On The Road to 2010 Emissions: Field Test Results and Analysis with DPF-SCR System and Ultra Low Sulfur Diesel Fuel

This paper reviews field test results in 23 Volvo D12C non-Exhaust Gas Recirculation (EGR) diesel engines using continuously regenerating Diesel Particulate Filter (DPF) with Selective Catalytic Reduction (SCR) and ultra low sulfur diesel fuel at 4-10 ppm. This 2-year field test provided an opportunity to measure on-road nitrogen oxide (NO x ) emissions, and to do in-depth analysis of the incombustible material remaining in the filters. In addition, two crankcase oils were used at 1.0% and 1.4% sulfated ash to provide enhanced information on the material collected in the filters, and on oil drain capability. The study demonstrates that the U.S. Environmental Protection Agency (EPA) 2007 emissions can be met. After 2 years in the field the 23 trucks using the DPF-SCR system are still providing a very high NO x conversion of 75% on fleet average. The filter material contained only 2 wt-% carbon, which demonstrates the effectiveness of the DPF-SCR system in combusting soot. The material in the filters is dominated by combustion products of lubricant additives. The particle size distribution is bimodal, with a large number of particles of 0.4 micron diameter and the remaining at 8 microns. Overwhelmingly, the majority of particles are submicron. There was no difference in the filter material from the two lubricants evaluated, but they did vary in their estimated oil drain capability. This paper also reviews maintenance practices in this successful 2-year "clean diesel" program.