Patent Application
20240426221
The present disclosure relates turbines and, more particularly, to a dovetail structure of a turbine blade with splines forming a fixing profile.
A turbine is used to generate power for propulsion, in some cases, by turning propellors, fans or helicopter blades through a gearbox. In some instances, the gearbox output is used to power electrical generators. In a gas turbine engine, fuel and compressed oxygen are combusted in a combustor to produce a high-temperature and high-pressure fluid. This fluid enters a turbine and interacts with rows or stages of turbine blades and vanes. This interaction causes the stages of turbine blades to rotate a rotor. The rotor rotation drives a compressor to compress the oxygen for the combustor and, as noted above, can be used to drive operations of a generator to produce electricity or for propulsion.
According to an aspect of the disclosure, a fir tree structure is provided and includes a part extending radially inwardly from a rotating part and having an inward taper. The part has a spline profile forming fixing lobes and necks, which are interleaved with the fixing lobes. The spline profile has constantly changing radii of curvature characterized in that the radii of curvature are relatively reduced in high stress locations and relatively increased in low stress locations.
In accordance with additional or alternative embodiments, the fixing lobes include an inboard fixing lobe and an outboard fixing lobe, which is wider than the inboard fixing lobe and the fixing necks include an inboard fixing neck, which is inboard from the outboard fixing lobe, and an outboard fixing neck, which is outboard of the outboard fixing lobe and wider than the inboard fixing neck.
In accordance with additional or alternative embodiments, the spline profile includes non-curvature portions at transitions between the fixing lobes and the fixing necks.
In accordance with additional or alternative embodiments, a plot of curvature along the outboard fixing neck exhibits a first hump, a second hump of significantly greater amplitude than the first hump and a third hump of slightly greater amplitude than the second hump.
In accordance with additional or alternative embodiments, the plot of the curvature along the outboard fixing neck is taken from a starting point at an outboard portion of the outboard fixing neck to an ending point at an inboard portion of the outboard fixing neck.
In accordance with additional or alternative embodiments, the second hump is interposed between the first and third humps.
In accordance with additional or alternative embodiments, the first, second and third humps have a similar pitch.
In accordance with additional or alternative embodiments, a plot of curvature along the inboard fixing neck exhibits a hump, a trough and an inflexion point between the hump and the trough that is closer to the hump.
In accordance with additional or alternative embodiments, the plot of the curvature along the outboard fixing neck is taken from a starting point at an outboard portion of the inboard fixing neck to an ending point at an inboard portion of the inboard fixing neck
According to an aspect of the disclosure, a fir tree structure of a turbine blade is provided and includes a blade part extending radially inwardly from the turbine blade and having an inward taper. The blade part has a spline profile forming blade fixing lobes and blade fixing necks, which are interleaved with the blade fixing lobes. The spline profile has constantly changing radii of curvature characterized in that the radii of curvature are relatively reduced in high stress locations and relatively increased in low stress locations.
In accordance with additional or alternative embodiments, the blade fixing lobes include an inboard blade fixing lobe and an outboard blade fixing lobe, which is wider than the inboard blade fixing lobe and the blade fixing necks include an inboard blade fixing neck, which is inboard from the outboard blade fixing lobe, and an outboard blade fixing neck, which is outboard of the outboard blade fixing lobe and wider than the inboard blade fixing neck.
In accordance with additional or alternative embodiments, the spline profile includes non-curvature portions at transitions between the blade fixing lobes and the blade fixing necks.
In accordance with additional or alternative embodiments, a plot of curvature along the outboard blade fixing neck exhibits a first hump, a second hump of significantly greater amplitude than the first hump and a third hump of slightly greater amplitude than the second hump.
In accordance with additional or alternative embodiments, the plot of the curvature along the outboard blade fixing neck is taken from a starting point at an outboard portion of the outboard blade fixing neck to an ending point at an inboard portion of the outboard blade fixing neck.
In accordance with additional or alternative embodiments, the second hump is interposed between the first and third humps.
In accordance with additional or alternative embodiments, the first, second and third humps have a similar pitch.
In accordance with additional or alternative embodiments, a plot of curvature along the inboard blade fixing neck exhibits a hump, a trough and an inflexion point between the hump and the trough that is closer to the hump.
In accordance with additional or alternative embodiments, the plot of the curvature along the outboard blade fixing neck is taken from a starting point at an outboard portion of the inboard blade fixing neck to an ending point at an inboard portion of the inboard blade fixing neck.
According to an aspect of the disclosure, a method of forming a fir tree structure of a turbine blade is provided. The method includes providing a part extending radially inwardly from the turbine blade and having an inward taper and forming the part to have a spline profile forming fixing lobes and fixing necks, which are interleaved with the fixing lobes. The forming of the part includes identifying high and low stress locations of the part and designing the spline profile to have constantly changing radii of curvature characterized in that the radii of curvature are relatively reduced in the high stress locations and relatively increased in the low stress locations.
In accordance with additional or alternative embodiments, the part includes a blade part.
In accordance with additional or alternative embodiments, the forming of the part includes machining.
Additional features and advantages are realized through the techniques of the present disclosure. Other embodiments and aspects of the disclosure are described in detail herein and are considered a part of the claimed technical concept. For a better understanding of the disclosure with the advantages and the features, refer to the description and to the drawings.
For a more complete understanding of this disclosure, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts:
The exemplary engine 20 generally includes a low speed spool 30 and a high speed spool 32 mounted for rotation about an engine central longitudinal axis A relative to an engine static structure 36 via several bearing systems 38. It should be understood that various bearing systems 38 at various locations may alternatively or additionally be provided, and the location of bearing systems 38 may be varied as appropriate to the application.
The low speed spool 30 generally includes an inner shaft 40 that interconnects a fan 42, a low pressure compressor 44 and a low pressure turbine 46. The inner shaft 40 is connected to the fan 42 through a speed change mechanism, which in exemplary gas turbine engine 20 is illustrated as a geared architecture 48 to drive the fan 42 at a lower speed than the low speed spool 30. The high speed spool 32 includes an outer shaft 50 that interconnects a high pressure compressor 52 and high pressure turbine 54. A combustor 56 is arranged in exemplary gas turbine 20 between the high pressure compressor 52 and the high pressure turbine 54. An engine static structure 36 is arranged generally between the high pressure turbine 54 and the low pressure turbine 46. The engine static structure 36 further supports bearing systems 38 in the turbine section 28. The inner shaft 40 and the outer shaft 50 are concentric and rotate via bearing systems 38 about the engine central longitudinal axis A which is collinear with their longitudinal axes.
The core airflow is compressed by the low pressure compressor 44 then the high pressure compressor 52, mixed and burned with fuel in the combustor 56, then expanded over the high pressure turbine 54 and low pressure turbine 46. The turbines 46, 54 rotationally drive the respective low speed spool 30 and high speed spool 32 in response to the expansion. It will be appreciated that each of the positions of the fan section 22, compressor section 24, combustor section 26, turbine section 28, and fan drive gear system 48 may be varied. For example, gear system 48 may be located aft of combustor section 26 or even aft of turbine section 28, and fan section 22 may be positioned forward or aft of the location of gear system 48.
With continued reference to
In conventional turbines, the curves of the outward projections and the recesses of a typical fir tree structure have simple geometries and uniform radii of curvatures over extended surface areas. In practice, such simple geometries and uniform curvatures were found to lead to non-optimal mechanical interactions and stress concentrations.
Therefore, a need exists for fir tree structures of turbine blades that have improved mechanical interactions and reduced or eliminated stress concentrations.
Thus, as will be discussed below, a fir tree structure of a turbine blade is provided with varying spline profiles. This fir tree structure can be used with gas turbine engines, such as the gas turbine engine 20 of
With reference to
As shown in
As, shown in
As shown in
With references to
Technical effects and benefits of the present disclosure are the provision of a fir tree structure of a turbine blade that is provided with varying spline profiles. This is enabled by machining and other similar processes. The varying spline profiles result in the fir tree structure being optimized for stress across varying operational ranges.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the technical concepts in the form disclosed. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the disclosure. The embodiments were chosen and described in order to best explain the principles of the disclosure and the practical application, and to enable others of ordinary skill in the art to understand the disclosure for various embodiments with various modifications as are suited to the particular use contemplated.
While the preferred embodiments to the disclosure have been described, it will be understood that those skilled in the art, both now and in the future, may make various improvements and enhancements which fall within the scope of the claims which follow. These claims should be construed to maintain the proper protection for the disclosure first described.
