Rotary kinetic fluid motors or pumps – With passage in blade – vane – shaft or rotary distributor...
Reexamination Certificate
2000-08-01
2001-06-19
Kwon, John (Department: 3747)
Rotary kinetic fluid motors or pumps
With passage in blade, vane, shaft or rotary distributor...
C415S116000
Reexamination Certificate
active
06247893
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to hydroelectric turbine installations. More particularly, this invention pertains to hydroelectric installations with means for enhancing the level of dissolved gas in water passing through the turbine.
BACKGROUND OF THE INVENTION
A significant environmental problem for many hydroelectric facilities is the water quality of turbine discharges. The primary water quality problem is often low dissolved oxygen (DO) levels which occur seasonally. During the summer months, thermal stratification of the reservoir produces a surface layer of less dense, warm water with relatively high dissolved oxygen and a lower, relatively cold oxygen-depleted layer resulting from the decay of organic material on the reservoir bottom. Hydraulic turbines draw their discharges from the lower level which can create water quality problems downstream of the facility.
Relicensing and rehabilitation of a hydroelectric facility offer an opportunity to address environmental and industrial development concerns over dissolved oxygen levels and other water quality regulations which affect hydropower releases. Rehabilitating an existing hydroelectric facility may include replacement of the runner. Replacing an existing runner with a new runner having integral passages, and providing air through existing structures or new structures of the installation to the integral passages, enhances dissolved oxygen levels in the water without material losses in efficiency or substantial increases in cost of rehabilitation.
Various attempts have been made to enhance the level of dissolved oxygen in water downstream of hydroelectric installations. For example, U.S. Pat. No. 4,789,051 to Fisher, Jr. discloses an apparatus comprising a manifold which contains a bounded air channel extending the length of the runner blade trailing edge. A plurality of holes are formed along the manifold extending between the channel and the turbine interior, the channel being in fluid communication with a source of oxygen. For the manifold to remain securely fastened over extended periods of operation, the trailing edge of the runner blade must be relatively thick, which may result in efficiency losses. Additionally, many installations have existing structures which make it impractical and thereby costly to provide air directly to the trailing edge of the runner blade.
Runner blade construction consists of either a solid casting or a fabrication. Most Francis runner blades built in the 70's and 80's were solid cast with extra material added in critical areas for final finishing. These castings were, and often still are, hand ground to templates and fixtures to meet the desired shapes. As machine tools have improved and the runner blade designs have become more computerized, critical areas and features of more complex geometries, such as integral passages, can nowadays be machined into the cast blades. However, this more modern machining approach has done little to improve the manufacturing cycle time, due to the long lead time associated with cast components, nor has it materially reduced manufacturing costs. Although fabricated blades offer improved cycle time and cost advantages, it has proven difficult in practice to fabricate blades having complex geometric features such as integral gas channels, particularly in the thinner portions of the blade.
The foregoing therefore indicates that prior art methods of feeding air directly to the trailing edge of the runner blade have not proved fully satisfactory in practice. Additionally, there is a need for a method of forming a runner blade having a gas channel of relatively complex geometry which offers improved cycle time and is less expensive than the prior art methods.
SUMMARY OF THE INVENTION
The present invention enhances the level of dissolved gas in water flowing through a Francis turbine comprising a crown, a band, and a plurality of blades extending between the crown and the band. At least one of the blades includes a leading blade portion and a rear edge in which a first slot extends along at least a portion of the rear edge. The blade also includes a trailing blade portion having a front edge in which a second slot extends along at least a portion thereof. The trailing blade portion is secured to the leading blade portion along the front edge and the rear edge, respectively, so that the first and second slots cooperate to form an integral passage in the blade. The turbine includes a means for discharging an oxygen containing gas from the integral passage.
The present invention also includes a method of making a reaction turbine blade for enhancing the level of dissolved gas in water passing through the turbine. The method comprises the steps of forming a first slot along the rear edge of the leading blade portion, forming a second slot along the front edge of the trailing blade portion, and forming a plurality of discharge passages in the trailing blade portion extending from the second slot to the trailing edge. The blade portions are secured together by joining the rear edge of the leading blade portion to the front edge of the trailing blade portion to form a substantially planar blade including a conduit formed by the first groove cooperating with the second groove. The planar blade is then press-formed to the shape of a hydrofoil.
The present invention further includes a method of making a reaction turbine blade having an integral gas passage, the method comprising machining a blank to have a blade profile and control points, securing a thin plate to a region of the blank to form a channel, pressing the blade to the shape of a hydrofoil, and removing the control points.
According to a further aspect of the present invention, the runner for a Francis turbine includes a means for discharging an oxygen containing gas from the band.
According to another aspect of the invention, a hydraulic turbine installation includes a control system for controlling an oxygen discharging means and thereby the level of dissolved oxygen in the water.
According to another aspect of the invention, a Kaplan turbine is used for enhancing the level of dissolved gas in water. The turbine comprises a hub and a plurality of blades pivotally connected to the hub so that the angular position of each blade relative to the hub (i.e., the pitch of each blade) is adjustable. The inner edge of each blade generally sweeps an exterior surface region of the hub during variations in pitch of the blades. At least one of the blades has a gas admission passage extending from the inner edge of the blade to a spaced apart region thereof. The hub comprises a plurality of groups of gas passages extending from a gas source to the exterior surface region. A flexible boot is secured to the blade and is effectively in contact with the exterior surface region associated therewith to form an interconnecting gas passage between at least one selected gas passage of the group of gas passages and the gas admission passage of the blade.
According to yet another aspect of the invention, the level of dissolved gas in water flowing through a turbine having a shaft and a runner secured to the shaft is enhanced by means of a runner including a hollow hub and a plurality of generally radially extending blades. The shaft has an opening extending therethrough to the hollow hub. The method involves forming in the runner at least one passage extending from the interior of the hub to an edge region of a respective one of the blades. The runner is installed in the water passageway and a chamber is formed in an upper interior region of the hollow hub to fluidly couple the opening in the shaft with the at least one passage in the runner. An oxygen containing gas is supplied to the opening in the shaft during operation of the turbine.
According to a further aspect of the invention, the level of dissolved gas in water flowing through a hydraulic turbine is enhanced by providing an inflatable shroud having an adjacent gas discharge opening. The shroud creates a lower pressure region, th
Beyer James R.
Fisher, Jr. Richard K.
Grubb Robert G.
Foley & Lardner
Kwon John
Voith Siemens Hydro Power Generation Inc.
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