Development of a Rotating Plasma Burner for the Regeneration of Diesel Particulate Filters

摘要

A Diesel Particulate Filter (DPF) is an effective technology for reducing Particulate Matter (PM) emitted from diesel engines. In modern light duty diesel engines, DPF is regenerated by the post-fuel-injection method. In this method, the fuel is injected into the combustion chamber during the expansion stroke to produce heat to burn out the PM trapped in the DPF. However, this method also causes several problems, such as complicated engine torque control and oil dilution by fuel. In this study, a rotating plasma burner was developed for DPF regeneration as an alternative to the postfuel-injection method. Since it is important to reduce the electric energy consumption for plasma generation, which is directly related with electric noise and system cost, several design factors, such as the boosting voltage of transformers, electrode gaps, and plasma frequency were evaluated. A transformer with a low boosting voltage is desirable to ensure low electric noise. A narrow electrode gap is preferred to minimize energy consumption, but too small of a gap distance should be avoided to prevent electrode contamination by fuel. An increase in frequency was also effective to decrease the instantaneous current of the transformer as well as electric noise. A large amount of fresh air enhanced the combustion characteristics of the plasma burner, but it also required more electric energy or a larger air compressor. The optimization of a flame protector was identified as another key design factor in this study. Therefore, several flame protectors were tested. The one with lots of small holes in the second layer was found to have better flame characteristics at a high exhaust gas flow rate. In conclusion, the new diesel fuel burner with rotating plasma was found to be effective in DPF regeneration.