The present invention relates to a nozzle box for a steam turbine for directing steam flow from a generally circumferential direction to a generally axial direction for flow through nozzles and particularly relates to a nozzle box having bridges tangentially leaned to match the angles of the leading edges of the partitions.
In steam turbines, nozzle boxes are provided for receiving a flow of steam and directing the steam through first stage nozzles. A nozzle box typically comprises a torus portion having one or more, generally four, inlets for receiving steam, a bridging portion for facilitating a change in the steam flow from circumferential to generally axial directions, and finally, a nozzle ring portion containing partitions defining nozzles for directing the steam flow onto the buckets of the rotor. Nozzle boxes are typically formed in nozzle box halves arranged in a 180° arc, the nozzle box halves having mating horizontal joints to form a continuous 360° nozzle. Conventional nozzle boxes, for example those disclosed in U.S. Pat. Nos. 6,631,858; 6,196,793; and 5,392,513 are representative examples of the foregoing arrangement. For example, as illustrated in U.S. Pat. No. 6,631,858, the bridge ring portion includes a plurality of bridges axially upstream from the nozzle partitions. It will be appreciated that because of structural concerns requiring a substantial number of bridges, the conventional bridge ring portion with multiple bridges has a tendency to restrict the steam entering the nozzles. The bridges, of course, are used to strengthen the nozzle box as well as to straighten the flow. However, conventional bridges afford substantial passage area loss and are generally not matched with the partitions. Accordingly, there is a need for a nozzle box which can efficiently straighten the steam path and reduce the passage area loss.
In a preferred embodiment of the present invention, there is provided a nozzle box for a steam turbine comprising: a nozzle ring portion about an axis and including a plurality of circumferentially spaced partitions, each partition having a leading edge forming an included angle relative to a radius from the axis passing through the leading edge; and a bridge ring portion about the axis for transitioning steam into the nozzle ring portion; the bridge ring portion including a plurality of circumferentially spaced bridges, each of selected bridges of the plurality thereof extending at an included angle relative to a radius about the axis corresponding to the angle of the leading edge at a like circumferential location about the axis.
In a further preferred object of the present invention, there is provided a nozzle box for a steam turbine comprising: a nozzle ring portion about an axis including a plurality of circumferentially spaced partitions, each partition having a leading edge extending along a tangent from an imaginary cylinder centered about the axis, the imaginary cylinder having a diameter less than the diameter of the nozzle ring portion; and a bridge ring portion about the axis for transitioning steam into the nozzle ring portion, the bridge ring portion including a plurality of circumferentially spaced bridges extending along tangents from the imaginary cylinder.
In a still further preferred aspect of the invention, there is provided a nozzle box for a steam turbine comprising: a nozzle ring segment about an axis including a plurality of circumferentially spaced partitions extending between radial inner and outer rings, each partition having a leading edge inclined relative to a radius about the axis through the leading edge; a bridge ring segment about the axis for transitioning steam into the nozzle ring segment and including a plurality of circumferentially spaced bridges, selected bridges thereof being inclined relative to radii about the axis corresponding to the inclinations of the leading edges about the axis at like circumferential locations about the axis.
One-half of a nozzle box generally designated 10 is illustrated in
Torus portion 12 lies in communication with one or more steam inlets 18 whereby steam flows from the inlets into the torus portion and in a generally circumferential steam flow direction. Bridge ring portion 14 includes a plurality of circumferentially spaced bridges 20 which extend between inner and outer walls 22 and 24, respectively, (
In accordance with a preferred aspect of the present invention, the bridges 20 of the bridge ring portion 14 are configured and arranged relative to the partitions 26 and particularly the leading edges 28 of the partitions to efficiently straighten the steam flow direction for entry into nozzles formed by the partitions. This reduces the loss of steam passage area typical of prior nozzle box designs.
Particularly, and referring to
More particularly, and referring to
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.
Number | Name | Date | Kind |
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2869821 | Halford et al. | Jan 1959 | A |
5259727 | Quinn | Nov 1993 | A |
5392513 | Mazzola et al. | Feb 1995 | A |
6196793 | Braaten | Mar 2001 | B1 |
6631858 | Farineau et al. | Oct 2003 | B1 |
Number | Date | Country |
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1332035 | Dec 1963 | FR |
11-343805 | Dec 1999 | JP |
Number | Date | Country | |
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20060182625 A1 | Aug 2006 | US |