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 cruicial for the internal combustion engine. Inadvertently, the size of the after treatment system also becomes bigger to cater to the norms. However, the 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 in such a way that the engine performance remain intact and the entire system is packaged within the vehicle boundary conditions. The after treatment system experiences severe vibration loads as well as thermal loads. Hence the designer faces the challenge of carefully design the system and its brackets to survive the desired engine life and to package the 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 litre, 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 for 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. Vibrational fatigue analysis and forced response analysis 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 evolve ensure the durability of the system.