In-depth disassembly of the core components of an air‑suspended centrifugal blower: From air bearings to intelligent control—how is an oil‑free, high‑speed blower engineered?

Against the backdrop of the “dual carbon” goals and industrial energy conservation and carbon reduction, Air-Suspension Centrifugal Blower It is rapidly replacing traditional Roots blowers and multi-stage centrifugal fans, and is widely used in municipal wastewater treatment, cement production, the chemical industry, food fermentation, pneumatic conveying, and flue gas desulfurization and denitrification.

The term “air‑borne suspension” is not merely a marketing buzzword; it stems from the technology’s core bearing— the aerodynamic journal bearing—which enables a high‑speed rotor to remain fully suspended on an air film during operation, achieving contactless, oil‑free lubrication.

So, what key components make up the interior of an air‑suspension centrifugal blower? What role does each component play? Where do the technical challenges lie? And how do intelligence, energy efficiency, and environmental protection come into play? This article provides a comprehensive overview.

I. System Overview: Establishing a High-Level Understanding First

An air‑suspended centrifugal blower is not a standalone device; rather, it is a highly integrated system that combines fluid mechanics, materials science, power electronics, automatic control, and IoT technologies.

Its core structure can be summarized as:

High-speed permanent-magnet synchronous motor + air‑floating bearing + three‑dimensional flow impeller + high-frequency inverter + intelligent control system + high-efficiency cooling and filtration system

The basic workflow is as follows:

1. Ambient air passes through an intake filter to remove dust and particulate matter.
2. The filtered air enters the fan unit, where a portion is directed into the impeller and compressed, generating pressurized gas.
3. Another portion serves as cooling air, flowing through the high-speed motor’s stator, rotor, and air bearings to carry away heat.
4. A high-frequency inverter drives a permanent‑magnet synchronous motor at high speed, with the motor directly coupling to the impeller—eliminating the need for a gear‑reduction gearbox.
5. The intelligent control system continuously monitors parameters such as flow rate, pressure, temperature, vibration, rotational speed, and power, and automatically adjusts the operating conditions.
6. The compressed gas is discharged through the diffuser and volute into the user’s pipeline network.

Compared with conventional Roots blowers, air‑suspended centrifugal blowers eliminate the gearbox, lubrication system, belt drive, and contact bearings, fundamentally reducing mechanical losses, oil contamination, and maintenance costs.

Next, we will break down its key components one by one.

II. Air‑bearing Technology: How to Make a Rotor Rotating at Tens of Thousands of RPM “Float” in the Air?

1. Operating principle: dynamic-pressure air film, rather than an external air source.

Air‑bearing technology is one of the most critical and technically demanding components of the entire machine.

It belongs to Hydrodynamic air-floating bearing , it does not require an external gas supply. Its basic principle is:

When the rotor spins at high speed, air between the journal and the bearing foil is drawn into the wedge-shaped clearance. As the clearance converges, the air is compressed, forming a pressurized gas film capable of supporting the load. Once the rotational speed reaches a certain threshold—known as the “take-off speed”—the gas‑film pressure becomes sufficient to fully lift the rotor, enabling contactless operation between the rotor and the bearing.

Simply put: The higher the rotational speed, the greater the gas‑film stiffness, and the more stable the levitation.

During the stationary and low-speed phases, contact friction occurs between the rotor and the bearing surfaces; therefore, the bearing surfaces require a high-performance wear-resistant coating. Upon startup, the bearings experience brief boundary lubrication; once “takeoff” is achieved, they transition to a wear-free operating regime.

2. Structural Composition: Radial Bearing and Thrust Bearing

Air‑bearing technology is broadly classified into two main types:

Radial bearing

The commonly used type is the wave‑foil aerodynamic journal bearing, which consists of two layers of foil:

• Flat foil : Forms an air film with the rotor surface, directly bearing the load;
• Wave foil : Located beneath the flat foil, it features a wavy profile, providing elastic support and structural damping.

The stiffness, wave height, wavelength, and material thickness of the foil‑type bearing directly influence its load‑carrying capacity, stiffness, and damping characteristics. An optimized foil design can effectively suppress sub‑synchronous vibrations in high‑speed rotors, thereby enhancing system stability.

Thrust bearing

It is used to withstand the axial forces generated during fan operation. Typically, it consists of a thrust disk and sector‑shaped foil pads on both sides. When the rotor undergoes axial displacement, the gas film on one side is compressed, leading to a pressure increase, while the pressure on the opposite side decreases, thereby generating a restoring force that achieves axial levitation.

3. Materials and Coatings: The Key to Determining Service Life

The foil material of air‑bearing systems is typically a nickel‑based superalloy, and common surface coatings include:

• Polytetrafluoroethylene-based composite material;
• Molybdenum disulfide;
• Graphite;
• Diamond-like carbon coating.

These coatings provide low-friction, wear‑resistant protection during start‑stop cycles, directly impacting bearing life and reliability. High‑end products can withstand over 20,000 start‑stop cycles and require no maintenance during normal operation.

4. Comparison with Magnetic Levitation Bearings

Air‑suspension solutions are distinguished by their simple structure, high reliability, and controllable costs, and have been successfully implemented in medium- and low‑power high‑speed blowers.

5. Key Takeaways: Technical Challenges of Air Bearings

• Micron-level gap control;
• Wave foil stiffness and damping matching;
• Start-stop wear-resistant coating life;
• Coupling between the rotor’s critical speed and the gas‑film stiffness;
• The influence of dust and moisture on the stability of the gas film.

This is also why air‑suspended blowers have extremely stringent requirements for inlet air filtration.

III. Three-Dimensional Flow Impeller: The Core Aerodynamic Component Driving Efficiency Breakthroughs

1. Function and Principle

The impeller is the only component in a fan that performs work on the gas. As it rotates at high speed, the impeller converts mechanical energy into both kinetic energy and pressure energy of the gas, which are then further transformed into pressure energy by the diffuser.

Air‑suspended centrifugal blowers are commonly used. Three-dimensional flow impeller 。

2. What is three-dimensional flow design?

Traditional two-dimensional flow design assumes that the airflow flows on a rotational surface, with radial velocity uniformly distributed along the blade height. In reality, however, the flow is a complex three-dimensional phenomenon, characterized by:

• The meridional velocity is non-uniform;
• Boundary-layer separation on the blade surface;
• Secondary flow;
• Tip leakage vortex.

The three-dimensional flow design, through CFD numerical simulation, simultaneously solves for the velocity distributions in the meridional plane, the rotational plane, and the radial direction, optimizing blade angles and load distribution, thereby:

• Reduce flow separation;
• Reduce secondary flow losses;
• Expand the scope of the high-efficiency zone;
• Improve isentropic efficiency.

The isentropic efficiency of a typical three-dimensional impeller can reach 85% to 90%, with a broad high-efficiency range and excellent performance under partial-load conditions.

3. Impeller Design and Material

Common forms:

• Closed impeller : With a wheel cover, it features low leakage losses and high efficiency;
• Semi-open impeller : No wheel cover, high strength, but relatively large leakage losses.

Regarding materials, selection should be based on rotational speed and the process medium:

• Cast/forged aluminum alloys: lightweight, suitable for medium to low rotational speeds;
• Precipitation-hardening stainless steel: high strength and corrosion resistance;
• Titanium alloy: high specific strength, suitable for high linear velocities;
• Nickel-based alloys may be used under special operating conditions.

At high rotational speeds, the impeller is subjected to substantial centrifugal stresses, making material strength, weld and machining quality, and the level of dynamic balancing critically important. Typically, dynamic balancing must meet ISO G0.4 standards, and an overspeed test is performed.

4. Matching with High-Speed Motors

The impeller is mounted directly on the motor shaft’s cantilever end, eliminating the need for a gearbox. Design considerations include:

• Rotor dynamics;
• Impeller mass and cantilever length;
• The critical speed is kept away from the operating speed.
• The pneumatic axial force is matched with the thrust bearing.

IV. High-Speed Permanent-Magnet Synchronous Motor: A Compact, High-Power-Density Powerhouse

1. Why use a high-speed motor?

Increasing the rotational speed of a centrifugal fan can significantly reduce both the impeller diameter and the overall unit size. Conventional motors typically operate at speeds below 3,000 rpm, necessitating a gear‑driven speed increaser. In contrast, air‑suspended centrifugal blowers utilize… Direct drive of high-speed permanent magnet synchronous motor , with rotational speeds reaching 20,000 to 60,000 rpm; some compact models can even attain 100,000 rpm.

Direct-drive advantages:

• Eliminate the gearbox, reducing transmission losses by approximately 3% to 5%.
• Reduce mechanical failure points;
• Compact structure and lightweight;
• Fast dynamic response.

2. Key Technologies in Motor Design

A high-speed permanent-magnet synchronous motor consists of a stator, rotor, permanent magnets, a protective sleeve, bearings, and other components.

Rotor and Permanent Magnet

Neodymium‑iron‑boron is commonly used for permanent magnets, while samarium‑cobalt is preferred for applications requiring higher temperature resistance. Because the rotor spins at high speeds, the permanent magnets are subjected to substantial centrifugal forces and must be protected by a high‑strength external housing; common materials include:

• Carbon fiber composite material;
• Titanium alloy;
• High-strength alloy steel.

The sheath design must take into account:

• Preload;
• Stress relaxation at elevated temperatures;
• Rotor eddy current losses.

Stator

High-speed motors operate at high frequencies, resulting in significant iron losses. The stator typically employs ultra-thin, high-grade silicon steel laminations with thicknesses as low as 0.1 to 0.2 mm to reduce high-frequency eddy-current losses.

Losses and Temperature Rise

High-speed motors have a high power density, and their losses include:

• Copper loss;
• Iron loss;
• Rotor eddy current losses;
• Wind-mo loss.

Windage losses are proportional to the square—or even higher powers—of the rotational speed; therefore, for high-speed motors, both the rotor surface finish and the design of the cooling‑gas flow passages must be meticulously optimized.

Typical high-speed permanent-magnet motors achieve efficiencies of 96% to 97%, significantly higher than those of conventional induction motors.

V. Inverters and Intelligent Control Systems: The “Brain and Nervous System” of the Entire Machine

1. High-frequency inverter

The supply frequency of high-speed motors is much higher than the mains frequency. Taking a 2-pole motor as an example:

• At 30,000 rpm, the fundamental frequency is 500 Hz.
• At 60,000 rpm, the fundamental frequency is 1,000 Hz.

Therefore, a high-frequency inverter must be used, with an output frequency typically ranging from 1,000 to 2,000 Hz.

The core technologies of high-speed inverters include:

• Sensorless Vector Control : No encoder is required; the rotor position is estimated using either back-EMF or a flux observer.
• Weak-field control : Constant-power operation is achieved in the high-speed region;
• Low-switching-loss modulation : Reduce harmonic losses under high fundamental frequency;
• Output filtering : Install reactors or sine wave filters to suppress higher-order harmonics and protect motor insulation.

2. Power Device Upgrades: Cutting-Edge Applications of SiC and GaN

The new generation of air‑suspension blowers is beginning to adopt Silicon Carbide (SiC) Power Module Compared with conventional IGBTs, SiC devices offer:

• Lower switching losses;
• Higher temperature resistance;
• Higher switching frequency;
• System efficiency can be further improved by 1% to 2%.
• The filter’s volume has been reduced.

This aligns perfectly with the demands for high frequency, high efficiency, and high power density, making it a key technological trend in air‑suspended blowers.

3. Intelligent Control Strategy

Modern air‑suspension centrifugal blowers no longer provide a constant‑speed airflow; instead, they adjust in real time according to operating conditions.

Common control modes:

• Constant pressure control;
• Constant flow control;
• Dissolved oxygen (DO) control, used for aeration in wastewater treatment;
• Ammonia nitrogen feedback control;
• Demand control, with automatic matching to pipeline network requirements.

Advanced control algorithms include:

• PID, fuzzy PID;
• Model Predictive Control;
• Active disturbance rejection control;
• AI adaptive adjustment.

4. The Internet of Things and Predictive Maintenance

Intelligentization has become standard equipment for air‑suspension blowers:

• Real-time monitoring: vibration, temperature, pressure, flow rate, rotational speed, power, and bearing condition;
• Edge computing: local data analytics for rapid response;
• Cloud platform: remote monitoring, data storage, and energy efficiency analysis;
• Fault Early Warning: Vibration spectrum analysis is used to detect early bearing wear, impeller imbalance, and signs of surge.
• PHM Health Management: Predicts the remaining useful life of bearings and provides maintenance alerts.

Some high-end models have also introduced Digital Twin , by employing a thermo-fluid-structural coupling model to simulate equipment conditions in real time, more precise operational and maintenance decisions can be made.

VI. Cooling System: Thermal Management That Determines Reliability

High-speed motors have a high power density, making cooling critical. The cooling methods for air‑suspended centrifugal blowers are broadly classified into two categories:

1. Air self-cooling

Using the filtered clean air, a portion is diverted into the motor’s cooling passages, flowing through:

• Stator outer surface / stator cooling air duct;
• The air gap between the rotor and the stator;
• Air bearing area.

After removing heat, the cooled air is discharged into the atmosphere or returned to the intake side.

Advantages: Simple structure; no circulating water system required.
Drawbacks: It requires clean, temperature‑controlled cooling air; high‑temperature, high‑humidity, and dusty environments necessitate special measures.

2. Water Cooling

A water jacket is installed on the motor housing to remove stator heat via circulating cooling water. This approach is commonly used for high‑power models or in environments with elevated ambient temperatures.

Advantages: Strong cooling performance, suitable for harsh environments.
Drawbacks: Requires an external circulating water system, increasing maintenance points.

3. Thermal Management Monitoring

The intelligent control system monitors in real time:

• Stator winding temperature;
• Bearing temperature;
• Cooling air temperature;
• Cooling water temperature/flow rate.

When the temperature exceeds the limit, the system automatically reduces the load or triggers an alarm to prevent high‑temperature demagnetization of the permanent magnets, bearing damage, and insulation aging.

VII. Spiral Case, Diffuser, Seals, and Filters: Essential Auxiliary Components That Should Not Be Overlooked

1. Diffuser

The high-speed gas exiting the impeller carries a substantial amount of kinetic energy. The diffuser converts this kinetic energy into pressure energy. Common configurations include:

• Bladeless diffuser: simple structure, gentle performance characteristics, suitable for a wide range of operating conditions;
• Vane diffuser: It offers strong pressure recovery but has a relatively narrow high-efficiency range and must be well matched to the impeller.

2. Volute casing

The volute collects the gas exiting the diffuser, further reducing its velocity while increasing its pressure, and then directs it into the discharge duct. The volute design has the following effects:

• Aerodynamic efficiency;
• Flow uniformity;
• Aerodynamic noise.

Optimizing the tongue position and the cross-sectional area distribution of the volute can reduce flow losses and noise.

3. Intake Air Filtration System

Air‑suspended bearings are extremely sensitive to particulate matter; therefore, the air‑intake filtration level is significantly higher than that of conventional Roots blowers. Multi‑stage filtration is typically employed:

• Primary filter;
• Medium-efficiency filter;
• High-efficiency filter;

Filtration efficiency is generally required to meet the ePM1 or ePM2.5 levels specified in ISO 16890, and a differential pressure alarm should be installed to alert users when filter replacement is necessary.

4. Sealing System

Although oil-free air‑suspension blowers operate without lubrication, it is still necessary to prevent compressed gas leakage and the ingress of external contaminants. Common sealing configurations include:

• Labyrinth seal;
• Carbon ring seal;
• Air seal.

The sealing design must be compatible with the high-speed rotor, controlling leakage while preventing rubbing caused by thermal expansion.

VIII. Energy-Saving and Environmental Protection Value: Why Is It Green Equipment?

1. No oil emissions

Air‑floating bearings require no lubricating oil, and their exhaust contains no oil mist, thereby meeting the stringent requirements of industries such as food, pharmaceuticals, electronics, and textiles for oil‑free compressed air.

2. Significant energy savings

Compared with conventional Roots blowers, air‑suspended centrifugal blowers typically achieve energy savings under actual operating conditions. 20%–45% 。

Energy-saving source:

• Permanent magnet synchronous motors have high efficiency.
• Direct drive without a gearbox, eliminating transmission losses;
• Air bearings exhibit extremely low frictional losses;
• The three-dimensional flow impeller boasts high efficiency;
• Variable-frequency control eliminates throttling losses associated with valves.
• The partial-load efficiency is significantly superior to that of Roots blowers.

3. Low noise, low vibration

Air‑suspension bearings operate without contact, resulting in minimal mechanical vibration. The entire unit is equipped with sound‑proof enclosures and silencers, keeping noise levels within 75–85 dB(A), making it well suited for noise‑sensitive areas such as municipal wastewater treatment plants.

4. Reduce carbon emissions

Based on an estimated annual operating time of 8,000 hours for a 75 kW wind turbine and a 30% energy‑saving rate, electricity consumption can be reduced by approximately 180,000 kWh per year, corresponding to a reduction of over 100 tonnes of CO₂ emissions. For group‑operated wastewater treatment plants or industrial parks, the potential for carbon emission reductions is substantial.

9. Key Considerations for Selection and Maintenance: Proper Use Is the Real Key

When selecting a model, please consider:

1. Flow rate, pressure range : Confirm the setpoint and adjustment range;
2. Start-stop frequency : The service life of air‑bearing units is affected by the number of start‑stop cycles; in applications involving frequent cycling, please confirm with the manufacturer.
3. Cooling method : Air cooling is suitable for clean environments, while water cooling is preferred in high-temperature, dusty conditions;
4. Filtration grade : Configure intake air filtration according to the on-site dust conditions;
5. Control System Protocol : Modbus, Profibus, Ethernet/IP, etc., ensuring compatibility with the host computer;
6. Surge protection : Verify whether automatic surge prevention control is in place.

Daily maintenance:

• Replace the air intake filter element regularly;
• Clean the cooling air flow path;
• Inspect the impeller for dust accumulation and corrosion.
• Back up the inverter parameters;
• Calibrate the sensor annually;
• Avoid prolonged operation in the surge region at low rotational speeds.

X. Conclusion

The air‑suspended centrifugal blower is a quintessential multidisciplinary product, integrating fluid mechanics, materials science, power electronics, and intelligent control. Its core components—air‑suspension bearings, a three‑dimensional flow impeller, a high‑speed permanent‑magnet synchronous motor, a high‑frequency inverter, and an intelligent control system—collectively underpin its technological advantages: oil‑free operation, high speed, high efficiency, intelligence, and environmental friendliness.

With the continued advancement of technologies such as SiC power devices, digital twins, AI‑based predictive maintenance, and new‑material coatings, air‑suspended centrifugal blowers will steadily evolve toward higher efficiency, greater reliability, and lower total lifecycle costs.

For industrial users, understanding the technical principles and key maintenance considerations of core components not only facilitates informed equipment selection but also maximizes the energy‑saving and environmentally friendly potential of the machinery, providing robust hardware support for enterprises’ green and low‑carbon transformation.

(This article was compiled by the AI technology team for industry discussion and reference. For product selection advice or technical consultations, please feel free to leave a comment.)