Design Evolution of an Exhaust After Treatment System Development for a High-Power Diesel Engine Adhering Global Emission Norms

With the advent of stricter emission norms such as Bharat Stage VI - Phase I and II, the design of the exhaust after treatment system becomes crucial for the internal combustion engine. Inadvertently, the size of the after-treatment system also becomes bigger to cater to the latest emission norms, which leads to increased resistance to the flow of exhaust gases through them. However, the resultant back pressure generated in these devices deteriorates the engine performance. Hence, the onus is on the engine designer to design the after-treatment system and the bracketing concept for mounting in such a way that the engine performance remains intact, and the entire system is packaged within the vehicle boundary conditions. The after-treatment system experiences severe vibrational loads as well as thermal loads. Hence, the designer faces the challenge of carefully designing the system and its brackets to survive the desired engine life and to package the entire system within the vehicle boundaries considering the thermal expansion of the system. Current work depicts the design evolution of the after-treatment system for 2.2-liter, 4-cylinder, high power diesel engine. Initially, commercially available AVL Boost software predicted the exhaust gas state along with the engine performance. With the one-dimensional simulation results and preliminary exhaust system design, a 3D CFD analysis was carried out. This predicted the temperatures at different locations of the computational domain of the after-treatment system. Subsequently, CAE analysis were carried out for modal analysis which predicted the first mode of 189Hz which was 9Hz above the target of 180Hz considering a factor of safety of 1.2. FRF analysis and fatigue analysis (TMF and HCF) were carried out to further predict the stresses on each part of the after-treatment system and to ensure that there were no stress peaks due to resonances. Thus, the exhaust after treatment design evolved in steps to ensure the durability of the exhaust system.