Conical helical of spiral combustor scroll device in gas turbine engine

A conical helical design for a turbine combustor scroll utilizes as much cavity of the combustor housing as possible by adding an axial shift and an irregular cross sectional shape in the scroll without adversely effecting aerodynamic performance. The axial shift region of the combustor scroll extends the cross-sectional area centroid of the scroll beyond the scroll's discharge area B-width. The resulting scroll design allows for the use of a high performance engine with a larger combustor while reducing the weight of the system by making the combustor housing as small as possible. Furthermore, the scroll design increases the air velocity for convection cooling by reducing the gap between the scroll and the housing. The turbine scroll of the present invention is useful in engines for which high performance is required, such as certain high performance aircraft.

BACKGROUND OF THE INVENTION

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 combustion exhaust product 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 inFIG. 8. A multiple component system accelerates the flow to supersonic speeds with a chiefly peripheral discharge and tubular diffuser to receive the supersonic flow.

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 inFIGS. 3 through 8of the patent. The axial shift affects only one common side of the rectangular shape, circumferentially around the housing. The axial shift of the cross-sectional area's center of gravity is progressive and remains on one side of the B-width.

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.

SUMMARY OF THE INVENTION

In one aspect of the present invention, a combustor scroll of a turbine engine comprises an air inlet; a combustion exhaust product discharge area 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; a combustion exhaust product discharge area 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; a combustion exhaust product discharge area 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, a combustion exhaust product discharge area 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 a combustion exhaust product discharge area 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.

DETAILED DESCRIPTION OF THE INVENTION

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 turbine scrolls have a spiral spline attached to a cylindrical or elliptical shape with a combustion exhaust gas inlet at a reference angle of 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”, which is well-understood by those skilled in the art as the area of combustion exhaust product discharge from the turbine scroll. As is well known by the skilled artisan, the B-width is important because it sets the vane throat area and sets the amount of airflow to the turbine; the B-Width dimension is defined according to the Mach Number criteria for optimizing the system operational efficiency. This conventional concept, however, is adequate only for a low cycle, low performance and less weight driven engines.

Referring toFIG. 1, there is shown a partial cross sectional view of the power section of a gas turbine engine of the present invention. A turbine scroll10to may be in communication with a combustor liner12wherein the combustion may take place. Air may enter the combustor liner through air inlet20and the combustion products may exhaust into turbine scroll10through a combustion exhaust inlet11. A combustor housing14may cover turbine scroll10and combustor liner12. A combustion exhaust product discharge area, also known as a B-width,16may attach to turbine scroll10at the end opposite that of combustor liner12. The helical design of turbine scroll10gives turbine scroll10a gradual helical shape to form an axial shift region18, a region of turbine scroll10that is shifted along the axis through which the scroll spirals (the x-axis inFIG. 3). Axial shift region18causes the cross-sectional area centroid of a portion of turbine scroll10to pass beyond B-width combustion exhaust product discharge area16. The axial shift region may be useful to provide for additional scroll volumes and a larger liner which may be useful during emergency starts of some turbine engines. Note that this may result in combustion exhaust product discharge area16also being axially shifted along the x-axis (seeFIGS. 2 and 4).

Axial shift region18combined with an irregular cross sectional area with a flat curve portion17may be formed at a location in said turbine scroll10such that the axial shift region18and 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 region18may not increase the size of the cavity required within combustor housing14, thus not requiring a larger combustor housing14and 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 scroll10by reducing the gap between turbine scroll10and combustor housing14. This increased air flow may be useful to help regulate the temperature of turbine scroll10, 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 area16to 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.

Referring now toFIG. 2, there is shown a perspective view of the combustor scroll used in the gas turbine engine ofFIG. 1. Turbine scroll10has a combustion exhaust inlet11. A portion of turbine scroll10may be helically offset to form axial shift region18. This offset is advantageous in that it provides a turbine scroll that is able to accommodate a larger liner as compared to a conventional scroll without such an offset axial shift region. Such a consideration is useful, for example, in emergency starts, when high performance of the turbine engine is critical. Axial shift region18may be designed to use existing space in the cavity formed by combustor housing14. Therefore, the additional air flow required for high performance engines may be obtained without increasing the weight of the system. Without axial shift region18and irregular cross sectional areas24with flat curve portion17, a larger turbine scroll would be necessary to accommodate the scroll requirements for a high performance gas turbine engine. Such a larger turbine scroll would result in the need for a larger engine size, including a larger combustor housing, thereby increasing the weight of the engine.

Referring now toFIG. 3, there is shown a schematic view of the conical helical concept of the spiral turbine scroll10ofFIG. 2. The figure shows the helical shape and irregular cross-sections24throughout selected portions of turbine scroll10. In addition to occupying previously unoccupied space within combustion housing14as stated above, it can be seen how irregular cross sections24may also accommodate the axial shift of combustion exhaust product discharge area16. Combustion exhaust enters turbine scroll10through combustion exhaust inlet11. Axial shift region18gives a cross-sectional area centroid that passes beyond the combustion exhaust product discharge area16. The cross-sectional area at combustion exhaust inlet11may be larger than the total cross-sectional area at discharge area16. Turbine scroll10may, if it could be straightened, form a conical shape from combustion exhaust product discharge area16at the top to combustion exhaust inlet11as the larger base of the conical shape. The irregular cross-sectional areas are shaded and defined as A1to A10inFIG. 3. In theory, there are finite cross sectional areas that can be generated by intersecting a plane normal to the helical spline25that defines the helical shape of the scroll. Each irregular cross sectional area dictates the airflow requirement and is bounded by curves, lines, and the spline25. The area centroid which is also known as the area center of gravity is defined as a point on an area in which all forces acting on it are in equilibrium. These points are defined as “Wn” inFIG. 3. These points may be on either side of the B-width. For example, the centroid area passing beyond the B-width in cross-sections A1to A6are designated W1to W6and are shown on the aft side of the B-Width16, while any cross sectional areas from A7to A10will be on the forward side of the B-width (16). Each cross sectional area has its own area centroid.

Referring toFIGS. 3 and 4, there is shown a partially cut-away view of the combustion system of the present invention. Fabrication of turbine scroll10may be accomplished by forming a thin sheet of metal. The open ends of the scroll may be welded to machined rings (not shown) that control air leakage at the turbine scroll10/combustor housing14junction as well as at the turbine scroll10/B-width combustion exhaust product discharge area16. A joining line22is shown as the location where the material may be joined in the turbine scroll manufacturing process. Joining line22is bent toward the outward edge of turbine scroll10to allow manufacturing to clamp the edges to hold its form during the welding process. Joining line22is shown inFIG. 3to show how the outward edge of turbine scroll10is offset down the helix of turbine scroll10at axial shift region18.

While the above describes fabrication of turbine scroll10by forming a thin sheet of metal, any method known in the art may be employed. For example, turbine scroll10may be fabricated from a casting process with the machined rings that control air leakage being integral with turbine scroll10.