Patent Application
20200248575
The present disclosure is directed to a treatment on a rotating hub beneath compressor cantilevered stators, and more particularly the implementation of spiraling grooves formed in the rotating hub underneath the cantilevered stators.
The aerodynamic load capacity and the efficiency of fluid flow machines such as blowers, compressors, pumps and fans, is limited in particular by the growth and the separation of boundary layers in the rotor and stator blade tip area near the casing or the hub wall, respectively. On blade rows with running gaps, this leads to re-flow phenomena and the occurrence of instability of the machine at higher loads. Fluid flow machines according to the state of the art either have no particular features to provide remedy in this area, or so-called casing treatments are used as counter-measure including the most varied configurations of chambers and/or angular slots, mostly in the casing above the rotor.
Compressors in gas turbine engines must have a wide enough operability range across a range of rotating speeds in order to efficiently operate. For example, at part load conditions when the airplane is at ground or flight-idle condition, the rotational speed of the gas turbine engine compressor shaft is reduced. Under these idling conditions the variable vanes are closed, further reducing the flow through the engine. These conditions all result in rotor and stator airfoils operating at off-design conditions, precipitating increased tip clearance leakage in rotors, and cantilevered stators, as well as flow separation, in particular near end walls.
What is needed is an improved form of rotor treatment that reduces the leakage and flow separation.
In accordance with the present disclosure, there is provided a casing treatment comprising a hub having a surface, the hub being rotatable about an axis within a casing of a gas turbine engine compressor, at least one spiral groove formed in the surface extending axially relative to the axis, a stator blade fixed to the casing, wherein a tip of the stator blade is proximate to the at least one spiral groove.
In another and alternative embodiment, the at least one spiral groove is a helix.
In another and alternative embodiment, the at least one spiral groove comprises an angle of inclination angled relative to the axis.
In another and alternative embodiment, the angle of inclination ranges from 45 degrees to 135 degrees.
In another and alternative embodiment, the casing treatment further comprises a flow path between the hub and the casing, wherein the at least one spiral groove is configured to add energy to a working fluid in the flow path, and minimize a leakage flow that moves opposite the flow path.
In another and alternative embodiment, the at least one spiral groove comprises a taper proximate at least one of an inlet and an outlet of each of the at least one spiral groove.
In another and alternative embodiment, the casing treatment further comprises multiple spiral grooves formed on the surface of the hub, wherein at least one of the multiple spiral grooves is configured to function at a predetermined operating condition of a compressor.
In accordance with the present disclosure, there is provided a gas turbine compressor section with a casing treatment comprising a casing proximate the gas turbine compressor section; a stator blade fixed to the casing; a rotary hub proximate a tip of the stator blade, the rotary hub configured to rotate around an axis; and at least one spiral groove formed in a surface of the rotary hub proximate the tip.
In another and alternative embodiment, the stator blade is a cantilever stator blade.
In another and alternative embodiment, the at least one spiral groove comprises an angle of inclination angled relative to the axis, wherein the angle of inclination ranges from 45 degrees to 135 degrees.
In another and alternative embodiment, the at least one spiral groove comprises a taper proximate at least one of an inlet and an outlet of each of the at least one spiral groove.
In another and alternative embodiment, the gas turbine compressor section with a casing treatment further comprising multiple spiral grooves formed on the surface of the hub, each of the multiple grooves being tailored for different operating conditions of the gas turbine compressor.
In another and alternative embodiment, a depth of the at least one spiral groove comprises a value as high as 10% of a chord of the blade.
In accordance with the present disclosure, there is provided a process for reducing a tip clearance leakage flow past a cantilever stator tip and hub in a gas turbine compressor section the process comprises forming a spiral groove in a surface of the hub; rotating the hub around an axis such that the spiral groove in the hub moves relative to the cantilever stator tip; and directing the tip clearance leakage flow in a counter direction along a flow path of the compressor proximate the cantilever stator tip.
In another and alternative embodiment, rotating the spiral groove further comprises producing additional work energy added to the working fluid flowing in the flow path of the compressor proximate the cantilever stator tip.
In another and alternative embodiment, the process further comprises aligning the spiral groove at an angle of inclination angled relative to the axis, wherein the angle of inclination ranges from 45 degrees to 135 degrees.
In another and alternative embodiment, the spiral groove comprises a taper proximate at least one of an inlet and an outlet of each of the at least one spiral groove.
In another and alternative embodiment, the process further comprises forming the spiral groove along the hub at an axial location relative to the cantilever stator tip.
In another and alternative embodiment, rotating the hub around the axis, such that the spiral groove in the hub moves relative to the cantilever stator tip, creates an axial motion of the spiral groove relative to the cantilever stator tip.
In another and alternative embodiment, the process further comprises forming multiple spiral grooves along the hub tailored for different operating conditions within the compressor.
The operability of high-pressure compressors which use cantilevered stators can be improved by applying casing treatment on the rotating hub underneath them. One form of treatment includes a single or multiple spiral grooves in the rotating hub, as illustrated in
Since the hub is rotating, the treatment can be designed such that it produces additional work, further energizing the flow. We propose grooves that spiral around the hub. In contrast to prior circumferential grooves of
Other details of the casing treatment are set forth in the following detailed description and the accompanying drawings wherein like reference numerals depict like elements.
Referring now to
An exemplary treatment 20 is formed in the hub 16. The treatment 20 can be formed in an outer surface 22 of the hub 16. In an exemplary embodiment, the treatment 20 can include a spiral groove 24 formed in the surface 22, see also
Referring also to
The exemplary design provides the advantage of when the hub is rotating: the spiral groove 24 moves underneath the stator 14 in the axial direction and creates an axial motion of the spiral groove 24 relative to the cantilever stator tip 15. As such the location relative to the stator 14 does not need to be specified. Further, the movement of the spiral grove 24 surface in axial (or flow) direction adds energy to the working fluid flow field 34, thus minimizing the leakage flow 28. The leakage flow 28 flows counter to the direction of the working fluid flow 34. The spiral groove 24 can be formed on the hub 16 at an axial location relative to the cantilever stator tip 15. The spiral groove 24 can be formed on the hub 16 between any two axial locations relative to the cantilever stator tip 15. The spiral groove 24 helps to prevent the tip clearance leakage flow 28.
The helix angle of inclination A, i.e. angle of the inclination from the circumferential direction, determines the speed at which the spiral groove surface moves in the axial direction. The circumferential direction is orthogonal to the axis 18. The larger the angle A the greater the axial surface movement of the working fluid 34. Depending on the helix angle A, the size of the spiral groove 24, and the chord of the stator 14, one or several spiral grooves 24 can be considered. In an exemplary embodiment, the spiral groove depth can be as large as 10% of the chord.
The exemplary embodiment in which there are two spiral grooves 24a, 24b, as seen in
Referring to
In alternative exemplary embodiments, utilization of spiral grooves 24 can also be beneficial on the hub of other rotating portions of the gas turbine engine, like parts with compressor blades, with a design that can cross the passage from blade to blade. In another alternative embodiment, the treatment 20 could be formed in a wall of the casing 12 proximate sections of rotary blades (not shown).
There has been provided a rotor treatment. While the rotor treatment has been described in the context of specific embodiments thereof, other unforeseen alternatives, modifications, and variations may become apparent to those skilled in the art having read the foregoing description. Accordingly, it is intended to embrace those alternatives, modifications, and variations which fall within the broad scope of the appended claims.
