RU2810835C1 - Vibration damper for smoke or ventilation pipe with variable aerodynamics - Google Patents

Abstract

FIELD: construction.

SUBSTANCE: vibration damper of a chimney or ventilation pipe with variable aerodynamics as part of the pipe has a composite cylindrical shape and consists of two vertical surfaces, where the radius of curvature of one surface is close to the radius of curvature of the vertical surface of the pipe, and the radius of curvature of the other surface is less than the radius of curvature of the vertical surface of the pipe, at the same time the damper oscillations have the ability to rotate around a vertical axis.

EFFECT: wind resonance is avoided at wind speeds that do not reach the maximum (calculated) wind speed for the design area without increasing the aerodynamic resistance of the pipe at the maximum (calculated) wind speed for the design area.

6 cl, 4 dwg

Description

The invention relates to construction when designing chimneys and ventilation pipes and can be used to avoid resonant vortex excitation of the pipe.

When high-rise structures (including pipes) are exposed to wind, air flows around the structure and alternately breaks off from the right and left, forming vortices. This phenomenon is periodic in nature and leads to resonant vortex excitation of the structure when the frequency of the breakdown of air vortices and the natural frequency of oscillations of the structure coincide.

A chimney interceptor is known (Patent RU No. 71731, Published: 03.20.2008, Bulletin No. 8), consisting of separate plates, one side adjacent to its outer surface, characterized in that the contour of the side of each plate adjacent to the outer surface of the chimney , is made along a radius determined by constructing three points of the segment, two of which are the ends of its chord equal to the length L of the plate, and the third, which determines the height of the segment, is found from the equality of the height of the plate segment and the height of the segment with the radius of the outer surface of the chimney and the chord l , determined by the relation

l=L×sinα,

where l is the chord of the segment with the radius of the outer surface of the chimney, mm;

L is the length of the interceptor plate, mm;

α - angle of inclination of the interceptor plate to the axis of the chimney, degrees.

This solution promotes non-periodic vortex shedding and, accordingly, is able to suppress the possibility of the formation of resonant vortex excitation of the pipe, but increases the aerodynamic drag of the structure, thereby increasing the wind load and the consumption of materials for the supporting structures of the designed pipe.

A vibration damper of a chimney is known, containing strip blades installed in a spiral in the upper part of the pipe and secured with an edge perpendicular to its outer surface (Patent RU No. 73048, Published: 05.10.2008, Bulletin No. 13), adopted as a prototype, characterized in that that the strip blades are made transversely corrugated.

This solution prevents periodic vortex shedding and, accordingly, is able to suppress the possibility of the formation of resonant vortex excitation of the pipe and helps to reduce the aerodynamic drag of the pipe structure, in contrast to traditional corrugated vibration dampers, however, it increases the complexity of the installation due to the complex shape and also increases the wind load and flow rate materials of the supporting structures of the designed pipe.

The basis of the invention is the goal of reducing the aerodynamic drag of the pipe at wind speeds that are maximum (design) for the design area, while at the same time avoiding the phenomenon of resonant vortex excitation observed at wind speeds less than the design, which will reduce the loads from wind influences and, accordingly, costs of materials for supporting pipe structures.

The technical result is the avoidance of wind resonance at wind speeds that do not reach the maximum (calculated) for the design area without increasing the aerodynamic resistance of the pipe at the maximum (calculated) wind speed for the design area.

The solution to the problem is achieved by the fact that the vibration damper is a moving (rotating) part of the structure and, turning around a vertical axis depending on the wind speed, changes the shape of the pipe section, avoiding resonant vortex excitation.

Description of drawings.

The essence of the invention is demonstrated in more detail by an example of implementation, illustrated by the Figures, which show:

Fig. 1 - Fragment of a pipe section with an “open” position of the vibration damper,

Fig. 2 - Fragment of a pipe section with a “closed” position of the vibration damper,

Fig. 3 - Graphs of the dependence of the vortex shedding frequency on the wind speed with the resonance frequency region of the structure.

Fig. 4 - An example of the use of the invention in a pipe design.

1 - Vibration damper

2 - Vertical axis of vibration damper rotation

3 - Pipe design

4 - Surface of the “open” vibration damper

5 - Surface of the “closed” vibration damper

6 - Graph of the dependence of the vortex shedding frequency on the wind speed in the “open” position of the vibration damper

7 - Area of operation of the structure in the “open” position of the vibration damper

8 - Graph of the dependence of the vortex shedding frequency on the wind speed in the “closed” position of the vibration damper

9 - Area of operation of the structure in the “closed” position of the vibration damper

10 - Area of resonance of the structure

The design of the pipe 3 contains vibration dampers 1 with an axis of rotation 2, having cylindrical or polyhedral surfaces 4 and 5 with certain radii of curvature, where the radius of curvature of surface 5 is close to the radius of curvature of the surface of the pipe, and the radius of curvature of surface 4 is smaller. By rotating 180 degrees about the vertical axis 2, the vibration damper 1 can be in the “open” position shown in FIG. 1, or the “closed” position shown in FIG. 2.

At a low average wind speed at a certain height of the pipe, vibration damper 1 has an “open” position (Fig. 1) and the frequency of vortex shedding according to the graph of the dependence of the frequency of vortex shedding on wind speed in the “open” position of vibration dampers 6 is in the area of operation of the structure in “ open” position of vibration dampers 7 (Fig. 3). When the vortex shedding frequency reaches close to the resonance region of structure 10, the vibration damper 1 rotates due to the stepper motor around the vertical axis 2 by 180 degrees and goes into the “closed” position (Fig. 2) and the vortex shedding frequency according to the graph of the dependence of the vortex shedding frequency on the speed wind in the “closed” position of the vibration dampers 8 goes into the area of operation of the structure in the “closed” position of the vibration dampers 9 (Fig. 3).

The number of vibration dampers and their dimensions are determined by calculation and the possibility of installation in the pipe structure. The need to install vibration dampers is determined from the condition of the possibility of the occurrence of resonant vortex excitation. The length of the vibration dampers along the height of the pipe can vary. The vibration damper can be divided and changed in quantity and shape along the height of the pipe to more accurately adjust the operation due to the variability of wind speed over height. The shape of the vibration damper surfaces can be cylindrical or multifaceted. It is possible to rotate the vibration dampers to an intermediate position between their “open” and “closed” states.

Claims (6)

1. A vibration damper for a chimney or ventilation pipe with variable aerodynamics as part of the pipe, characterized in that the surface of the vibration damper has a composite cylindrical shape and consists of two vertical surfaces, where the radius of curvature of one surface is close to the radius of curvature of the vertical surface of the pipe, and the radius of curvature of the other surface is less than the radius of curvature of the vertical surface of the pipe, at the same time the vibration damper has the ability to rotate around a vertical axis. 2. The vibration damper according to claim 1, characterized in that the surface of the vibration damper has a multifaceted shape. 3. Vibration damper according to claim 1, characterized in that the outer surface is made of metal. 4. Vibration damper according to claim 1, characterized in that the outer surface is made of composite material. 5. Vibration damper according to claim 1, characterized in that the outer surface is made of plastic. 6. Vibration damper according to claim 1, characterized in that the rotation is carried out by an electric motor.