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Abstract
Vehicles are provided with air filtration systems to clean the air before it enters the
engines, hence protecting it and prolonging its service life.
Three groups of filters (FI, FII and FIII) are manufactured having 28 pleats. Each group
is made from a different material and with a different thickness. The air
permeability of filter FI is 616 [l/m2s] that of filter FII is 270 [l/m2s] and that of filter
FIII is 550 [l/m2s]. Their thicknesses are: 0.5, 0.66 and 0.71 [mm] respecvely. Tests
are performed on a standard test rig for testing automotive air filters. A controlled
heating unit is added to the test rig to change the temperature of air upstream the
tested filters. In order to study the effect of the operating conditions on the
performance of the filters, tests are conducted at several airflow rates varying from
0.12 to 2.59 [m³/min] and at temperatures that are changed from 30 to 70 [ºC].
These values are typical to the operating conditions to which an air filter is
subjected. The displacement occurring in the pleats is measured with the help of a
strain gages bonded to the surface of pleats. The values of these displacements are
recorded on a PC using a data acquisition card.
The displacement is found to increase as the air flow rate increased, yet the
amount of increase decreased as the temperature increased. This increase is
greatest when the filter is loaded with dust.
The comparison between the displacements of the pleats of the three filters
showed that at low temperatures and small amounts of trapped dust, the first two
filters behaved nearly the same. At higher values of temperatures and greater
amounts of trapped dust, the second type of filter exhibited higher displacements
compared to the first filter and the difference between the behaviors of the two
filters is highly recognized. On the other hand, the third filter always exhibited
higher displacement values compared to those of the other two filters.It is found that when the amount of dust increased on the surface of the pleat, the
effective filtration area decreased. The increase in filter efficiency is greatest at the
beginning of filter’s operation, then this area decreases gradually with the increase
in the amount of trapped dust due to contact between pleats.