CN117262115A

CN117262115A - Novel tension leg type floating wind power platform and installation method thereof

Info

Publication number: CN117262115A
Application number: CN202311332591.8A
Authority: CN
Inventors: 王俊荣; 王成真; 何春蕾; 李华军; 何旷; 何镇阳; 徐思捷; 孙培瑜
Original assignee: Ocean University of China
Current assignee: Ocean University of China
Priority date: 2023-10-16
Filing date: 2023-10-16
Publication date: 2023-12-22

Abstract

The invention relates to the technical field of ocean floating wind power engineering, in particular to a novel tension leg type floating wind power platform and an installation method thereof. The floating structure comprises a central upright post, a plurality of floating boxes and a cable, wherein the plurality of floating boxes are arranged at intervals along the outer side of the central upright post; the upper end of the end face of the free end of the buoyancy tank is provided with a plurality of cable guides, and the outer surface of the central upright column above each buoyancy tank cable guide is correspondingly provided with a cable guide; the bottom end of a complete continuous cable is connected with the foundation and sequentially passes through the cable guide of the buoyancy tank and the cable guide on the corresponding central upright post; the number of cables arranged on each buoyancy tank corresponds to the number of cable guides. The structural stress can be effectively improved without obviously increasing the design and construction cost, and the stability of the platform in the installation process is ensured.

Description

Novel tension leg type floating wind power platform and installation method thereof

Technical Field

The invention relates to the technical field of ocean floating wind power engineering, in particular to a novel tension leg type floating wind power platform and an installation method thereof.

Background

Offshore wind power is the subject of current research on great heat. The wind energy stored on the sea is far more than on land, and the wind energy resources of deep open sea are far more than off-shore. When the water depth exceeds 60m, the cost of the fixed platform is too high, and the advantages of the floating wind power platform are obvious. TLP (Tension Leg Platform, tension leg platform, abbreviated TLP) is currently an emerging offshore wind platform with significant advantages in terms of its extremely small pitch and roll angles and small displacement.

At present, the research on the TLP is an important subject in the current maritime industry, and the TLP has wide application prospect in the offshore wind power field. As the dimensions of TLP platforms increase, their overall strength is often difficult to ensure, requiring the provision of steel ropes or struts to ensure their strength.

Seastar TLP is an important structural form. In general, the larger the megawatt wind power platform, the larger its main scale. When the Seastar TLP is used as a large megawatt wind level platform, the buoyancy tank is long, the tension legs have larger pretension, the tension on the tension legs is transferred to the buoyancy tank, larger bending moment can be generated at the joint of the buoyancy tank and the central upright post, and great test is brought to the strength design of the whole wind power platform structure.

The adoption of the variable cross section design of the buoyancy tank has become an important application in the structural design of the wind power platform because the material performance can be utilized more effectively. However, even with the buoyancy tanks of variable cross-section design, sometimes the strength requirements are not met, and additional structure is required to improve the stress on the ocean platform. The method commonly adopted at present is to add stay bars or steel ropes.

The existing strut is generally provided with one or several struts in the main body structure of the TLP, one end of the strut is connected to the buoyancy tank, and the other end of the strut is connected to the central column. However, if the strength requirement of the wind power platform is ensured by arranging diagonal braces, a plurality of key nodes are generated, the stress of the key nodes is very complex, and the processing technology requirement on the nodes is very high. Moreover, the design is easier to cause fatigue problem under the condition of bearing ocean environmental load, and hidden danger is brought to the safe service of the platform.

When adding a plurality of tendons to a TLP, a plurality of tendons are typically provided on the TLP, with one end of each of the tendons being connected to a buoyancy tank and the other end of each of the tendons being connected to a center column. The problem with this approach is that the platform body of the TLP is somewhat resistant to bending moments and must be pre-tensioned in order for the ropes to function. The service time of the ocean platform is as long as decades, once the steel cable is loosened, the auxiliary effect of the ocean platform on the strength of the ocean platform is lost, the tension of the steel cable must be monitored at all times, and when the ocean platform is lower than the standard, the ocean platform needs to be further tensioned to ensure the good auxiliary effect of the steel cable.

In addition, the installation of TLPs is also a problem that must be considered in the platform design and construction process. Normally, when the TLP is towed, if the buoyancy tank is not immersed in the water, the large water plane of the platform can ensure good stability of the platform, but with continuous pressurization, the platform sinks, the water plane is only the area of the central upright post, and at this time, the tension legs are not connected, so that the platform is extremely prone to capsizing. In order to ensure the safe construction of the whole engineering, a method is generally adopted to reduce the center as much as possible and install the engineering at a time when the sea condition is good. However, in the actual construction process, the center cannot be lowered infinitely, and the weight is unreasonable and the cost is increased due to the fact that the center is lowered in pursuit of one taste; in addition, sea conditions are often unpredictable, adding a lot of uncertainty to the construction of the project.

Disclosure of Invention

The invention aims to overcome the defects in the prior art, and provides a novel tension leg type floating wind power platform and an installation method thereof, which can effectively improve structural stress without remarkably increasing design and construction cost and ensure the stability of the platform in the installation process.

The technical scheme of the invention is as follows: the novel tension leg type floating wind power platform comprises a central upright post and a plurality of buoyancy tanks which are arranged at intervals along the outer side of the central upright post, wherein the novel tension leg type floating wind power platform further comprises a mooring rope;

the upper end of the end face of the free end of the buoyancy tank is provided with a plurality of cable guides, and the outer surface of the central upright column above each buoyancy tank cable guide is correspondingly provided with a cable guide;

the bottom end of a complete continuous cable is connected with the foundation and sequentially passes through the cable guide of the buoyancy tank and the cable guide on the corresponding central upright post;

the number of cables arranged on each buoyancy tank corresponds to the number of cable guides.

In the invention, the floating box is in a variable cross section shape, the bottom surface of the floating box and the bottom surface of the central upright post are positioned on the same horizontal plane, and the height of the free end of the floating box is smaller than the height of the connecting end of the floating box and the central upright post.

The cable guide includes the cable guide support, and the longitudinal section of cable guide support is right triangle-shaped, includes:

the bevel edge is fixedly connected with the buoyancy tank and/or the central upright post;

two right-angle side edges;

the roller wheels are arranged at right angles of the cable guide support in a rolling mode, and the mooring ropes are attached to the outer surfaces of the roller wheels.

The upper end of the end face of the free end of the buoyancy tank is provided with a chute, the bottom surface of the chute is an inclined plane, and a plurality of cable guides are arranged on the inclined plane at intervals;

the bevel edge of the cable guide is fixedly connected with the inclined plane, and two right-angle side edges of the cable guide are respectively arranged along the vertical direction and the horizontal direction;

the rollers on the cable guides are fixedly connected through rotating shafts, and two ends of each rotating shaft are respectively connected with the buoyancy tank in a rotating mode.

And a chain stopper is arranged at the cable guide of the central upright post.

The section of the cable between the foundation and the cable guider of the buoyancy tank is arranged along the vertical direction to form tension legs;

the section of the cable between the cable guide of the buoyancy tank and the corresponding central upright post is obliquely arranged to form a stay cable.

The invention also comprises an installation method of the novel tension leg type floating wind power platform, which comprises the following steps:

s1, towing a structural body formed by connecting a central upright post and a buoyancy tank to an installation site, respectively arranging cable guides on the buoyancy tank and the central upright post, and connecting the bottom of a cable with a foundation of a platform;

s2, the upper end of the mooring rope sequentially passes through the cable guides of the buoyancy tanks, and then is inclined and passes through the cable guides above the central upright post which are correspondingly arranged, the upper end of the mooring rope is connected with the traction device, and the outer side of each buoyancy tank is respectively provided with the traction device;

s3, the traction device pulls the cables on each buoyancy tank to enable the cables to be tensioned and in a pretensioned state, and pretension in a plurality of cables connected with the traction device is controlled through the traction device;

s4, pumping ballast water into the wind power platform, increasing the weight of the platform and beginning to sink until the draft of the platform reaches the design draft, and immersing the buoyancy tank on the sea surface;

and S5, after the platform reaches the specified draft, locking the position of the cable, disconnecting the traction device from the cable, discharging the ballast water until the tension legs reach the set pretension, and completing the installation process of the platform.

The traction device adopts a tug or winch, and the winch adopts a marine winch or a temporary winch arranged on a platform floating body.

In step S5, the position of the cable is locked by the chain stopper at the center pillar cable guide.

In step S3, ballast water is pumped into the wind power platform through a marine ballast device;

in step S5, ballast water in the wind power platform is discharged by the ship ballast device.

The beneficial effects of the invention are as follows:

(1) The wind power platform is acted by bending moment and overturning moment generated by pretension of tension legs, so that the strength of the joint of the buoyancy tank and the central upright post is particularly critical;

(2) The whole cable is complete and continuous from the foundation to the central upright post through the cable guider on the buoyancy tank, and the tension on the stay cable is dynamically balanced with the tension of the tension leg, so that manual monitoring and adjustment are not needed;

(3) In the installation process of the wind power platform, a winch or a tug can be used for tensioning a cable, so that the cable has a certain pretension, a certain auxiliary effect is achieved on the pressurizing load sinking process of the platform, and the installation process is safer.

Drawings

FIG. 1 is a schematic structural diagram of a novel tension leg type floating wind power platform according to the invention;

FIG. 2 is a schematic view of the structure of the fairlead arranged at the free end of the buoyancy tank;

FIG. 3 is a schematic illustration of the force applied at the free end of the buoyancy tank;

FIG. 4 is a schematic illustration of a tug pulling a cable;

FIG. 5 is a schematic illustration of ballast water being pumped into a wind platform;

fig. 6 is a schematic diagram of discharging ballast water of a wind power platform.

In the figure: 1 a central upright; 2, a buoyancy tank; 3 a mooring rope; 4, a cable guide; 5, a cable guiding bracket; 6, a roller; 7, rotating shaft; 8 bevel grooves.

Detailed Description

In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings.

In the following description, specific details are set forth in order to provide a thorough understanding of the present invention. The present invention may be embodied in many other forms than those herein described, and those skilled in the art may readily devise numerous other arrangements that do not depart from the spirit of the invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

As shown in fig. 1 to 2, the novel tension leg type floating wind power platform of the invention comprises a central upright 1 positioned at the center, and the central upright 1 is cylindrical. Several buoyancy tanks 2 are arranged at intervals along the lower part of the annular outer surface of the central upright 1, in this embodiment, three buoyancy tanks 2 are arranged at even intervals on the annular outer side of the central upright 1. The top end of the central upright column 1 is provided with a platform for installing an offshore wind turbine.

In this application, square buoyancy tanks can be used, and cylindrical buoyancy tanks can also be used. When a square buoyancy tank is adopted, the cross section of the buoyancy tank is square; when a cylindrical buoyancy tank is used, the cross section of the buoyancy tank is circular.

In this embodiment, the cross section of the buoyancy tank is rectangular, and the longitudinal section is trapezoidal. That is, the buoyancy tank 2 in the present application adopts a variable cross-section design. The reason for this is that the bending moment of the free end of the buoyancy tank is smaller, and the bending moment is larger as the buoyancy tank is closer to the joint of the buoyancy tank and the central upright post. Therefore, the cross section of the buoyancy tank in the embodiment gradually transits from a small cross section to a large cross section along the direction from the free end to the joint of the buoyancy tank and the central upright post, and the cross section area gradually becomes larger. Through the variable cross section design of the buoyancy tank, the surplus material performance of the free end of the buoyancy tank with small bending moment can be effectively avoided, and the construction cost of the wind power platform is reduced.

In this embodiment, the bottom surface of the buoyancy tank 2 is on the same level as the bottom surface of the central column 1. The top surface of the buoyancy tank 2 is inclined, and the height of the free end of the buoyancy tank is smaller than that of the connection end of the buoyancy tank and the central upright post.

The tension leg in this application adopts hawser 3, and the surface of every buoyancy tank and the center pillar of buoyancy tank top all is equipped with the conductor 4, and hawser 3 passes the conductor on every buoyancy tank in proper order and corresponds the conductor of center pillar of buoyancy tank top, and the conductor has played the guide effect to the hawser. The quantity of hawser and the quantity of buoyancy tank are between this application and correspond the setting.

In this embodiment, two cable guides 4 are provided on the outer side of each buoyancy tank 2, and two cable guides 4 are provided correspondingly on the outer side of the center pillar above each buoyancy tank. Therefore, each buoyancy tank is provided with two cables 3, and the two cables 3 are arranged in parallel. The number of cables is twice that of the buoyancy tanks, and the number of cables is equal to that of the cable guides on the buoyancy tanks.

One end of the buoyancy tank 2 is fixedly connected with the central upright 1, and the other end of the buoyancy tank 2, namely the free end of the buoyancy tank, is provided with a cable guide. In this embodiment, the upper end of the free end surface of the buoyancy tank is provided with an inclined surface groove 8, the bottom of the inclined surface groove 8 is in an inclined surface shape, and the cable guide is arranged on the inclined surface. The stress analysis shows that the resultant force direction of the cable guider is inclined downwards along the angular bisectors of the cables at two sides of the cable guider, and the inclined plane is vertical to the resultant force direction of the cable guider, so that the parts are prevented from being sheared. The specific inclination of the inclined plane can thus be determined on the basis of the angle of the cable brackets on both sides of the fairlead.

As shown in fig. 2, the cable guide comprises a cable guide bracket 5, and the longitudinal section of the cable guide bracket is in a right triangle shape, so that the cable guide bracket 5 comprises two right-angle side edges and a bevel edge, a roller 6 is arranged at the right-angle part of the cable guide bracket, and the roller 6 is rotationally connected with the cable guide bracket through a rolling bearing.

The bevel edge of the cable guide bracket 5 is fixed on the bevel surface of the buoyancy tank. The roller 6 is rotationally connected with the buoyancy tank through a rotating shaft 7. In this embodiment, the rotating shaft 7 sequentially passes through the plurality of rollers 6, the rollers 6 are all fixed on the rotating shaft 7, and two ends of the rotating shaft 7 are respectively connected with the buoyancy tank in a rotating way. The cable 3 is disposed along the outer surface of the fitting roller 6. The guide cable bracket 5 supports the roller and simultaneously realizes that the inclined plane is vertical to the resultant force direction born by the guide cable device.

The outer surface of the central upright column right above each buoyancy tank is also respectively provided with a cable guide. The cable guide may be a structure of a cable guide provided on the buoyancy tank. At this time, the bevel edge of the cable guide bracket is fixedly connected with the outer surface of the central upright post. The cable is attached to the outer surface of the roller. The cable guide of the central upright post is also provided with a chain stopper. In the process of the movement of the mooring rope, the roller wheels on the mooring rope guider play a role in guiding the mooring rope.

The bottom end of the cable 3 is connected with the foundation, and the cable 3 passes through the cable guide on the buoyancy tank and the cable guide on the central upright post in turn upwards and can be connected with an external winch or tug. In the installation process of the wind power platform, the winch or the tug plays an auxiliary role.

The cable from the foundation to the buoyancy tank and then to the central column is a continuous cable. In the in-service process of the wind power platform, the bottom end of the cable is connected with the foundation of the wind power platform, and the upper end of the cable sequentially passes through the cable guide on the buoyancy tank and the cable guide on the outer surface of the central upright post right above the cable guide. The cable connecting in turn the foundation, the fairleads of the buoyancy tank and the fairleads of the corresponding central column is thus a complete continuous cable.

The section of the cable between the foundation and the cable guide of the buoyancy tank is arranged in the vertical direction to form tension legs. The section of the cable between the cable guide of the buoyancy tank and the cable guide of the central upright post is obliquely arranged to form a stay cable.

Because the whole cable is continuous, the tension on the stay cable between the cable guide of the buoyancy tank and the cable guide on the corresponding central upright post is equal to the tension on the tension leg between the foundation and the cable guide of the buoyancy tank, the tension of the stay cable and the tension leg form dynamic balance, and the stay cable can dynamically improve structural stress along with the tension change on the tension leg. When the sea condition is severe, the tension on the tension leg is large, and the tension on the stay cable is also large; when the sea condition is good, the tension on the tension leg is smaller, and the tension of the stay cable is also reduced, so that manual intervention and adjustment are not needed.

The stress schematic diagram of the wind power platform is shown in fig. 3, at this time, the stay cable and the tension leg respectively generate tension to the free end of the buoyancy tank, the resultant force direction of the two tension forces is that the upper part of the free end of the buoyancy tank points to the left and the lower part, and the force arm from the force to the joint of the buoyancy tank and the central upright post is obviously smaller than the length of the buoyancy tank. The specific magnitude of the resultant force, and the length of the arm of force, is related to the angle of cable stay, and therefore, the specific calculation process of the resultant force is not described herein. But the atress condition of buoyancy tank is become the bending combination in this application by current pure bending, so in the structure of wind-powered electricity generation platform in this application, the moment of flexure that its buoyancy tank tip produced can obviously be less than the scheme that tension leg directly acted on the buoyancy tank among the prior art.

The application further comprises an installation method of the tension leg type floating wind power platform, which comprises the following steps.

The first step, connecting the central upright post and the floating box to form a structural body, towing the structural body to an installation site by using a wet towing method, and installing the cable guide on annular outer surfaces of the upper parts of the floating box and the corresponding central upright post respectively according to installation requirements.

The connection of the cable and the foundation is completed underwater, and the upper end of the cable is bound with a pontoon, so that the pontoon is exposed out of the sea surface.

And secondly, pulling the cable by using a traction device, removing the pontoon bound at the upper end of the cable, passing the cable through the cable guide at the free end of the pontoon, and then pulling the cable to the cable and passing through the corresponding cable guide arranged on the central upright post. At this point, a length of cable remains at the upper end of the cable guide, which may be connected to a traction device. The traction device can be connected by a tug or a winch. Wherein the winch may be a marine winch or a temporary winch mounted on a TLP float.

In this embodiment, a tug is taken as an example, and a mounting process of a wind power platform is specifically described.

And thirdly, after the tug is in place, pulling the mooring rope on each buoyancy tank. As shown in fig. 4, in this embodiment, three buoyancy tanks are provided, one tug is provided on the outer side of each buoyancy tank, and a plurality of cables disposed on the same buoyancy tank are connected to the tugs disposed on the outer side of the buoyancy tank. Thus in this embodiment three tugs are used, each of which can simultaneously control the pretension in several cables of the buoyancy tanks connected thereto.

During the operation of the tug, the rope is tensioned and is in a pretensioned state. The pretension of the cable is reasonably controlled according to different platform installation requirements, the capability of the traction device and the specific sea condition of the day. Typically, the pretension is maintained between 100 and 200 tons.

The cable in the pretension state can effectively prevent the wind power platform from overturning in the installation process, and plays a great auxiliary role in the platform installation process.

Fourth, as shown in fig. 5, ballast water is pumped into the wind power platform by using the marine ballast device, and the weight of the platform increases to start sinking. In the process that the platform continuously sinks, after the sea surface submerges the buoyancy tank, the draft of the platform continues to increase until the whole platform reaches the design draft.

The whole process is carried out with the aid of cables which have been pre-tensioned, so that the platform has good stability.

Fifth, as shown in fig. 6, after the specified draft is reached, the position of the cable is locked by the chain stopper at the center pillar fairlead, at which time the length of the cable is no longer changed. And (3) disconnecting the tug from the cable, discharging the ballast water by using the marine ballast device until the tension legs reach the pre-tension designed in advance, and removing the ballast device to complete the installation process of the platform.

The novel tension leg type floating wind power platform and the installation method thereof provided by the invention are described in detail. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims. The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. The utility model provides a novel tension leg formula floating wind-powered electricity generation platform, includes the center pillar and follows the outside interval of center pillar and set up a plurality of buoyancy tanks, its characterized in that:

the device also comprises a cable;

2. The novel tension leg type floating wind power platform as claimed in claim 1, wherein,

the buoyancy tank is of a variable cross section shape, the bottom surface of the buoyancy tank and the bottom surface of the central upright post are located on the same horizontal plane, and the height of the free end of the buoyancy tank is smaller than that of the connecting end of the buoyancy tank and the central upright post.

3. The novel tension leg type floating wind power platform as claimed in claim 1, wherein the cable guide comprises a cable guide bracket, the longitudinal section of the cable guide bracket is in a right triangle shape, and the cable guide bracket comprises:

two right-angle side edges;

4. The novel tension leg type floating wind power platform as claimed in claim 3, wherein,

5. The novel tension leg type floating wind power platform as claimed in claim 1, wherein,

and a chain stopper is arranged at the cable guide of the central upright post.

6. The novel tension leg type floating wind power platform as claimed in claim 1, wherein,

7. A method of installing a novel tension leg type floating wind power platform as claimed in any one of claims 1 to 6, comprising the steps of:

8. The method of claim 7, wherein the towing means is a tug or winch, the winch being a marine winch or a temporary winch mounted on a platform buoy.

9. The method according to claim 7, characterized in that in step S5 the position of the cable is locked by means of a chain stopper at the center post cable guide.

10. The method of claim 7, wherein the step of determining the position of the probe is performed,