Design of a vehicle exhaust particulate filter

The Air Quality Index in Hong Kong frequently stays at a high level. A major pollutant source is the diesel particulates emitted from diesel vehicles. In order to reduce particulate emissions, a particulate filter can be used. This study was aimed to evaluate the effectiveness of three different types of particulate filter design, viz. rectangular fiber, net and wire filters. The designs were tested under different engine speeds and loading conditions to compare the size and amount of particles collected, their filtering efficiency and back pressure generated. It was found that the net filter performance was not so good as originally expected. Its back pressure was high and the particulate filter efficiency was low. The wire filter showed a good filter efficiency in capturing small-size particulates. The rectangular fiber filter can trap larger size particulates with a relatively good efficiency than the other two designs. In fact, its performance is comparable to that available on the market.