The fan is a machine that converts input mechanical energy into pressure potential energy, transporting gas by increasing gas pressure. We generally refer to fluid equipment with an exhaust pressure of less than 200 kPa as fans, which typically include ventilators and blowers.

As one of the three major general-purpose devices in industry, fans play a crucial role in industrial production, mainly applied in power transmission, ventilation, and combustion media. At the same time, fans also account for 10-30% or even higher electricity consumption in industrial production.

Development History

The invention of the fan can be traced back to ancient China, where simple wooden grain grinding windmills were already manufactured. Its working principle is fundamentally similar to that of modern centrifugal fans, converting manually input mechanical energy into aerodynamic energy, and its use is also very similar to modern fans, filtering out the grain husk and transporting it. It wasn't until 1862 that Western countries began to invent centrifugal fans, and it took more than a hundred years for fans to gradually evolve into the form used today.

Equipment Classification

Modern fans can be classified into three types based on the direction of gas flow: centrifugal fans, axial fans, and rotary fans. The comparison of the three types of fans is as follows:

1. Axial Fan. The airflow enters the fan's impeller axially, flowing approximately along the axis direction on a cylindrical surface. The structure of axial fans is relatively simple, and their use is also relatively singular, generally only used in ventilation and air exchange places. Their exhaust wind pressure is relatively low, and when calculating efficiency, they can generally be regarded as incompressible fluids, thus having higher efficiency, not falling within the scope of magnetic levitation blower transformation.

2. Rotary Fan. Works by changing the volume of the gas chamber through the rotation of the rotor. The Roots blower belongs to the rotary fan category and is currently the main object of energy-saving transformation using magnetic levitation blowers. Roots blowers are widely used in gas-solid two-phase flow pneumatic conveying, sewage aeration treatment, and other processes. Due to their high noise, low energy efficiency, and significant environmental pollution, energy-saving transformation of Roots blowers has become the primary transformation target.

1. Centrifugal Fan. After the airflow enters the fan's impeller axially, it mainly flows radially. This type of fan is made based on the principle of centrifugal action, including centrifugal ventilators, centrifugal blowers, and centrifugal compressors. Magnetic levitation blowers, according to the above classification, belong to centrifugal blowers, but their impellers are made of titanium alloy, adopting a three-dimensional flow design to reduce gas flow resistance. The bearings are magnetic levitation bearings, with zero contact between the main shaft and the bearings, reducing mechanical friction compared to ordinary bearings, while also reducing the use of lubricating oil, achieving modern intelligent control and remote monitoring. Compared to ordinary centrifugal fans, they have higher operational efficiency, higher intelligence, and a higher degree of modernization.

Energy-saving Analysis

Currently, the main object of transformation and replacement with magnetic levitation blowers is the Roots blower. Compared to the Roots blower, the energy-saving of magnetic levitation blowers is mainly reflected in the following aspects:

Using magnetic levitation bearings, utilizing magnetic principles to suspend the motor and impeller's main shaft, with no contact, no friction, and no lubrication, completely eliminating mechanical wear in the bearing part, resulting in an energy-saving rate of about 5%.

The impeller adopts a three-dimensional flow design, using high-strength aerospace forged aluminum alloy or titanium alloy , significantly reducing flow resistance compared to traditional centrifugal fan impellers, thereby improving operational efficiency. In contrast, the Roots blower's variable volume operation mode leads to increased internal leakage as operating pressure rises, resulting in low operational efficiency. The adiabatic efficiency of a Roots blower with an exhaust pressure of 80 kPa is only about 60%, while the adiabatic efficiency of magnetic levitation blowers can reach 80%-90%.

Using high-speed direct-drive permanent magnet synchronous motors, the motor efficiency can reach 97%, which is 8-10% higher than that of ordinary three-phase asynchronous motors. The high-speed direct-drive transmission method reduces mechanical friction compared to gears or belts, and under variable frequency operating conditions, permanent magnet motors are also more energy-efficient.

Transformation Comparison

Compared to traditional industrial fans, the use of magnetic levitation fans for transformation not only generates considerable energy-saving benefits but also offers advantages such as lower noise, aesthetically pleasing appearance, and an intelligent operating interface, greatly surpassing traditional fans in the industrial field. Taking the transformation of Roots blowers as an example, the comparison before and after the transformation is as follows:

Author's Summary

On December 31, 2020, the National Development and Reform Commission, the Ministry of Science and Technology, the Ministry of Industry and Information Technology, and the Ministry of Natural Resources jointly issued the "Green Technology Promotion Catalog (2020)", in which "Comprehensive Energy-saving Technology for Magnetic Levitation Centrifugal Blowers" ranked second, also being the first item in energy-saving technology in the industrial field. Prior to this, magnetic levitation blower technology had been included in the "National Industrial Energy-saving Technology Equipment Recommendation Catalog (2019)" and the "National Major Energy-saving Low-carbon Technology Catalog 2017 Energy-saving Section". This shows that the maturity and reliability of magnetic levitation blower technology have also been recognized by relevant departments.

The implementation of magnetic levitation blowers in the industrial blower field is revolutionary, with a significant increase in energy-saving rates, substantial improvements in the operating environment, and the emergence of intelligence from scratch, all reflecting the absolute advantages of magnetic levitation blowers compared to traditional fans. Among the implemented transformation projects, in addition to the high energy-saving rate of Roots blower transformations, other types of fans also show certain energy-saving rates, and the noise, intelligence level, and operating environment will qualitatively improve after transformation. Since its establishment, the Chongqing Energy Conservation Center has been committed to promoting advanced energy-saving technologies, and the center will support the transformation of magnetic levitation blower technology, driving this revolution in the traditional industrial fan industry!