Integrated Exhaust Manifold Design & Optimization of it through HCF and LCF Simulations for a BS6 Compliant Diesel Engine

This paper discusses design and optimization process for the integration of exhaust manifold with turbocharger for a 3 cylinder diesel engine, simulation activities (CAE and CFD), and validation of manifold while upgrading to meet current BS6 emissions. Exhaust after-treatment system needs to be upgraded from a simple DOC (Diesel Oxidation Catalyst) to a complex DOC+sDPF (Selective catalytic reduction coated on Diesel Particulate Filter) to meet the BS6 emission norms for this engine. To avoid thermal losses and achieve a faster light-off temperature in the catalyst, the exhaust after-treatment (EATS) system needs to be placed close to the engine - exactly at the outlet of the turbocharger. This has given to challenges in packaging the EATS. The turbocharger in case of BS4 is placed near the 2^nd cylinder of the engine, but this position will not allow placing the BS6 EATS. Hence, the turbocharger position must be shifted to such an extent that it is placed before the first cylinder resulting in an overhanging design. This needed sufficient design optimization through CAE and CFD simulations. CFD simulations are performed to predict the surface temperatures of the manifold using conjugate heat transfer (CHT) analysis. HCF and LCF simulations were performed to optimize the wall thickness and merging radii given along with the stiffening ribs in the exhaust manifold. The overhang design of turbocharger posed a challenge in sealing the exhaust manifold and cylinder head joinery, this has been optimized using CAE simulations. The paper also discusses the correlation between simulation and validation results. The finalized design has been validated on both engine testbed and vehicle successfully.