Numerical Analysis on the Potential of Reducing DPF Size Using Low Ash Lubricant Oil 2018-01-1760

Diesel particulate filter (DPF) is necessary for diesel engines to meet the increasingly stringent emission regulations. Many studies have demonstrated that the lubricant derived ash has a significant effect on DPF pressure drop and engine fuel economy, and this effect becomes more and more severe with the increasing of operating hours of the DPF because the ash accumulated in the DPF cannot be removed by regeneration. It is reported that most of the DPFs operated with more ash than soot in the filter for more than three quarters of the time during its lifetime [1]. In order to mitigate this problem, the original engine manufacturers (OEM) tend to use an oversized DPF for the engine. However, it will increase the costs of the DPF and reduce the compactness of the engine aftertreatment system.

With the development of the lubricant additives technology, some OEMs and lubricant oil manufacturers are concerning that if there is any possibility to reduce DPF size using low ash lubricant oil. In this work, a numerical DPF model was built to estimate the DPF pressure drop at different soot loading and ash loading levels. With the model, the lifetime averaged fuel penalty of the DPFs with different sizes and operating with different ash content lubricant oils were calculated. Based on the calculation results, the potential of reducing DPF size using low ash lubricant oil was analyzed under the same design criteria of engine fuel consumption penalty. The analysis results show that the DPF size can be reduced by about 6% by lowering the lubricant oil ash content from 1.0% to 0.75%, and 14% by lowering from 1.0% to 0.5%. The DPF size can be maximally reduced by lowering the lubricant oil ash content from 1.0% to 0.25%, which can reduce about 22% of the DPF size. While the DPF size can be only reduced by 7% by using no ash lubricant oil because of no “membrane effect” of the ash on the soot depth filtration in the DPF. The role of engine-out particulate matters (PM) emission and DPF regeneration control strategy on this potential was also studied, and the potential is slightly increased when the engine has a higher engine-out PM emission or a DPF regeneration control strategy with ash effects corrections is applied.