Multi-stage shroud for a fluid power turbine

Abstract

While adhering to the size constraints imposed by the shallow body of water (e.g., a river) into which the hydrodynamic turbine can be immersed, the multi-stage shroud described herein enables the increase and maximization of the water mass flow and pressure drop at the flow channel cross-section of the hydrodynamic turbine, thereby maximizing the generated power output. Therefore, the multi-stage shroud described herein can be configured such that water can flow through the hydrodynamic turbine in a substantially stable mass flow, thereby eliminating instabilities, eliminating vortices, minimizing cavitation, and reducing fluid separation to a negligible level. The multi-stage shroud may include an inlet, an outlet, and multiple stages that can extend between the inlet and outlet, allowing water to flow through the multi-stage shroud in the direction of water flow.

Description

[0001] Related patent applications

[0002] This application claims priority to the following patent application: U.S. Provisional Patent Application No. 62 / 818.252, filed on March 14, 2019, entitled "Drainage Tube Assembly for a Turbine," the disclosure of which is incorporated herein by reference.

[0003] FIELD OF THE DISCLOSURE The present disclosure relates generally to turbines and, more particularly, to multi-stage shrouds for fluid power turbines. Background Art

[0004] A fluid power turbine (also known as a damless turbine) is configured to be immersed in a body of water in which water can flow naturally in the direction of the flow. A fluid power turbine may include a rotor, a hub, and blades, which may extend radially from the hub, for example, to form a flow cross section. Thus, water may flow through the turbine from a section upstream of the flow cross section toward a section downstream of the flow cross section, so that the blades may capture kinetic energy contained in the water flow. This kinetic energy may be converted into a power output, thereby generating energy.

[0005] It is known to install a draft tube assembly or a cover downstream of a fluid power turbine in order to increase the water flow and the pressure drop at the flow passage cross section of the turbine, thereby achieving the purpose of increasing the overall efficiency of the turbine and the power output of the turbine. However, the dimensions of these draft tube assemblies or covers are designed so that they cannot be immersed in shallow bodies of water (such as rivers). In fact, reducing the overall height of such an assembly would result in a cavity volume and length at the flow passage cross section of the turbine, which is not feasible both operationally and economically.

[0006] Therefore, there is a need for an improved draft tube assembly or shroud that can be configured to increase water flow and pressure drop at the flow path cross-section of the fluid turbine to maximize the power output generated, while complying with the size constraints provided by the shallow bodies of water (such as rivers) in which the fluid turbine can be immersed. Summary of the invention

[0007] In some embodiments, a multi-stage cover portion is provided, which is used to receive at least a portion of a fluid dynamic turbine, the fluid dynamic turbine including a hub and blades, the blades extending radially from the hub, the multi-stage cover portion including: an inlet; an outlet; and a plurality of stages extending between the inlet and the outlet for receiving the fluid dynamic turbine in the plurality of stages, the stages defining a water flow channel for allowing water to flow through the water flow channel from the inlet toward the outlet along a water flow direction; wherein the stages define a height that is substantially constant along the water flow direction; and wherein at least one of the stages defines a width that increases along the water flow direction.

[0008] In some embodiments, multiple stages include an inlet draft tube, which includes: an inlet draft tube inlet; an inlet draft tube outlet; and an inlet peripheral wall, which extends between the inlet draft tube inlet and the inlet draft tube outlet and defines an inlet water flow channel, which is used to allow water to flow through the inlet water flow channel from the inlet draft tube inlet toward the inlet draft tube outlet along the water flow direction, and the inlet peripheral wall includes an inner surface and an outer surface.

[0009] In some embodiments, the plurality of stages further include an intermediate draft tube, the intermediate draft tube including: an intermediate draft tube inlet configured to receive an inlet draft tube outlet; an intermediate draft tube outlet; and an intermediate peripheral wall extending between the intermediate draft tube inlet and the intermediate draft tube outlet and defining an intermediate water flow channel for allowing water to flow through the intermediate water flow channel from the intermediate draft tube inlet toward the intermediate draft tube outlet along a water flow direction, the intermediate peripheral wall including an inner surface and an outer surface.

[0010] In some embodiments, the multi-stage cover portion includes a first water passage at the intermediate draft tube inlet, the first water passage being formed between the outer surface of the inlet peripheral wall and the inner surface of the intermediate peripheral wall, for allowing water to flow through the first water passage from the intermediate draft tube inlet toward the intermediate draft tube outlet.

[0011] In some embodiments, the cross-section at the inlet of the intermediate draft tube is larger than the cross-section at the outlet of the inlet draft tube.

[0012] In some embodiments, the first water passage extends along a periphery of the inlet draft tube inlet.

[0013] In some embodiments, the plurality of stages further include an outlet draft tube, the outlet draft tube comprising: an outlet draft tube inlet, the outlet draft tube inlet being configured to receive an intermediate draft tube outlet; an outlet draft tube outlet; and an outlet peripheral wall extending between the outlet draft tube inlet and the outlet draft tube outlet and defining an outlet water flow channel, the outlet water flow channel being used to allow water to flow through the outlet water flow channel from the outlet draft tube inlet toward the outlet draft tube outlet along a water flow direction, the outlet peripheral wall comprising an inner surface and an outer surface.

[0014] In some embodiments, the multi-stage cover portion further includes a second water passage at the outlet draft tube inlet, the second water passage being formed between the outer surface of the intermediate peripheral wall and the inner surface of the outlet peripheral wall, for allowing water to flow from the outlet draft tube inlet toward the outlet draft tube outlet through the second water passage.

[0015] In some embodiments, the cross-section of the outlet draft tube at the inlet is larger than the cross-section of the intermediate draft tube at the outlet.

[0016] In some embodiments, the second water passage extends along a periphery of the intermediate draft tube inlet.

[0017] In some embodiments, the intermediate draft tube defines an intermediate draft tube width that increases along a water flow direction according to a first non-linear relationship.

[0018] In some embodiments, the outlet draft tube defines an outlet draft tube width that increases along the direction of water flow according to a second non-linear relationship.

[0019] In some embodiments, the outlet drainage tube width increases from the outlet drainage tube inlet toward the outlet drainage tube outlet.

[0020] In some embodiments, the inlet draft tube defines an inlet draft tube length and an inlet draft tube width that increases along a segment of the inlet draft tube length according to a third non-linear relationship.

[0021] In some embodiments, the width at the outlet is greater than the height at the outlet.

[0022] In some embodiments, the multi-stage cover portion further comprises a base for supporting the plurality of stages on the base.

[0023] In some embodiments, the base defines an open configuration for enabling water to flow beneath the plurality of stages along the length of the plurality of stages in a direction of water flow.

[0024] In some embodiments, the base includes a main frame for supporting the plurality of stages, and a plurality of support legs extending downwardly from the main frame.

[0025] In some embodiments, the base further includes a leveling mechanism configured to level the plurality of stages relative to a direction of water flow.

[0026] In some embodiments, the multi-stage cover further includes a hub support structure extending from the multiple stages for supporting at least a portion of the fluid turbine in the stages, the hub support structure including a plurality of spaced-apart hub support members each extending between an inner surface of the inlet draft tube and the hub.

[0027] In some embodiments, the multi-stage cover portion further includes an external reinforcement structure, which is used to reinforce the multiple stages and extends from the multiple stages, and the external reinforcement structure includes a plurality of spaced-apart upper ribs, each of which extends upward from an outer surface of the inner guide tube, an outer surface of the intermediate guide tube, and an outer surface of the outlet guide tube.

[0028] In some embodiments, the multi-stage cover further includes an inner reinforcement structure for reinforcing the multiple stages, the inner reinforcement structure including a plurality of spaced-apart struts, each strut extending between a lower portion of the inner surface of the outlet draft tube and an upper portion of the inner surface of the outlet draft tube. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a front perspective view of a multi-stage cover portion according to one embodiment;

[0030] Figure 2 yes Figure 1 An isometric side perspective view of a multi-stage hood portion of FIG.

[0031] Figure 3 yes Figure 1 A front view of a multi-stage cover portion.

[0032] Figure 4 yes Figure 1 Rear view of the multi-stage cover.

[0033] Figure 5 yes Figure 1 A side view of a multi-stage cover portion.

[0034] Figure 6 is along Figure 7 A cross-sectional view of a multi-stage cover portion taken along line AA.

[0035] Figure 7 yes Figure 1 A top plan view of a multi-stage hood portion.

[0036] Figure 8 is along Figure 5 A cross-sectional view of a multi-stage cover portion taken along line BB. DETAILED DESCRIPTION

[0037] The multi-stage cover described herein enables the water flow and pressure drop at the flow path cross section of the fluid power turbine to be increased, thereby maximizing the power output generated, while complying with the size constraints provided by the shallow body of water (e.g., a river) in which the fluid power turbine can be immersed. Therefore, the multi-stage cover described herein can be configured to enable water to flow through the fluid power turbine in a substantially steady stream.

[0038] In one embodiment, the multi-stage cover is configured to receive a fluid power turbine at least partially in the multi-stage cover, and may include an inlet, an outlet, and a plurality of stages that may extend between the inlet and the outlet, so that water can flow through the multi-stage cover in the direction of water flow. The fluid power turbine may include a rotor, a hub, and blades that may extend radially from the hub to form a flow channel cross section. The hub may extend at least partially in the flow direction so that the power output can be maximized. The multi-stage cover defines a height that enables the stage (and turbine) to be fully immersed in the water body. For example, the height of the multi-stage cover can be kept substantially constant along the length of the multi-stage cover or along the direction of water flow, so that the multi-stage cover and the fluid power turbine device can operate in a shallow river. In addition, the width of the stage or some of the stages can be increased along its length (or a segment of its length) so that a substantially stable water flow can flow through the stage or some of the stages, more specifically, so that a substantially stable water flow can flow through the stage or some of the stages at the flow channel cross section of the fluid power turbine. Therefore, this configuration of the multi-stage cover can eliminate fluid separation to a negligible level when water flows through the stages, and can minimize the generation of vortices around the fluid power turbine to a negligible level. Therefore, a significant water flow and pressure drop can be generated at the flow cross section of the turbine.

[0039] In one embodiment, the multi-stage cover portion may include a plurality of drainage tubes (e.g., two or more drainage tubes), and the plurality of drainage tubes may be configured so that water can flow through the plurality of drainage tubes in the direction of water flow. In one case, the multi-stage cover portion may include an inlet drainage tube and an outlet drainage tube. Alternatively, the multi-stage cover portion may be a three-stage cover portion, and include an intermediate drainage tube at the downstream of the inner drainage tube and the upstream of the outlet drainage tube. For example, the hub and blades of the fluid power turbine may be at least partially received in the inner drainage tube. As will be described in more detail below, each drainage tube has an inlet and an outlet, and the outlet may be received in the inlet of the corresponding downstream drainage tube. For example, the outlet of the inner drainage tube may be configured to be received in the inlet of the intermediate drainage tube, and similarly, the outlet of the intermediate drainage tube may be configured to be received in the inlet of the outlet drainage tube, so that the multi-stage cover portion may further include a first water passage at the inlet of the intermediate drainage tube, and a second water passage at the inlet of the outlet drainage tube. In one case, the first water passage can be provided between the outer surface of the inlet draft tube and the inner surface of the intermediate draft tube, for example, at the periphery of the inner draft tube, and the second water passage can be provided between the outer surface of the intermediate draft tube and the inner surface of the outlet draft tube, for example, at the periphery of the intermediate draft tube. Thus, the first water passage and the second water passage can enable water that is not supplied to the flow passage cross section of the fluid power turbine to flow through the first water passage and the second water passage to, for example, combine with water flowing through the multi-stage cover in the water flow direction. Such a feature of the cover can enable a stable water flow to pass through the draft tube, thereby enabling a stable and increased water flow to be generated at the flow passage cross section of the turbine. Due to the increase in the width of the draft tube (mainly 400 and 500) and through the first water passage and the second water passage, the multi-stage cover can maintain a quasi-laminar flow around the inner surface of the inlet draft tube, so that the effective vortex-free flow and separation-free flow can be maintained through the draft tube while the cover can have an operationally and economically feasible length, and more importantly, the effective vortex-free flow and separation-free flow can be maintained at the flow passage cross section of the turbine. The cavity volume at the flow passage cross section of the turbine can also be minimized.

[0040] Referring now to the drawings and more particularly to the Figures 1 to 8In an embodiment, a multi-stage cover (100) is provided, which is configured to receive a fluid power turbine (200) therein. The multi-stage cover (100) can be configured so that the multi-stage cover can be completely immersed in a body of water together with the turbine (200). For example, the multi-stage cover (100) can be fixed to a bed of a body of water. The fluid power turbine (200) can include an introduction nose (210), an outer rotor (220), blades (230, 232, 234, 236) and an inner stator inside the rotor, and the blades can extend radially from the outer rotor to form a flow channel cross section. It should be noted that the fluid power turbine (200) can be of any shape, size or configuration, as long as the fluid power turbine can be at least partially introduced into the multi-stage cover (100) so that water flowing downstream from the flow channel cross section can flow through at least a portion of the cover (100). Thus, the shape, size or configuration of the rotor (220), the shape, size or configuration of the lead-in nose (210), and the size and configuration of the blades (230, 232, 234, 236) and the rotor (220) may vary. Figures 1 to 4 The fluid kinetic turbine (200) is shown as including four blades (230, 232, 234, 236), but it should be noted that the number of blades extending from the hub (220) may vary.

[0041] Still refer to Figures 1 to 8In an embodiment, the multi-stage cover (100) includes an inlet (110) and an outlet (120), and the outlet can be arranged opposite to the inlet (110). The multi-stage cover (100) further includes a plurality of stages (130), which can extend between the inlet (110) and the outlet (120). As described above, the stage (130) can be configured to at least partially receive the fluid power turbine (200) in the stage, so that water can flow through the stage (130) from a section of the stage (130) located upstream of the blades (230, 232, 234, 236) (i.e., upstream of the flow passage cross section) toward a section of the stage (130) located downstream of the blades (230, 232, 234, 236) (i.e., downstream of the flow passage cross section), and then flow through the outlet (120). The plurality of stages (130) together define a flow channel (135), and the flow channel defines a water flow direction (WF). The multi-stage hood (100) further defines a height (H) and a length (L), and the stages (130) may define a width (Wi) at an inlet (110) of the multi-stage hood (100), and a width (Wo) at an outlet (120) of the multi-stage hood. In one embodiment, the height (H) of the hood (100) may enable the stages (130) (and the turbine (200)) to be fully submerged in a substantially shallow body of water. For example, the height (H) of the hood (100) may be substantially constant along the length (L) of the hood (or along the direction of water flow (WF)), and the width (Wo) at the outlet (120) of the hood (100) may be greater than the width (Wi) at the inlet (110) of the hood (100). More specifically, the width of one or more of the stages (130) (or segments of the width of the stage) may increase along the water flow direction (WF) from the inlet of the stage toward the outlet of the stage, as will be described in more detail below. Figure 6 and Figure 8 As best shown in FIG. 1 , the rotor ( 220 ) may extend in the direction of water flow (WF) so that water may flow substantially into the flow path cross section of the turbine ( 200 ), which may increase the power output from the turbine.

[0042] Still refer to Figures 1 to 8 In an embodiment, the multi-stage cover portion (100) may include a plurality of draft tubes, such as draft tubes (300, 400, 500) (i.e., stage (130)). In fact, the multi-stage cover portion (100) may include an inlet draft tube or a first stage draft tube (300). The inlet draft tube (300) may include an outer wall (312), which defines an inlet (320), an outlet (330), and a flow channel (310) for allowing water to flow through the flow channel along a water flow direction (WF). In other words, the inlet draft tube (300) may extend along a water flow direction (WF), and the outer wall (312) may define the flow channel (310). As in Figure 6 and Figure 8 As best shown in FIG. 1 , water (water flow 700) can thus flow through the flow channel (310) formed by the peripheral wall (312) from the inlet (320) through the upstream section (322) of the inlet draft tube (300) (i.e., upstream of the blades (230, 232, 234, 236) or the flow passage cross section), through the downstream section (324) of the inlet draft tube (300) (i.e., downstream of the blades (230, 232, 234, 236) or the flow passage cross section), and then through the outlet (330). The peripheral wall (312) of the inlet draft tube (300) includes an inner surface (332) and an outer surface (334) opposite the inner surface (332). The inlet draft tube (300) defines an overall height (H1), a length (L1), a width (Wi1) at the inlet (320), a width (Wo1) at the outlet (330), a height (Hi1) at the inlet (320), and a height (Ho1) at the outlet (330). In one embodiment, the inlet draft tube (300) may define a height (H1) such that the inlet draft tube may be fully immersed in a shallow body of water. More specifically, the inlet draft tube (300) may define a height (H1) that may be substantially constant along the length (L1) of the inlet draft tube (or along the direction of water flow (WF)). In other words, the height (Hi1) at the inlet (320) may substantially correspond to the height (Ho1) at the outlet (330). However, it should be noted that the width (Wo1) at the outlet (330) may be greater than the width (Wi1) at the inlet (320). For example, the width of the inlet draft tube (300) may increase along the length (L1) of the inlet draft tube from the inlet (320) toward the outlet (330), or alternatively, along a segment of the length (L1) of the inlet draft tube. However, it should be noted that the width (Wi1) at the inlet (320) may substantially correspond to the width (Wo1) at the outlet (330), or alternatively, the width of the inlet draft tube (300) may remain substantially constant along the length (L1) of the inlet draft tube. In one embodiment, the height of the inlet draft tube (300) can be increased or decreased along the length (L1) of the inlet draft tube according to a hydraulic profile designed and optimized to stabilize the flow through the turbine flow channel and eliminate flow oscillations and fluid separation through the turbine flow channel, while the width of the outlet draft tube (500) can be increased along a section of the length (L1) of the outlet draft tube according to another hydraulic profile designed and optimized to stabilize the flow in the inlet draft tube (300), the intermediate draft tube (400) and the outlet draft tube (500) while eliminating oscillations and fluid separation through the turbine flow channel.

[0043] Still refer to Figures 1 to 8In an embodiment, the multi-stage cover (100) may further include a hub support structure (336), which may be configured to support the hub (220) of the turbine (200) along the axis (X), so that once the cover (100) and the turbine (200) assembly have been immersed in the water body, the hub support structure can extend in the direction of water flow (WF). The hub support structure (336) may include hub support members (338, 344, 350, 356), which may extend between the inner surface (332) of the inlet draft tube (300) and the stationary portion (i.e., the inner stator) of the hub (220). In one embodiment, as in Figure 1, the hub support member (338) may extend between a lower right section of the inner surface (332) at the inlet (320) and a right front section of the lower portion of the hub (220). The hub support member (344) may extend between a lower left section of the inner surface (332) at the inlet (320) and a left front section of the lower portion of the hub (220). The hub support member (350) may extend between a lower right section of the inner surface (332) at the outlet (330) and a right rear section of the lower portion of the hub (220). Finally, the hub support member (356) may extend between a lower left section of the inner surface (332) at the outlet (330) and a left rear section of the lower portion of the hub (220). In one embodiment, the hub support members (338, 344, 350, 356) can be inclined inwardly at an angle toward the central axis (X) (i.e., toward the center of the inlet draft tube (300)). As shown, the draft tube ends (340, 346, 352, 358) can be fixed to the lower section of the inner surface (332), while the hub ends (342, 348, 354, 360) can be fixed to the stationary section of the hub (220). Suitable mechanical fasteners can be used to fix the ends (342, 348, 354, 360) and ends (340, 346, 352, 358) of the hub support members (338, 344, 350, 356) to the hub (220) and the inlet draft tube (300). Alternatively, the ends (342, 348, 354, 360) and the ends (340, 346, 352, 358) of the hub support members (338, 344, 350, 356) may be secured to the hub (220) and the inlet draft tube (300) using fasteners or other known techniques (e.g., by welding). It should be further noted that the hub support structure (336) may be of any shape, size, or configuration so long as the hub support structure is capable of supporting the turbine (200) and the hub (220) of the turbine extending at least partially in the direction of water flow (WF), and so long as water is capable of flowing through the inlet draft tube (300) with minimal longitudinal obstruction, thereby enhancing water flow through the shroud (100). For example, in one embodiment, the hub support structure (336) may have a hydraulic profile along the direction of water flow (WF). In another case (not shown), for example, the hub support structure may extend from the riverbed so that water can flow through the inlet draft tube (300) without being obstructed by components such as the hub support members (338, 344, 350, 356). The hub support structure (336) may further include a passage configured to receive an electric underwater cable to output electrical power generated by a generator (not shown) of the turbine inside the turbine hub (220) and other electrical wires, including optical fibers (not shown) extending from the fluid power turbine (200).

[0044] Still refer to Figures 1 to 8In an embodiment of the multi-stage cover portion (100), the multi-stage cover portion (100) may further include an intermediate draft tube or a second stage draft tube (400), which may be located downstream of the inlet draft tube (300). The intermediate draft tube (400) may include an outer wall (412) defining an inlet (420), an outlet (430), and a flow channel (410) for allowing water to flow through the flow channel along a water flow direction (WF). In other words, the intermediate draft tube (400) may extend along a water flow direction (WF), and the outer wall (412) may define the flow channel (410). As in Figure 6 and Figure 8 As best shown in , water (water flow 700) can thus flow from the outlet (330) of the inlet draft tube (300) toward the outlet (430) of the intermediate draft tube (400) through the flow channel (410) formed by the peripheral wall (412). The intermediate draft tube (400) also has an inner surface (432) and an outer surface (434) opposite the inner surface (432). The intermediate draft tube (400) defines a height (H2), a length (L2), a width (Wi2) at the inlet (420), a width (Wo2) at the outlet (430), a height (Hi2) at the inlet (420), and a height (Ho2) at the outlet (430). In one embodiment, the intermediate draft tube (400) can define a height (H2) such that the intermediate draft tube can be fully submerged in a shallow body of water. More specifically, the intermediate draft tube (400) may define a height (H2) that may be substantially constant along the length (L2) of the intermediate draft tube (or along the direction of water flow (WF)). For example, the height (Hi2) at the inlet (420) may substantially correspond to the height (Ho2) at the outlet (430) of the intermediate draft tube (400). Figure 5 and Figure 6 As best shown in FIG. 1 , the height (Hi2) at the inlet (420) can be slightly greater than the height (Ho2) at the outlet (430). More specifically, the height (H2) of the intermediate or second stage draft tube (400) can decrease along the length (L2) of the intermediate or second stage draft tube (or along the direction of water flow (WF)) from the inlet (420) toward the outlet (430), or alternatively, along a segment of the length (L2). Other configurations of the intermediate draft tube (400) are also possible. However, as shown in FIG. Figure 7 and Figure 8As best shown in FIG. 4 , it should be noted that the width (Wo2) at the outlet (430) can be greater than the width (Wi2) at the inlet (420). More specifically, the width of the intermediate draft tube (400) can increase along the length (L2) of the intermediate draft tube (or along the direction of water flow (WF)) from the inlet (420) toward the outlet (430), or alternatively, along a segment of the length (L2) of the intermediate draft tube. In one embodiment, the height of the intermediate drainage tube (400) can be increased or decreased along the length (L2) of the intermediate drainage tube according to a hydraulic profile, and the hydraulic profile is designed and optimized to eliminate fluid separation on the inner side of the drainage tube (300, 400, 500) and stabilize the flow, while the width of the intermediate drainage tube (400) can be increased along the length (L2) of the intermediate drainage tube according to another hydraulic profile, and the other hydraulic profile is designed and optimized to eliminate fluid separation on the inner side of the drainage tube (300, 400, 500) and at the flow channel cross section and stabilize the flow.

[0045] Still refer to Figures 1 to 8 In an embodiment of the multi-stage cover portion (100), the multi-stage cover portion (100) may further include an outlet draft tube or a third stage draft tube (500), which may be located downstream of the intermediate draft tube (400). The outlet draft tube (500) may include an outer wall (512) defining an inlet (520), an outlet (530), and a flow channel (510) for allowing water to flow through the flow channel along a water flow direction (WF). In other words, the outlet draft tube (500) may extend along a water flow direction (WF), and the outer wall (512) may define the flow channel (510). As in Figure 6 and Figure 8 As best shown in , water (water flow 700) can thus flow from the outlet (430) of the intermediate draft tube (400) toward the outlet (530) of the outlet draft tube (500) through the flow channel (510) formed by the peripheral wall (512). The outlet draft tube (500) also includes an inner surface (532) and an outer surface (534) opposite the inner surface (532). The outlet draft tube (500) defines a height (H3), a length (L3), a width (Wi3) at the inlet (520), a width (Wo3) at the outlet (530), a height (Hi3) at the inlet (520), and a height (Ho3) at the outlet (530). As shown in Figure 5 and Figure 6As best shown in FIG. 1 , in one embodiment, the outlet drainage tube (500) can define a height (H3) such that the outlet drainage tube can be fully immersed in a shallow body of water. More specifically, the height (H3) can be substantially constant along the length (L3) of the outlet drainage tube (or along the direction of water flow (WF)). For example, the height (Hi3) at the inlet (520) can substantially correspond to the height (Ho3) at the outlet (530) of the outlet drainage tube (500). Specifically referring to Figure 5 and Figure 6 , the height (Ho3) at the outlet (530) may be slightly greater than the height (Hi3) at the inlet (520). More specifically, the height of the outlet drainage tube (500) may increase along the length (L3) of the outlet drainage tube (or along the water flow direction (WF)) from the inlet (520) of the outlet drainage tube (500) toward the outlet (530) of the outlet drainage tube, or along a section of the length (L3). Other configurations of the outlet drainage tube (500) are also possible. However, as in Figure 7 and Figure 8 As best shown in FIG. 1 , it should be noted that the width (Wo3) at the outlet (530) can be greater than the width (Wi3) at the inlet (520). More specifically, the width of the outlet draft tube (500) can increase along the length (L3) of the outlet draft tube (or along the direction of water flow (WF)) from the inlet (520) of the outlet draft tube (500) toward the outlet (530) of the outlet draft tube, or alternatively, along a segment of the length (L3) of the outlet draft tube. In one embodiment, the height of the outlet drainage tube (500) can be increased or decreased along the length (L3) of the outlet drainage tube according to a hydraulic profile designed and optimized to eliminate fluid separation on the inside of the drainage tube (300, 400, 500) and at the cross-section of the flow channel to a negligible level and stabilize the flow, while the width of the outlet drainage tube (500) can be increased along the length (L3) of the outlet drainage tube according to another hydraulic profile designed and optimized to eliminate fluid separation on the inside of the drainage tube (300, 400 and 500) and at the cross-section of the flow channel to a negligible level and stabilize the flow.

[0046] Now more specifically refer to Figure 6 and Figure 8In one embodiment, the inlet draft tube (300) may be at least partially engaged in the flow passage (410) of the intermediate draft tube (400), and the intermediate draft tube (400) may be at least partially engaged in the flow passage (520) of the outlet draft tube (500). In fact, the outlet (330) of the inner draft tube (300) may be received in the inlet (420) of the intermediate draft tube (400), and the outlet (430) of the intermediate draft tube (400) may be received in the inlet (520) of the outlet draft tube (500), so that the multi-stage cover portion (100) may further include a first water passage (140) at the inlet (420) of the intermediate draft tube (400), and a second water passage (142) at the inlet (520) of the outlet draft tube (500). In one embodiment, the first water passage (140) may be disposed at the periphery of the outlet (320) of the inlet draft tube (300) so that water (water flow (800)) may flow through the passage formed between the outer surface (334) of the inlet draft tube (300) at the outlet (330) of the inlet draft tube and the inner surface (432) of the intermediate draft tube (400) at the inlet (420) of the intermediate draft tube. On the other hand, the second water passage (142) may be disposed at the periphery of the outlet (430) of the intermediate draft tube (400) so that water (water flow (900)) may flow through the passage formed between the outer surface (434) of the intermediate draft tube (400) at the outlet (430) of the intermediate draft tube and the inner surface (532) of the outlet draft tube (500) at the inlet (520) of the outlet draft tube. Therefore, in one case, the height (Hi2) at the inlet (420) may be greater than the height (Ho1) at the outlet (330), and the height (Hi3) at the inlet (520) may be greater than the height (Ho2) at the outlet (430), while the width (Wi2) at the inlet (420) may be greater than the width (Wo1) at the outlet (330), and the width (Wi3) at the inlet (520) may be greater than the width (Wo2) at the outlet (430). Other configurations of the drainage tubes (300, 400, 500) are possible as long as water can flow through the inlets (420, 520) of the drainage tubes (400, 500).

[0047] Now more specifically refer to Figure 8It should be noted that the inlet draft tube (300) may include a substantially straight portion (361) (i.e., a left substantially straight portion and a right substantially straight portion (361)) and a diverging wall portion (362) (i.e., a left diverging wall portion and a right diverging wall portion (362)) surrounding the outlet (330), and the diverging wall portion may extend from the straight portion (361) (or the water flow direction (WF)) at a diverging angle (θ1). For example, the diverging angle (θ1) may be between about 2° and about 60°, between about 10° and about 40°, or between about 25° and about 35°. For example, the width of the inlet draft tube (300) may increase along a segment of the length (L1) of the inlet draft tube according to a hydraulic profile designed and optimized to eliminate fluid separation at the inner side of the draft tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. However, it should be noted that in another case, the width of the inlet draft tube (300) can be increased along a segment of the length (L1) of the inlet draft tube according to a hydraulic profile designed and optimized to eliminate fluid separation at the inner side of the draft tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. It should be further noted that the peripheral wall (312) can be of any shape, size or configuration as long as the width of the inlet draft tube (300) can be increased along at least one segment of the length (L1) of the inlet draft tube. For example, the segment can be arranged around the outlet (330) and near the first water passage 140.

[0048] Now more specifically refer to Figure 6It should be noted that the inlet draft tube (300) may include a substantially straight portion (363) (i.e., an upper substantially straight portion and a lower substantially straight portion (363)) and, for example, a converging wall portion (364) (i.e., an upper converging wall portion and a lower converging wall portion (364)) between the flow channel cross section and the outlet (330), and the converging wall portion may extend from the straight portion (363) at a converging angle (θ2). For example, the converging angle (θ2) may be between about 1° and about 20°, between about 5° and about 15°, or between about 8° and about 12°. For example, the converging wall portion (364) may have a hydraulic profile that is designed and optimized to eliminate fluid separation at the inside of the draft tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. Therefore, the height of the inlet draft tube (300) can be reduced along a section of the length (L1) of the inlet draft tube according to a hydraulic profile designed and optimized to eliminate fluid separation at the inner side and flow channel cross section of the draft tubes (300, 400, and 500) to a negligible level and stabilize the flow. However, it should be noted that in another case, the height of the inlet draft tube (300) can be increased along a section of the length (L1) of the inlet draft tube according to a hydraulic profile designed and optimized to eliminate fluid separation at the inner side and flow channel cross section of the draft tubes (300, 400, 500) to a negligible level and stabilize the flow. It should be further noted that the peripheral wall (312) can be of any shape, size or configuration as long as the height of the inlet draft tube (300) allows the hood (100) to be fully immersed in the water body and as long as the outlet (330) can be received in the inlet (420) to form a water passage (140).

[0049] Now more specifically refer to Figure 8It should be noted that the intermediate drainage tube (400) may include an inlet portion (461) (i.e., a left inlet portion and a right inlet portion (461)) surrounding the inlet (420), and an outlet portion (462) (i.e., a left outlet portion and a right outlet portion (462)) surrounding the outlet (430). For example, the outlet portion (462) may extend from the water flow direction (WF) or the axis (X) at a divergence angle (θ3). In some embodiments, the divergence angle (θ3) may be between about 8° and about 90°, between about 10° and about 60°, or between about 45° and about 55°. For example, the outlet portion (462) may have a hydraulic profile that is designed and optimized to eliminate fluid separation at the inner side and flow channel cross section of the drainage tube (300, 400, 500) and stabilize the flow. Therefore, as described above, the width of the intermediate draft tube (400) can increase along the length (L2) of the intermediate draft tube or a segment of the length (L2) of the intermediate draft tube according to the following hydraulic profile: the hydraulic profile is designed and optimized to eliminate the fluid separation at the inner side and flow channel cross section of the draft tube (300, 400, 500) to a negligible level and stabilize the flow. It should be further noted that the peripheral wall (412) can be of any shape, size or configuration as long as the width of the intermediate draft tube (400) can increase along at least one segment of the length (L2) of the intermediate draft tube. For example, the segment can be arranged around the outlet (430) and near the second water passage 142. It should also be noted that the width increase rate of the outlet portion (462) of the intermediate draft tube (400) can be greater than the width increase rate of the inlet portion (461) of the intermediate draft tube (400).

[0050] Now more specifically refer to Figure 6, it should be noted that the intermediate drainage tube (400) can include an upper portion (463) and a lower portion (464). Each of the upper portion (463) and the lower portion (464) can extend from the water flow direction (WF) or the axis (X) at a convergence angle (θ4). For example, the convergence angle (θ4) can be between about 1° and about 20°, between about 5° and about 15°, or between about 8° and about 12°. As described above, the upper portion (463) and the lower portion (464) can have a substantially straight profile. Therefore, the height of the intermediate drainage tube (400) can be reduced along the length (L2) of the intermediate drainage tube according to the following hydraulic profile: the hydraulic profile is designed and optimized to eliminate fluid separation at the inner side and flow channel cross section of the drainage tube (300, 400, 500) to a negligible level and stabilize the flow. However, it should be noted that in another case, the height of the intermediate draft tube (400) can be increased along the length (L2) of the intermediate draft tube or a segment of the length of the intermediate draft tube according to the following hydraulic profile: the hydraulic profile is designed and optimized to eliminate the fluid separation at the inner side of the draft tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. It should be further noted that the peripheral wall (412) can be of any shape, size or configuration as long as the height of the intermediate draft tube (400) can enable the cover (100) to be fully immersed in the water body and as long as the outlet (430) can be received in the inlet (520) to form the water passage (142).

[0051] Refer to Figure 8It should be noted that the outlet draft tube (500) may include an inlet portion (576) (i.e., a left inlet portion and a right inlet portion (576)) surrounding the inlet (520), and an outlet portion (577) (i.e., a left outlet portion and a right outlet portion (577)) surrounding the outlet (530). For example, the outlet portion (577) may extend from the water flow direction (WF) or the axis (X) at a divergence angle (θ5). In some embodiments, the divergence angle (θ5) may be between about 8° and about 90°, between about 10° and about 85°, or between about 60° and about 60°. For example, the outlet portion (577) may have a hydraulic profile that is designed and optimized to eliminate fluid separation at the inner side of the draft tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. Thus, as described above, the width of the outlet drainage tube (500) can increase along the length (L3) of the outlet drainage tube or a segment of the length (L3) of the outlet drainage tube according to the following hydraulic profile: the hydraulic profile is designed and optimized to eliminate fluid separation at the inner side of the drainage tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. It should be further noted that the peripheral wall (512) can be of any shape, size or configuration as long as the width of the outlet drainage tube (500) can increase along at least one segment of the length (L3) of the outlet drainage tube. For example, the segment can be arranged around the outlet (530). It should also be noted that the width increase rate of the outlet portion (577) of the outlet drainage tube (500) can be greater than the width increase rate of the inlet portion (576) of the outlet drainage tube (500).

[0052] Refer to Figure 6, it should be noted that the outlet draft tube (500) may include an upper portion (578) and a lower portion (579). Each of the upper portion (578) and the lower portion (579) may extend from the water flow direction (WF) or the axis (X) at a divergent angle (θ6). For example, the convergence angle (θ6) may be between about 1° and about 85°, between about 2° and about 60°, or between about 4° and about 40°. As described above, the upper portion (578) and the lower portion (579) may have a substantially straight profile. Therefore, the height of the outlet draft tube (500) may be slightly reduced along the length (L3) of the outlet draft tube, according to the hydraulic profile: the hydraulic profile is designed and optimized to eliminate fluid separation at the inner side of the draft tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. However, it should be noted that in another case, the height of the outlet drainage tube (500) can increase along the length (L3) of the outlet drainage tube or a segment of the length of the outlet drainage tube according to the following hydraulic profile: the hydraulic profile is designed and optimized to eliminate fluid separation at the inner side of the drainage tube (300, 400, 500) and the flow channel cross section to a negligible level and stabilize the flow. It should be further noted that the peripheral wall (512) can be of any shape, size or configuration as long as the height of the outlet drainage tube (500) allows the cover (100) to be completely immersed in the water body. It should be noted that the width of the inlet drainage tube (300), the intermediate drainage tube (400) and / or the outlet drainage tube (500) can increase along the length of the inlet drainage tube, the intermediate drainage tube and / or the outlet drainage tube or one or more segments of the length of the inlet drainage tube, the intermediate drainage tube and / or the outlet drainage tube according to a substantially linear relationship and / or a nonlinear relationship. Similarly, the height of the inlet drainage tube (300), the intermediate drainage tube (400) and / or the outlet drainage tube (500) may increase and / or decrease along the length of the inlet drainage tube, the intermediate drainage tube and / or the outlet drainage tube or along one or more segments of the length of the inlet drainage tube, the intermediate drainage tube and / or the outlet drainage tube in a substantially linear relationship and / or a non-linear relationship.

[0053] Therefore, if Figure 6 and Figure 8As best shown, once the multi-stage cover (100) and turbine (200) arrangement has been fully submerged in a body of water and the turbine (200) is in operation, water (stream (700)) can flow through the inlet (320) of the inlet draft tube (300), through the upstream section (322) of the inlet draft tube (300), through the downstream section (324) of the inlet draft tube (300), and then through the outlet (330) of the inlet draft tube (300). When the water discharged from the outlet (330) can flow through the intermediate draft tube (400) toward the outlet (430) of the intermediate draft tube, the water that does not enter the inlet draft tube (300) (i.e., the flow (800)) can flow through the first water passage (140) provided at the inlet (420) at the periphery of the inlet draft tube (300), and can merge with the water flow (700) flowing through the intermediate draft tube (400) along the water flow direction (WF). For example, the water flow (800) can flow along the inlet portion (461) and the outlet portion (462) of the inner surface (432) of the peripheral wall (412). Similarly, when water discharged from the outlet (430) of the intermediate draft tube (400) (i.e., water flows (700, 800)) can flow through the intermediate draft tube (500) toward the outlet (530), water (flow (900)) that has not entered the inlet draft tube (300) or the intermediate draft tube (400) can flow through the second water passage (142) at the inlet (520) provided at the periphery of the intermediate draft tube (400), and can merge with the water flows (700, 800) flowing through the outlet draft tube (500) along the water flow direction (WF). For example, the water flow (900) can flow along the inlet portion (576) and the outlet portion (577) of the inner surface (532) of the peripheral wall (512).

[0054] Thus, the multi-stage shroud (100) described herein enables the water flow and pressure drop at the flow passage cross section of the turbine (200) to be increased to maximize the power output generated while complying with the size constraints provided by the shallow body of water (e.g., a river) in which the turbine (200) can be immersed. Thus, the multi-stage effect (at the periphery of the outlets (330, 430)) provided by the multi-stage shroud (100) can enable water to flow through the turbine (200) in a substantially steady flow (without oscillation, with negligible vortices and fluid separation). The height (H) of the multi-stage shroud (100) can remain substantially constant along the length (L) of the multi-stage shroud or along the direction of water flow (WF), so that the multi-stage shroud (100) and turbine (200) arrangement can operate in shallow rivers. The width of the draft tube (300, 400, 500) can be increased along at least one section of the length (L1, L2, L3) of the draft tube so that an optimized water mass flow can flow through the draft tube, more specifically, at the flow passage cross section of the turbine (200). Therefore, this configuration of the multi-stage cover (100) can eliminate fluid separation when water flows through the draft tube (300, 400, 500) and prevent the generation of vortices around the turbine (200) to a negligible level. Therefore, a significant water flow and pressure drop can be generated at the flow passage cross section of the turbine (200). The water channel (140, 142) further enables water that is not supplied to the flow passage cross section of the turbine (200) to combine with water flowing through the draft tube (400, 500). This feature of the cover (100) can enable a stable water flow to pass through the drainage tube (300, 400, 500), thereby generating a stable and increased water flow at the flow passage cross section of the turbine (200) to increase the power output of the turbine. Due to the increased width along the length (L2, L3) of the drainage tube and through the first water passage (140) and the second water passage (142), the multi-stage cover (100) can maintain a quasi-laminar flow around the inner surface (432, 532) of the drainage tube (400, 500), so that when the length (L) of the cover (100) is operationally and economically feasible, an effective vortex-free flow and a separation-free flow can be maintained through the drainage tube (300, 400, 500), and thereby an effective vortex-free flow and a separation-free flow can be maintained at the flow passage cross section of the turbine (200). The cavity volume at the flow passage cross section of the turbine (200) has been minimized by design to a negligible level.

[0055] The configuration of the multi-stage shroud (100) and the different stages (130) of the multi-stage shroud (e.g., the inlet draft tube (300), the intermediate draft tube (400), and the outlet draft tube (500)) provide the widest lateral range not present in the prior art for such a short length of the optimized multi-stage shroud (100), which can enable significant pressure drop and water flow rate to be generated at the flow passage cross section of the turbine (200). When having positive lateral gradient openings, especially in the intermediate draft tube (400) and the outlet draft tube (500), the first water passage (140) and the second water passage (142) formed at the inlet (420, 520) can help obtain a substantially stable mass flow at the flow passage cross section of the turbine (200) by preventing the generation of vortices and eliminating fluid separation to a negligible level. Therefore, due to the high-speed water flow generated near the inner surface (432) and the outer surface (434) of the intermediate draft tube (400), and the high-speed water flow generated near the inner surface (532) and the outer surface (534) of the outlet draft tube (500), the water flowing through the multi-stage cover (100) can be substantially free of separation and vortex. Therefore, a substantially stable water flow can flow through the draft tubes (300, 400, 500) (and the turbine (200)), while turbulent, unstable water can flow at the inlet (110) of the multi-stage cover (100). In addition, the cover (100) can increase the pressure drop at the outlet (120) and can limit cavitation within the flow channels (310, 410, 510) and at the tips of the blades (230, 232, 234, 236) to a negligible level.

[0056] Refer to Figures 1 to 8In an embodiment, the multi-stage cover (100) may optionally include a base (10) for supporting the stages (130) (e.g., the draft tubes (300, 400, 500)) on the multi-stage cover and above the waterway bed. The base (10) may include a main frame (12), a surface (16) facing the ground, and side walls (30, 32), and the main frame may define a draft tube receiving surface (14). The base (10) may further include a plurality of support legs (22, 24, 26, 28), which may extend downward from the main frame (12) so that the base (10) can be open along the water flow direction (WF) (i.e., water can also flow under the stages (130) along the overall length (L) of the cover (100)). This open configuration of the base (10) allows water to flow around the draft tubes (300, 400, 500). Enabling water to flow in the direction of the water along the length (L) of the shroud (100) below the draft tubes (300, 400, 500), for example between the left support legs (24, 28) and the right support legs (22, 26), can have a significant impact on the overall water flow through the turbine (200), because the lack of flow through the bottom of the turbine (200) can actually create less negative pressure fields at the outlet (120) of the shroud (100), and therefore less negative pressure fields at the outlet of the turbine (200), thereby reducing the power output of the turbine. Therefore, this open configuration of the base (10) can enable those negative fields to be generated at the outlets (430, 530) of the draft tubes (400, 500).

[0057] It should be noted that the base (10) may be of any shape, size or configuration, so long as the base is capable of supporting the stage (130) (e.g., the draft tube (300, 400, 500)) above the bed of the waterway and causing minimal pressure drop to the flow below. In one embodiment, the base (10) may be designed to provide as little longitudinal obstruction as possible to water flowing below the draft tube (300, 400, 500) in the direction of water flow (WF). For example, the support legs (22, 24, 26, 28) may have a hydraulic profile in the direction of water flow (WF).

[0058] Furthermore, in one embodiment, the support legs (22, 24, 26, 28) can be independently adjusted so that the base (10) and therefore the draft tubes (300, 400, 500) can be leveled at the appropriate 3-axis position to maximize the turbine power output. By providing the support legs (22, 24, 26, 28) with an adjustable leg type mechanism, once the turbine (200) and cover (100) assembly has been lowered to the desired position and orientation, the locking mechanism can be released and can enable the turbine (200) and cover (100) assembly to be locked in an optimal position relative to the bed of the waterway. Considering the strong currents that sometimes exist in rivers, as well as the depth and unevenness of the river bed, installing a conventional turbine can be labor intensive and can require specialized skills. In fact, experienced divers may be required, which can be very expensive and risky. This adjustable leg type mechanism can overcome these disadvantages.

[0059] Return to reference Figure 1 , Figure 4 , Figure 6 and Figure 8 In one embodiment, the multi-stage cover portion (100) may optionally include a reinforcing structure (562) for enhancing flow stability and / or providing structural stability to the multi-stage cover portion (100), more specifically, to the outlet draft tube or the third stage draft tube (500). For example, the reinforcing structure (562) may also help prevent water flow oscillations. The reinforcing structure (562) may include spaced apart struts (564, 570) that may extend between a lower portion of the inner surface (532) and an upper portion of the inner surface. As in Figure 1As best shown in FIG. 1 , the strut (564) can extend between a lower right portion of the inner surface (532) of the outlet drainage tube (500) between the inlet (520) and the outlet (530) of the outlet drainage tube and a right upper portion of the inner surface (532). On the other hand, the strut (570) can extend between a lower left portion of the inner surface (532) of the outlet drainage tube (500) between the inlet (520) and the outlet (530) of the outlet drainage tube and a left upper portion of the inner surface (532). For example, the lower end portions (566, 572) of the strut can be fixed to the lower portion of the inner surface (532) of the outlet drainage tube (500), while the upper end portions (568, 574) of the strut can be fixed to the upper portion of the inner surface (532) of the outlet drainage tube (500). In one embodiment, the struts (564, 570) can be inclined inwardly at an angle toward the central axis (X) (i.e., toward the center of the outlet drainage tube (500)). The strut lower ends (566, 572) and the strut upper ends (568, 574) of the struts (564, 570) can be fixed to the lower and upper portions of the inner surface (532) of the outlet drainage tube (500) using any suitable mechanical fasteners. Alternatively, the strut lower ends (566, 572) and the strut upper ends (568, 574) of the struts (564, 570) can be fixed to the outlet drainage tube (500) using other known techniques (e.g., by welding). It should also be noted that the struts (564, 570) can be integrally formed with the peripheral wall (512). It should be further noted that the reinforcing structure (562) can be of any shape, size or configuration, so long as the reinforcing structure is capable of structurally reinforcing the turbine (100) and / or at least partially helping to enhance water flow stability, and so long as water is able to flow through the outlet draft tube (500) with as little longitudinal obstruction as possible, thereby enhancing water flow through the multi-stage cover (100). For example, in one embodiment, the reinforcing structure (562) can have a hydraulic profile along the direction of water flow (WF). It should be further noted that the reinforcing structure (562) can be coupled to the inlet draft tube (300) and / or the intermediate draft tube (400), rather than being disposed on the outlet draft tube (500). Finally, it should be noted that the struts (564, 570) can be configured to eliminate flow resonances and attenuate certain turbulent flow-induced frequencies in the draft tube (500).

[0060] Still refer to Figures 1 to 8In an embodiment, the multi-stage cover (100) can optionally include a reinforcing structure (155) that can extend upward from the stage along the length (L) of the multi-stage cover (100), or alternatively extend upward from the stage along segments of the length (L). In one case, the reinforcing structure (155) can include spaced-apart upper ribs (160, 170). In addition to providing structural stability to the multi-stage cover (100) by connecting the guide tubes (300, 400, 500) together, the ribs (160, 170) can further enhance water flow around the guide tubes and above the flow channel (135), thereby enhancing water flow through the multi-stage cover (100) and the turbine (200) at the flow channel cross section of the multi-stage cover and the turbine. Therefore, the ribs (160, 170) can help increase the power output of the fluid power turbine (200). Each rib (160, 170) may extend upward from an outer surface (334, 434, 534) of the draft tube (300, 400, 500) between the inlet (110) and the outlet (120) of the multi-stage cover (100). In practice, the upstream end (172) of the rib (160, 170) may be arranged around the inlet (320) of the inlet draft tube (300), while the downstream end (174) of the rib (160, 170) may be arranged around the outlet (530) of the outlet draft tube (500).

[0061] In one embodiment, the inner drainage tube (300) may include a connection member (370) that can extend upward from the outer surface (334), the intermediate drainage tube (400) may include a connection member (470) that can extend upward from the outer surface (434), and the outer drainage tube (500) may include a connection member (580) that can extend upward from the outer surface (534). The connection members (370, 470, 580) can be secured to the outer surfaces (334, 434, 534) of the drainage tubes (300, 400, 500) using suitable mechanical fasteners or other known techniques (e.g., by welding). It should also be noted that the connection members (370, 470, 580) can be integrally formed with the peripheral wall (312, 412, 512).

[0062] As in Figure 7As best shown in FIG. 1 , each upper rib (160, 170) may include an upstream segment (176) that may extend upward from an outer surface (334, 434) located between an inlet (320) of the inlet draft tube (320) and an intermediate draft tube (400), and a downstream segment (180) that may extend upward from an outer surface (434, 534) located between an intermediate draft tube (400) and an outlet (530) of the outlet draft tube (500). As shown, the downstream segment (180) may extend from the upstream segment (176) at a divergent angle (θ7). Thus, the downstream segment (180) may be inclined outwardly at an angle from a central axis (X) of the draft tubes (300, 400, 500). In one embodiment, each upper rib (160, 170) may include a lower segment (182) for connecting to the peripheral wall (312), a lower segment (184) for connecting to the peripheral wall (412), and a lower segment (186) for connecting to the peripheral wall (512). In practice, the lower segment (182) may be fixed to a connecting member (370) extending from the peripheral wall (312), the lower segment (184) may be fixed to a connecting member (470) extending from the peripheral wall (412), and the lower segment (186) may be fixed to a connecting member (580) extending from the peripheral wall (512). The lower segments (182, 184, 186) of the upper ribs (160, 170) may be fixed to the connecting members (370, 470, 580) using suitable mechanical fasteners or other known techniques (e.g., by welding). It should also be noted that the upper ribs (160, 170) can be integrally formed with the peripheral wall (312, 412, 512). The upper ribs (160, 170) can take any shape, size, or configuration, as long as the upper ribs are capable of connecting at least some of the stages or draft tubes together, as long as the upper ribs are capable of enhancing water flow over the draft tubes, and / or as long as water can flow over the draft tubes with as few longitudinal obstructions as possible. For example, in one embodiment, the upper ribs (160, 170) can have a hydraulic profile at least partially along the water flow direction (WF).

[0063] In one embodiment, the height (H) of the multi-stage cover (100) may be between about 1 meter and about 10 meters, between about 2 meters and about 6 meters, or between about 3 meters and about 5 meters. For example, the overall height (H1) of the inlet draft tube (300) may be between about 1 meter and about 10 meters, between about 2 meters and about 6 meters, or between about 3 meters and about 5 meters, the overall height (H2) of the intermediate draft tube (400) may be between about 1 meter and about 10 meters, between about 2 meters and about 6 meters, or between about 3 meters and about 5 meters, and the overall height (H3) of the outlet draft tube (500) may be between about 1 meter and about 10 meters, between about 2 meters and about 6 meters, or between about 3 meters and about 5 meters. In addition, as described above, the height (Hi1) at the inlet (320) of the inlet draft tube (300) may be slightly greater than the height (Ho1) at the outlet (330). For example, the height (Hi1) may be greater than the height (Ho1) at the outlet (330) by more than about 104%, greater than about 108%, or greater than about 112%. In addition, the height of the intermediate draft tube (400) may decrease along the length (L2) of the intermediate draft tube or along the direction of water flow (WF). For example, the height (Hi2) at the inlet (420) may be greater than the height (Ho2) at the outlet (430) by more than about 104%, greater than about 108%, greater than about 112%, or greater than about 115%. In addition, in one case, the height Ho3 at the outlet (530) may be greater than the height Ho2 at the outlet (430) and may substantially correspond to the height Hi2 at the inlet (420) of the intermediate draft tube (400). In one embodiment, the height (Hi2) at the inlet (420) of the intermediate drainage tube (400) may substantially correspond to the height (Hi1) at the inlet (320) of the inlet drainage tube (300), and the height (Ho2) at the outlet (430) of the intermediate drainage tube (400) may substantially correspond to the height (Ho1) at the outlet (430) of the inlet drainage tube (300).

[0064] In one embodiment, the width (Wi) at the entrance (110) can be between about 1 meter and about 10 meters, between about 2 meters and about 6 meters, or between about 3 meters and about 5 meters, and the width (Wo) at the exit (120) can be between about 2 meters and about 20 meters, between about 8 meters and about 15 meters, or between about 10 meters and about 13 meters.

[0065] In one embodiment, the width (Wi) at the inlet (110) may substantially correspond to the height (H) of the multi-stage cover portion (100), and the width (Wo) of the multi-stage cover portion (100) at the outlet (120) may be greater than the height (H) of the multi-stage cover portion (100). For example, the width (Wo) at the outlet (120) may be at least about 1.5 times greater, at least about 2 times greater, or at least about 3 times greater than the height (H) of the multi-stage cover portion (100). In one case, the width (Wo) at the outlet (120) of the multi-stage cover portion (100) may be at least 1.5 times greater, at least about 2 times greater, or at least about 3 times greater than the width (Wi) at the inlet (110).

[0066] In one embodiment, the width (Wi1) at the inlet (320) may substantially correspond to the height (Hi1) at the inlet (320), and the width (Wo1) at the outlet (330) may be greater than the height (Hi1) at the outlet (330). The width (Wo1) at the outlet (330) may be greater than the width (Wi1) at the inlet (320). For example, the width (Wo1) at the outlet (330) may be at least about 105%, at least about 110%, or at least about 115% greater than the width (Wi1) at the inlet (320).

[0067] In one embodiment, the width (Wi2) at the inlet (420) may be greater than the height (Hi2) at the inlet (420), and the width Wi2 at the inlet (420) may be greater than the width (Wo1) at the outlet (330). Moreover, the height (Hi2) at the inlet (420) may be greater than the height (Hi1) at the outlet (330). In addition, the width (Wo2) at the outlet (430) may be greater than the height (Ho2) at the outlet (430). In one case, the width (Wo2) at the outlet (430) may be greater than the width (Wi2) at the inlet (420) by at least about 108%, at least about 115%, at least about 120%, at least about 130%, or at least about 140%.

[0068] In one embodiment, the width (Wi3) at the inlet (520) may be greater than the height (Hi3) at the inlet (520), and the width (Wi3) at the inlet (520) may be greater than the width (Wo2) at the outlet (430). Moreover, the height (Hi3) at the inlet (520) may be greater than the height (Ho2) at the outlet (430). In addition, the width (Wo3) at the outlet (530) may be greater than the height (Ho3) at the outlet (530). For example, the width (Wo3) at the outlet (530) may be at least about 108%, at least about 115%, at least about 120%, at least about 130%, or at least about 140% greater than the width (Wi3) at the inlet (520).

[0069] In one embodiment, the length (L) of the multi-stage shroud (100) may be at least about 10 times greater than the height (H) of the multi-stage shroud (100), at least about 6 times greater than the height (H) of the multi-stage shroud (100), or at least about 4 times greater than the height (H) of the multi-stage shroud (100). It should be noted that due to the special geometry of the multi-stage shroud (100) (i.e., the special geometry of the draft tubes (300), (400), (500)), the ratio between the length (L) and the height (H) of the multi-stage shroud (100) (also referred to as the length to turbine diameter ratio) may be reduced relative to known multi-stage shrouds or draft tube assemblies. For example, the length (L) of the multi-stage shroud (100) may be between about 2 meters and about 4 meters, between about 3 meters and about 6 meters, or between about 4 meters and about 8 meters. It should also be noted that the length (L1) of the inlet draft tube (300) may be at least about 15%, at least about 20%, or at least about 30% of the length (L) of the multi-stage hood portion (100), the length (L2) of the intermediate draft tube (400) may be at least about 5%, at least about 15%, or at least about 25% of the length (L) of the multi-stage hood portion (100), and the length (L3) of the outlet draft tube (500) may be at least about 5%, at least about 15%, or at least about 25% of the length (L) of the multi-stage hood portion (100).

[0070] In one embodiment, the length (L2) of the intermediate draft tube (400) may be less than the length (L1) of the inlet draft tube (100). For example, the length (L2) may be at least less than about 80% of the length (L1), at least less than about 70% of the length (L1), at least less than about 60% of the length (L1), at least less than about 50% of the length (L1), or at least less than about 40% of the length (L1). Similarly, the length (L3) of the outlet draft tube (500) may be less than the length (L1) of the inlet draft tube (300). For example, the length (L3) may be at least less than about 80% of the length (L1), at least less than about 70% of the length (L1), at least less than about 60% of the length (L1), at least less than about 50% of the length (L1), or at least less than about 40% of the length (L1). In one instance, the length (L3) of the outlet draft tube (500) may substantially correspond to the length (L2) of the intermediate draft tube (400).

[0071] Therefore, in one embodiment, as in Figure 1 , Figure 3 and Figure 4 As best shown in , the inlet (110) of the upstream stage in the stage (130) can have a substantially circular cross-section, while the outlet (120) of the downstream stage in the stage (130) can have a substantially elliptical cross-section. In fact, for example, the inlet (320) of the inlet draft tube (300) can have a substantially circular cross-section, the outlet (330) of the inlet draft tube (300) can have a substantially elliptical cross-section, the inlet (420) of the intermediate draft tube (400) can have a substantially elliptical cross-section, the outlet (430) of the intermediate draft tube (400) can have a substantially elliptical cross-section, the inlet (520) of the outlet draft tube (500) can have a substantially elliptical cross-section, and the outlet (530) of the outlet draft tube (500) can have a substantially elliptical cross-section.

[0072] It should also be noted that the cross-section at the outlet (330) of the inner draft tube (300) may be a fraction of the percentage of the cross-section at the inlet (420) of the middle draft tube (400), so that water can flow through the inlet (420) of the middle draft tube. Similarly, the cross-section at the outlet (430) of the middle draft tube (400) may be a fraction of the percentage of the cross-section at the inlet (520) of the outlet draft tube (500), so that water can flow through the inlet (520) of the outlet draft tube.

[0073] It should also be noted that in one embodiment, the thickness of the peripheral wall (312, 412, 512) can vary along the length (L1, L2, L3) of the peripheral wall (or a segment of the length of the peripheral wall), or alternatively, can remain substantially constant along the length (L1, L2, L3) of the peripheral wall. For example, the thickness of the peripheral wall (312) forming the inlet draft tube (300) at the inlet (320) can be greater than the thickness at the outlet (330). It should further be noted that the peripheral wall (312, 412, 512) can be of any shape, size or configuration, so long as the peripheral wall is capable of providing the desired structural and mass flow stability, vortex elimination and fluid separation, particularly, providing the desired structural and mass flow stability, vortex elimination and fluid separation at the flow passage section of the multi-stage cover portion (100).

[0074] As mentioned above, despite Figures 1 to 8 300, 400, 500 are shown, but it should be noted that two or more stages may be provided to form a multi-stage cover. For example, the multi-stage cover may include a first stage draft tube and a second stage draft tube, so that only one water passage can be formed at the inlet of the second stage draft tube. In other cases, more than three stages may also be provided. For example, (n) stages may be provided so that (n-1) water passages are formed between the (n) stages.

[0075] In the following description, the same reference numerals represent similar elements. In addition, for the sake of simplicity and clarity, i.e., in order not to overly clutter the drawings with multiple reference numerals, not all drawings contain reference numerals for all parts and features, and the reference numerals for some parts and features may appear only in one drawing, and the parts and features of the present disclosure shown in other drawings can be easily inferred from these drawings. The embodiments, geometric configurations, materials and / or dimensions shown in the drawings are optional and are given for example purposes only.

[0076] In addition, it should be understood that unless otherwise specified, position descriptions such as "above", "below", "upstream", "downstream", "left", "right", etc. should only be used in the context of the drawings and should not be considered limiting. In addition, the drawings are intended to illustrate certain features of the drainage tube assembly and are not necessarily drawn to scale.

[0077] In order to provide a more concise description, some of the quantitative expressions given herein may be qualified with the term "about." It should be understood that, regardless of whether the term "about" is explicitly used, each quantity given herein is intended to represent the actual given value, and is also used to represent an approximate value based on such given value that one of ordinary skill in the art would reasonably infer, including approximate values ​​resulting from the experimental and / or measurement conditions used for such given value.

[0078] It should be understood that the words and terms used in this article should not be interpreted as limiting, but are for description purposes only. The principles and uses of the teachings of the present disclosure can be better understood with reference to the attached description, drawings and examples. It should be understood that the details set forth herein should not be interpreted as limiting the application of the present disclosure.

[0079] In addition, it should be understood that the present disclosure can be performed or implemented in various ways, and the present disclosure can be implemented in embodiments other than those outlined in the above description. It should be understood that the terms "comprise", "include" and their grammatical variations do not exclude the addition of one or more components, features, steps or entireties or groups thereof, and these terms should be interpreted as illustrating components, features, steps or entireties. If the specification or claims refer to "additional" elements, this does not exclude the presence of more than one additional element. It should be understood that in the case where the claims or specifications refer to "one" or "an" element, such reference should not be interpreted as having only one such element. It should be understood that in the case where the specification states that a component, feature, structure or characteristic "may", "may", "can" or "may" be included, the specific component, feature, structure or characteristic is not necessarily included.

[0080] The descriptions, examples, methods and materials provided in the claims and specification should not be interpreted as limiting, but rather as illustrative only. Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention belongs. It should be understood that the methods described herein may be performed in the order described, or in any suitable order.

[0081] A number of alternative embodiments and examples are described and shown herein. The embodiments of the invention described above are exemplary only. Those of ordinary skill in the art will appreciate the features of the various embodiments and the possible combinations and variations of the components. Those of ordinary skill in the art will further appreciate that any embodiment may be provided in any combination with other embodiments disclosed herein. It should be understood that the present invention may be embodied in other specific forms without departing from the central features of the present invention. Therefore, the examples and embodiments of the present invention are considered to be illustrative rather than restrictive in all respects, and the present invention is not limited to the details given herein. Therefore, although specific embodiments have been shown and described, many modifications are still conceivable. Therefore, the scope of the present invention is intended to be limited by the scope of the appended claims.

Claims

1. A multi-stage cover portion for receiving at least a portion of a fluid power turbine, the fluid power turbine comprising a hub and blades, the blades extending radially from the hub, the multi-stage cover portion comprising: Entrance; exit; as well as a plurality of discrete stages extending between the inlet and the outlet for receiving the fluid kinetic turbine therein, the plurality of discrete stages defining a water flow passage for flowing water therethrough in a water flow direction from the inlet toward the outlet; wherein the plurality of discrete stages define a substantially constant height along the direction of water flow; wherein the cover portion further comprises a reinforcement structure extending upwardly from the plurality of discrete stages, the reinforcement structure being adapted to promote water flow around the plurality of discrete stages, wherein at least one of the plurality of discrete stages defines a width that increases nonlinearly along the direction of the water flow, wherein the plurality of discrete stages include an inlet drainage tube, an intermediate drainage tube, and an outlet drainage tube, and Wherein, the multi-stage cover portion further includes an external reinforcement structure, which is used to reinforce the multiple discrete stages and extends from the multiple discrete stages, and the external reinforcement structure includes a plurality of spaced-apart upper ribs, each of which extends upward from the outer surface of the inlet guide tube, the outer surface of the intermediate guide tube, and the outer surface of the outlet guide tube.

2. The multi-stage cover portion according to claim 1, wherein: The inlet drainage tube comprises: inlet drainage tube inlet; an inlet drainage tube outlet; and An inlet peripheral wall extends between the inlet drainage pipe inlet and the inlet drainage pipe outlet and defines an inlet water flow channel, wherein the inlet water flow channel is used to allow water to flow through the inlet water flow channel from the inlet drainage pipe inlet toward the inlet drainage pipe outlet along the water flow direction, and the inlet peripheral wall includes an inner surface and an outer surface.

3. The multi-stage cover portion according to claim 2, wherein: The intermediate drainage tube comprises: an intermediate drainage tube inlet configured to receive the inlet drainage tube outlet; intermediate drainage tube outlet; and An intermediate peripheral wall extends between the intermediate drainage tube inlet and the intermediate drainage tube outlet and defines an intermediate water flow channel, wherein the intermediate water flow channel is used to allow water to flow through the intermediate water flow channel from the intermediate drainage tube inlet toward the intermediate drainage tube outlet along the water flow direction, and the intermediate peripheral wall includes an inner surface and an outer surface.

4. A multi-stage cover portion according to claim 3, comprising a first water passage at the inlet of the intermediate drainage pipe, wherein the first water passage is formed between the outer surface of the inlet outer wall and the inner surface of the intermediate outer wall to allow water to flow from the inlet of the intermediate drainage pipe toward the outlet of the intermediate drainage pipe through the first water passage.

5. The multi-stage cover portion according to claim 4, wherein: The cross section at the inlet of the intermediate drainage tube is larger than the cross section at the outlet of the inlet drainage tube.

6. The multi-stage cover portion according to claim 5, wherein: The first water passage extends along a periphery of the inlet draft tube inlet.

7. The multi-stage cover portion according to claim 3, wherein: The outlet drainage tube comprises: an outlet drainage tube inlet configured to receive the intermediate drainage tube outlet; an outlet drainage tube outlet; and An outlet peripheral wall extends between the outlet drainage pipe inlet and the outlet drainage pipe outlet and defines an outlet water flow channel, wherein the outlet water flow channel is used to allow water to flow through the outlet water flow channel from the outlet drainage pipe inlet toward the outlet drainage pipe outlet along the water flow direction, and the outlet peripheral wall includes an inner surface and an outer surface.

8. The multi-stage cover portion according to claim 7 further comprises a second water passage at the inlet of the outlet draft tube, wherein the second water passage is formed between the outer surface of the intermediate peripheral wall and the inner surface of the outlet peripheral wall to allow water to flow from the inlet of the outlet draft tube toward the outlet of the outlet draft tube through the second water passage.

9. The multi-stage cover portion according to claim 8, wherein: The cross section at the inlet of the outlet drainage tube is larger than the cross section at the outlet of the intermediate drainage tube.

10. The multi-stage cover portion according to claim 8, wherein: The second water passage extends along the periphery of the intermediate draft tube inlet.

11. The multi-stage cover portion according to claim 7, wherein: The intermediate drainage tube defines an intermediate drainage tube width, and the intermediate drainage tube width increases along the water flow direction according to a first nonlinear relationship.

12. The multi-stage cover portion according to claim 7, wherein: The outlet drainage tube defines an outlet drainage tube width, and the outlet drainage tube width increases along the water flow direction according to a second nonlinear relationship.

13. The multi-stage cover portion according to claim 12, wherein: The outlet drainage tube width increases from the outlet drainage tube inlet toward the outlet drainage tube outlet.

14. The multi-stage cover portion according to claim 7, wherein: The inlet draft tube defines an inlet draft tube length and an inlet draft tube width, and the inlet draft tube width increases along a segment of the inlet draft tube length according to a third non-linear relationship.

15. The multi-stage cover portion according to claim 7, wherein: The width of the multi-stage cover portion at the outlet is greater than the height of the multi-stage cover portion at the outlet.

16. The multi-stage cover portion of claim 7, further comprising a base for supporting the plurality of discrete stages thereon.

17. The multi-stage cover portion according to claim 16, wherein: The base defines an open configuration for enabling water to flow beneath the plurality of discrete stages along their lengths in the direction of water flow.

18. The multi-stage cover portion according to claim 17, wherein: The base includes a main frame for supporting the plurality of discrete stages, and a plurality of support legs extending downwardly from the main frame.

19. The multi-stage cover portion according to claim 17, wherein: The base further includes a leveling mechanism configured to level the plurality of discrete stages relative to the water flow direction.

20. The multi-stage cover portion according to claim 7, further comprising a hub support structure extending from the plurality of discrete stages for supporting at least a portion of the fluid turbine in the plurality of discrete stages, the hub support structure comprising a plurality of spaced-apart hub support members, each of the support members extending between an inner surface of the inlet draft tube and the hub.

21. The multi-stage cover portion according to claim 1, further comprising an internal reinforcement structure for reinforcing the plurality of discrete stages, the internal reinforcement structure comprising a plurality of spaced-apart struts, each of the struts extending between a lower portion of an inner surface of the outlet draft tube and an upper portion of an inner surface of the outlet draft tube.

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