Patent Application
20110079308
This invention relates to exhaust-gas ductwork and more specifically, to a drain configuration in the exhaust-gas duct of a gas turbine.
On a standard vent-fan, exhaust-gas duct section, there is a drain that allows water, sand and/or other particulates to exit the duct. This drain, however, also allows some exhaust gas flowing through the duct to escape which, depending on the exhaust gas composition, may result in a hazardous gas cloud below the drain. As a result, external devices in the immediate area of the drain are required to be rated for use in a hazardous area, and any electrical devices in those areas any are also required to be explosion proof.
There remains a need, therefore, for an exhaust-gas duct with a drain configuration that allows water sand and/or other particulates to exit the duct, but that also minimizes if not eliminates any potential for a hazardous gas bubble or cloud in an area adjacent the drain.
In a first exemplary but nonlimiting aspect, there is provided an exhaust gas duct comprising a hollow duct section having a peripheral wall, a slot in the peripheral wall, the slot opening in a direction counter to a flow direction through the hollow duct section; and a baffle plate located on an exterior surface of the peripheral wall, upstream of the slot relative to the flow direction.
In another aspect, there is provided an exhaust gas duct comprising a hollow duct section having a top wall, bottom wall and a pair of side walls, a lateral slot in the bottom wall, the lateral slot opening in a direction counter to a flow direction through the hollow duct section; and a baffle plate located on an exterior surface of the bottom wall upstream of the lateral slot relative to the lateral flow direction.
In still another aspect, there is provided an exhaust gas duct for removing exhaust gases from a gas turbine comprising a hollow duct section having a top wall, bottom wall and a pair of side walls; a lateral slot in the bottom wall extending substantially between the side walls, the lateral slot opening in a direction counter to a flow direction of exhaust gas through the hollow duct section; and a baffle plate located on an exterior surface of the bottom wall, upstream of the lateral slot relative to the flow direction, the baffle plate formed with a plurality of laterally-spaced apertures, and wherein the lateral slot is defined by vertically-spaced, axially overlapping portions of the bottom wall.
With reference now to
Referring now to
As seen in
Forward (upstream relative to the flow direction) of the lateral slot 32 is a vertical baffle plate 42 extending substantially vertically downwardly from an exterior surface of the bottom wall portion 38. In the exemplary but nonlimiting embodiment, the baffle plate 42 is located upstream of the lower edge 34 of the slot 32 by a distance of about three inches (dimension C). The baffle plate 42, as best seen in
The baffle plate 42 may have a height of about four inches (dimension D), and apertures 46 may have a width of about nine inches (dimension E). The apertures 46 preferably have a height equal to the height of the slot 32 (dimension D), in this example about one inch (dimension F). The apertures 46 may be spaced from each other by about 0.5 inch (dimension G) in this example embodiment. The baffle plate 92 itself should have a width at least equal to the width of the duct section 16.
It will be appreciated, of course, that the various dimensions may vary with specific duct sizes/applications. Thus, the dimensional relationships may be stated differently to cover a wider range of duct sizes. For example, the distance (dimension C) between the duct opening or slot 32 and a baffle plate may be between 200% and 500% of the height (dimension A) of the slot or opening 32.
The height of baffle plate 42 (dimension D) may be between 75%-300% of the height (dimension A) of the opening or slot 32.
The open area of the baffle plate 42, i.e. the cumulative open areas of the apertures 46, may be in a range of 50%-98% of the baffle plate area, and the height of the apertures 46 (dimension F) may be between 40-175% of the height (dimension A) of the duct opening or slot.
In all cases, the horizontal or lateral slot 32 serves to entrain outside or ambient air into the exhaust gas flowing through the duct section 16, and thus prevent exhaust air from escaping the duct. At the same time, the baffle plate 42 prevents high velocity ambient wind from reversing this effect, i.e., from drawing hazardous gas from the duct section 16 through the lateral slot 32 and out into the ambient surroundings. More specifically, the apertures 46 act as a wind-breaker which simultaneously facilitates drawing air into the duct section 16 while preventing exhaust gases from being drawn out of the duct. The above arrangement has proven effective in maintaining control of potentially hazardous gas, until it exits the duct beyond the vertical portion 20.
It will be appreciated, of course, that that the theory and application described herein is also applicable to non-rectangular ducts (for example, round ducts defined by a peripheral wall or other hollow duct shapes) discharging a media where the removal of particulate matter in a direction opposite the normal flow direction, or entrainment of external media, is desired.
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.
