A Novel Electrostatic Method of Ultrafine PM Control Suitable for Low Exhaust Temperature Applications

A novel type of electrostatic diesel particulate reduction device has been developed which is intended for use in low exhaust temperature applications. Tests were conducted to assess the performance of the technology with particular emphasis on temperature dependence and ultrafine particle removal efficiency. Rolling road dyno tests were used to enable the tests to be performed with conditions as close as possible to real on road driving. The device works by electrostatically ionizing the particulate matter which is then attracted onto an earthed surface where agglomeration occurs. This process results in a reduction in ultrafine particles which combine together with other particles to form larger agglomerates. Larger agglomerated particles are less of a health risk and are easier to remove by filtration or other means. The device was tested over a range of operating conditions on a number of vehicles and it was found in all of the tests that the device significantly reduced the emission of ultrafine particles (85 - 99%). These results were consistent over the entire drive cycle from engine cold start proving the non-temperature dependence of the technology and its suitability to low exhaust temperature applications such as urban driving where catalysis can be less effective. Conventional forecourt diesel fuel was used in all of these tests. This paper presents a selection of the test results, gives an introduction to the technology, an explanation of the ionization and agglomeration processes and details the test methods used to obtain the results.