Experimental investigation on particle number emission from diesel engine with bipolar discharge coagulation

A self-made wire-to-cylinder bipolar discharge apparatus was employed on a 4-cylinder diesel engine to evaluate the effect of discharge voltage on particle emissions. An engine exhaust particle sizer was used to analyze the particle number distribution and the filter efficiency of diesel particulate filter. Emission characteristics such as particle number distribution, total particle number concentration and count mean diameter at different discharge voltages were evaluated. Filter efficiencies of diesel particulate filter at 0 and 10 kV were also determined. The results showed that particle number concentrations within the range of 6.04-93.1 nm decreased, while those within the size range of 93.1-220.7 nm increased. The reduction rate of particle number concentration and total particle concentration decreases with the increase in discharge voltage, while the count mean diameter increases. At 100% load, the average filter efficiency of the diesel particulate filter improved by 10% with increment in discharge voltage from 0 to 10 kV, and also increased by 15% within the size range of 6.04-16.5 nm. The test results showed that bipolar discharge coagulation could reduce the total particle number concentration, and also enhance the count mean diameter and filter efficiency of diesel particulate filter.