Research into a Two-Stage Filtration System of Inlet Air to the Internal Combustion Engine of a Motor Vehicle

The necessity of using two-stage (multicyclone–partition) inlet air filters for engines of motor vehicles operated in dusty air conditions is demonstrated. Due to the lack of information in the literature on the description of the air filtration process in the two-stage system (multicyclone–partition), its experimental tests were performed. Due to the high cost of testing the original two-stage air filter, the original test methodology of testing a single cyclone and a paper filter with an appropriately sized surface was used. When testing the assembly (cyclone–paper filter), conditions similar to the actual operating conditions of a two-stage air filter were used, including the filtration speed in the paper filter, the dust concentration in the inlet air, and the cyclone inlet speed. The characteristics of various filter baffles with appropriately sized surface area operating in three filter assemblies, the “cyclone–test filter”, and without a cyclone were determined depending on the mass of dust supplied to the assembly or directly to the filter. Experimental tests showed the existence of an initial (short) filtration period, which was characterized by low values of filtration efficiency well below the required level of 99.9%. This phenomenon occurred regardless of whether the paper filter was operated directly after the cyclone or without the cyclone. However, with the mass of dust delivered to the filter, the efficiency and precision increase and in a short time achieve the required values, which are maintained for the rest of the filter’s operation. The air behind the paper filter contained dust grains of 10–25 µm with the required 2–5 µm. The increase in the pressure drop was lower for the paper filter operating in an assembly (cyclone–paper filter). Therefore, the operating time of the unit (cyclone–paper filter) to reach the permissible flow resistance value was four times longer than that of the paper filter, as could be demonstrated.