The air filter serves as a critical first line of defense in internal combustion engine systems—ranging from automobiles and construction machinery to power generation equipment. Its primary function is to remove dust and airborne particles, ensuring the engine receives clean air, thereby enhancing combustion efficiency and prolonging engine life. The following will introduce the common types of air filters.

1. Dry Air Filter

Structure and Principle

Dry air filters mainly use paper, synthetic fiber or non-woven fabric materials as filter elements to block solid particles in the air through the principle of physical interception. Its filter element is usually arranged in a folded shape to increase the surface area of the filter material to improve the filtration efficiency.

Application Scenarios

It is widely used in automobiles, motorcycles, air compressors and other equipment, and is the type with the highest market share at present.

Advantages

• Simple structure and low cost;

• Easy to install and replace;

• Long filter life (depending on the environment).

Disadvantages

• The filter element cannot be washed;

• The filter material needs to be replaced after clogging;

• The filtering ability of ultrafine particles is limited.

2. Wet air filter (Oil-Wet Filter)

Structure and principle

The wet air filter uses a layer of filter material coated with special filter oil. The dust particles in the air are adhered to after contacting the oil film. This structure improves the capture efficiency of tiny particles.

Application scenarios

Applicable to high dust environments, such as mines, agricultural machinery, construction equipment, etc.

Advantages

• The filter element can be cleaned repeatedly and continued to be used;

• High filtration efficiency, especially suitable for dusty environments;

• Extend the service life of the equipment.

Disadvantages

• Large maintenance workload;

• If not properly cleaned, it may cause secondary pollution;

• Oil separation may affect some sensitive parts of the system.

3. Oil Bath Air Filter

Structure and principle

The oil bath filter uses the principle of gravity and inertia to make the dusty air pass through the oil pool first, and the dust particles are captured and sunk into the oil, and then further filtered through a metal filter soaked in oil. It is a common filtering method for early heavy vehicles and machinery.

Application scenarios

Old diesel engines, construction machinery, large agricultural machinery, etc.

Advantages

• Stable filtering effect;

• Suitable for harsh working conditions, long life;

• Reusable, environmentally friendly.

Disadvantages

• Cleaning is more cumbersome;

• Oil mist may have adverse effects on the environment or downstream equipment;

• Large volume, not suitable for modern small vehicles.

4. High-Efficiency Particulate Air Filter (HEPA Filter)

Structure and Principle

HEPA (High-Efficiency Particulate Air) filter element is generally made of glass fiber and has extremely high filtering capacity. It can remove particles above 0.3 microns through multi-level interception, inertial collision and diffusion mechanisms, with an efficiency of up to 99.97%.

Application scenarios

Indoor air purifiers, high-end automotive air conditioning systems, hospital clean rooms, laboratories and other environments with extremely high air quality requirements.

Advantages

• Extremely high filtering effect;

• Also good interception effect on particles such as viruses and bacteria;

• Improve air cleanliness and ensure health.

Disadvantages

• High resistance, needs to be used with a strong fan;

• Cannot be washed, and needs to be replaced regularly;

• Relatively high cost.

5. Electrostatic Air Filter

Structure and Principle

The electrostatic filter applies a charge to the air, so that the particles are charged and adsorbed on the filter plate with the opposite charge. The filter material is usually made of conductive metal or plastic.

Application scenarios

Household central air conditioning system, industrial clean space, air purifier, etc.

Advantages

• Low resistance, small wind resistance;

• Washable, economical and environmentally friendly;

• Long service life.

Disadvantages

• Sensitive to humidity, efficiency decreases in humid environment;

• The filter element needs to be cleaned regularly, and the maintenance requirements are high;

• The filtration efficiency of large particles is not as good as that of mechanical filter materials.

Summary and selection suggestions

When choosing the right type of air filter, you should consider the use environment, filtration requirements, maintenance capabilities and cost budget:

Automobile engine intake system: dry filter is preferred, and some high-performance vehicles can choose HEPA or wet type;

High dust environment equipment: wet or oil bath filter is recommended;

HVAC system: electrostatic or HEPA+activated carbon composite type can be used to improve indoor air quality.

A well-designed and efficient air filtration system not only enhances equipment performance but also plays a crucial role in improving the health and quality of the human living environment.