Effect of Baffle Height on the in-Cylinder Air-Fuel Mixture Preparation in a Gasoline Direct Injection Engine – A Computational Fluid Dynamics Analysis

Abstract

<div class="section abstract"><div class="htmlview paragraph">In-cylinder fluid dynamics enhance performance and emission characteristics in internal combustion (IC) engines. Techniques such as helical ports, valve shrouding, masking, and modifications to piston profiles or vanes in ports are employed to achieve the desired in-cylinder flows in these engines. However, due to space constraints, modifications to the cylinder head are typically minimal. The literature suggests that introducing baffles into the combustion chamber of an IC engine can enhance in-cylinder flows, air-fuel mixing, and, subsequently, stratification. Studies have indicated that the height of the baffles plays a significant role in determining the level of improvement in in-cylinder flow and air-fuel mixing. Therefore, this study employs Computational fluid dynamics (CFD) analysis to investigate the impact of baffle height on in-cylinder flow and air-fuel mixing in a four-stroke, four-valve, spray-guided gasoline direct injection (GDI) engine. The maximum allowable baffle height is limited to the minimum distance between the piston and cylinder head surface when the piston is at the top dead centre (TDC). The analysis involves varying the baffle height from 1 mm to 3 mm. Additionally, a new discretisation scheme is introduced to assess the mixing level within the combustion chamber. The results indicate a significant influence of baffle height on in-cylinder flows. Notably, a 1 mm baffle height yields a flow and mixing pattern similar to that of the base engine without baffles. As the baffle height increases, the in-cylinder flows are altered, leading to the formation of multiple vortices due to the presence of baffles. Furthermore, an increase in baffle height enhances mixture stratification, confining more fuel toward the spark plug location.</div></div>