A fan is a driven fluid machine that relies on the input of mechanical energy to increase the pressure of the gas and exhaust the gas. Gas compression and gas transportation machinery is a machine that converts rotating mechanical energy into gas pressure energy and kinetic energy, and transports the gas out. Fans in China are short for gas compression and gas conveying machinery. Fans can be divided into many different types according to a variety of classification methods. Blower, ventilator, wind generator, etc. are often said.
It can be known from the principle of fluid mechanics that the air volume of the fan is greatly related to the speed of the motor: the air volume of the fan is proportional to the speed of the fan, the wind pressure of the fan is proportional to the square of the speed of the fan, and the shaft power of the fan is equal to the air volume and wind The product of pressure, so the shaft power of the fan is also proportional to the cubic power of the fan's speed. With the continuous improvement, development and progress of frequency conversion technology in recent years. The frequency conversion speed regulation performance of the fan is more and more developed, which saves energy to a large extent, and has been widely used in various fields. The energy-saving benefits obtained by the fan frequency conversion energy-saving method have brought a lot of economic benefits to enterprises in all walks of life, and greatly promoted the automation development process of social industrial production.
First, the frequency conversion energy saving principle of the fan
At present, most of the fan equipment uses asynchronous motors to directly drive the fans to save energy. This method has certain defects and problems, such as poor electrical protection characteristics, excessively high current, Generate mechanical shock, etc. When the load of the motor is too large, it will affect and reduce the service life of the equipment to a certain extent. It will also cause some mechanical failures, and often the motor will be burnt and burned.
Fan frequency converter is a new type of energy-saving product in modern society. Under the condition that the pipeline performance curve is unchanged, variable speed adjustment uses variable speed to change the performance curve of the fan, and then change its operating point. Fan frequency converter has many advantages such as easy operation, high control accuracy, high performance, no maintenance and so on. In the case that other conditions have not changed, it is necessary to change the asynchronous motor, and the input power frequency of the secondary terminal to change the speed of the motor is the basic working principle of the variable frequency speed regulation technology of the fan. The relationship between the motor speed and the input frequency of the working power is proportional: n = 60 (fs) / p. In the formula, n is used to indicate the speed, f is used to indicate the input frequency, s is used to indicate the motor slip rate, and p is used to indicate Number of motor pole pairs. For the control of the exit baffle, when the opening degree is reduced, the wind resistance will increase, which is not suitable for large-scale adjustment of the air volume. The control of the inlet baffle is relatively broader than that of the outlet baffle for controlling the air volume. The shaft power when the opening is reduced is generally proportional to the air volume, but it is still not as good as the energy saving effect of frequency conversion.
Generally, it is considered that when the operating air volume is not the rated air volume of the fan design, if the throttle control is used for adjustment, the resistance of the pipe network is changed by reducing the opening of the damper, so that the curve of the pipe network characteristics becomes steep, causing the flow at the operating point. Lower the pressure and increase the pressure. With the speed control method, the baffle is fully opened, and the pipe network resistance is constant. If you want to ensure the same air volume, you need to reduce the speed of the fan and reduce its pressure.
Second, the problem of fan frequency conversion energy saving
In the production process of enterprises in all walks of life, the application of fans is more common. Traditional throttling methods are mainly carried out by using deflectors, resulting in fans that do not have high operating efficiency, resulting in a large degree of energy. It is a waste situation, and the cost of continuous maintenance and repair of the fan also increases the production cost of the enterprise to a certain extent. Most of the fans and blowers used by enterprises are centrifugal fans. The control of air volume by centrifugal fans is mainly adjusted by the damper baffle at the inlet of the fan, which will not only waste a lot of energy, but also cause vibration during fan operation Large, high noise, negative pressure in the furnace of the equipment is not stable enough, prone to a variety of adverse conditions such as heating. In the actual production process of the enterprise, the amount of steam used is small. Generally, contactors are used to control the boiler blast and induced air. Frequent start-stops cause a lot of waste of energy and unstable operating conditions. problem.
Three, fan inverter energy saving
3.1 Fan inverter energy saving system
In the process of variable frequency speed regulation of the fan, the resistance of the pipe network does not change, and the fan operates under similar conditions, and the efficiency of the fan will not change much or even remain unchanged. When the fan keeps running in the high-efficiency zone, and the flow rate is decreasing, the wind pressure is also declining. The energy saving effect of the fan is the best when it meets the needs of working conditions. The most effective way to save energy is to adjust the frequency of the fan. The requirements of the fans for overload capacity are not high, and the requirements for the speed are not very high. When selecting, use the common frequency converters of ordinary functions. In general, the frequency conversion speed regulation of the fan is preferably not lower than 50% of the rated speed, and it is best to control it between 70% and 100%. The frequency conversion speed regulation of the fan can determine its minimum speed according to the road characteristic curve of the ventilation duct under actual conditions.
3.2 Fan energy saving methods
Fan frequency conversion energy saving has various power saving methods such as reducing running time, using high-efficiency machines and equipment, reducing aerodynamics, and so on. Fan frequency conversion and energy saving include electromagnetic speed regulation motor speed regulation, rotor circuit string resistance speed regulation, pole changing speed regulation, hydraulic coupling clutch speed regulation, pressure regulation speed regulation, voltage regulation frequency regulation speed and other speed regulation methods. The speed control of the fan is an energy saving method to reduce aerodynamics. It mainly uses the principle that the power of the shaft is proportional to the cubic power of the speed. It has obvious energy saving efficiency compared with the commonly used method of controlling the air volume by adjusting the opening of the damper. .
3.3 Calculation of energy saving
Take a 30kW blower as an example: The blower runs continuously for 24 hours. During the operation, the 10-hour operation is at 90% load. The frequency is calculated according to 46Hz. The motor when the baffle is adjusted The power consumption is calculated according to 98%; the blower runs at 50% load for fourteen hours, its frequency is calculated at 20Hz, and the power consumption of the motor when the baffle is adjusted is calculated at 70%. If the annual operating time of the blower is three hundred days, the total energy saved in a year is 98254kW · h. If calculated based on 0.6 yuan per kilowatt-hour, the total electricity cost saved by the energy-saving method of variable frequency speed regulation is 58952 yuan. It can be seen that the energy-saving method of fan frequency conversion can save energy to a large extent, and save a lot of production costs for the production activities of enterprises.
3.4 Fan frequency conversion energy saving effect
The use of fan frequency conversion energy-saving methods can achieve very good results, for example: the noise and vibration generated by fan frequency conversion energy-saving methods are greatly reduced; the safety and stability of fan operation is improved; a large amount of energy is saved, and the company Production costs, etc.
In order to ensure the safe, stable and reliable production activities of enterprises, a variety of production machinery such as fans and pumps must retain a certain margin when they are designed to be driven with power, such as induced fans, axial fans , exhaust Fan, blower, centrifugal pump, drainage pump, etc. Most of the loads such as fans and pumps are selected according to the required amount of work at full load. In the application of actual working conditions, most of the time is not working at full load.
Fourth, the conclusion
At present, fans are widely used in all walks of life in China. Frequency conversion energy saving of fans is a modern and mature energy-saving technology that can improve energy utilization to a certain extent. It is believed that with the rapid development of economy and science and technology, the frequency conversion and energy saving methods of fans will also make greater progress, and better and more efficient energy saving methods are continuously researched in order to use the fans more effectively for modern industries.