Investigation of The Slip Mechanism of Ash in Diesel Particulate Filter

Abstract

Diesel engine vehicles are equipped with a particulate matter (PM) sensor for the on-board diagnostics (OBD) of the diesel particulate filter (DPF). It has been previously reported that a fraction of the ash generated by diesel engines can pass through the DPF, causing malfunction of the PM sensor. However, the slip mechanism of the ash accumulated in the DPF is still not well understood. In this study, the slip mechanism of ash stored in a DPF has been elucidated using a DPF, in which surrogate ash was stored. Quantitative measurements of the component of ash passing through the DPF were performed using an HPLC, by varying the factors that influence the mass of the ash passing through the DPF, such as the mass flow of water, inlet gas temperature, exhaust gas flow rate, and the mass of ash stored in the DPF. The main contributing factor for the occurrence of ash slip was found to be the mass of liquid water passing through the DPF. The components of ash passing through the DPF were mainly Ca²⁺ and SO₄^2-, which indicates that the CaSO₄ in the ash dissolves in the condensed water in the exhaust. Using experimental data, the estimation method for the mass of ash passing through the DPF was also investigated.