Theoretical and Experimental Studies of Uneven Dust Suction from a Multi-Cyclone Settling Tank in a Two-Stage Air Filter  
[PERSON]  
1 Faculty of Mechanical Engineering, Military University of Technology, 2 gen, Sylwestra Kaliskiego St., 00-908 Warsaw, Poland; [EMAIL_ADDRESS]; Tel. : +48-261-837-121  
journals and camshafts) in internal combustion engines. Moreover, mineral dust grains have very irregular shapes with sharp edges. Most dangerous for two cooperating engine components are dust particles whose diameter \(d_{p}\) is equal to oil film thickness \(h_{min}\) between two surfaces at that moment. In an internal combustion engine, there are many elements that cooperate in movement and are lubricated with oil. Oil film thickness depends on the engine operating parameters and oil properties, and therefore they assume various values--most often in the range of \(h_{min}\) = 0-10 \(\upmu\)m [7; 8]. Dust sucked in with the air enters the piston, which makes the cylinder and piston top degrade the most, as well as the top piston rings. Abrasive engine component degradation is caused mainly by particles with a size of 1-40 \(\upmu\)m, with the most dangerous dust grains in the range of 1-20 \(\upmu\)m [9; 10; 11]. Dust grains below 50-100 \(\upmu\)m are simply sucked in with the intake air. It follows that the intake air filters in internal combustion engines should retain all dust grains above 1 \(\upmu\)m. This is a complicated problem considering that military vehicles are most often equipped with combustion engines with high power and high air demand, with which a significant dust mass enters. For example, the engine of a PT-91 tracked vehicle with a capacity of 700 kW draws in more than 3400 m\({}^{3}\)/h of atmospheric air per hour. If the dust concentration in the air is 2.5 g/m\({}^{3}\), the motor draws in more than 8 kg of dust per hour along with the air. To remove such a large dust mass in a short time with the required efficiency of 99.5% and an accuracy above 1 \(\upmu\)m, two-stage air filters are used, which differ in their principle and operation mode, design, separation barrier type, and operation efficiency. The first stage of air separation is a multi-cyclone, which is a group of individual cyclones arranged in parallel (next to each other), fixed with their ends in common lower and upper plates, which guarantee a common air inlet and outlet--Figure 1.  
The second stage of air separation is a partition element (filter cartridge), which, due to space limitations and the desire to increase filter material surface area, is most often made of a pleated filter paper. The operation essence of the \"multi-cyclone-porous partition\" filter is that the multi-cyclone is characterized by the possibility of separating large dust masses from the polluted air without increasing pressure drop, but with much lower efficiency (87-95%) and accuracy (\(d_{p}\) > 15-35 \(\upmu\)m) than a paper filter. The remaining insignificant dust mass is then directed to the filter element, most often made of pleated paper, having a low and limited absorbency (in the range of 150-250 g/m\({}^{2}\)), but characterized by high accuracy (above \(d_{p}\) = 2-5 \(\upmu\)m) and high separation efficiency (above \(\varphi\) = 99.5%) [11; 12; 13; 14; 15; 16]. As a result, air is supplied to the engine cylinders with the required purity and, at the same time, the operation time of the separation system is extended. Thus, the vehicle's service interval, which is limited by the achievement of a certain pressure drop value, is the permissible resistance \(\Delta p_{Hdep}\). Significant dust masses separated by the cyclones are collected in a multi-cyclone dust settling tank common to all cyclones.