Patent Application
20180355732
The present invention relates generally rotor assemblies having a casing around a rotor and blades such as a fan, compressor, or turbine in a gas turbine engine and, more specifically, to sealing the clearances between the blade tip and casing in such rotor assemblies.
In a turbomachine such as a gas turbine engine, air acts as the working fluid and is compressed by a fan, a compressor, or a combination of the fan and compressor. The compressed air is mixed with fuel and combusted in a combustor, and the combustion gases are expanded through a turbine to extract energy. The extracted energy may be used, for example, to generate electricity or to rotate one or more shafts which may be coupled to the fan and/or compressor. In applications where the turbine engine is providing motive force to a vehicle such as an aircraft, combustion gases may additionally be ejected from the turbine to provide thrust.
Each of the fan, compressor, and turbine comprise one or more sets of blades attached about a rotatable shaft or a disc which is coupled to a rotatable shaft. During operation, the blades rotate with the shaft or disc. In the fan and compressor, the rotation of the blades increases the pressure of the air; conversely, in the turbine the rotation of the blades decreases the pressure of the combustion gases and extracts work.
Each set of blades is typically circumferentially encased by an engine casing or a shroud.
Although blade tip clearances 105 are a preferred method of preventing contact between the blade tip and the casing (commonly referred to as “rub”), which can lead to damage of the blade and/or casing and even engine failure, blade tip clearances 105 are problematic in that they result in leakage from a relatively high pressure side of a blade to a relatively low pressure side of a blade during operation. Stated differently, air or combustion gases may leak from the pressure side of the blade to the suction side of the blade. Such leakage generally decreases the efficiency of the fan, compressor, and/or turbine, and may in some applications result in decreased stall margin. The magnitude of the tip clearance relative to the spanwise dimension of the airfoil expressed as a percentage can be termed the clearance to span ratio. A change in tip clearance for a large clearance to span ratio, such as at the rear of a compressor, will be more impactful to the efficiency aforementioned.
It is thus desirable to provide a system and method of reducing leakage across the blade tip 109 while ensuring that a rotating blade 101 does not contact the casing 103 in a manner that will cause damage to the engine. Reducing blade tip leakage would increase the efficiency of the fan, compressor, and/or turbine, and may in some applications result in increased stall margin. Further, reducing blade tip leakage may additionally allow for the optimizing of additional aero and mechanical requirements such as flow, pressure ratio, weight, and cost, among other variables.
The present application discloses one or more of the features recited in the appended claims and/or the following features which, alone or in any combination, may comprise patentable subject matter.
According to an aspect of the present disclosure, a rotor assembly comprised of a casing, which encases a rotor, which is coupled to at least one rotor blade comprised of a root portion, a main airfoil body extending radially from the root portion. The airfoil body is comprised a pressure side surface and a suction side surface, joined at and extending between a leading edge and a trailing edge, and a blade tip sealing portion, forming the distal end of the rotor blade. The blade tip sealing portion is comprised of a blade tip platform facing the casing and extending at least between the distal edges of the pressure side surface and the suction side surface of said the airfoil body. A plurality of sealing members extends radially from the blade tip platform, and are positioned on the blade tip platform to extend between a pressure side edge and a suction side edge at an angle substantially perpendicular to an air flow across the blade tip platform, and are spaced between the leading edge and the trailing edge of the main airfoil body to effect an overlap of adjacent sealing members in the direction of the air flow.
In one embodiment the sealing members are positioned to effect greater spacing between the members near the edges of the blade relative to the spacing between members near the mid-chord of the blade. In another embodiment the sealing members are positioned to effect greater spacing between the members near the mid-chord of the blade relative to the members near the edges of the blade. In yet another embodiment the plurality of sealing members may have a uniform radial dimension. An embodiment may also consist of the plurality of sealing members may have a differing radial dimension. In another embodiment each of the plurality of sealing members may have a varying radial dimension along the length thereof. In yet another embodiment the elongated sealing members are positioned to effect uniform spacing between the members along the blade tip chord. A final embodiment may comprise of elongated sealing members positioned to effect non-uniform spacing between the members along the blade tip chord.
Another aspect of the disclosure regarding a rotor assembly having a casing, a rotor encased by the casing, and a rotor blade coupled to the rotor having a blade tip spaced from the casing, may be a method of reducing a tip leakage air flow between the blade tip and the casing from a pressure side of the rotor blade to a suction side of the rotor blade during rotation of the rotor, which may comprise of determining a primary direction of the tip leakage air flow relative to a blade tip chord, positioning a plurality of elongated sealing members on a radially outward facing surface of the blade tip at an angle substantially perpendicular to the primary direction of the tip leakage air flow, and spaced along the blade tip chord to effect an overlap of adjacent sealing members in the direction of the tip leakage air flow.
One embodiment of the method may comprise positioning a blade tip platform over the blade tip, the blade tip platform having a surface facing the casing and extending at least between the distal edges of the pressure side and suction side of the blade and from the midchord toward the leading edge and trailing edge of the blade. Another embodiment of the method may comprise the blade tip platform extending to the leading edge and trailing edge of the blade. Yet another embodiment of the method may comprise positioning the elongated sealing members to effect uniform spacing between the members along the blade tip chord. An embodiment of the method may also comprise positioning the elongated sealing members to effect non-uniform spacing between the members along the blade tip chord. A further embodiment of the method may comprise positioning the elongated sealing members to effect greater spacing between the members near the edges of the blade relative to the spacing between members near the mid-chord of the blade. A further embodiment may also comprise positioning the elongated sealing members to effect greater spacing between the members near the mid-chord of the blade relative to the members near the edges of the blade.
An embodiment of the method may comprise positioning a plurality of elongated sealing members having a uniform radial dimension. Another embodiment of the method may comprise positioning a plurality of elongated sealing members having a differing radial dimension. Yet another embodiment of the method may comprise positioning a plurality of elongated sealing members each having a varying radial dimension along the length thereof. An embodiment of the method may also comprise providing an abradable region on the casing adjacent the blade tip, dimensioning the sealing members in the radial direction to effect contact between at least a portion of each sealing member and the abradable region; and rotating the rotor to effect rub between the plurality of sealing members and the abradable region, wherein said rub causes a plurality of annular channels to be formed in the abradable region with each one of said plurality of annular channels corresponding to a respective one of said plurality of sealing members.
Yet another aspect of the rotor assembly having a casing, a rotor encased by the casing, and a rotor blade coupled to the rotor having a blade tip spaced from the casing, may be a method of reducing a tip leakage air flow between the blade tip and the casing from a pressure side of the rotor blade to a suction side of the rotor blade during rotation of the rotor, comprised of positioning a blade tip platform over the blade tip with a surface facing the casing and extending at least between the distal edges of the pressure side and suction side of the blade and between the leading edge and trailing edge of the blade, positioning a plurality of elongated sealing members on the surface of the blade tip platform having a selected lateral cross-sectional shape at a selected angle relative to the blade tip chord and being spaced in a selected chord-wise spacing pattern along the blade tip chord, determining the flow rate and direction of the tip leakage airflow, and varying one or more of the selected lateral cross-sectional shape, the selected angle relative to the blade tip chord, and the selected chord-wise spacing pattern to effect a change in the flow rate of the tip leakage air flow.
The following will be apparent from elements of the figures, which are provided for illustrative purposes and are not necessarily to scale.
While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. It should be understood, however, that the present disclosure is not intended to be limited to the particular forms disclosed. Rather, the present disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the appended claims.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to a number of illustrative embodiments illustrated in the drawings and specific language will be used to describe the same.
This disclosure presents embodiments to overcome the aforementioned deficiencies in fan, compressor, and turbine blades of a turbine engine. More specifically, the present disclosure is directed to systems and methods for reducing or eliminating leakage through the blade tip clearance. The present disclosure is directed to sealing mechanisms for the clearance between the blade tip and casing in a fan, compressor, or turbine of a turbine engine.
Blade tip platform 142 comprises a surface 143 that faces the casing 103 and extends at least between the distal edges of the second side surface 126 and the first side surface 124 of said main airfoil body 122. In some embodiments blade tip platform 142 comprises a flange 146 or lip that extends beyond leading edge 128, trailing edge 130, first side surface 124, and/or second side surface 126. In addition to providing support for the plurality of sealing members 144, blade tip platform 142 improves the stiffness or rigidity of blade tip 109, with improved performance of the blade 101 in regards to resistance of bending and untwist. In some embodiments blade 101 and blade tip platform 142 are integrally formed.
A plurality of sealing members 144 extend radially outward from blade tip platform 142. Sealing members 144 may be referred to as ridges, rails, or protrusions. In some embodiments sealing members 144 may be elongate structures positioned on surface 143 of blade tip platform 142 and extending between the distal edges of first side surface 124 and second side surface 126. As explained further below with reference to
The height, spacing, angle (relative to the axis of rotation or relative to a pressure side or suction side of the blade), thickness, and quantity of sealing members 144 may be optimized based on the specific application of the disclosed blade tip sealing portion 140. Sealing members 144 may have any number of shapes, profiles, heights, circumferential widths, spacing, and variability of geometries along the blade tip. Some examples of the lateral cross-sectional shapes of the members are shown in
In some embodiments sealing members 144 are positioned on surface 143 to effect uniform spacing between the members 144 along the blade tip chord. In other embodiments sealing members 144 are positioned on surface 143 to effect non-uniform spacing between the members 144 along the blade tip chord.
In some embodiments sealing members 144 are positioned on surface 143 to effect greater spacing between the members 144 near the leading edge 128 and trailing edge 130 relative to the spacing between members 144 near the mid-chord of blade tip 109. In some embodiments sealing members 144 are positioned on surface 143 to effect greater spacing between the members 144 near the mid-chord of blade tip 109 relative to the spacing between members 144 near the leading edge 128 and trailing edge 130.
In some embodiments sealing members 144 positioned on surface 143 have a uniform radial dimension and lateral cross-sectional shape. In other embodiments sealing members 144 positioned on surface 143 have a non-uniform or differing radial dimension and lateral cross-sectional shape. In some embodiments sealing members 144 positioned on surface 143 have a uniform radial dimension along the length of the sealing members 144. In other embodiments sealing members 144 positioned on surface 143 have a non-uniform or varying radial dimension along the length of the sealing members 144.
In some embodiments the sealing members 144 of a blade tip sealing portion 140 are configured to contact the radially inner surface of casing 103.
In some embodiments, the sealing members 144 of a blade tip sealing portion 140 are configured to extend into and contact an abradable region 155 of the casing 103.
As the blade 101 rotates during operation of the turbine engine, sealing members 144 contacting the abradable region 155 will likely rub annular pathways into the abradable region 155 that correspond to each sealing member 144. Contact between the abradable region 155 of casing 103 and one or more sealing members 144 forms a seal that reduces or eliminates leakage through the blade tip clearance 105.
In some embodiments such as that illustrated in
In some embodiments sealing members 144 may extend into annular channels 157 pre-formed in an abradable region 155 of casing 103 and/or the casing 103 itself.
In implementing the embodiment of
In some embodiments a plurality of sealing members 161 extend radially inwardly from the radially inner surface 107 of the casing 103.
In some embodiments, a blade tip sealing portion 140 comprises a plurality of sealing members 144 as illustrated in
In some embodiments, such as that illustrated in
In some embodiments, sealing members 144 may be positioned substantially perpendicular to a primary leakage vector V, or substantially perpendicular to a primary direction of the tip leakage air flow indicated by the direction of arrow V.
In some embodiments, the angle of each sealing member 144 may be measured relative to the axis of rotation of the turbine engine, fan, compressor, and/or turbine. In some embodiments, each sealing member 144 is positioned along the blade tip 109 to have a unique angle compared with other sealing members 144 positioned along that blade tip 109. The angle may be measured relative to a leakage vector or the axis of rotation. In some embodiments, one or more sealing members 144 positioned along the blade tip 109 may have an angle that is different from the angle of another sealing member 144 positioned along that blade tip 109. The angle may be measured relative to a leakage vector or the axis of rotation.
In some embodiments the angle of each sealing member 144 positioned along the blade tip 109 is adjusted to be perpendicular to the direction of primary leakage at that particular chord-wise position. Similarly, in some embodiments the shape of each sealing member 144 positioned along the blade tip 109 is optimized based on the direction of primary leakage at that particular chord-wise position.
The present disclosure additionally provides methods for reducing or eliminating leakage through the blade tip clearance 105 in a fan, compressor, or turbine of a turbine engine. A primary direction of tip leakage air flow is determined relative to a blade tip chord. A blade tip platform is positioned over the blade tip. As described above, the blade tip platform 142 has a surface 143 facing the casing 103 and extending between the distal edges of the pressure side 124 and suction side 126 of blade 101, as well as between the leading edge 128 and trailing edge 130 of blade 101. A plurality of sealing members 144 are positioned on the surface 143 of the blade tip platform 142. As described above, the sealing members 144 may be positioned at an angle substantially perpendicular to the primary direction of tip leakage air flow. Sealing members 144 may also be spaced along the blade tip chord to effect overlap of adjacent sealing members 144 in the direction of the tip leakage air flow.
In another method of the present disclosure, the method comprises positioning a blade tip platform over the blade tip, positioning a plurality of elongated sealing members on the surface of the blade tip platform, and rotating the rotor or effect rub between the plurality of sealing members and the abradable region. As discussed above, the blade tip platform having a surface facing the abradable region of the casing and extending at least between the distal edges of the pressure side and suction side of the blade and between the leading edge and trailing edge of the blade. The sealing members are dimensioned such that at least a portion of each sealing member contacts the abradable region. The rub of sealing members against the abradable region 155 causes a plurality of annular channels to be formed in the abradable region with each one of said plurality of annular channels corresponding to a respective one of said plurality of sealing members.
In some embodiments the method further includes determining a primary direction of the tip leakage air flow relative to a blade tip chord. In some embodiments the method further includes positioning the plurality of elongated sealing members on the surface of the blade tip platform at an angle substantially perpendicular to the primary direction of the tip leakage air flow. In some embodiments the method further includes positioning the plurality of elongated sealing members on the surface of the blade tip platform at a spacing along the blade tip chord to effect overlap of adjacent sealing members in the direction of the tip leakage air flow.
In still another method of the present disclosure of reducing blade tip clearance leakage, the method comprises positioning a blade tip platform over the blade tip, positioning a plurality of elongated sealing members on the surface of the blade tip platform, determining the flow rate and direction of the tip leakage airflow, and varying one or more of the selected lateral cross-sectional shape, the selected angle relative to the blade tip chord, and the selected chord-wise spacing pattern to effect a change in the flow rate of the tip leakage air flow.
As described above, the blade tip platform has a surface facing the casing and extending at least between the distal edges of the pressure side and suction side of the blade and between the leading edge and trailing edge of the blade. The plurality of elongated sealing members that are positioned on the blade tip platform before the step of determining flow rate and direction of the tip leakage airflow have a selected lateral cross-sectional shape, are positioned at a selected angle relative to the blade tip chord, and are spaced in a selected chord-wise spacing pattern along the blade tip chord.
The present disclosure provides systems and methods for reducing leakage through the blade tip clearance 105. The disclosure is applicable to fan, compressor, and turbine blades of a turbine engine. In some embodiments, the present disclosure may be applied to certain stages of a compressor or turbine but not to all stages. The advantages realized by the present disclosure are most advantageous in compressor blade systems, where the clearance to span ratio is more favorable for the benefit. For example, at higher clearance to span ratios the importance of reducing leakage is increased.
The present disclosure provides many advantages over previous blade and blade tip clearance designs. Most notably, the present disclosure significantly reduces or even eliminates leakage across the blade tip clearance. Decreasing such leakage improves efficiency of the associated fan, compressor, or turbine and may increase stall margin as well. Decreasing blade tip clearance leakage also allows for consideration and optimization of other design factors to meet various aero and mechanical requirements.
Although examples are illustrated and described herein, embodiments are nevertheless not limited to the details shown, since various modifications and structural changes may be made therein by those of ordinary skill within the scope and range of equivalents of the claims.
