What is the operating principle of an air filter?

The operating principle of an air filter relies on a filtration medium as the primary means of removing contaminants. As air passes through the filter, the filter medium traps impurities—causing them to adhere to the filter—thereby achieving the desired air-purification effect. Detailed descriptions of various types of air filters are provided below:

1.Dry-inertial air filters: These consist of components such as a dust-removal hood, guide vanes, a dust-discharge port, and a dust-collection cup. They operate by utilizing the suction generated by the engine cylinder during the intake stroke, which creates a pressure differential between the inside and outside of the filter housing. External air is drawn in at high velocity, causing heavier dust particles to be flung into the dust-collection cup, effectively filtering the air.

2. Wet-inertial air filters: These primarily consist of a central tube and an oil reservoir (oil bath). As air enters the filter, it travels downward through the central tube at a very high velocity. Upon striking the surface of the oil in the reservoir, the airflow is forced to change direction abruptly—shifting upward and creating a swirling motion. Due to inertia, heavier dust particles fail to follow the change in airflow direction and instead become trapped in the oil, thereby filtering the air.

3. Paper-element air filters: These consist of a paper filter element and a sealing gasket. As air enters the filter, dust particles are either separated from the airflow or become trapped/adhered to the surface of the paper filter element.

4. Wet-type (oil-wetted) air filters: These consist of a metal mesh screen saturated with engine oil. As air passes through this oil-wetted metal mesh, small dust particles are captured; some of these particles then adhere to the oil and drain back into the oil reservoir.