Roots blower and screw blower are two common types of blowers, with differences in structure, working principle, performance characteristics, and applications. Here is a detailed comparison between the two:
1、 Structure and Working Principle
1. Roots blower
Structure: The Roots blower is mainly composed of two impellers arranged side by side in an 8-shaped shape, with very small gaps between the blades on the impellers and the casing. The key components are two rotating Roots impellers, which mesh with each other inside the casing through gear transmission and maintain a gap between them, forming a gas sealed working chamber.
Working principle: Roots blower generates airflow by two or more rotating blade rotors moving relative to each other inside the cylinder. When the rotor rotates, the cavity continuously sucks in air and discharges it outward, thereby generating airflow. Roots blower belongs to the "external compression" type, with no volume change during the conveying process and no internal pressure change (relying on pipeline back pressure).
2. Screw blower
Structure: The screw blower consists of a main screw and a secondary screw, which mesh with each other inside the casing. The outer surface of the main screw usually has spiral threads that can mesh with the auxiliary screw inside the casing. The auxiliary screw is a screw that meshes with the main screw, usually located inside the main screw and forms a meshing relationship with the threads of the main screw. The meshing motion of the main screw and the auxiliary screw forms a gas sealed working chamber.
Working principle: The screw blower alternately expands and contracts the working volume through the rotational motion of the screw inside the casing, thereby inhaling gas and increasing pressure. Two parallel screw rotors mesh with each other in an "∞" - shaped cylinder to form a working volume. The rotor rotates at high speed in the opposite direction through a synchronous gear, and the working volume changes periodically with the rotation of the rotor, achieving gas compression simultaneously during gas transportation.
2、 Performance characteristics
1. Roots blower
Airflow and pressure: Roots blowers are generally suitable for medium to low pressure ranges, with pressures generally between 0.1 and 1 bar and a wide range of airflows.
Flow stability: Due to the influence of centrifugal force, the pulse is large, and the pulse torque will produce intermittent noise and vibration. The flow stability at the outlet is slightly inferior to that of screw fans.
Noise and vibration: Roots blowers typically produce high levels of noise and vibration, reaching around 110-120 decibels.
Maintenance cost: The maintenance cost is relatively low, but the requirement for high precision may lead to difficulty and cost increase in maintenance. At the same time, the failure rate is high during long-term operation, so one in use and one backup are often used.
Lifespan: The structure is simple and has a long service life, but it may be easily damaged under high pressure.
2. Screw blower
Airflow and pressure: Screw fans can generate higher pressure, usually up to 2-10 bar, suitable for environments that require higher pressure. For every 0.1 bar increase in work pressure, the outlet temperature rises by 8 ℃. At the same time, screw fans also have a large range of air volume.
Flow stability: The airflow is smoother, with good continuity, less leakage, and lower pressure pulses, making it suitable for applications that require high stability.
Noise and vibration: Screw fans are relatively quiet and have low vibration, making them suitable for places with strict noise requirements, generally around 60-85 decibels.
Maintenance cost: The initial investment is high, but in the long run, the energy consumption and maintenance cost are relatively low, especially with the increase of usage time and equipment pressure, the advantage is more obvious, and it can operate continuously.
Efficiency and lifespan: Due to the internal compression process, screw fans have high working efficiency and stable gas supply. The complex structure leads to increased costs, but proper maintenance can ensure a longer service life.
3、 Application Fields
1. Roots blower:
Widely used in fields such as sewage treatment, mining ventilation, chemical production, and food processing. During the sewage treatment process, Roots blowers can effectively transport concrete and suspended solids, ensuring the normal operation of the sewage treatment system; In mine ventilation, Roots blowers can provide fresh air to the mine, ensuring the health and well-being of miners; In chemical production, Roots blowers can provide gas to reaction vessels, promoting the progress of chemical reactions; In food processing, Roots blowers can be used to transport materials such as grains and candies.
2. Screw blower:
In the field of environmental protection, screw blowers can be used in the aeration system of sewage treatment plants to provide necessary oxygen for biological reactions.
In the food processing industry, screw blowers can be used for drying, cooling, and conveying materials.
It can also be applied to multiple industries such as textiles, papermaking, and chemicals, providing necessary power for the process flow of these industries.
4、 Summary and selection suggestions
Summary: Roots blowers and screw blowers each have their own advantages and disadvantages. Roots blower has a simple structure and low maintenance cost, but it produces significant noise and vibration; Screw blower has the advantages of energy saving, stable operation, and low noise, but the initial investment is relatively high.
Selection suggestion: When making a decision, it should be based on the actual needs of the usage scenario (such as flow, pressure, noise requirements, etc.), evaluating long-term operating costs (including energy consumption and maintenance costs), and considering the impact of equipment stability and noise level on the working environment. Roots fans are suitable for applications with high flow rates and low pressure requirements, while screw fans are more suitable for applications that require high pressure and stable airflow.
In summary, Roots blowers and screw blowers each have their own unique characteristics, and when selecting, multiple factors need to be considered comprehensively to determine the most suitable equipment type.
