Roots blower is a type of positive displacement fan, which works based on two interlocked rotors (impellers) rotating in the opposite direction inside the cylinder, and periodically changing the volume of the air chamber to achieve gas suction, delivery, and discharge. The following is its detailed working principle:
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**1、 Core working principle**
1. * * Rotor motion**
-Two three or two bladed rotors (impellers) are kept in mesh through synchronous gears and rotate in opposite directions at the same speed (one clockwise and one counterclockwise).
-Maintain a gap (usually 0.1~0.4 mm) between the rotor and the inner wall of the cylinder, and between the rotors, without direct contact, to avoid wear and tear.
2. Gas transportation process**
-* * Inhalation stage * *: When the rotor rotates, the volume of the air chamber on the inlet side increases, forming negative pressure, and external gas is sucked in.
-Closed conveying: Gas is surrounded by the rotor and cylinder to form a closed chamber, and is pushed along the inner wall of the cylinder towards the exhaust port side as the rotor rotates.
-Exhaust stage: When the rotor rotates to the exhaust port, the volume of the air chamber decreases, and the gas is forcibly compressed and discharged (note: the Roots blower itself does not compress gas, and pressure is generated by system resistance).
3. * * No internal compression characteristics**
-Unlike screw fans or centrifugal fans, the gas pressure of Roots fans is not generated by mechanical compression inside the fan, but by the resistance at the back of the system (such as pipes and valves) that forces the gas to increase in pressure.
-Constant flow rate: When the speed remains constant, the output flow rate is basically unaffected by pressure changes.
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**2、 Dynamic schematic diagram**
```
Air inlet → | rotor A | rotor B | → exhaust outlet
(Formation of air chamber movement during rotation)
```
-Arrow direction: Gas flow path.
-* * Key point * *: The rotor completes one gas delivery cycle for every 120 ° rotation (three blade type) or 180 ° rotation (two blade type).
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**3、 Summary of Characteristics**
1. * * Advantages**
-Stable flow rate: The speed and flow rate have a linear relationship, which is suitable for scenarios that require constant flow rate.
-* * Simple structure * *: No complex components such as valves or pistons, easy to maintain.
-* * Stain resistant * *: capable of conveying dusty and humid gases (with appropriate filtering optional).
2. * * Disadvantages**
-* * High noise * *: High frequency noise caused by rotor engagement and airflow pulsation (requires muffler).
-* * Low efficiency * *: Compared to screw fans or centrifugal fans, it consumes more energy (especially under high-pressure conditions).
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**4、 Association with dual stage serial design**
-Double stage series connection: Connect two Roots blowers in series, with the stage outlet connected to the second stage inlet, and achieve higher pressure through two-stage pressurization (such as single-stage 0.5 bar, two-stage up to 1.0 bar).
-* * Precautions * *: An intercooler is required to lower the gas temperature to prevent overheating from affecting efficiency and lifespan.
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**5、 Application scenario examples**
-Low pressure pneumatic conveying: such as pipeline transportation of grain and fly ash.
-Sewage treatment aeration: Constant flow rate ensures oxygen supply to microorganisms.
-* * Vacuum adsorption * *: Can be used as a vacuum pump when reversed.
Understanding its working principle is helpful for selection and maintenance, such as avoiding overpressure operation (requiring valve installation), regularly checking clearances, etc. If more in-depth technical details are needed (such as flow calculation, gap adjustment), further exploration can be conducted!
