BACKGROUND
The present disclosure relates to shrouded fluid turbines that use an impeller to generate power from the passage of a fluid stream, such as a wind stream or a water stream. The fluid turbine contains moveable aerodynamic components or members that can be used to control the impeller speed or to minimize dynamic loads experienced in high fluid velocity conditions.
Conventional horizontal axis wind turbines (HAWTs) used for power generation have two to five open blades arranged like a propeller, the blades being mounted to a horizontal shaft attached to a gear box which drives a power generator. The blades generally rotate at a rotational speed of about 10 to 22 rpm, with tip speeds reaching over 200 mph. HAWTs will not exceed the Betz limit of 59.3% efficiency in capturing the potential energy of the wind passing through it.
A shrouded wind turbine is a type of HAWT. Shrouded turbines comprise a shroud that surrounds the blades. The ducted nature of the shroud allows a rotor/stator assembly to be used to capture the wind energy. Generally, the stator is upstream of the rotor. Upstream stator vanes direct incident wind onto the rotor blades. However, the stator may also be located downstream of the rotor.
Wind turbines are generally configured to be most efficient within a given range of wind speeds. When the fluid load on the turbine is too high (i.e. high winds), the wind turbine blades can be stressed beyond their tolerances and crack or break.
BRIEF DESCRIPTION
Disclosed herein are shrouded fluid turbines that include moveable or mobile components to reduce loads and/or control the impeller speed. Among other things, these components assist in generating various amounts of energy and in controlling fluid flows. This is beneficial such as for keeping the power generator within its cut in/cut out range, reducing the possibility of damage to the turbine. Other benefits may be set forth below.
In this regard, disclosed in certain embodiments is a shrouded fluid turbine that includes an impeller and a turbine shroud surrounding the impeller. The impeller includes a stator and a rotor. The stator and/or the rotor has one or more moveable components/members for controlling the fluid stream in the fluid turbine.
The stator may be made from a stator hub and one or more of stator vanes extending radially from the stator hub. The moveable component is part of at least one of the stator vanes. The moveable component may include a stationary member and a first moveable member which are located longitudinally to each other along the stator hub. The first moveable member is able to pivot relative to the stationary member about a radial axis.
In some embodiments, the stationary member defines a leading edge of the stator vane. The stationary member and the first moveable member are pivotally engaged along a back end of the stationary member and a front end of the first moveable member. The first moveable member defines a trailing edge of the stator vane.
The stator vane may also have a plurality of moveable members, a front end of each moveable member being pivotally engaged to a back end of another member. The front end of one moveable member is pivotally engaged to a back end of the stationary member.
In other embodiments, the stationary member defines the leading edge and a trailing edge of the stator vane. The first moveable member forms a portion of an upwind or downwind surface of the stator vane, the radial axis of the first moveable member being located in a central portion of the stationary member. In more specific embodiments, the stator vane has two moveable members. The first moveable member forms a portion of the upwind surface of the stator vane, and the second moveable member forms a portion of the downwind surface of the stator vane. The radial axes of both moveable members are located in the central portion of the stationary member.
In other embodiments, the stationary member defines the leading edge and a trailing edge of the stator vane. The first moveable member forms a portion of an upwind or downwind surface of the stator vane. The first moveable member is located along the trailing edge of the stationary member and may be deployed downstream of the trailing edge of the stator vane. In some embodiments, the first moveable member is deployed by rotating about a radial axis which is located along the trailing edge of the stationary member. In other embodiments, the first moveable member is deployed by extending longitudinally outwards from the trailing edge of the stationary member.
In particular embodiments, the first moveable member has a nonlinear edge. For example, the nonlinear edge may have a sawtooth, sinusoidal, or curved shape. In other embodiments, the first moveable member may have a plurality of fluid passages between an upper surface and a lower surface, or may have an asymmetrical shape along a radial length of the stator vane.
Also disclosed are embodiments wherein the stator is made up of a stator hub and one or more stator vanes extending radially from the stator hub. At least one of the stator vanes includes the moveable component. The moveable component may be made from a leading edge member, an upper surface segment, a lower surface segment, and a trailing edge member. A back end of the leading edge member is longitudinally engaged with a forward edge of the upper surface segment and a forward edge of the lower surface segment. A front end of the trailing edge member is longitudinally engaged with a rear edge of the upper surface segment and a rear edge of the lower surface segment. The upper surface segment and the lower surface segment can move longitudinally relative to the leading edge member and the trailing edge member to change the camber of the stator vane. Either the leading edge member or the trailing edge member may be fixed to the stator hub.
The stator vane may include a plurality of linear motion actuators located within either the leading edge member or the trailing edge member. Cables extend from the linear motion actuators to an upper surface and a lower surface of the other edge member (i.e. the trailing edge member or the leading edge member, respectively).
In different embodiments, the stator vane contains a drive pulley located within one of the edge members and a cable engaging the drive pulley. Both free ends of the cable are attached to one or more fixed points within the other edge member. A constant distance exists between the drive pulley and the one or more fixed points. The upper surface segment and the lower surface segment engage the cable on opposite sides of the drive pulley.
In yet other embodiments, linear motion actuators are used to engage the back end of the leading edge member to the forward edge of the upper surface segment and the forward edge of the lower surface segment, and to engage the front end of the trailing edge member with the rear edge of the upper surface segment and the rear edge of the lower surface segment.
Disclosed in some further embodiments is a rotor that comprises the moveable component. The moveable component includes a hollow rotor blade (i.e. a stationary member) and a gate (i.e. a moveable member). An upstream surface and a downstream surface of the hollow rotor blade each have a fluid passage. Located within the hollow rotor blade is the gate, which includes an insert for each fluid passage operatively connected to a pivoting arm, the pivoting arms engaging a weighted member which engages a tension member. The pivoting arms and the tension member cooperate so that below a given fluid velocity threshold, the inserts align with the fluid passages to prevent fluid flow through the fluid passages, and above the given fluid velocity threshold, the inserts are removed from the fluid passages to create an aperture through the hollow rotor blade. Additionally, a plurality of inserts may be mounted on a plate that is connected to a pivoting arm.
The fluid turbine may further include an ejector shroud that is substantially downstream of the turbine shroud and coaxial with the turbine shroud.
The present disclosure also relates to methods for controlling the load experienced by an impeller of a fluid turbine. The fluid turbine includes an impeller for generating power from a fluid stream, and a turbine shroud surrounding the impeller. The impeller includes a stator and a rotor. The stator and/or the rotor contains a moveable component. The moveable component can be moved between a first position and a second position to control the load. The motion of the moveable component may be actively controlled by the user, or the motion may occur passively (i.e. without explicit instructions from the user) as the result of a change in ambient conditions.
These and other non-limiting features or characteristics of the present disclosure will be further described below.
BRIEF DESCRIPTION OF THE DRAWINGS
The following is a brief description of the drawings, which are presented for the purposes of illustrating the disclosure set forth herein and not for the purposes of limiting the same.
FIG. 1 is a front left perspective view of an embodiment of a shrouded fluid turbine of the present disclosure.
FIG. 2 is a rear right perspective view of the shrouded fluid turbine of FIG. 1.
FIG. 3 is a cross-sectional view of the shrouded fluid turbine of FIG. 1 taken along line 3′-3′.
FIG. 4 is a smaller view of FIG. 3 showing areas of magnification.
FIG. 5 and FIG. 6 are magnified views of the mixing lobes of the fluid turbine of FIG. 4.
FIG. 7 is a rear view of the shrouded fluid turbine of FIG. 1. The blades of the impeller are removed from this figure so that other aspects of the fluid turbine can be more clearly seen and explained.
FIG. 8 is a front view of a turbine stator comprising stator vanes with a stationary member and at least one moveable member.
FIG. 9 is a top view of the stator vane of FIG. 8, having a stationary member and only one moveable member (i.e. flap).
FIG. 10 is a cross-sectional view of the stator vane of FIG. 9 with the flap located at a zero flap angle.
FIG. 11 is a cross-sectional view of the stator vane of FIG. 9 with the flap located at a positive flap angle.
FIG. 12 is a CFD generated graph showing the percentage of power produced by the rotor as a function of the stator flap angle.
FIG. 13 is an exploded view of a stator vane having an outer cover, a stationary member, and a plurality of moveable members.
FIG. 14 is a shrouded fluid turbine mounting a stator having the stator vane of FIG. 13.
FIG. 15 is a magnified view of the stator vane mounted on the shrouded fluid turbine of FIG. 14.
FIG. 16 is a shrouded fluid turbine mounting a set of stator vanes in a closed or stowed state.
FIG. 17 is a magnified view of the stator vane of FIG. 16, illustrating a stator having a moveable member (flap) that rotates along the trailing edge of the stationary member.
FIG. 18 is a shrouded fluid turbine showing the stator vanes of FIG. 17 in an open or deployed state.
FIG. 19 is a magnified view of the stator vane of FIG. 18 with the flap in an open or deployed state. Here, the flap rotates to the deployed state.
FIG. 20 is a shrouded fluid turbine showing the stator vanes of FIG. 17 in an open or deployed state.
FIG. 21 is a magnified view of the stator vane of FIG. 20 with the flap in an open or deployed state. Here, the flap extends out to the deployed state.
FIG. 22 is a shrouded fluid turbine mounting a variant of the stator vane of FIG. 16 in an open or deployed state.
FIG. 23 is a magnified view of the stator vane of FIG. 22, where the trailing edge of the flap has a sawtooth edge.
FIG. 24 is a shrouded fluid turbine mounting another variant of the stator vane of FIG. 16 in an open or deployed state.
FIG. 25 is a magnified view of the stator vane of FIG. 24, where a plurality of fluid passages run through the flap.
FIG. 26 is a shrouded fluid turbine mounting another variant of the stator vane of FIG. 16 in an open or deployed state.
FIG. 27 is a magnified view of the stator vane of FIG. 26, where the flap has an asymmetric shape, such as the triangular shape shown here.
FIG. 28 is a front view of a shrouded fluid turbine where the flaps on the stator vanes are partially deployed.
FIG. 29 is a side cut-away view of a shrouded fluid turbine mounting another stator vane.
FIG. 30 is a magnified view of the stator vane of FIG. 29, which comprises two moveable members (i.e. flaps) with a rotational axis in the central portion of the stationary member.
FIG. 31 is a side view of a stator vane having a leading edge member, a trailing edge member, an upper surface segment, and a lower surface segment. The stator vane is depicted in a positive camber position.
FIG. 32 is a magnified view of the connection between the leading edge member, upper surface segment, and lower surface segment of FIG. 31.
FIG. 33 is a side view of the stator vane of FIG. 31 in a neutral position.
FIG. 34 is a side view of the stator vane of FIG. 31 in a negative camber position.
FIG. 35 is a perspective view of the stator vane of FIG. 31.
FIG. 36 is a magnified view of FIG. 35 showing a method of constructing the stator vane of FIG. 31.
FIG. 37 is a cut-away side view of the stator vane of FIG. 31.
FIG. 38 is a magnified view of FIG. 37 showing another method of constructing the stator vane of FIG. 31.
FIG. 39 is a side cross-sectional view of another method of constructing the stator vane of FIG. 31.
FIG. 40 is a side view of another method of constructing the stator vane of FIG. 31.
FIG. 41 is a cut-away side view of a stator using stator vanes of FIG. 31 mounted on a shrouded fluid turbine.
FIG. 42 is a magnified view of the stator vanes of FIG. 41.
FIG. 43 is a perspective exterior view of a rotor having fluid passages and a moveable component.
FIG. 44 is a magnified view of a blade of the rotor of FIG. 43 in a closed state, with inserts inserted in the fluid passages.
FIG. 45 is a magnified view of a blade of the rotor of FIG. 43 in an open state, with inserts removed from the fluid passages.
FIG. 46 is a duplicate of the rotor of FIG. 43.
FIG. 47 is a magnified, cut-away view of the rotor blade.
FIG. 48 is a side cross-sectional view showing the moveable component in the interior of the rotor blade in a closed state.
FIG. 49 is a side cross-sectional view showing the moveable component in the interior of the rotor blade in an open state.
DETAILED DESCRIPTION
A more complete understanding of the components, processes, and apparatuses disclosed herein can be obtained by reference to the accompanying figures. These figures are intended to demonstrate the present disclosure and are not intended to show relative sizes and dimensions or to limit the scope of the present disclosure.
Although specific terms are used in the following description, these terms are intended to refer to particular structures in the drawings and are not intended to limit the scope of the present disclosure. It is to be understood that like numeric designations refer to components of like function.
The term “about” when used with a quantity includes the stated value and also has the meaning dictated by the context. For example, it includes at least the degree of error associated with the measurement of the particular quantity. When used in the context of a range, the term “about” should also be considered as disclosing the range defined by the absolute values of the two endpoints. For example, the range “from about 2 to about 4” also discloses the range “from 2 to 4.”
A Mixer-Ejector Power System (MEPS) provides an improved means of generating power from fluid streams such as wind currents. A primary shroud contains an impeller which extracts power from a primary fluid stream. A mixer-ejector pump is included that ingests flow from the primary fluid stream and secondary flow, and promotes turbulent mixing. This enhances the power system by increasing the amount of fluid flow through the system, reducing back pressure on turbine blades, and reducing noise propagating from the system.
The term “impeller” is used herein to refer to any assembly in which one or more blades are attached to a shaft and able to rotate, allowing for the generation of power or energy from fluid rotating the blades. Examples of impellers include a propeller or a rotor/stator assembly. Any type of impeller may be enclosed within the turbine shroud in the fluid turbine of the present disclosure.
The front of the fluid turbine indicates the direction from which fluid enters the fluid turbine. The leading edge of a turbine shroud may be considered the front of the fluid turbine, and the trailing edge of an ejector shroud may be considered the rear of the fluid turbine. A first component of the fluid turbine located closer to the front of the turbine may be considered “upstream” of a second component located closer to the rear of the turbine. Put another way, the second component is “downstream” of the first component.
The present disclosure relates to a shrouded fluid turbine including an impeller, a turbine shroud that surrounds the impeller, and an optional ejector shroud downstream of and coaxial with the turbine shroud. Mixing elements may be present on the trailing edge of the turbine shroud. In particular, the shrouded fluid turbine includes one or more moveable mechanisms or members for reducing loads and/or controlling rotor speed. The members may be present on one or more stator vanes, and/or on one or more rotor blades of the impeller.
The instant disclosure relates to several findings. First, it was found that using a rotor/stator assembly as an impeller in a shrouded fluid turbine achieves high efficiency when the stator comprises stator vanes that have moveable components allowing the camber of the vanes to be changed. This allows the stator vanes to continue directing incident fluid onto the rotor blades in varying fluid speeds and conditions. Separately, it was found that various rotor configurations could also increase control of the fluid turbine in different fluid velocity conditions. The shrouded fluid turbine itself includes a turbine shroud surrounding the impeller and sometimes an ejector shroud downstream of and coaxial with the turbine shroud. The turbine shroud includes a plurality of mixing lobes on a trailing edge, such that the trailing edge has a circular crenellated shape. The mixing lobes may extend into an inlet end of the ejector shroud.
The fluid turbine can be any type of shrouded fluid turbine, for example, a wind turbine or a water turbine. In this regard, the aerodynamic principles of a wind turbine also apply to hydrodynamic principles in a water turbine, etc.
Initially, it may be helpful to describe a fluid turbine in which the stators, rotors, and shrouds of the present disclosure can be used, to provide context for an further explanation of their aspects.
A shrouded fluid turbine is shown in FIGS. 1-7. The shrouded fluid turbine 100 comprises an aerodynamically contoured turbine shroud 110, an aerodynamically contoured nacelle body 150, an impeller 140, and an aerodynamically contoured ejector shroud 120. The turbine shroud 110 includes a front end 112 and a rear end 114. The ejector shroud 120 includes an inlet end 122 and an exhaust end 124. Support members 106 connect the turbine shroud 110 to the ejector shroud 120.
The impeller 140 surrounds the nacelle body 150. Here, the impeller is a rotor/stator assembly comprising a stator 142 having stator vanes 144 and a rotor 146 having rotor blades 148. The rotor 146 is shown here as being downstream and “in-line” with the stator vanes 144. Put another way, the leading edges of the rotor blades are substantially aligned with the trailing edges of the stator vanes. The impeller is also shown here located at the front end 112 of the turbine shroud. The rotor blades are held together by a rotor hub, and the rotor 146 is rotationally engaged to the nacelle body 150. In particular embodiments, the stator has nine stator vanes 144, and the rotor has seven rotor blades 148. The impeller 140 is configured to be exposed to ambient fluid flow. Put another way, in these embodiments there are no components which hinder the impeller from direct exposure to ambient fluid flow. The impeller is also a single stage turbine, and does not contain multiple stages.
The nacelle body 150 is connected to the turbine shroud 110 through the stator 142, or by other means. The nacelle comprises an inlet 154, an outlet 156, and a central channel 152 between the inlet 154 and the outlet 156 that extends through the nacelle body 150. The stator 142 and rotor 144 are shown here as engaging the nacelle body 150 at the front end 112 of the turbine shroud, or in other words at the inlet 154 of the nacelle body. It is contemplated that the nacelle body and the stator can be made as one integral piece, or as two separate components that are then joined together. The nacelle body can contain the power generator (not shown).
Some variations on the placement of the rotor and stator are not shown here, but are contemplated as being within the scope of this disclosure. In one variation, the stator 142 is downstream of the rotor 144. In another variation, the stator 142 and rotor 144 engage the nacelle body 150 at the rear end 114 of the turbine shroud (i.e. at the outlet 156 of the nacelle body), or possibly at the inlet end 122 of the ejector shroud (depending on the length of the nacelle body). In such embodiments, the stator may be connected to the ejector shroud 120 instead of the turbine shroud 110.
The turbine shroud has the cross-sectional shape of an airfoil with the suction side (i.e. low pressure side) on the interior of the shroud. The turbine shroud may be configured to provide a rotor inlet velocity within the turbine shroud of at least 2.5 times the free stream fluid velocity to which the fluid turbine is exposed. The rear end 114 of the turbine shroud also has mixing lobes 116. The mixing lobes extend downstream beyond the rotor blades. Put another way, the trailing edge 118 of the turbine shroud is formed from a plurality of mixing lobes. The rear or downstream end of the turbine shroud is shaped to form two different sets of mixing lobes 116. High energy mixing lobes 117 extend inwardly towards the central axis 105 of the mixer shroud. Low energy mixing lobes 119 extend outwardly away from the central axis 105. These mixing lobes are more easily seen in FIG. 2.
A mixer-ejector pump (indicated by reference numeral 101) comprises an ejector shroud 120 downstream of and coaxial with the turbine shroud 110. In some example embodiments, the mixing lobes 116 may extend downstream and into an inlet end 122 of the ejector shroud 120. Put another way, the rear end 114 of the turbine shroud 110 may extend into the inlet end 122 of the ejector shroud 120. In accordance with other embodiments, the mixing lobes 116 may be separated from the inlet end 122 of the ejector shroud 120 by a gap (not shown).
The turbine shroud's entrance area and exit area will be equal to or greater than that of the annulus occupied by the impeller. The internal flow path cross-sectional area formed by the annulus between the nacelle body and the interior surface of the turbine shroud is aerodynamically shaped to have a minimum cross-sectional area at the plane of the turbine and to otherwise vary smoothly from their respective entrance planes to their exit planes. The ejector shroud entrance area is greater than the exit plane area of the turbine shroud.
Several optional features may be included in the shrouded fluid turbine. A power take-off, in the form of a wheel-like structure, can be mechanically linked at an outer rim of the impeller to a power generator. The generator may be located upwind or downwind of the rotor/stator. Sound absorbing material can be affixed to the inner surface of the shrouds, to absorb and prevent propagation of the relatively high frequency sound waves produced by the turbine. The fluid turbine can also contain blade containment structures for added safety. The shrouds may have an aerodynamic contour in order to enhance the amount of flow into and through the system. The inlet and outlet areas of the shrouds may be non-circular in cross section such that shroud installation is easily accommodated by aligning the two shrouds. A swivel joint may be included on a lower outer surface of the turbine for mounting on a vertical stand/pylon, allowing the turbine to be turned into the fluid in order to maximize power extraction. Vertical aerodynamic stabilizer vanes may be mounted on the exterior of the shrouds to assist in keeping the turbine pointed into the fluid.
The area ratio of the ejector pump, as defined by the ejector shroud 120 exit area over the turbine shroud 110 exit area, may be in the range of about 1.5 to about 3.0. The number of mixing lobes can be between 6 and 28. The height-to-width ratio of the lobe channels may be between about 0.5 and about 4.5. The mixing lobe penetration may be between about 50% and about 80%. The nacelle body 150 plug trailing edge angles may be thirty degrees or less. The length to diameter (L/D) of the overall fluid turbine may be between about 0.5 and about 1.25.
Referring now to FIGS. 3-7, the turbine shroud 110 shown here has a set of nine high energy mixing lobes 117 that extend inwards toward the central axis 105 of the turbine. The turbine shroud also has a set of nine low energy mixing lobes 119 that extend outwards away from the central axis. The high energy mixing lobes alternate with the low energy mixing lobes around the trailing edge 118 of the turbine shroud. The impeller 140, turbine shroud 110, and ejector shroud 120 are coaxial with each other, i.e. they share a common central axis 105.
The trailing edge 118 of the turbine shroud 110 has a circular crenellated shape. The trailing edge can be described as including several inner circumferentially spaced arcuate portions 181 which each have the same radius of curvature. Those inner arcuate portions 181 are evenly spaced apart from each other. The inner arcuate portions 181 are generally located on an inner circle 192 having radius of curvature 197. Between portions are several outer arcuate portions 183, which each have the same radius of curvature. The outer arcuate portions 183 are generally located on an outer circle 190 having radius of curvature 195. The radius of curvature 197 for the inner arcuate portions 181 is different from the radius of curvature 195 for the outer arcuate portions 183, but the inner arcuate portions and outer arcuate portions have the same center (i.e. along the central axis 105). The outer radius of curvature 195 is generally greater than the inner radius of curvature 197. The inner arcuate portions 181 and the outer arcuate portions 183 are then connected to each other by radially extending portions 185. This results in a circular crenellated shape. The term “crenellated” as used herein does not require the inner arcuate portions, outer arcuate portions, and radially extending portions to be straight lines, but instead refers to the general up-and-down or in-and-out shape of the trailing edge. This crenellated structure forms two sets of mixing lobes, high energy mixing lobes 117 and low energy mixing lobes 119. Also shown in FIG. 7 is the leading edge (not visible) of the turbine shroud, indicated here as dotted circle 194, has a front radius of curvature 199. The front radius of curvature 199 can be greater than, substantially equal to, or less than the outer radius of curvature 195.
Referring now to FIG. 3, free stream fluid (indicated generally by arrow 160, and which may be, for example, air or water) passing through the stator 142 has its energy extracted by the rotor 146. High energy fluid indicated by arrow 162 bypasses the turbine shroud 110 and stator 142, flows over the exterior of the turbine shroud 110, and is directed inwardly by the high energy mixing lobes 117. The low energy mixing lobes 119 cause the low energy fluid exiting downstream from the rotor 146 to be mixed with the high energy fluid 162.
Referring now to FIG. 5, a tangent line 171 is drawn along the interior trailing edge indicated generally at 172 of the high energy mixing lobe 117. A rear plane 173 of the turbine shroud 110 is present. A line 174 is formed normal to the rear plane 173 and tangent to the point 175 where a low energy mixing lobe 119 and a high energy mixing lobe 117 meet. An angle Ø2 is formed by the intersection of tangent line 171 and line 174. This angle Ø2 is between 5 and 65 degrees. Put another way, a high energy mixing lobe 117 forms an angle Ø2 between 5 and 65 degrees relative to a longitudinal axis of the turbine shroud 110. In particular embodiments, the angle Ø2 is from about 35° to about 50°.
In FIG. 7, a tangent line 176 is drawn along the interior trailing edge indicated generally at 177 of the low energy mixing lobe 119. An angle Ø is formed by the intersection of tangent line 176 and line 174. This angle Ø is between 5 and 65 degrees. Put another way, a low energy mixing lobe 119 forms an angle Ø between 5 and 65 degrees relative to a longitudinal axis of the turbine shroud 110. In particular embodiments, the angle Ø is from about 35° to about 50°.
Mixing lobes may be present on the turbine shroud. As shown in FIG. 2, the ejector shroud 120 has a ring airfoil shape and does not have mixing lobes. If desired, though, mixing lobes may also be formed on a trailing edge 128 of the ejector shroud.
In one aspect of the present disclosure, stators comprising moveable components or members are disclosed. Three types of stators are considered. In the first type, the stator vane is made of a stationary member and one or more moveable members that extend longitudinally along the length of the stator hub (i.e. in line with the turbine shroud), which allow the camber of the stator vane to be changed. In the second type, the stator vane comprises a base (i.e. stationary member) and a flap (i.e. moveable member) which opens outwardly from the base. In the third type, the middle or central portion of the stator vane is made from two surface segments. By changing the exposed lengths of the central surface segments, the camber of the stator vane can be changed. The stators disclosed herein can be used to control the load experienced by the impeller of the fluid turbine containing the stator. The moveable component is moved between a first position and a second position to control the load.
FIG. 8 is a front view of a stator of the present disclosure. FIG. 9 is a top view of the stator of FIG. 8, looking down into the side of one stator vane, upwind surface of a second stator vane, and the downwind surface of a third stator vane. The stator 200 comprises a stator hub 210 and stator vanes 220 extending radially from the stator hub. The stator hub 210 shown here is formed from a cylindrical sidewall 212 surrounding and defining a central passageway 214. Embodiments are also contemplated where the stator hub is formed from a sidewall and does not have a central passageway. As shown here, the vanes 220 are evenly spaced about the stator hub sidewall 212. In particular embodiments, the stator 200 has nine stator vanes 220.
Each stator vane has a root 222 and a tip 224 at opposite ends of the vane, with a vane length 226 (see FIG. 9) extending from the root to the tip. The vane may have an airfoil shape, or the vane may be symmetrical, as will be further described herein. The stator 200 also has a central longitudinal axis 205 (see FIG. 9), corresponding to the horizontal axis of the shrouded fluid turbine (see reference numeral 105 in FIG. 1).
One example embodiment of a stator of the first type is shown in FIGS. 9-12. Initially, arrow 201 indicates the direction of incoming fluid into the stator. Here, each stator vane 220 is formed from a stationary member 240 (i.e. base) and a first moveable member 260 (i.e. flap). The stationary member 240 and the first moveable member 260 are located longitudinally to each other along the stator hub 210. As depicted here, the stationary base is upstream of the first moveable member, so that the front end 246 of the stationary base 240 defines the leading edge 228 of the stator vane. The stationary base 240 also has a back end 248 opposite the front end 246. The moveable member 260 is downstream of the stationary member 240. In this embodiment, the moveable flap 260 defines the trailing edge 230 of the stator vane, and the stationary member does not define any part of the trailing edge. The stationary base 240 has a root end 242 and a tip end 244, corresponding to the root 222 and the tip 224 of the stator vane. The moveable flap 260 also has a root end 262 and a tip end 264, also corresponding to the root 222 and the tip 224 of the stator vane. The trailing edge 230 of the stator vane 220 is located on a back end 268 of the moveable flap 260. The moveable flap 260 also has a front end 266 opposite the back end 268. The root end 242 of the stationary base 240 is connected to the stator hub 210. The root end 262 of the moveable flap 260 is not connected to the stator hub 210.
The back end 248 of the stationary base and the front end 266 of the moveable flap are pivotally engaged by a connector 280. The connector 280 defines a radial rotational axis 285, or in other words the radial axis 285 is normal to the stator hub 210, which is in the axial direction defined by central longitudinal axis 205. The moveable flap 260 can pivot or rotate relative to the stationary member about this radial axis 285, to change the shape of the stator vane 210 and change the incidence of fluid on the rotor blades downstream of the stator. Generally speaking, the back end 248 of the stationary base and the front end 266 of the moveable flap are shaped to join the base 240 and the flap 260 together, and to allow the flap 260 to pivot relative to the stationary base 240.
The root end 242 of each stator vane stationary member 240 has a pitch angle Ø where the stationary member 240 connects to the stator hub sidewall 212. This root pitch angle is measured between the central longitudinal axis 205 and the chord 252 of the stationary base 240 at the root. This example stator has a non-zero pitch angle Ø, which is measured from the leading edge 228 of the stator, and as a result θ cannot exceed 90 degrees. In embodiments, θ is from greater than 0 to less than 90 degrees. In other embodiments, θ is from 5 to 30 degrees, or from 15 to 45 degrees, or from 30 to 70 degrees.
The stationary member 240 (base) has a length 252 between the root end 242 and the tip end 244. The moveable member 260 (flap) also has a length 272 between the root end 262 and the tip end 264. In embodiments, the length 252 of the stationary base and the length 272 of the moveable flap are equal.
It should be noted that as depicted here, the leading edge 228 of the stator vane is formed from the stationary member 240, while the trailing edge 230 is formed from the moveable member 260. It is also possible that the leading edge 228 of the stator vane is formed from the moveable member 260, while the trailing edge 230 is formed from the stationary member 240. Thus, the stationary member 240 will define either the leading edge or the trailing edge, but will not define both edges at the same time. It should also be noted that with respect to the members making up the stator vane, the terms “front end” and “back end” are intended to denote opposite ends of the member, and should not be construed as defining the position of a given end of the member relative to the other components of the fluid turbine.
Referring now to FIG. 10, each stator vane 220 has a constant chord 232 and cross-section along the length 226 of the vane. Put another way, the vane has a constant pitch angle θ along the length 226 of the vane. In addition, each stationary base 240 has a constant chord 250 and each moveable flap 260 has a constant chord 270. In embodiments, the chord 250 of the stationary base is greater than the chord 270 of the moveable flap. It should be noted that the chord 232 of the stator vane is measured when the chord 250 of the stationary base and the chord 270 of the moveable flap are parallel to each other.
In FIG. 11, the stator vane 320 is shown here with a symmetrical shape. The moveable member 360 is at a positive flap angle. The flap angle is positive when the flap 360 is oriented in the direction of the upper surface 354 of the stationary member 340, and is negative when the flap is oriented in the direction of the lower surface 356 of the stationary member 340. The flap angle θF is measured between the stationary member chord 350 and the moveable member chord 370 at the rotational axis 385.
FIG. 10 and FIG. 11 illustrate the ability of the moveable member 260/360 to rotate about the rotational axis 285/385 of the connector 280/380, or in other words to move relative to the stationary member 240/340. In embodiments, the stator vane flap 260/360 can rotate for an angle θF from minus 25 degrees to plus 25 degrees, the angle being formed between the chord 250/350 of the stationary member and the chord 260/360 of the moveable member at the rotational axis formed by connector 280. In FIG. 10, the flap 260 is at an angle of 0°. These two figures also illustrate a first position and a second position in which the moveable component, i.e. the stator vane, can be moved to control the load experienced by the stator/rotor assembly of the fluid turbine.
Referring to FIG. 9 and FIG. 10, the aspect ratio is the ratio of the length 226 of the stator vane divided by the chord (i.e. breadth) 232 of the stator vane 220. In this embodiment, the chord 232 is constant along the length 226 of the stator vane. However, if the chord 232 varies along the length 226 of the vane, the aspect ratio is determined as the ratio of the length squared divided by the area of the stator vane (i.e. including both the stationary base 240 and the moveable flap 260) when viewed from the top (i.e. the planform of the vane), like the view of FIG. 9. In embodiments, the stator vane 220 has an aspect ratio of from 2 to 30, including from 10 to 25.
All of the stator vane flaps 260 may be set at the same flap angle at any given time. In some embodiments, the stator 200 comprises a single mechanism for rotating the stator vane flaps 260. In other embodiments, each stator vane flap can be independently controlled. It is contemplated that the control mechanism is an active one.
In some versions or embodiments, the control mechanism is sensitive to incident fluid flow properties. Put another way, fluid flow factors such as incident fluid velocity, pressure and temperature are associated with different rotations of the flaps about their rotational axis. Turbine geometry is generally highly dependent on an operational range defined by preselected flow characteristics. For example, by increasing the flap angle in response to an increase in incident flow velocity, the turbine can maintain high efficiency beyond typical off-design thresholds.
In the stators of the present disclosure, the rotation of the moveable member 260 modifies the exit angle of the stator vane 220 independent of the angle of attack. A higher exit angle is required to efficiently direct a high velocity flow onto a rotor, but a high angle attack in a high velocity flow can cause flow separation and other efficiency losses. The addition of the moveable member allows the stator to maintain a low angle of attack while having a freely adjustable exit angle. In other words, the angle of attack on the leading edge 228 is not modified, just the exit angle on the trailing edge 230 of the stator vane flap.
FIG. 12 is a graph showing the values calculated by computational fluid dynamics (CFD) for the percentage of the power generated by the rotor when plotted as a function of the stator flap angle in degrees. The fluid stream in this calculation was in an axial direction. A linear relationship is noted and the line y=2.224X+45.968 is fitted to the values. It is seen that the rotor generated its maximum power at a stator flap angle of 25° . In contrast, a stator flap angle of less than −20° actually caused power to be expended rather than produced.
The embodiment of FIGS. 9-12 contains a stationary member and one moveable member. This design can be generalized to include a stationary member and a plurality of moveable members. The stator vane comprises the stationary member and a plurality of moveable members. The stationary member and the moveable members are arranged longitudinally in a row along the stator hub. The front end of each member is pivotally engaged to the back end of an upstream member. The stationary member can be located in any position in the row.
FIGS. 13-15 illustrate an example of this design, where the stator vane 310 has a total of four segments or members that make up the cross section of an airfoil. The stator vane comprises an outer cover 320 that covers a set of pivotally engaged members that make up the airfoil. The outer cover provides a relatively smooth surface for the air to flow over the airfoil cross section of the stator vane. The outer surface is shown separated from the segments.
Here, the stator vane is shown with the front end 332 of stationary member 330 defining the leading edge 312 of the stator vane. The back end 334 of the stationary member is pivotally engaged with a front end 342 of a first moveable member 340. The back end 344 of the first moveable member is pivotally engaged with a front end 352 of a second moveable member 350. The back end 354 of the second moveable member is pivotally engaged with a front end 362 of a third moveable member 360. The back end 364 of the third moveable member defines the trailing edge 314 of the stator vane. In this embodiment, the stationary member 330 does not make up any part of the trailing edge 314 of the airfoil shape of the stator vane. Similarly, none of the moveable members make up any part of the leading edge 312 of the airfoil shape of the stator vane. Although four segments are shown, the stator vane may be comprised of more or fewer segments.
FIG. 15 is a magnified view showing the stator vane mounted on a nacelle 308 of a wind turbine 300 with the moveable members configured for high camber. The rotor 306 is visible downstream of the stator. The outer cover is not shown for illustration purposes. A root end or distal end of the stationary member 330 is fixedly attached to the nacelle 308. A tip end or proximal end of the stationary member may also be fixedly attached to the turbine shroud (not shown). The nacelle may include a short riser 316 above its surface to which the stator vane is mounted. The first moveable member 340, second moveable member 350, and third moveable member 360 follow downstream of the stationary member 330.
As shown here, the stationary member 330 defines the leading edge 312 of the stator vane and does not define any part of the trailing edge 314 of the stator vane. In some other embodiments, the stationary member 330 defines the trailing edge 314 of the stator vane and does not define any part of the leading edge 312 of the stator vane. In still other embodiments, a first moveable member defines the leading edge 312, a second moveable member defines the trailing edge 314, and the stationary member 330 is located in the row between the first and second moveable members.
FIGS. 16-28 illustrate various example embodiments of stators of the second type, in which the stator vane comprises a stationary member (i.e. a base) and a moveable member (i.e. a flap) which opens outwardly from the base. In these embodiments, the stationary member defines both the leading edge and the trailing edge of the stator vane. The moveable member forms an upwind surface of the stator vane. When opened or deployed, the moveable member is deployed downstream of the trailing edge of the stationary member. The deployment can occur in at least two ways: by rotation of the moveable member about a radial axis, or by extension of the moveable member longitudinally from the trailing edge of the stationary member.
FIG. 16 shows a wind turbine 400 and FIG. 17 shows a magnified view of a stator vane 410. The stator vane comprises a stationary member 420 (i.e. base) and a first moveable member 430 (i.e. flap). The stationary member 420 defines the leading edge 412 and the trailing edge 414 of the stator vane. The stationary member 420 also has a trailing edge 424 along the trailing edge 414 of the stator vane. The first moveable member 430 is located adjacent the trailing edge 414 of the stator vane and forms a portion of the upwind surface 416 of the stator vane. Put another way, the first moveable member is located in the upwind surface. The rotor 406 is visible downstream of the stator vanes 410. In this figure, the first moveable member is in a closed or stowed state, i.e. a first position. Here, the flap 430 has a generally rectangular shape. The distal side surface 432 and the proximal side surface 434 of the flap are of equal lengths when measured from the trailing edge.
FIG. 19 shows the first moveable member in an open or deployed state, i.e. a second position. In this figure, the stationary member 420 and the first moveable member 430 are pivotally engaged along a radial axis 405 which is located along the trailing edge 424 of the stationary member 420. The flap rotates about this axis 405 to be deployed downstream of the trailing edge 414; this rotation is indicated by arrow 409. An interior surface 436 of the flap, which was previously hidden, now becomes an upwind surface. A pocket or recess 421 in the upwind surface 416, in which the flap 430 rests when stowed, is now exposed. The trailing edge 438 of the flap 430 is further downstream than the trailing edge 424 of the stationary member.
FIG. 21 also shows the first moveable member 430 in an open or deployed state. However, this embodiment differs from that of FIG. 19 in the mechanism by which deployment occurs. Here, the first moveable member 430 extends longitudinally from the trailing edge 424 of the stationary member. This can be done, for example, when the first moveable member 430 is connected to the stationary member 420 along distal side surface 432 and proximal side surface 434. In this embodiment, the interior surface of the flap becomes a downwind surface (not visible). The extension is represented via arrow 411.
FIG. 23 shows a further variation. Here, the trailing edge 438 formed by the flap 430 upon deployment has a nonlinear shape. For example, as illustrated here, the trailing edge has a sawtooth shape. Other nonlinear shapes which are contemplated include a sinusoidal shape and a crenellated shape. Put another way, the flap comprises a nonlinear edge. FIG. 23 also shows the flap 430 deploying via extension rather than rotation, as indicated by the straight edge 427 (which would otherwise have a nonlinear shape that complements the shape of trailing edge 438).
FIG. 25 shows another variation. Here, an array or plurality of fluid passages 450 is present between an upper surface 452 and a lower surface (not visible) of the flap. This allows air to flow through the flap. The fluid passages 450 may generally be of any shape, though here they are shown as circular apertures.
In FIG. 27, a further variation is illustrated wherein the flap 430 has an asymmetrical shape along a radial length of the stator vane. This is reflected in the distal side surface 432 and the proximal side surface 434 of the flap having different lengths when measured from the trailing edge 414 of the stationary member 420 to the trailing edge 438 of the flap 430. In the embodiment depicted, the distal side surface has a shorter length than the proximal side surface. However, the opposite may also be true.
The variations shown in FIGS. 22-27 (sawtooth edge, fluid passages, asymmetrical shape) may also be combined as desired. In addition, these embodiments depict a stator vane with a single moveable member or flap. It is contemplated that a single stator vane may also include a plurality of such moveable flaps, and/or that each stator vane on a stator may have moveable flaps. Each moveable flap may be independently controlled in those embodiments.
FIG. 28 is a front view of the wind turbine 400 wherein some the stator vanes 410 have deployed flaps 430. Deployment of the flaps changes the flow of fluid incident to the rotor blades, providing additional control of the rotor speed to keep the power generator within its cut in/cut out range. It is contemplated that the flaps on the stator vanes of the stator can be controlled independently to provide finer control over the fluid flow. As shown here, there are nine stator vanes, with four having flaps deployed and five having flaps stowed (reference numeral 431). Put another way, some of the stator vanes are in a first position and some of the stator vanes are in a second position that allow for control of the load experienced by the impeller on the fluid turbine.
FIG. 29 and FIG. 30 show another example embodiment of the stator vane. Again, the stationary member 420 defines both the leading edge 412 and the trailing edge 414 of the stator vane 410. Here, however, the moveable member(s) rotate(s) about a radial axis that is located in a central portion 423 of the stationary member. This embodiment shows two moveable members or flaps; however, embodiments with one or more flaps are also contemplated. The first moveable member 430 forms a portion of the upwind surface 416 of the stator vane. The second moveable member 460 forms a portion of the downwind surface 418 of the stator vane. Here, the moveable members are shown in a deployed state. The radial axis 435, 465 of each moveable member is located in a central portion 423 of the stationary member. The moveable members (i.e. flaps) are shown as extending along the entire radial length of the stator vane; however, variations are also contemplated where the flap extends along a portion of the radial length (i.e. not along the entire radial length). Arrows 407 depict the direction of wind travel around the stator vane 410 and rotor blade 406.
FIGS. 33-42 illustrate various embodiments of stators of the third type. In these stator vanes, the middle or central portion of the stator vane is made from two surface segments. By changing the exposed lengths of the central surface segments, the camber of the stator vane can be changed.
A side view of one example embodiment is seen in FIGS. 31-34. Here, the stator vane 510 comprises a leading edge member 520, an upper surface segment 530, a lower surface segment 540, and a trailing edge member 550. The leading edge member 520 defines the leading edge 512 of the stator vane at a front end 522. The leading edge member 520 includes an upper surface 526 and a lower surface 528 along a back end 524. The upper surface 526 of the leading edge member is longitudinally engaged with the forward edge 532 of the upper surface segment 530. The lower surface 528 of the leading edge member is longitudinally engaged with the forward edge 542 of the lower surface segment 540. More generally, the back end 524 of the leading edge member is longitudinally engaged with the forward edges 532, 542 of the upper and lower surface segments. The trailing edge member 550 defines the trailing edge 514 of the stator vane at a rear end 554. The trailing edge member includes an upper surface 556 and a lower surface 558 along a front end 552. The upper surface 556 of the trailing edge member is longitudinally engaged with the rear edge 534 of the upper surface segment. The lower surface 558 of the trailing edge member is longitudinally engaged with the rear edge 544 of the lower surface segment. More generally, the front end 552 of the trailing edge member is longitudinally engaged with the rear edges 534, 544 of the upper and lower surface segments. Either the leading edge member 520 or the trailing edge member 550 is stationary, i.e. attached to the stator hub.
The upper surface segment 530 and the lower surface segment 540 move longitudinally relative to the leading edge member 520 and the trailing edge member 550 to change the camber of the stator vane. Put another way, the exposed surface area of the upper surface segment and the lower surface segment change as the camber is changed. The stator vane of FIG. 31 has a positive camber. The stator vane of FIG. 33 has zero camber. The stator vane of FIG. 34 has a negative camber.
FIG. 35 and FIG. 36 illustrate some components that drive the longitudinal lateral motion and engagement of the various moving parts. Lateral motion guides 560 comprise slots and pins, with a plurality of slots in one surface and a plurality of pins in the mating surface, such that the components are able to move longitudinally with respect to one another while remaining engaged. One method of moving the upper and lower surface segments 530, 540 is shown wherein a pair of linear motion actuators 562 is housed in one of the edge members, here the leading edge member 520. Cables 564 extend from the linear motion actuators 562 to the upper and lower surfaces of the other edge member, i.e. upper and lower surfaces 556, 558 of the trailing edge member 550. Generally, the cables have the same length. Thus, when for example the cable leading to the lower surface 558 is shortened and the cable leading to the upper surface 556 is lengthened, the change in lengths will cause the exposed surface area of upper surface segment 530 to increase and cause the exposed surface area of lower surface segment 540 to decrease. These change in lengths change the camber, thus impacting the airfoil shape of the stator vane. It is also contemplated that the linear motion actuators 562 are housed in the trailing edge member 550, and that the cables 564 extend to the upper and lower surfaces 526, 528 of the leading edge member 520.
In FIG. 35 and FIG. 36, the stator vane 510 is shown in three different positions. Two positions (positive, neutral) configurations are shown in dotted lines. The negative camber configuration is shown in solid lines. Again, the moveable component (i.e. the stator vane) can be moved between two different positions to control the load experienced by the impeller incorporating this stator vane.
FIG. 37 and FIG. 38 illustrate another method of actuating motion between the various components. Here, a drive pulley 566 is located within one of the edge members, here the leading edge member 520. A single cable 564 engages the drive pulley. Each end of the cable 564 is attached to a fixed point on the other edge member, i.e. trailing edge member 550, the fixed point being shown here as single point 568 (although the ends can be attached to separate fixed points if desired). The distance between the drive pulley and the fixed point(s) 568 is constant, or fixed. The upper surface segment 530 and the lower surface segment 540 engage the cable 564 on opposite sides of the drive pulley 566. As the drive pulley is rotated either clockwise or counter-clockwise, one side is shortened while the opposite side is lengthened, thus causing the upper and lower surface segments to move and shorten/lengthen the surfaces of the airfoil shape.
Another method is illustrated in FIG. 39. A first linear motion actuator 570 is axially engaged and pivotally engaged with a fixed point 572 along the upper surface 526 of the leading edge member 520, and also axially engaged and pivotally engaged with a fixed point 574 along the upper surface 556 of the trailing edge member 550. A second linear motion actuator 580 is axially engaged and pivotally engaged with a fixed point 582 along the lower surface 528 of the leading edge member 520, and also axially engaged and pivotally engaged with a fixed point 584 along the lower surface 558 of the trailing edge member 550. As depicted here, fixed points 574 and 584 are the same point, though of course they can be separate points. Telescoping linear motion actuators are common and may employ screw drive, pneumatics, or other means to cause elongation. By lengthening one actuator while shortening the opposite actuator, the airfoil camber may be changed as the leading edge member 520 and trailing edge member 550 move relative to upper surface segment 530 and lower surface segment 540.
Another method is illustrated in FIG. 40. Linear motion actuator 590 connects upper surface 526 of the leading edge member 520 with the forward edge 532 of upper surface segment 530. Linear motion actuator 592 connects lower surface 528 of the leading edge member 520 with the forward edge 542 of lower surface segment 540. Linear motion actuator 594 connects upper surface 556 of the trailing edge member 550 with the rear edge 534 of upper surface segment 530. Linear motion actuator 596 connects lower surface 558 of the trailing edge member 550 with the rear edge 544 of lower surface segment 540. The upper and lower surface segments 530, 540 are engaged to the leading and trailing edge members 520, 550, as previously described and can move relative to them. As the linear actuators are lengthened or shortened, the airfoil camber is altered.
FIG. 41 and FIG. 42 show stator vanes of the third type in a positive camber configuration on a wind turbine 500. The distal end of the leading edge member 520 engages the nacelle 508 and the proximal end of the leading edge member engages the turbine shroud 503. The upper surface segment 530 and lower surface segment 540 can be seen on various stator vanes.
The various stator vanes depicted above can be moved between a first position and a second position to control the load experienced by the fluid turbine. It is contemplated that the moveable component of these stator vanes can be moved actively or passively. By “actively”, it is contemplated that the moveable component receives an instruction from a controller, for example from a computer program running instructions or from a user of the fluid turbine. By “passively,” it is contemplated that the moveable component does not receive an instruction from a controller, but rather moves based on changes in ambient conditions. For example, it is contemplated that the moveable member 430 described in FIGS. 17-19 could be designed to passively open when the fluid velocity exceeds a given threshold and “blows” the moveable member out of the pocket 421.
In a further aspect of the present disclosure, rotors comprising moveable components are disclosed. The rotor blade is hollow. The upstream surface and the downstream surface of the rotor blade each contain a fluid passage. Located within the hollow rotor blade is a gate that opens and closes the fluid passages depending on the rotational speed of the rotor. This rotational speed is dependent upon the fluid velocity. Above a given fluid velocity threshold, the gate opens the fluid passages to create an aperture through the rotor blade that the fluid can flow through. Put another way, the rotor may contain a moveable component made up of a stationary member and a moveable member. The stationary member is the outer rotor blade skin, which is hollow. The moveable member is the gate.
FIGS. 43-49 provide various views of one example embodiment. FIG. 43 is an exterior view of the overall rotor 600. FIG. 44 is a magnified view of the hollow outer rotor blade skin 610. Here, fluid passages 620 having the shape of circular apertures are seen in the upstream surface 612 of the rotor blade. However, the fluid passages may have any shape. Inserts 630 are seen inserted into the fluid passages 620 to prevent fluid flow through the rotor blade. FIG. 45 is a magnified view of the rotor blade skin 610 wherein the inserts have been removed so that fluid can flow through the fluid passages 620. The downstream surface 614 is visible through the fluid passages.
FIGS. 47-49 show various interior views of the rotor blade skin 610. In FIG. 47, the upstream surface 612 and the downstream surface 614 are shown. Fluid passages 620 are present in both surfaces. Arrow 605 indicates a radial axis. The gate 640 that controls fluid flow is also visible. The gate 640 comprises an insert 630 for each fluid passage. The insert covers the fluid passage and prevents fluid flow through the fluid passage. It is contemplated that the insert may have, for example, a half-sphere, cylindrical, or circular cone shape.
As seen in FIG. 48 and FIG. 49, the insert(s) 630 is/are operatively connected to a pivoting arm 642. For example, as seen in FIG. 49, the inserts may be mounted onto a plate 644 which is connected to a pivoting arm 642. It is contemplated that there are two pivoting arms 642, one for the fluid passage(s) on the upstream surface 612 and one for the fluid passage(s) on the downstream surface 614. The pivoting arms 642 engage a weighted member 650. The weighted member 650 in turn engages a tension member 660. The tension member is connected to the rotor at the distal end 602, or in other words at the center of the rotor, not the tip of the rotor blade. An example of a tension member is a spring. The tension member acts to bias the gate in the direction towards the center of the rotor.
FIG. 48 illustrates the rotor blade in a closed state, i.e. when the inserts 630 are aligned with the fluid passages 620 of the rotor blade skin 610. In this illustration, the rotor is exposed to a fluid velocity which is below a given threshold. The tension in the tension member 660 is stronger than the rotational force, and the tension member thus maintains the bias of the gate 640 towards the distal end 602, as indicated by arrow 619. The pivoting arms 642 are biased away from the weighted member 650 and towards the rotor blade surfaces 612, 614. Below the fluid velocity threshold, there may be some “give” in the pivoting arms 642 so that although the tension member and weighted member may move relative to the distal end 602, the inserts 630 remain aligned with the fluid passages 620.
FIG. 49 illustrates the rotor blade in an open state. In this illustration, the rotor is exposed to a fluid velocity above the given threshold. This generates a force (indicated by arrow 615) that causes the weighted member 650 to move away from the distal end 602, overcomes the bias towards the center of the rotor, and causes the tension member 660 to move or stretch such that the pivoting arms 642 can no longer travel. This causes the plate 644 and the inserts 630 mounted thereon to be removed from the fluid passages 620. Fluid can consequently flow through the fluid passages 620. This will cause the rotational speed of the rotor to decrease, reducing the load on the rotor in high fluid velocity conditions. These figures illustrate an embodiment wherein the moveable member of the rotor blade, i.e. the gate, moves passively in response to an increased rotor speed which can occur when the ambient conditions change, e.g. when the fluid velocity increases relative to its prior speed.
The stators, rotors, and shrouds of the present disclosure can be made using materials and methods known in the art.
The present disclosure has been described with reference to several different embodiments. Modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the present disclosure be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Patent Application
20110274533
