Abstract
Research and/or Engineering Questions/Objective
EU6 emission legislation enforces NOx emission to reduce more than 50% as compared to EU5. Thus, A2.5 EU6 diesel engine should be designed to minimize engine out NOx and additionally adopted a SCR after-treatment system. Due to the limited underfloor space of “STAREX” vehicle equipped with A2.5 diesel engine, Cu/Zeolite SCR Catalyst was coated as washcoat on the DPF substrate. Thus, SDPF (SCR coated on DPF) can be the catalytic filter combined with DPF and SCR, which has two functions of purifying soot and engine out NOx at the same time. Since SDPF does not contain precious metals such as Pt/Pd, which accelerate soot regeneration rate, development work should focus to increase soot regeneration rate. The peak inside temperature should be controlled to maintain under lower limit value to prevent thermal damage of SCR washcoat. Therefore, SDPF system should be optimized to improve both performances of regenerating soot and purifying engine out NOx.
Results
As a first step, engine hardware has been optimized to minimize engine out NOx emission. Combustion chamber and injector were designed to have lower compression ratio and better fuel mixing with fresh air. The result shows that engine out NOx can be reduced by more than 20%, and at the same time fuel efficiency improved by 0.5% as compared to EU5 engine. Even though A2.5 EU6 engine reduced engine out NOx by more than 20%, it was not sufficient to meet EU6 emission legislation. Thus, A2.5 EU6 engine implemented SCR catalyst to complement the NOx reduction by up to EU6 legislation. In our work, the optimal performance of SDPF has been accomplished by hardware optimization together with engine mapping. Result also shows that SDPF can have better NOx purification efficiency in the low temperature condition because it can quickly delivery exhaust heat to the SCR catalyst.
Limitations of this study
This optimization works will be further verified in our next SCR projects.
What does the pater offer that is new in the field including in comparison to other work by the authors?
In our work, “SCR control logic mapping tool with matlab simulink” has been developed to minimize the test procedures. SDPF inside temperature, NOx purification efficiency and UREA injection has been calibrated by simulation and then verified in detail by performing engine test. Result shows that model tool can estimate SCR conversion efficiency by the accuracy of 1.6%, and replace the engine test for SDPF calibration. It is expected that this tools be usefully applied for our following SCR projects
Conclusions
The STAREX equipped with A2.5 EU6 engine can successfully accomplish EU6 emission standard with SDPF system. Two functions of SCR and DPF were integrated into SDPF system, and successfully optimized to get the optimal performance in this work.
Key Words : Diesel Engine, Aftertreatment System, emission legislation, SCR, DPF, SDPF