Roots blower belongs to * * positive displacement blower * *, which has essential differences in working principle and performance characteristics from common centrifugal blowers. The following is a detailed explanation of its core classification and characteristics:
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**1. Classified by working principle**
|* * Type * * | * * Working Principle * * | * * Represents Fan * * | * Roots Fan Positioning * *|
|----------------|-----------------------------|------------------|-----------------------------|
|* * Volumetric * * | Transporting gas through changes in enclosed chamber volume | Roots blower, screw blower | Core type, relying on rotor engagement to squeeze gas|
|* * Power type * * | Transporting gas through impeller kinetic energy conversion | Centrifugal fan, axial flow fan | Not included in this category|
**Core Features * *:
-* * Forced delivery * *: The gas flow rate is proportional to the rotational speed and is almost unaffected by the outlet pressure.
-* * No internal compression * *: The increase in pressure depends on the back pressure of the system (an external pressure relief valve is required to prevent overpressure).
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**2. Subdivide types by structure**
**(1) Standard Roots blower**
-* * Rotor profile * *: Two bladed (high pulse) or three bladed (smooth airflow, mainstream choice).
-Pressure range: single-stage ≤ 98kPa, two-stage series ≤ 196kPa.
-Typical flow rate: 0.5~500 m3/min.
**(2) Variant design**
|* * Variant Types * * | * * Features * * | * * Application Scenarios * *|
|--------------------|-------------------------------------|---------------------------|
|* * Water cooled Roots blower * * | Cylinder with cooling water jacket, high temperature resistance (≤ 200 ℃) | Chemical high-temperature gas transportation|
|* * Dense Roots blower * * | Compact design, noise<80dB | Silent requirements in places such as hospitals and food factories|
|Explosion proof Roots blower * * | Motor and casing comply with ATEX/GB3836 standards | Explosive environments in coal mines and petrochemicals|
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**3. Comparison with similar volumetric fans**
|* * Comparison item * * | * Roots blower * * | * * Screw blower * * | * Spiral vane vacuum pump * *|
|------------------|------------------------------|---------------------------|-------------------------|
|* * Compression method * * | No internal compression | Internal compression (higher pressure) | Internal compression (high vacuum)|
|Ultimate pressure * * | Single stage -80kPa (vacuum) | Can reach 0.4MPa (positive pressure) | Can reach -0.009MPa|
|Efficiency * * | 50~70 | 60~75 | 40~60|
|* * Maintenance cost * * | Low (regular replacement of bearings/gears only) | High (professional repair required for rotor coating wear) | High (frequent wear of rotor blades)|
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**4. Summary of Performance Characteristics**
-Advantages:
Stable flow rate, suitable for processes that require constant gas volume (such as aeration and transportation).
Simple structure, resistant to dust/corrosion (achieved through material upgrades).
Quick start stop, no need to consider surge issues like centrifugal fans.
-Limitations:
The noise is relatively loud (requiring a muffler, the three bladed type can reduce it to below 85dB).
Efficiency lower than centrifugal fans, high energy consumption in high-pressure scenarios.
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**5. Industry standards and selection criteria**
-* * Standard * *: ISO 1217 (Performance Testing of Positive Displacement Compressors).
-Standard: JB/T 8941.1-2014 "Roots Blowers for General Use".
-* * Selection key * *:
1. * * Flow rate * *: According to process requirements+10 margins.
2. * * Pressure * *: system resistance+medium resistance (such as liquid column height).
3. * * Medium characteristics * *: Corrosive gases require stainless steel, and dust requires wear-resistant coatings.
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**6. Classic application scenarios**
-* * Environmental Protection * *: Sewage treatment aeration, desulfurization and oxidation.
-* * Industrial * *: Pneumatic conveying (cement, flour), vacuum packaging.
-Energy: Blast furnace coal injection, biogas boosting.
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Roots blowers occupy an irreplaceable position in the fields of medium and low pressure and high flow due to their reliable, durable, and easy to maintain characteristics. For scenarios with higher pressure or strict cleanliness requirements, a combination of screw fans or centrifugal fans can be considered for use.
