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To reach close to zero tailpipe NOx emissions, a double-SCR (selective catalytic reduction) system is proposed. In that, the first SCR unit would be placed upstream of the diesel particulate filter (DPF) and the second SCR unit downstream of DPF. This study focused on the experiments of the first SCR unit. The experiments were conducted utilizing a new, 4.4-liter heavy duty diesel engine that was connected to a research facility for studying after-treatment systems in controlled environment. Three different SCR’s: a vanadium-based SCR (V-SCR), a copper-based SCR (Cu-SCR) and a vanadium-based SCR including an ammonia slip catalyst (V-SCR+ASC) were studied. Studies were done at different exhaust temperatures from 215°C to 350°C. Emissions of NO, NO2, NH3, N2O, CO, CO2 and hydrocarbons were measured by FTIR. Particulate emissions (PM, PN) were studied as a part of the experiments. The results showed that the three SCR units performed differently.

A new tool for SCR (selective catalytic reduction) testing is developed. This side stream test bench has an advantage to test smaller catalysts with a proper exhaust. The exhaust mass flow and temperature are adjustable. A control program is developed to adjust and save the needed parameters. NOx sensors are utilized in the test bench to measure the levels upstream and downstream of SCR reactor. In this study one SCR with a volume of 40.5 dm3 is tested with exhaust flows ranging from 400 to 600 kg/h and exhaust temperatures from 280 to 360°C. The tests are conducted using exhaust gas from a medium-speed diesel engine running on heavy fuel oil. A decrease from 75% to 99% (depending on test conditions) was observed in NOx over the catalyst. In addition HC and PM were found to decrease while CO was increased over the catalyst. The controlling of exhaust flow and temperature with the test bench succeeded with only minor errors.

Under on-road driving conditions, the engine load and speed and the cooling effect of ambient air may affect the functioning of exhaust aftertreatment devices. In this paper, we studied the effects of these parameters on the functioning of the combination of a Diesel Oxidation Catalyst and a Particle Oxidation Catalyst (DOC+POC). In the engine tests, the engine load and speed were observed to affect the nonvolatile particle reduction efficiency curve of the DOC+POC; while the nonvolatile core particle (Dp ≺ 15 nm) reduction was high (97-99%) in all the engine test modes, the reduction of soot varied from 57% at low load to 70% at high load. Because the change in engine load and speed affected both the exhaust temperature and flow velocity, the effects of these parameters were measured separately in an aerosol laboratory.

This study presents emission results measured with renewable and synthetic diesel fuels. Three engines and five city buses were studied. The efficiency of diesel oxidation catalyst combined to particle oxidation catalyst (POC®) was measured with two engines. The studied diesel fuels were EN590, FAME, HVO and GTL. In most cases all regulated emissions decreased with HVO and GTL fuels compared to conventional EN590 diesel fuel. With FAME, the NOx emissions were higher compared to EN590, but other emissions were reduced. Alternative fuels had a positive effect on emissions, which are considered harmful to human health.

State-of-art light duty diesel vehicles and heavy duty diesel engines are utilized in studying the effect of a novel particle oxidation catalyst (POC®) on particle emission. In addition to the regulated particulate matter (PM) emission measurement, a real time mass emission and particle number size distribution measurements are utilized in testing. The results show that the particle oxidation catalyst can have a significant decreasing effect on the diesel exhaust particle emissions. For example, in light duty applications PM reductions of 55-61% were achieved over the New European Driving Cycle (NEDC) when using a POC of same size as the engine volume. The usage of a DOC in combination with the POC ensures proper regeneration of the POC substrate. The size distribution measurements revealed that the particle number collection efficiency for smaller particles i.e. the nanoparticles was very high, being close to 100 %.