The present invention generally relates a conical helical concept of a spiral combustor scroll within the combustion system of a gas turbine engine. More specifically, the present invention relates to a scroll designed to utilize as much cavity of combustor housing as possible, and largest possible liner by adding an axial shift and an irregular cross sectional shape in the scroll without adversely effecting aerodynamic performance.
A combustor scroll in a turbine engine is used to deliver the exhaust gases of combustion in such a manner as to drive a turbine. A conventional combustor scroll has a spiral spline attached to a cylindrical or elliptical shape with an air inlet at zero degrees while the air exhaust typically discharges radially or axially toward the inner diameter. A material capable of withstanding high temperatures is usually used to fabricate the body through a forming process or cast. The center of the scroll's cross-sectional area, also known as the cross-sectional area centroid, is not allowed to axially cross the center plane of the “B-width”, or air discharge area. This conventional concept, however, is adequate for only low cycle, low performance and less weight driven engines.
U.S. Pat. No. 3,837,760 discloses a turbine engine that employs an axial type compressor that uses a scroll curvature design to change air particle flow velocities through various vane angle arrangements. See B, D and U in
U.S. Pat. No. 5,266,033 discloses a centrifugal compressor collector in which the radial cross-sectional area of the housing progressively changes. This progressive change is due to the variation of the housing's axial height as shown in
U.S. Pat. No. 5,317,865 discloses a turbine engine design that utilizes an inline combustor integral with the turbine scroll to minimize radial height of the engine. The inline combustor/scroll also minimizes the pressure drop of the combustor inlet air by eliminating the turns associated with a reverse flow can style combustor. The combustor is spiral shaped and positioned between the compressor and turbine which allows the direction of flow of air or working gas to remain substantially unchanged from the compressor to the turbine.
As can be seen, new engine designs have resulted in new technical challenges that require an improved turbine scroll shape. Such a turbine scroll must have the ability to accommodate a larger liner than usual due to emergency starting requirements. The liner and scroll must utilize as much cavity in the combustor housing as possible without adversely effecting performance. This allows a smallest possible combustor housing design and therefore reduce the weight of the entire system.
In one aspect of the present invention, a combustor scroll of a turbine engine comprises an air inlet; an air discharge having a B-width; and an axial shift region providing a portion of the combustor scroll to have an irregular cross-sectional area with its centroid passing beyond the B-width.
In another aspect of the present invention, a combustor scroll of a turbine engine comprises an air inlet; an air discharge having a B-width; and an axial shift region providing a portion of the combustor scroll to have an irregular cross-sectional area centroid passing beyond the B-width; wherein the combustor scroll has a substantially helical configuration; and the combustor scroll has a substantially conical shape with a cross-sectional area decreasing from the air inlet to the air discharge.
In yet another aspect of the present invention, a turbine engine comprises a combustor scroll having an air inlet; an air discharge having a B-width; and an axial shift region providing a portion of the combustor scroll to have a cross-sectional area centroid passing beyond the B-width.
In a further aspect of the present invention, a turbine engine comprises a combustor scroll having an air inlet, an air discharge having a B-width, and an axial shift region providing a portion of the combustor scroll to have a cross-sectional area centroid passing beyond the B-width, wherein the combustor scroll has a substantially helical configuration; and the combustor scroll has a substantially conical shape with a cross-sectional area decreasing from the air inlet to the air discharge.
In still a further aspect of the present invention, a method for making a turbine engine, comprises attaching a first, air inlet end of a combustor scroll to a combustor liner of the turbine engine; attaching a second, opposite end of the combustor scroll to an air discharge having a B-width; providing an axial shift region in the combustor scroll, the axial shift region resulting in a portion of the combustor scroll having a cross-sectional area centroid passing beyond said B-width.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following drawings, description and claims.
The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.
The present invention provides a turbine combustor scroll designed to utilize as much cavity of combustor housing as possible by adding an axial shift and an irregular cross sectional shape in the scroll without adversely effecting aerodynamic performance. The resulting scroll design reduces the weight of the system by making the combustor housing as small as possible while providing more space for installation and accommodating a larger liner. Moreover, a combustor scroll having an irregular cross-sectional area is designed to allow for a larger air flow, as compared to conventional scrolls, without adversely affecting the output gas characteristics, such as velocity and volume. Furthermore, the scroll design increases the air velocity for diffusion cooling by reducing the gap between the scroll and the housing, thus causing the same amount of air to flow through a smaller area. The turbine scroll of the present invention is useful in engines for which high performance is required, such as certain high performance aircraft.
Conventional combustor scrolls have a spiral spline attached to a cylindrical or elliptical shape with an air inlet at zero degrees while the air exhaust typically discharges radially or axially toward the inner diameter. The centers of the scroll's cross-sectional areas are often not allowed to pass through the system “B-width”. This conventional concept, however, is adequate only for a low cycle, low performance and less weight driven engines.
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Axial shift region 18 combined with an irregular cross sectional area with a flat curve portion 17 may be formed at a location in said turbine scroll 10 such that the axial shift region 18 and overall diameter can be smaller and may occupy a space that was previously unoccupied by the same engine with a conventional turbine scroll. In other words, the addition of axial shift region 18 may not increase the size of the cavity required within combustor housing 14, thus not requiring a larger combustor housing 14 and not requiring additional size or weight. Moreover, the occupation of such previously empty space results in an increase in air velocity for diffusion cooling of the exterior of turbine scroll 10 by reducing the gap between turbine scroll 10 and combustor housing 14. This increased air flow may be useful to help regulate the temperature of turbine scroll 10, as the larger sized combustor of a high performance turbine engine may generate heat greater than that of a conventional engine. Additional cooling may help regulate the temperature of the air at discharge area 16 to be similar to that of a conventional engine, thus removing any requirements to make downstream changes in design from that of a conventional turbine engine.
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While the above describes fabrication of turbine scroll 10 by forming a thin sheet of metal, any method known in the art may be employed. For example, turbine scroll 10 may be fabricated from a casting process with the machined rings that control air leakage being integral with turbine scroll 10.
It should be understood, of course, that the foregoing relates to preferred embodiments of the invention and that modifications may be made without departing from the spirit and scope of the invention as set forth in the following claims.