stage turbine disk assembly421. The described arrangement may also be used in other stages.

The preswirler470includes an outer ring471and an inner ring472defining a passage for cooling air53there between. The outer ring471may include an outer flange473and an outer cylindrical portion480. The outer flange473may be thickened and may be configured to include first holes482(only one is visible inFIG. 2; seeFIGS. 3 and 5). The outer cylindrical portion480may extend aft from the aft end of the outer flange473.

FIG. 3is an elevation view of an upper portion of the preswirler470of the first stage turbine nozzle assembly451. Referring now toFIG. 2andFIG. 3, the inner ring472is located radially inward from the outer ring471. The inner ring472of the preswirler470may include an inner flange474, an inner cylindrical portion481, and a back portion475as shown inFIG. 2. The inner ring472may also include angled holes490and first stress relief region491as shown inFIG. 3, as well as second stress relief region492(shown inFIG. 4). Inner flange474may be spaced apart from the outer flange473. The inner flange474may be thickened as shown inFIG. 2and may be configured to include second holes483(only one is visible inFIG. 2; seeFIGS. 3 and 5). In the embodiment shown inFIG. 3, inner ring472includes bosses476. Each boss476includes a second hole483.

Referring again toFIG. 2, the inner cylindrical portion451may be located radially inward and within the outer cylindrical portion480. Inner cylindrical portion481and outer cylindrical portion480may define a radial gap54there between. Swirl vanes may span radial gap54from inner cylindrical portion481to outer cylindrical portion480. Swirl vanes may be angled relative to the axis of the preswirler470. The back portion475may extend radially outward from the aft end of the inner flange474to the forward end of the inner cylindrical portion481. Back portion475may also extend axially aft from inner flange474to inner cylindrical portion481.

Angled holes490may be formed in the inner ring472of preswirler470. In the embodiment shown inFIG. 2, angled holes490are formed in back portion475.

The diaphragm460has a mounting portion468with diaphragm cooling passages. The mounting portion468includes outer diameter holes465and inner diameter holes466. Outer diameter holes465align with first holes482and inner diameter holes466align with second holes483.

The preswirler470may be mounted to the diaphragm460by a plurality of outer diameter couplers461and a plurality of inner diameter couplers462. Each first hole482may receive an outer diameter coupler461and each second hole483may receive an inner diameter coupler462. An outer diameter coupler461passes through an outer diameter465and into a first hole482. An inner diameter coupler462passes through an inner diameter hole466and into a second hole483. The preswirler470configured for mounting to the diaphragm460may be configured with at least ten first holes482and at least ten second holes483to sufficiently seal the preswirler470to the diaphragm460and prevent uncontrolled leakage.

In one embodiment, the outer diameter couplers461, outer diameter holes465, and first holes482each total eighteen, while the inner diameter couplers462, inner diameter holes466, and second holes483also each total eighteen. However, any number of outer diameter couplers461, outer diameter holes465, first holes482, inner diameter couplers462, inner diameter holes466, and second holes483may be used. The outer diameter couplers461may secure the inner turbine seal402to the diaphragm460. In one embodiment the outer diameter couplers461and the inner diameter couplers462may be bolts. Alternative couplers such as rivets may also be used. The first holes482and the second holes483may be threaded. Some embodiments that encompass bolting the preswirler470to the diaphragm460do not include a press fit or an interference fit between the preswirler470and the diaphragm460.

FIG. 4is a cross-sectional view of the preswirler shown inFIG. 3. The preswirler depicted inFIG. 4may be used in the gas turbine engine100ofFIG. 1. As previously mentioned, angled holes490may be formed in inner ring472. In the embodiment shown inFIG. 4, angled holes490are formed in back portion475. Angled holes490follow a vector which is angled in at least one plane. A component of this vector, line97, may be located on a plane perpendicular to a radial extending from the axis of the preswirler470and may be angled relative to the axial direction99of the preswirler470illustrated by angle98, the angle between lines94and97inFIG. 4. Line94is a reference line located on the plane perpendicular to the radial extending from the axis of preswirler470and is oriented in axial direction99. Line97may also be in the turbine rotor disk rotational direction to direct the gas or air in the same rotational direction as the turbine rotor disk. In one embodiment, angle98is from twenty to eighty-five degrees. In another embodiment, angle98is from sixty-five to eighty degrees. In another embodiment, angle98is sixty-eight degrees. In yet another embodiment, angle98is seventy-five degrees. The diameter of angled holes490may be sized based on the cooling flow needed. In one embodiment, the diameter of each angled hole490taken at a cross-section normal to the angled hole490is sized from ⅛″ to 3/16″. In another embodiment, the diameter of each angled hole490taken at a cross-section normal to the angled hole490is 0.136″.

A first stress relief region491may be formed contiguous each angled hole490. Each first stress relief region491is in flow communication with the angled hole490. Each first stress relief region491may be an elongated recess and may recede into inner ring472thereby widening the opening of the angled hole490. Each first stress relief region491may have an angle similar to the angle of the contiguous angled hole490. Each first stress relief region491may have a curved profile and may include multiple curves, arcs, or radii. First stress relief region491may be an elongated scoop. The scoop may be wider than the diameter of angled hole490. The elongated length of the scoop may be biased away from angled hole490along line97, as illustrated inFIG. 4. In one embodiment, each first stress relief region491is located upstream of an angled hole490and recedes axially aft into inner ring472. In another embodiment each first stress relief region491is located downstream of an angled hole490and recedes axially forward into inner ring472.

A second stress relief region492may be formed contiguous each angled hole490. Each second stress relief region492is in flow communication with the angled hole490. Each second stress relief region492may be an elongated recess and may recede into inner ring472thereby widening the opening of the angled hole490. Each second stress relief region492may have an angle similar to the angle of the contiguous angled hole490. Each second stress relief region492may have a curved profile and may include multiple curves, arcs, or radii. Second stress relief region492may be an elongated scoop. The scoop may be wider than the diameter of angled hole490. The elongated length of the scoop may be biased away from angled hole490along line97, as illustrated inFIG. 4. In one embodiment, each second stress relief region492is located downstream of an angled hole490opposite an upstream first stress relief region491. The second stress relief region492recedes axially forward into inner ring472. In another embodiment, each second stress relief region492is located upstream of an angled hole490opposite a downstream first stress relief region491. The second stress relief region492recedes axially aft into inner ring472.

Each first stress relief region491and second stress relief region492may be formed by manufacturing processes such as ball milling, electrical discharge machining, or drilling.

The preswirler470depicted inFIG. 3andFIG. 4has a reformed connection. Inner ring472includes a plurality of bosses476. Each boss476may be a thickened material and may be configured to receive an inner diameter coupler462for mounting the preswirler470to the diaphragm460. A second hole483is machined into each boss476.

FIG. 5is a perspective view of the preswirler470. The preswirler470ofFIG. 5may be used in the gas turbine engine100ofFIG. 1. The preswirler470includes an outer ring471with a plurality of first holes482. The outer ring471also includes a plurality of cooling holes486. At least a portion of the cooling air entering radial gap54(depicted inFIG. 2) exits the preswirler470through the cooling holes486. The preswirler470also includes an inner ring472with a plurality of second holes483.

Preswirler470may include any number of angled holes490. In one embodiment preswirler470includes from nine to eighteen angled holes490. In another embodiment preswirler470includes nine angled holes490. In yet another embodiment preswirler470includes eighteen angled holes490. In the embodiment depicted inFIG. 5, the preswirler470includes the same number of first holes482, second holes483, and angled holes490. At least a portion of the cooling it entering the preswirler470exits the preswirler470through the angled holes490.

One or more of the above components (or their subcomponents) may be made from stainless steel and/or durable, high temperature materials known as “superalloys”. A superalloy, or high-performance alloy, is an alloy that exhibits excellent mechanical strength and creep resistance at high temperatures good surface stability, and corrosion and oxidation resistance. Superalloys may include materials such as HASTELLOY, INCONEL, WASPALOY, RENE alloys, HAYNES alloys, INCOLOY, MP98T, TMS alloys, and CMSX single crystal alloys.

INDUSTRIAL APPLICABILITY

Gas turbine engines may be suited for any number of industrial applications such as various aspects of the oil and gas industry (including transmission, gathering, storage, withdrawal, and lifting of oil and natural gas), the power generation industry, cogeneration, aerospace and other transportation industries.

Operating efficiency of a gas turbine engine generally increases with a higher combustion temperature. Thus, there is a trend in gas turbine engines to increase the temperatures. Gas reaching a turbine first stage415from a combustion chamber310may be 1000 degrees Fahrenheit or more. To operate at such high temperatures a portion of the compressed air of the compressor200of the gas turbine engine100may be diverted through internal passages or chambers to cool the turbine rotor blades425in the turbine first stage415.

The gas reaching the turbine rotor blades425in the turbine first stage415may also be under high pressure. The cooling air diverted from the compressor200may need to be at compressor discharge pressure to effectively cool turbine rotor blades425in the turbine first stage415and other components of the turbine400. Gas turbine engine100components containing the internal passages for the cooling air such as a diaphragm460and a preswirler470may be subject to elevated levels of stress.

Cooling air with a substantially axial flow is diverted from the compressor discharge to a path for cooling air50. The cooling air passes through the diaphragm cooling passage and into the preswirler470passage for cooling air53. A portion of the cooling air may be directed radially outward and into radial gap54. The cooling air from radial gap54may be discharged from the preswirler470with a tangential component from an aft end of radial gap54or from cooling holes486and into the first stage turbine disk assembly421with a tangential component that matches the angular velocity of the first stage turbine disk assembly421.

A matching angular velocity between the cooling air and the first stage turbine disk assembly421may be desirable because it may prevent the first stage turbine disk assembly421from increasing the velocity of the cooling air. An increase in velocity of the cooling air would result in an increase in temperature and a pressure drop in the cooling air, which may reduce the effectiveness of the cooling air in cooling the first stage turbine disk assembly421. An increase in velocity of the cooling air may also result in a loss in efficiency due to the work imparted by the first stage turbine disk assembly421on the cooling air to change the velocity of the cooling air. Once the cooling air passes into the first stage turbine disk assembly421the cooling air cools the first stage turbine disk assembly421including the turbine rotor blades425.

It was discovered through research and testing that a preswirler connected to a diaphragm by a press fit or an interference fit, and a plurality of mounting bolts located near the outside diameters of a preswirler and a diaphragm may deform due to the temperature, pressure, and forces of the cooling air. This deformation to the various components may permit an uncontrolled leakage of cooling air to components aft of a preswirler in the gas turbine engine such as the next stage turbine rotor disk and dampers.

In order to control the flow of cooling air to the next stage turbine rotor disk and dampers, a seal between the diaphragm460and the preswirler470may need to be maintained to prevent cooling air from leaking and a path for cooling air may need to be added to properly cool components aft of the preswirler470. It was determined through research, computer modeling, and testing that a more rigid connection may prevent deformation of the preswirler and the subsequent uncontrolled leakage.

A more rigid connection may be formed by constraining the preswirler470and the diaphragm460by a plurality of outer diameter couplers461and a plurality at inner diameter couplers462. The outer diameter couplers461are placed through the outer diameter holes465and into the first holes482in the outer flange473. The inner diameter couplers462are placed through the inner diameter holes466and into the second holes483of the inner ring472. This more rigid may increase the contact area between the preswirler470and the diaphragm460which may reduce stress and wear of various gas turbine engine components.

With the use of angled holes490the amount of cooling air reaching the next stage turbine rotor disk and dampers may be predicted. It was further determined that angled holes490may provide a controlled flow of cooling air to the components aft of the preswirler470in the gas turbine engine100. A portion the cooling air entering the passage for cooling air53may exit the preswirler through angled holes490. A skewed angle of angled holes490may help generate a circumferential swirl in the cooling air exiting through angled holes490with a velocity that matches the preswirler470exit swirl velocity generated by the swirl vanes. Matching the preswirler470exit swirl velocity may prevent temperature increases and pressure losses in the cooling air which may lead to a more efficient use of the cooling air.

The skewed angles of angled holes490may lead to increased stress in regions of the preswirler470. It was determined that first stress relief region491and second stress relief region492may reduce stress concentrations in preswirler470.

FIG. 6is a flowchart of a method for forming cooling holes with stress relief regions in a preswirler. The method includes forming an angled hole490relative to an axial direction99in the preswirler at step510. The angled hole490may follow a vector which is angled in at least one plane. A component of this vector may be located on a plane perpendicular to a radial extending from the axis of the preswirler470. Forming an angled hole490is followed by step520. At step520a first stress relief region491is formed in the preswirler contiguous to the angled hole490and in flow communication with the angled hole490. In one embodiment, first stress relief region491is formed upstream of angled hole490. In another embodiment, first stress relief region491is formed downstream of angled hole490.

Forming cooling holes with stress relief regions in a preswirler may also include forming a second stress relief region492in the preswirler470contiguous to the angled hole490and in flow communication with the angled hole490at step530. In one embodiment, second stress relief region492is formed downstream of angled hole490, opposite first stress relief region491. In another embodiment, second stress relief region492is formed upstream of angled hole490, opposite first stress relief region491.

In one embodiment angled hole490is drilled into preswirler470. In some embodiments a ball milled operation is used to form the first stress relief region491. Some embodiments also include forming the second stress relief region492with a ball milled operation. At least one embodiment includes, forming eighteen angled holes490, eighteen first stress relief regions491, and eighteen second stress relief regions492.

The use of a more rigid connection with angled holes490may lead to longer service life hours for preswirler470and the components in the next stage of the turbine400as well as an efficient use of the cooling air bled from compressor200.

The preceding detailed description is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. The described embodiments are not limited to use in conjunction with a particular type of gas turbine engine. Hence, although the present disclosure, for convenience of explanation, depicts and describes particular preswirlers and associated processes, it will be appreciated that other preswirlers and processes in accordance with this disclosure can be implemented in various other turbine stages, configurations, and types of machines. Furthermore, there is no intention to be bound by any theory presented in the preceding background or detailed description. It is also understood that the illustrations may include exaggerated dimensions to better illustrate the referenced items shown, and are not consider limiting unless expressly stated as such.