Patent Application
20130230379
The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a rotating turbomachine component having a tip leakage flow guide.
Many turbomachines include a compressor portion linked to a turbine portion through a common compressor/turbine shaft or rotor and a combustor assembly. The compressor portion guides a compressed air flow through a number of sequential stages toward the combustor assembly. In the combustor assembly, the compressed air flow mixes with a fuel to form a combustible mixture. The combustible mixture is combusted in the combustor assembly to form hot gases. The hot gases are guided to the turbine portion through a transition piece. The hot gases expand through the turbine rotating turbine blades to create work that is output, for example, to power a generator, a pump, or to provide power to a vehicle. In addition to providing compressed air for combustion, a portion of the compressed airflow is passed through the turbine portion for cooling purposes.
In some cases, the hot gases expanding through the turbine portion leak or pass over tip end portions of the turbine blades. In order to reduce leakage, manufactures maintain tight clearances between the tip end portions and stationary components of the turbomachine. Generally, seals are provided on the stationary component or turbine shroud. While effective, existing seals still allow a portion of the hot gases or leakage gases to pass over the tip end portion. The tight clearance established by the seal causes the leakage gases to exit at an angle that is generally parallel to an axis defined by a turbomachine rotor. In contrast, hot gases passing along the gas path exit the rotor blades at an angle. Interactions between the leakage gases and the hot gases flowing along the gas path create localized pressure drops that have a negative impact on turbomachine performance.
According to one aspect of the exemplary embodiment, a rotating turbomachine component includes a base portion and an airfoil portion extending from the base portion. The airfoil portion includes a base portion and a tip end portion that is cantilevered from the base portion. A tip leakage flow guide is provided at the tip end portion of the airfoil portion. The tip leakage flow guide includes one or more turning vane members configured and disposed to guide a leakage flow from the tip end portion at a flow angle that substantially coincides with a flow angle of gases flowing downstream from the rotating turbomachine component.
According to another aspect of the exemplary embodiment, a method of operating a turbomachine includes passing hot gases from a combustor assembly toward a plurality of buckets, guiding the hot gases onto the plurality of buckets, directing the hot gases downstream relative to the plurality of buckets along a gas path at a first flow angle, passing a portion of the hot gases over a tip end portion of the plurality of buckets at a second flow angle that is distinct from the first flow angle, and guiding the portion of the hot gases from the tip end portion of the plurality of buckets at a third flow angle that substantially coincides with the first angle.
According to yet another aspect of the exemplary embodiment, a turbomachine includes a compressor portion, a combustor assembly fluidly connecting the compressor portion and a turbine portion mechanically linked to the compressor portion and fluidly connected to the combustor assembly. The turbine portion includes a rotating component having a base portion and an airfoil portion extending from the base portion. The airfoil portion includes a first end connected to the base portion and a tip end portion that is cantilevered from the base portion. A tip leakage flow guide is provided at the tip end portion of the airfoil portion. The tip leakage flow guide includes one or more turning vane members configured and disposed to guide a leakage flow from the tip end portion at a flow angle that substantially coincides with a flow angle of gases flowing downstream from the rotating turbomachine component. A turning vane support member is positioned at the tip end portion. The turning vane support member includes an upstream end and a downstream end. The one or more turning vane members project outward from the turning vane support member
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
With reference to
In the exemplary embodiment shown, turbine portion 6 includes a housing 19 that encases a first, stage 20 and a second stage 21 that define gas path 18. First stage 20 includes a plurality of first stage stators or nozzles, one of which is indicated at 30, supported to turbine housing 19 through a nozzle platform 31. First stage 20 also includes a plurality of first stage buckets or blades, one of which is indicated at 32, mounted to a first stage rotor wheel 34. Blades 32 are spaced from a stationary shroud member 35. Blades 32 include a base portion 38 and an airfoil portion 40. Airfoil portion 40 includes a first end 42 coupled to base portion 38 and a second end or tip end portion 44 that is spaced from stationary shroud member 35. Second stage 21 includes a plurality of second stage stators or nozzles, one of which is indicated at 48 supported to turbine housing 19 through a nozzle platform 49. Second stage 21 also includes a plurality of second stage buckets or blades, one of which is indicated at 50. At this point it should be understood that the number of stages in turbine portion 6 could vary.
In accordance with an exemplary embodiment, turbomachine 2 includes a tip leakage flow guide 60 that conditions tip leakage flow passing over tip portions of blades 32. As best shown in
Combustion gases flow along gas path 18 and pass over nozzles 30 and are guided toward blades 32. A first or main flow 85 passes over blades 32 and a second or leakage flow 88 passes over tip end portion 44 along gas path 18. Main flow 85 flows at a first flow angle as a result of interactions with blade 36. Leakage flow 88 flows at a second flow angle, that is distinct from the first flow angle, and which runs generally parallel to shaft 12. Turning vane member 80 is configured to condition or turn leakage flow 88 exiting tip end portion 44 to create a turned flow 91 that returns to gas path 18 at a third flow angle that substantially coincides with the first flow angle of main flow 85 flowing downstream from blades 32. By matching the third flow angle with the first flow angle, undesirable interactions between turned flow 91 and main flow 85 are reduced. In this manner, turning vane member 80 reduces losses within turbine portion 6 associated with pressure variations along gas path 18 resulting from undesirable interactions between leakage flow 88 and the main flow 85. In the event that nozzles 30 form part of a last stage (not separately labeled) of turbine portion 6, turning vane 80 may be configured to guide the leakage flow gases at an angle that generally corresponds to the flow angle of gases flowing downstream toward and along a radial diffusion section (not shown) of turbine portion 6 so as to enhance pressure recovery.
In accordance with one aspect of the exemplary embodiment illustrated in
At this point it should be understood that the exemplary embodiments provide a system for redirecting tip leakage flow back into the gas path to reduce undesirable interactions with the main flow. Reducing undesirable interactions with the main flow leads to a reduction in pressure losses that may detract from turbine performance. It should also be understood that while shown in connection with a gas turbomachine, the exemplary embodiments could also be employed in a steam turbomachine.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
