BACKGROUND

[0001] 1. Field

[0002] Disclosed embodiments are generally related to gas turbine engines and, more particularly to the junction between the compressor section and the turbine section.

[0003] 2. Description of the Related Art

[0004] A gas turbine engine typically has a compressor section, a combustion section having a number of combustors and a turbine section. Ambient air is compressed in the compressor section and conveyed to the combustors in the combustion section. The combustors combine the compressed air with a fuel and ignite the mixture creating combustion products. The combustion products flow in a turbulent manner and at a high velocity. The combustion products are routed to the turbine section via transition ducts. Within the turbine section are rows of vane assemblies. Rotating blade assemblies are coupled to a turbine rotor. As the combustion product expands through the turbine section, the combustion product causes the blade assemblies and turbine rotor to rotate. The turbine rotor may be linked to an electric generator and used to generate electricity.

[0005] The interplay between components can impact the efficiency of the engine as well as the life span of the components.

SUMMARY

[0006] Briefly described, aspects of the present disclosure relate to the junction between the compressor section and the turbine.

[0007] An aspect of the disclosure may be a gas turbine engine comprising a compressor section for compressing air for the gas turbine engine. The gas turbine engine also has a turbine section for generating electricity located downstream of the compressor section, wherein the turbine section has a pre-swirl section for delivering a fluid flow to the turbine section. The gas turbine engine also has a rotating flange joint joining the compressor section and the turbine section, wherein the rotating flange joint forms part of the pre-swirl section.

[0008] Another aspect of the present disclosure may be a pre-swirl section for a gas turbine engine comprising: a pre-swirl cavity for receiving a fluid flow, wherein a rotating flange joint forms a portion of the pre-swirl cavity, wherein the rotating flange joint joins a combustor section and a turbine section.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Fig. 1 is a schematic sectional view of a gas turbine engine showing a rotating flange joint.

[0010] Fig. 2 is a schematic sectional view of a pre-mix section.

[0011] Fig. 3 is a schematic section view of a gas turbine engine that has a rotating flange joint located in the pre-mix section.

[0012] Fig. 4 shows another view of the rotating flange joint.

DETAILED DESCRIPTION

[0013] To facilitate an understanding of embodiments, principles, and features of the present disclosure, they are explained hereinafter with reference to implementation in illustrative embodiments. Embodiments of the present disclosure, however, are not limited to use in the described systems or methods.

[0014] The components and materials described hereinafter as making up the various embodiments are intended to be illustrative and not restrictive. Many suitable components and materials that would perform the same or a similar function as the materials described herein are intended to be embraced within the scope of embodiments of the present disclosure.

[0015] In some gas turbine engines a rotating flange joint 10 is located in the midsection of the gas turbine engine. At this location the rotors of the compressor section 4 are joined to the rotors of the turbine section 6. The turbine section 6 is located downstream of the compressor section 4. An example of this is shown in Fig. 1. [00161 As the gas turbine engine is operated the rotating flange joint 10 will create a disturbance in the fluid flow moving through the gas turbine engine. Herein the term "fluid flow" is generally referring to a cooling fluid flow used in the gas turbine engine, for example air. The disturbance caused by the rotation of the rotating flange joint 10 will result in heating of the fluid flow due to the absorption of the rotational energy by the fluid flow. The raising of the temperature of the fluid flow may be significant and the higher temperatures can impact the life span of components in the gas turbine engine.

[0017] Fig. 2 shows a pre-swirl section 8 that is located further downstream in the gas turbine engine shown in Fig. 1. The pre-swirl section 8 is used to deliver a cooling fluid flow (represented by the arrows) to rotating blades in the turbine section 6. The fluid flow used in the pre-swirl section 8 is taken from the fluid flow taken compressor section 4 that is intended for cooling rotating blades. The fluid flow is accelerated and turned in the pre-swirl section 8 so that it enters the rotating receiver passages 14 in the seal disk 16 in an efficient manner. The stationary pre-swirl section 8 is capable of delivering fluid flow at over swirled conditions. An over swirled condition is a condition where the swirl ratio that is greater than 1. The "swirl ratio" is the absolute tangential velocity of the fluid flow divided by local rotor speed.

[0018] In order to avoid a drop in swirl ratio as the fluid flow moves radially outward, radial pumping fins 18 may be used. Preferably the swirl ratio is 1.0 or close thereto in order to avoid the reduced swirl ratio that is caused by the movement of the fluid flow radially outwards. A swirl ratio less than 1.0 as it enters the turbine section 6 will result in pressure loss when entering the turbine blades and thereby impact the efficiency of the gas turbine engine.

[0019] The inventor has recognized that in order to better control the heat generated by a rotational flange joint additional fluid flow is desired however the additional fluid flow comes at the expense of the efficiency of the gas turbine engine. Therefore, by utilizing the fluid flow used in the pre-swirl section and subsequently taking advantage of the rotation of the rotating flange joint one can improve overall efficiency of the gas turbine engine as well as potentially increase the life span of components. It should be understood that the advantages recognized herein can be applied to various rotating flange joints in the area between compressor and turbine sections, such as the rotating flange joint between an air separator and shaft, as well as the area between the compressor shaft and the turbine shaft In those instances where an air separator is not used the flange between the compressor and turbine may be relevant.

[0020] Turning to Fig. 3 a gas turbine engine 100 that employs a pre-swirl section 20 is shown that further employs a rotating flange joint 25. The rotating flange joint 25 is located further downstream in the gas turbine engine 100 than where rotating flange joint 10 is located in Fig. 1. The rotating flange joint 25 is located so that a rotating surface 26 of the rotating flange joint 25 forms a portion of the pre-swirl cavity 27 in the pre-swirl section 20. A view looking downstream towards the turbine section 6 is shown in Fig. 4 and provides another view of the rotating flange joint 25 illustrating sunken bolts 22.

[0021] A higher swirl ratio as the fluid flow enters the pre-swirl cavity 27 results in lower pressure in the pre-swirl cavity 27. Lower pressure in the pre-swirl cavity 27 will reduce leakage from seals into the surrounding passages.

[0022] A fluid flow delivered to the turbine section 6 with a higher swirl ratio permits the fluid flow to behave in a free vortex manner as it flows radially outwards towards the turbine section 6. With the fluid flow behaving in a free vortex manner the swirl ratio will decrease as the radius of the turbine system 6 increases. By "radius" it is meant the distance from the axis of the gas turbine engine. Therefore, at a lower radius of the turbine system 6, the cooling fluid flow coolant is at a swirl ratio of about 1.2 and is then reduced to 1.0 as it moves radially outwards, thereby matching rotor speed by the time it reaches the blade supply cavity for optimum entry (i.e. entry of the fluid with minimum pressure loss and avoid rotor work on fluid).

[0023] Moving the rotating flange joint 25 into the pre-swirl section 20 provides a two-fold advantage. First, the rotating flange joint 25 can be cooled by incoming fluid flow used for the pre-swirl section 20 and second, the rotating flange joint 25 can provide additional swirl of the fluid flow for the pre-swirl section 20 so as to increase the swirl ratio.

[0024] Fluid flow intended for cooling blades in the turbine section 6 passes through inlet channel 21 and is swirled by pre-swirled vane 23. The fluid flow then enters the pre-swirl cavity 27. The rotating vertical surface 26 further swirls the fluid flow while receiving the cooling benefits of the fluid flow.

[0025] The rotating flange joint 25 forms an efficient over swirled pre swirl section 20 while the rotating flange joint 25 is being cooled. Through the use of the rotating vertical surface 26. The rotating vertical surface 26 helps to preserve the swirl of the fluid flow exiting the inlet channel 21 before it gets to turbine section 6. The rotating vertical surface 26 also helps to minimize stationary surfaces within the pre- swirl cavity 27. A stationary surface can hinder the swirl of the fluid flow and thus potentially impact the efficiency of the gas turbine engine 100. Bolts 22 used with the rotating flange joint 25 are countersunk into the rotating flange joint 25 so that the bolt heads are flush or slightly inside this rotating flange joint 25 (as shown in Fig. 4).

[0026] By exposing the rotating flange joint 25 to fluid flow in the pre-swirl section 20 any power from the rotating flange joint 10 is absorbed without significant temperature rise. Previously, seal failures in the engine mid-section would sometimes lead to starvation of purge flow to rotating flange joint, leading to over-temperature of the rotating flange joint Because the rotating flange joint 25 is exposed to the fluid flow in the pre-swirl section 20 the durability of the rotating flange joint 25 can be extended.

[0027] The pressure of the pre-swirl cavity 27 may be constantly monitored health monitoring system of the gas turbine engine 100, which will shut down the gas turbine engine 100 if pressure falls below a critical level. The health monitoring system will further insure that the joining of the compressor section 4 and the turbine section 6 by the rotating flange joint 25 is also protected by the supervisory instrumentation and related control safeguards, typically intended to monitor the pre- swirl section 20.

[0028] Still referring to Fig. 3, the pre-swirl vane 23 delivers the fluid flow out of the inlet channel 21 and into the pre-swirl cavity 27 at slight over swirled conditions. The over swirl condition is a condition where the swirl ratio is greater than 1.0, such as 1.1. As the pre-swirled fluid flow travels radially-inwards towards angled receiver holes 29, the swirl ratio increases to 1.2 due to the free vortex-type flow in the pre- swirl cavity 27 and increasing swirl ratio as the fluid flow moves radially inward.

[0029] The rotating vertical surface 26 forming a portion of the pre-swirl cavity helps to preserve the swirl effectiveness, i.e. it helps preserve the fluid flow at a swirl ratio of 1.2. The fluid flow then enters and leaves the rotating angled receiver holes 29 that are angled in the direction of rotation of the rotors of the combustion section 4 and rotors of the turbine section 6. The angled entry of the angled receiver holes 29 maintains the swirl ratio of the fluid flow at 1.2. The angled range may be up to 30° relative to the axis of rotation. By starting from the over swirled condition of having a swirl ratio of 1.2, fluid flow then flows radially outwards in a free vortex to the turbine section 6. As the fluid flow moves radially outwards in a free vortex, the swirl ratio decreases to 1.0 and arrives at the turbine section entry point 7 at rotor speed with minimal pressure loss.

[0030] Placement of the rotating flange joint 25 in the pre-swirl section 20 turns the windage heating typically caused by the rotating flange joint 25 into an advantage in terms of swirling the fluid flow. This rotating vertical surface 26 ensures that the coolant flow stays highly swirled with minimal swirl decay once the fluid flow exits the pre-swirl vane 23 into the pre-swirl cavity 27. The over swirled fluid flow in the pre-swirl section 20 matching swirl velocities at flow interfaces (both stator-to rotor and rotor to rotor) results in lowest pressure loss across the entire path.

[0031] Thus the placement of the rotating flange joint 25 within the pre-swirl section 20 can result in more efficient gas turbine engine with improved life span of the gas turbine components.

[0032] While embodiments of the present disclosure have been disclosed in exemplary forms, it will be apparent to those skilled in the art that many modifications, additions, and deletions can be made therein without departing from the spirit and scope of the invention and its equivalents, as set forth in the following claims.