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Emission Reduction in a GDI Engine with Different Injection Timings – A CFD Investigation

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Spark ignition dominates the personal transportation segment. These engines have been well developed over 100 years. In order to meet the stringent emission norms, the performance of the engines has to be enhanced. In this regard CFD plays an important role in designing a better engine. In this paper the results of a three dimensional reactive flow simulation conducted on a commercial SI engines are presented.  The simulations were conducted at an engine speed of 1000rpm with fuel injected directly into the cylinder. Three modes of fuel injections are analyzed. They are during opening of intake valve (case-1), during peak valve lift (case-2) and after the closure of intake valve (case-3). The injected fuel quantity is such that when all the injected fuel evaporates completely it would produce a stoichiometric mixture in the combustion chamber. The early injection (case-1) gives better performance in terms of higher peak pressure, early heat release, better homogeneous mixture and lowest emission compared to the other two cases. Compared with case-1, case-2 have 1.91% less maximum pressure, 4.3% lower CO2, 7.62% higher CO and 64.42% higher NOx. Whereas in case-3, 38.63% less maximum pressure, 34.78% lower CO2, 35.32% higher CO and 56.5% higher NOx.
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Trimmed Mesh; Start of Injection; Combustion; GDI

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