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0ПРИБОРОСТРОЕНИЕ, МЕТРОЛОГИЯ И ИНФОРМАЦИОННО-ИЗМЕРИТЕЛЬНЫЕ ПРИБОРЫ И СИСТЕМЫ
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© Qin Hongwu, Li Xinze, Chye En Un, V. V. Voronin, 2021
RESEARCH ON THE MECHANISM OF WIND TURBINE BLADES ICE COATING AND ANTI-ICING METHODS
Qin Hongwu - PhD, Assistant Professor, Director of Russia Institute, e-mail: hongwuqin@live.ru; Li Xinze - PhD, Assistant Professor, Electronic Information Engineering College, e-mail: 2361298215@qq.com (Changchun University, Changchun, China); Chye En Un - Doctor of Technical Sciences, Professor, Head of the Department "Automation and System Engineering", e-mail: 000487@pnu.ed.ru; Voronin V. V. - Doctor of Technical Sciences, Professor, Department "Automation and System Engineering", , e-mail: 004183@pnu.edu.ru (Pacific National University)
When wind turbine runs in the environment of high wind speed, low temperature and high humidity for a long time, blade icing often occurs. Blade icing will lead to a significant decline in the output power of wind turbines, and even lead to downtime. Therefore, the anti-icing methods of wind turbines have become a hot issue in the world. This paper discusses the causes of blade icing of wind turbine. Through an example, the influence of blade icing on the output power of wind turbine is analyzed by calculating the power coefficient of wind turbine. Finally, the common methods of blade anti-icing and deicing are listed, and their advantages and disadvantages are analyzed.
Key words: blade icing; wind turbine power; anti-icing methods.
1. Research status of wind turbine blade icing 1.1. Causes of wind turbine blade icing
In the process of the development of new energy, the use of wind power has attracted the attention of all countries in the world because of its short construction period, low environmental requirements, rich reserves and high utilization rate. Wind energy has many advantages, such as clean, pollutionfree, widely distributed, large storage capacity and so on.
Wind energy resources are greatly affected by topography, and most of the world's wind energy resources are concentrated in coastal and open conti-
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13г
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nental contraction zones. Therefore, most of the wind power plants are located in the plateau, ridge, peak and other high altitude areas and high latitude areas with abundant wind energy resources. For wind turbines, the most important factors affecting the icing of wind turbine blades are environmental factors, including temperature, wind speed, and liquid water content in the air. Ice can adhere to most known polymers, including polyurethane resin coating of wind turbine blades. Therefore, when the wind turbine blades are in the environment of low temperature, high humidity and high wind speed, different degrees of blade icing will inevitably occur. Due to the different geographical location, wind energy resources in China are mainly concentrated in the northeast, northwest and North China and other areas with open terrain and cold climate. These areas will be affected by the cold air in winter and spring, which leads to the formation of rime or mixed rime on the blade surface of wind turbine. During the long-term operation of wind turbine, the blade surface becomes rough due to the stains on the blade surface and the falling off of leading edge coating, which makes the blade surface easier to freeze.
1.2. Wind turbine blade icing hazards
When the blade surface freezes, it will cause the following hazards:
1. The ice layer will change the surface roughness of the blade and reduce the aerodynamic performance of the blade, thus reducing the output power of the unit. In serious cases, the blade torque will be reduced to zero, and the unit will stop power output completely.
2. Ice coating on the blade surface will increase the load of the blade and other key components. Uneven ice coating may also cause blade vibration, resulting in larger amplitude of the blade and speeding up the life loss of the key components of the unit.
3. Blade icing will increase the measurement error of wind speed and direction measuring instrument, cause the wrong operation of the unit, make the fan out of the best operation state, and reduce the power output of the unit.
4. When the ice layer of the blade melts and falls off, because most of the ice layer is located at the tip of the blade, the falling ice has a large centrifugal force, which will make the ice fly out along the rotation direction of the blade, which will damage other units nearby and cause hidden danger to the life safety of workers.
RESEARCH ON THE MECHANISM OF WIND TURBINE BLADES ICE COATING AND ANTI-ICING METHODS
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Fig. 1. Blade icing
1.3. Influence of blade icing on wind turbine power
The theory mainly analyzes the wind turbine flow velocity and the force on the wind wheel, obtains the change of momentum and kinetic energy in the direction of the main axis, and obtains the ideal output power and efficiency. The single flow tube model of momentum theory is shown in Fig. 3, which makes some ideal simplifications and assumptions for fans:
1. It is assumed that the flow is complete axial flow;
2. It is assumed that the air flow is incompressible, steady and even symmetrical;
3. The friction of the air flow passing through the blade is ignored;
4. The air flow satisfies the mass continuity equation.
Fig. 2. Single flow tube model of wind turbine
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Fig. 3. Steady state power curve of wind turbine
After the air flow passes through the fan, the wind speed decreases from V1 upstream of the fan blade to V2 in the downstream. The effect of air flow on the blade axial thrust is based on the momentum theorem:
F■ t = m■ V -m■ V2
The axial thrust of the fan can be calculated as follows:
Ft = pAV (V - V),
where Ft is the axial thrust of the fan, M is the mass of air flowing through the unit time, p is the air density, A is the swept area when the fan blade rotates, V is the wind speed at the fan blade, and it is assumed that the wind speed is equal at all places on the whole rotating plane of the fan blade.
The relationship between the wind speed at the blade and the wind speed far upstream and far downstream of the blade is as follows:
v = 1(v+v2)
It is necessary to define a very important parameter in the aerodynamic performance calculation of horizontal axis fan blade: axial induction factor a.
v
a = —
V
where V is the axial induced velocity.
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ANTI-ICING METHODS
Therefore, the wind speed at the fan blade is:
V = V - v = V (1" a)
Therefore, the kinetic energy of the fan can be calculated. If all of the energy can be converted into output, the output power of the fan can be expressed as:
1 , 1 ,
P • t = W = - mV2 — mK2 2 1 2 2
P = 2pAVx 3(1 - a)2 a
The power factor of the fan, i.e. the utilization rate of wind energy, is as follows:
P
Cp =--= 4(1 - a)2 a
2 ^
By derivative calculation, the maximum wind energy utilization coefficient is obtained when a = 1/3.
C = 0.593
pmax
Blade icing affects the aerodynamic performance of the blade. Due to the change of the airfoil parameters, C is reduced, which leads to the loss of power generation when the wind speed is lower than the rated wind speed. The following is the steady-state power curve of wind turbine before and after blade icing.
In this case, the wind turbine reaches the rated power when the wind speed reaches 10.9 m/s. It can be clearly observed that the power curve drops sharply when the wind speed is between 10.9 m/s and 13.2 m/s, which indicates that the blade of the wind turbine stalls when there is icing on the blade surface, and the control system cannot accurately adjust the pitch action of the wind turbine near the rated wind speed. In this section of wind speed range, the blades of wind turbine may work under stall conditions, which may cause large amplitude vibration of blades and affect the safe and stable operation of wind turbine. Therefore, it is necessary to deal with the icing of wind turbine blades in time.
2. Anti-icing methods of fan blades
In the aviation field, two systems will be used to remove the ice layer of the wing, namely anti-icing system and deicing system. The deicing system removes the ice layer from the wing, while the anti-icing system prevents the wing from icing. These two types of systems have also been tried and tested on the fan blades. Wind turbine blade anti-icing and deicing method has been one
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of the hot research directions at home and abroad. Anti-icing system is the so-called active deicing system, which uses some specific means to prevent the blade surface from icing. The common technologies are as follows.
1. Anti-icing coating. A kind of hydrophobic coating is used on the blade surface to reduce the adhesion of super-cooling droplets on the fan blade, so as to achieve the purpose of anti-icing. At present, the commonly used types of anti-icing coatings are polytetrafluoroethylene, endogenic acid and silicone. But its disadvantage is that the coating is easy to aging and fall off, which needs regular maintenance and repair.
2. Liquid anti-icing. When the anti-icing liquid is applied on the surface which is easy to be covered with ice, the anti-icing liquid will be mixed with water to reduce the freezing point and the possibility of ice layer.
3. Hot air anti-icing. Hot air anti-icing is the use of heat energy for anti-icing treatment, through a variety of heat sources to improve the temperature of blades and key components of wind turbine, to prevent it from falling below the freezing point, in order to prevent icing. Hot air anti-icing is divided into two kinds of anti-icing technologies: electric heating anti-icing and air heating anti-icing. Generally, in the production of blades, the electric heating anti-icing device will be set inside the blades to provide the energy required for anti-icing by converting the electric energy into heat energy; the fan blades will also be installed with warm air circulation pipes to heat the various components by warm air.
Wind turbine blade deicing technology, also known as passive deicing, uses some equipment or technology to remove the ice layer on the blade surface, which is suitable for wind turbines with serious icing conditions. If it is not treated, the power of the wind turbine will be reduced, or even the power output will be completely stopped. The commonly used blade deicing techniques are as follows.
1. Mechanical deicing. Mechanical deicing is a method that directly smashes the ice layer on the blade by machinery or manual, and then uses centrifugal force, gravity, vibration and other ways to make the ice break away from the blade surface. This technology is the most commonly used passive deicing technology with low cost, simple implementation and good deicing effect. But the need to stop the blade rotation will affect the power output of the wind turbine.
2. Thermal energy deicing. The principle of thermal energy deicing is consistent with that of thermal energy anti-icing. Various kinds of thermal energy are used to make the temperature of the fan blade reach above the freezing point, so that the ice layer attached to the blade melts and falls off, so as to achieve the purpose of deicing.
RESEARCH ON THE MECHANISM OF WIND TURBINE BLADES ICE COATING AND ANTI-ICING METHODS
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3. Deicing by expansion pipe. Expansion tube deicing is also known as pneumatic belt deicing. The principle is to arrange expandable rubber tubes on the blade surface in advance, use the volume change generated by rubber tube expansion to break the ice layer on the blade surface, and then use the centrifugal force and gravity generated by blade rotation to make the ice fall off. After that, the compression pump is used to make the hose shrink to prepare for the next deicing. Its disadvantage is that it is difficult to maintain, and its service life is low, so it needs to be replaced frequently.
3. Conclusion
As a new type of energy, wind power generation accounts for an increasing proportion in the energy structure of countries all over the world. However, with the global climate conditions getting worse and worse, wind power generation is restricted more and more seriously in the icing period, which affects the power generation efficiency of wind turbines to a great extent. Therefore, solving the problem of wind turbine blade icing has great significance for improving the output power of wind turbines in the icing period is of a great practical significance.
4. Acknowledgement
In this paper, the research activities have been funded by Jilin Provincial Science and Technology Department (No. 202523GH010277329).
References
1. Xu J, Tan W, Li T. Predicting fan blade icing by using particle swarm optimization and support vector machine algorithm [J]. - Computers & Electrical Engineering, 2020. - 87:106751.
2. Wei K, Yang Y, Zuo H, et al. A review on ice detection technology and ice elimination technology for wind turbine [J]. - Wind Energy, 2020. - 23(3): 433-457.
3. Peng C, He J, Chi H, et al. Icing Prediction of Fan Blade based on a Hybrid Model [J]. - International Journal of Performability Engineering, 2019. - 15(11): 2882.
4. Jia P, Chen G. Wind Power Icing Fault Diagnosis Based on Slow Feature Analysis and Support Vector Machines [C] //2020 10th International Conference on Power and Energy Systems (ICPES). IEEE, 2020. - P. 398-403.
5. Jiang W, Jin J. Intelligent Icing Detection Model of Wind Turbine Blades Based on SCADA data [J]. arXiv preprint arXiv:2101.07914, 2021.
Заглавие: Исследование механизма обледенения лопастей ветротурбин и методов борьбы с обледенением
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Авторы:
Цинь Хуну - Чанчуньский университет, Чанчунь, КНР Ли Кинзе - Чанчуньский университет, Чанчунь, КНР
Чье Ен Ун - Тихоокеанский государственный университет, Хабаровск, Российская Федерация
Воронин В.В. - Тихоокеанский государственный университет, Хабаровск, Российская Федерация
Введение: Работа ветротурбин при высокой скорости ветра, низкой температуры и высокой влажности в течение длительного времени часто приводит к обледенению лопастей. Это в свою очередь приводит к значительному снижению выходной мощности ветрогенераторов и даже к выходу из строя. Поэтому актуальной проблемой является разработка и исследование методов борьбы с обледенением ветротурбин. В данной работе рассматриваются причины обледенения лопастей ветрогенератора. На примере расчета коэффициента мощности ветротурбины анализируется влияние обледенения лопастей на выходную мощность ветротурбины. Также рассмотрены общепринятые методы противообледенительной обработки лопастей, проанализированы их преимущества и недостатки.
Ключевые слова: обледенение лопастей; мощность ветряных турбин; методы борьбы с обледенением.
