Patent Application
20120321441
The invention relates to rotors used in the compressor of a gas turbine engine.
The compressor section of a gas turbine engine used in power generation applications typically includes a plurality of disc-shaped compressor rotors which abut one another. A plurality of rotating compressor blades extend radially outward from the outer circumferential edge of each of the compressor rotors. Each compressor rotor is typically shaped such that circumferential flanges extend outward from both circular faces of the disc, the circumferential flanges being located adjacent the outer edge of the disc.
When plurality of compressor discs are stacked together to form the compressor section of a gas turbine engine, the circumferential flanges of adjacent compressor rotors abut one another. As a result, a cavity is formed between each adjacent pair of compressor discs, the cavity being located radially inward of the mating circumferential flanges.
Air or gases trapped in the cavity formed between adjacent compressor discs can act as a thermal insulator, which can result in temperature gradients between adjacent compressor discs. These temperature gradients can cause stress to develop between adjacent compressor discs. The temperature gradients can also negatively impact the tip clearance between the rotating compressor blades attached to the compressor discs and/or the compressor stator vanes.
During startup or shutdown of a gas turbine engine, thermal gradients between the various elements of the compressor section are inevitable. The thermal insulating effect of the air or gases trapped in the cavities between adjacent compressor rotor discs can extend the time that those thermal gradients exist, as well as increase the stress on the components of the compressor section, and possibly negatively impacting the rotor blade and/or stator vane clearances for an extended period of time.
In addition, when there is a temperature difference between a cavity located between adjacent compressor rotor discs and an area radially outward of the cavity, it is possible for a pressure gradient to develop between the cavities and the area radially outward of the cavities. This pressure gradient can also negatively impact compressor and turbine performance.
In one aspect, the invention could be embodied in a compressor rotor for a turbine engine that includes a disc of material having first and second circular faces, and a circular flange that protrudes outward from the first circular face of the disc adjacent an outer edge of the disc. At least one ventilation slot is located in the circular flange, the at least one ventilation slot comprising a depression in the circular flange, the depression having a longitudinal axis that extends substantially in a radial direction of the disc. The disc may also include a second circular flange that protrudes outward from the second circular face of the disc adjacent an outer edge of the disc, where at least one ventilation slot is located in the second circular flange, the at least one ventilation slot comprising a depression in the second circular flange, the depression having a longitudinal axis that extends substantially in a radial direction of the disc.
In another aspect, the invention could be embodied in a method of manufacturing a compressor rotor for a turbine engine. The method includes forming a disc of material having first and second circular faces and a circular flange that protrudes outward from the first circular face of the disc adjacent an outer edge of the disc. The method also includes forming at least one ventilation slot in the circular flange, the at least one ventilation slot comprising a depression in the circular flange, the depression having a longitudinal axis that extends substantially in a radial direction of the disc.
The following detailed description of preferred embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention.
As illustrated in
The cavities formed between adjacent compressor rotor discs can help to cause thermal and pressure gradients develop between the various elements of the compressor section. Those thermal and pressure gradients can negatively impact the life and performance of the compressor section and the turbine engine. The thermal gradients can induce stress in the elements of the compressor and negatively impact the clearances of the compressor rotating blades 130, 132, 134 and the stator vanes 140, 142, 144.
To help prevent thermal and pressure gradients from developing, one or more ventilation slots 210 may be cut in the circular flanges 202, 211 of the compressor rotor discs. The ventilation slots allow air or gas to freely flow back and forth between the cavities formed between adjacent compressor rotor discs and the areas located radially outward of the cavities.
The ventilation slots can take the form of elongated depressions that are formed or cut into the circular flanges 202, 211.
Although the embodiment illustrated in
In the embodiments illustrated in
A compressor section of a turbine engine could be formed such that each compressor rotor disc has ventilation slots in a circular flange on only one side face of the rotor disc. When a plurality of such compressor rotor discs are stacked together, the ventilation slots will ensure that the cavities formed between each adjacent pair of discs will be vented to the area radially outward of the cavities.
Alternatively, two different types of compressor discs could alternate with one another in a stack of rotors. The first type of compressor rotor would have no ventilation slots. The second type of rotor would have ventilation slots located in the circular flanges located on both side faces. This arrangement would also ensure that the cavities formed between each adjacent pair of rotors will be vented to the area radially outward of the cavities.
When a turbine engine having compressor rotor discs with ventilation slots is first put into operation, the various elements of the compressor section will all begin to heat up. Because the ventilation slots allow air or gases to flow into and out of the cavities between adjacent compressor rotor discs, no pressure gradients are likely to develop. Also, if one region becomes hotter than another region, the pressure of the gas in the hotter region will increase, which will cause gas from the hotter region to flow into an adjacent cooler (lower pressure) region. This movement of gas from a hotter region to a cooler region will help to reduce temperature gradients between different regions of the compressor section. And, as noted above, this will help to reduce thermally induced stress. This same process also occurs upon shutdown of the turbine engine when different regions will cool at different rates.
The number and size of the ventilation slots can be based on the volume of air that is expected to aspirate into or out of a cavity during startup or shutdown of a turbine engine. The volume of airflow, in turn, may be based on the cavity size, the location of the cavity in the compressor, the anticipated cavity surface temperatures, and the flow path of air or gas through the compressor. Thus, all of these factors could influence the number and location of the ventilation slots.
Properly designed ventilation slots will improve rotor life by reducing transient thermal and pressure gradients experienced by different portions of the compressor, and as between adjacent discs. The ventilation slots will also improve compressor efficiency by minimizing purged regions within the compressor. Providing ventilation slots is also expected to improve the predictability of rotor metal temperatures as compared to compressor rotors lacking ventilation slots. Further, upon startup and shutdown, the provision of ventilation slots is expected to reduce the time required before all elements of the compressor reach a stable, steady state operating condition.
Although
Although
As noted above, some embodiments may have ventilation slots formed in the circular flanges formed on both side faces of the compressor rotor. In these embodiments, the ventilation slots may be mirror images of each other on both side faces. Alternatively, although the same number of ventilation slots are provided on both side faces, the ventilation slots located in the circular flange on the first side face of the compressor rotor may be circumferentially offset from the ventilation slots located on the circular flange on the second side face of the rotor. In still other embodiments, a greater number of ventilation slots may be provided on a first face of the compressor rotor than on the second face of the rotor.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof
While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.
