**Detailed explanation of the working principle of Roots blower**
Roots blower is a type of volumetric gas conveying equipment, whose core principle is to use two interlocked rotors (impellers) to rotate in the opposite direction inside the casing, forcibly pushing the gas to achieve directional conveying. The following is a step-by-step analysis:
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**1、 Core work process**
1. * * Inhalation stage**
-When the impeller disengages from the inlet, a gradually expanding cavity is formed between the impeller and the casing → negative pressure is generated inside the cavity → external gas is sucked in.
2. * * Closed conveying stage**
-The impeller continues to rotate, enclosing the gas in a sealed chamber composed of the impeller and the casing.
-Key characteristic: The gas is not compressed at this stage and is only pushed forward as the impeller rotates.
3. * * Exhaust Stage**
-When the impeller rotates to connect with the exhaust port, the chamber volume decreases → gas is forcibly discharged.
-Pressure source: The exhaust pressure is determined by the resistance of the backend system (such as pipeline and valve resistance).
```plaintext
[Schematic diagram of work cycle]
① Inhalation → ② Closed conveying → ③ Exhaust → Recirculation in a loop
```
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**2、 Core structural function**
|* * Component * * | * * Function * *|
|----------------|-------------------------------------------------------------------------|
|The impeller is usually a two blade or three blade type, precision machined (with a clearance of 0.15~0.4mm), and maintains non-contact meshing through synchronous gears|
|* * Synchronous gear * * | Ensure that the two impellers rotate in opposite directions with a phase difference of 180 ° to avoid collision|
|The casing is made of cast iron or stainless steel material, forming a sealed chamber that can withstand gas pressure|
|* * Import and Export * * | One way valve design (some models) to prevent gas backflow|
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**3、 Key job characteristics**
1. * * Volumetric principle**
-Constant flow rate: Theoretical flow rate is only related to impeller speed and volume, and is not related to outlet pressure.
-Formula *:` Q = 4 × V × n × η`
-V: Impeller displacement per revolution (m3/r)
-N: Speed (rpm)
-η: volumetric efficiency (usually 0.75~0.85).
2. * * No internal compression**
-The gas in the chamber is not actively compressed, and the pressure increase is only caused by exhaust resistance.
-Result: The efficiency is lower than that of screw compressors, but the structure is simpler and more reliable.
3. * * Forced delivery**
-Even if the outlet pressure fluctuates (such as pipeline blockage), the flow rate can still be maintained stable (to prevent overpressure).
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**4、 Performance Characteristics Comparison**
|* * Features * * | * Roots blower * * | * * Centrifugal fan * * | * * Screw compressor * *|
|----------------|----------------------------|----------------------------|--------------------------|
|* * Flow regulation * * | Can only be adjusted through speed regulation | Can be adjusted through valves | Speed+bypass valve regulation|
|* * Efficiency * * | Medium (50~70) | High (80~90) | High (75~85)|
|* * Noise * * | High (75-95 dB) | Low (65-85 dB) | Medium (70-90 dB)|
|* * Maintenance cost * * | Low (no vulnerable parts) | Medium (requires regular calibration) | High (complex lubricating oil system)|
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**5、 Typical application scenarios**
1. * * Sewage treatment * *: Aeration tank oxygen supply (pressure 39.2~58.8 kPa).
2. * * Pneumatic conveying * *: Pushing granular materials (such as cement and flour).
3. * * Vacuum adsorption * *: When used in reverse, it serves as a vacuum pump (negative pressure -50 kPa).
4. * * Chemical process * *: Gas circulation in reaction kettle (requires explosion-proof design).
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**6、 Frequently Asked Questions and Answers**
**Q: Why is the exhaust temperature of Roots blower higher**
-Reason: The lack of internal compression causes adiabatic compression of gas to occur at the moment of exhaust, converting energy into thermal energy.
-Solution: Install a cooler or reduce the compression ratio.
**Q: How to determine impeller wear**
-Symptoms: Decreased airflow and decreased current.
-* * Testing * *: Measure the radial clearance with a feeler gauge (>0.4mm needs to be replaced).
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**Summary: Roots blower forcibly delivers gas through impeller engagement, suitable for low-pressure constant flow scenarios. It has the advantages of simple structure and durability, but attention should be paid to pressure limitation (usually ≤ 98 kPa) and noise control. When selecting, priority should be given to matching flow and system resistance requirements.
