Characteristics of ash formed by different lubricant additives and its effect on DPF performance

Abstract

Diesel Particulate Filter (DPF) is an important technology to reduce diesel exhaust particles. The ash formed by the combustion of lubricant oil will be deposited in the DPF, which will affect the filtration efficiency of DPF. In this paper, the ash generated in the burner by combustion of two lubricant additives mixed with diesel fuel were obtained by the burner test of ash rapid loading. The microscopic morphology of ash was studied by scanning electron microscopy and the fractal dimension was calculated based on fractal theory. Chemical composition analysis was performed using energy-dispersive X-ray spectroscopy. The filtration efficiency of DPF was tested with EEPS 3090 when loaded with different ash fractions. The results show that the average fractal dimension of Mg-based ash (1.5791) is higher than that of Ca ash (1.5420), indicating a more detailed surface structure at the microscopic level. This suggests that Mg-based ash is more likely to plug, sinter and even form bridging phenomenon in the DPF inlet channel. The filtration efficiency of DPF increases and then decreases with the loading of ash. The capture efficiency of large particles of 40–200 nm is increasing with the loading of Ca-based ash. However, due to the higher fractal dimension, the loading of Mg-based ash can significantly improve the capture efficiency of small particles of about 10 nm. This work is beneficial to explain the influence of ash on the efficiency of DPF in filtering particles of different sizes.