According to the principle of filtration, air filters can be divided into filter type, centrifugal type, oil bath type and composite type. The air filters commonly used in engines are mainly inertial oil bath air filters, paper dry air filters, polyurethane filter air filters and so on. The inertial oil bath air filter has three stages of inertial filtration, oil bath filtration, and filtration filtration. The latter two types of air filters are mainly filtered through the filter element. Inertial oil bath type air filter has the advantages of small air intake resistance, can adapt to dusty and sandy working environment, long service life, etc. It was previously used on a variety of models of automobile and tractor engines. However, such air filters have low filtration efficiency, heavy weight, high cost, and inconvenient maintenance, and have been gradually eliminated in automobile engines. The filter element of paper dry air filter is made of resin-treated microporous filter paper. The filter paper is porous, loose, folded, has certain mechanical strength and water resistance, has high filtration efficiency, simple structure, light weight and cost. Low, easy maintenance and other advantages, is the most widely used automotive air filter. Polyurethane air filter element is made of soft, porous, sponge-like polyurethane with strong adsorption capacity. This type of air filter has the advantages of paper dry air filter, but its mechanical strength is low. It is widely used. The disadvantages of the latter two types of air filters are their short service life and unreliable operation under harsh environmental conditions. https://www.dtsanyparts.com/filt...ers-for-sy215-sy235.html