Tower: Breaking wind ring of tower anti-vibration measures


Release time:

2022-08-01

Towers: Tall buildings resonate under the influence of wind. Once the vibration damage is serious, the tower flange will leak, the anchor bolts will be loose, and the heavy tower will be damaged by fatigue, causing accidents. So avoid resonance.

Towers: Tall buildings resonate under the influence of wind. Once the vibration damage is serious, the tower flange will leak, the anchor bolts will be loose, and the heavy tower will be damaged by fatigue, causing accidents. So avoid resonance.

One of the anti-vibration measures is the use of spoilers such as windscreens.

Axial-fin or helical-fin spoilers are installed in the upper 1/3 of the tower height.

The length l of the axial fin is 0.75 -0.9 times the diameter D of the column, and the width b of the fin is 0.069 times D. The number of fins on the same circumference is 4, and the angle between them is 90°. The fins on adjacent circumferences are staggered by 30 degrees, and for column equipment with axial fins, the resonance amplitude will be reduced by about 1/2.

When the fins are helical, they have a head count of 3, staggered by 120. The pitch t is 5 times the diameter d, and the width w of the fins is 0.1 times the diameter d, where the diameter refers to the outer diameter of the column, including insulation. Spiral paper is more efficient than axial fins.

Let's take a look at the anti-vibration structure and windproof ring on the chimney.

The wind deflector is a part on the chimney. In order to avoid or reduce the resonance of the chimney caused by the Karman vortex caused by the airflow, the upper section of the chimney is welded with spiral wound strips or fins. There are also axial arrangements.

When the fluid flows laterally through the cylinder, vortices are generated alternately on both sides of the back of the cylinder, and after separation, a vortex tail is formed, also known as "Karman vortex".

The vortex is generated by the mutual conversion of kinetic energy and pressure energy after the fluid is blocked, and the pressure changes along the circumference of the cylinder and the thickness of the boundary layer. The higher pressure of the fluid outside the boundary layer forces the particles with lower pressure inside the boundary layer to flow in the opposite direction, thereby thickening the boundary layer, forming a vortex, and then separating from the cylinder. As the flow rate increases, the vortex lengthens and disappears. When the vortex on one side grows and separates, the vortex on the other side is forming and growing, thereby alternately forming two rows of vortex wakes, similar to a "vortex street". The vortices in the Karman vortex street are generated, separated and dissipated at a certain frequency, and the pressure on both sides of the cylinder changes periodically at the same frequency. When the vortex shedding frequency is equal to the natural frequency of a certain mode of the cylinder, the cylinder will vibrate violently, which is an induced vibration. Experiments show that the vortex shedding frequency is related to the outer diameter of the cylinder and the fluid velocity. When the tower frame is subjected to wind load, when the above conditions are met, periodic eddy currents will appear and induce vibration, which may lead to equipment failure and damage in severe cases.

The chimney design should avoid resonance caused by eddy currents. Increasing the stiffness of the chimney or adding a concrete lining can improve the chimney's resistance to vibration. But a more effective method is to weld a helical outer "windshield" to the top of the chimney.

Jiangsu Kaitong Boiler and Pressure Vessel Co., Ltd. is mainly engaged in non-standard vessels, towers, condensers, chemical equipment, steam boilers, electric boilers, hot water boilers, heat exchangers, low nitrogen boilers, reactors, storage tanks, Gas storage tanks, high-efficiency heat exchangers, etc. In line with the corporate philosophy of "creating green energy equipment for human beings and creating technological products for the industry", the company always adheres to the operation of "market-oriented, innovation-driven, quality-based survival, and development-oriented growth". The concept, will rely on the continuous innovation of science and technology and advanced modern management concepts, to produce high-quality, high-performance boiler and pressure vessel products, as well as good service to win the trust of the majority of users; willing to work together with the majority of users, mutual benefit, Work together to create a brilliant future for the enterprise.

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Jiangsu Kaitong Boiler and Pressure Vessel Co., Ltd.

Address: No. 3, Fuyou Road, Huoqiao, Guangling Economic Development Zone, Yangzhou City, Jiangsu Province
Tel: 086-514-87790780  

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