Understand automotive filters: Classification and Performance testing

Automotive filters can be classified into four major categories based on their applications, namely, cabin air conditioning filters, oil filters, gasoline filters and engine air filters. Their function is to filter out dust and pollutants in the air, impurities in fuel oil and dirt in engine oil.

Carriage air conditioning filter

The air conditioning filter in the cabin is a combination of air filters and filters in the automotive air conditioning system. It is mainly used to filter out fine particles (such as dust and dirt) and gases (such as benzene, formaldehyde, SO2, etc.) that are invisible to the naked eye, remove unpleasant odors, and maintain good air quality inside the cabin. This can reduce or even eliminate allergic reactions caused by contact with fine particles for drivers and passengers, such as tearing, itching and other physical discomforts. In addition, the air conditioning filter in the car compartment also has the function of effectively protecting the car's air conditioning system, preventing the air conditioning system from getting moldy and developing unpleasant odors due to continuous contact with air containing impurities, and maintaining the working efficiency of the air conditioning system in heating or cooling.

The air conditioning filters in the carriage are divided into single-effect filters and double-effect filters. Single-effect filters are mainly used to filter particulate matter, while double-effect filters, due to the use of activated carbon filter materials, can simultaneously filter particulate matter and vehicle exhaust.

For the particulate matter filtration test, the efficiency test uses KCl or A2 dust aerosol to measure the metric efficiency. The dust holding test uses A2 dust aerosol to measure the weighing efficiency and dust holding capacity. In addition, the relationship between air volume and resistance needs to be tested.

The standard stipulates the testing methods, but does not specify the qualification standards or classification methods. It was also mentioned that the performance of the filters in actual use might not match the ranking given in the test. Then, in order to better evaluate the filter, it is recommended to combine the results of laboratory tests with the air quality in the cabin of the car installed with the filter after it has been working under the same conditions for a certain period of time, and make a comprehensive rating of the filter.

For the test of gas filtration, n-butane, toluene and SO2 are used as test pollutants to test the adsorption performance (efficiency, dirt-holding capacity - time curve) and desorption performance of the filter.

Oil filter

The oil filter is located in the engine lubrication system. Upstream is the oil pump, and downstream are the various components in the engine that need lubrication. Its main function is to filter out harmful impurities in the engine oil, supply clean engine oil to the crankshaft, connecting rod, camshaft, piston rings, etc., to play a role in lubrication, cooling and cleaning, and extend the service life of components.

Oil filters are classified by structure into replaceable type, rotary type and centrifugal type. The filter materials used include filter paper, felt, metal mesh, nonwoven fabric, etc.

Gasoline filter

The gasoline filter is a filtering device installed on the pipeline between the fuel tank and the engine. It is mainly used to filter impurities in the fuel oil. Although the quality of fuel has improved in recent years and the impurities have decreased, there are still impurities. If impurities fall off from the fuel tank during transportation, they may be added when refueling. If they are used directly without filtration, it may cause abnormal wear to the engine.

At present, there are generally two structures of fuel filter elements. One is integrated with the fuel pump in the instrument, and the entire fuel filter element is installed in the fuel tank. The filter elements of this structure are generally designed to be larger and have a greater capacity. Another type is the external fuel filter element, which is installed outside the fuel tank. This type of filter element has a smaller capacity.

The test items for gasoline filters include cold and hot alternating test, pressure drop - flow characteristic test, vibration fatigue test, pneumatic sealing test, hydraulic pulse fatigue test, etc.

Engine air filter

The air filter element is used to filter the gas that is about to enter the engine, removing impurities from the air to prevent impurities from entering the cylinder and causing abnormal wear of the cylinder, thereby shortening the service life of the engine. According to application, they can be divided into two major categories: automotive and industrial. According to structure, they can be classified into dry air filters and oil-immersed air filters. The air filter is composed of two parts: the filter element and the housing. The main requirements are high filtration efficiency, low flow resistance, and the ability to be used continuously for a relatively long time.