Effect of combustion chamber geometry on air flow and combustion in a direct injection diesel engine

Abstract

The DI diesel engine performance is greatly influenced by incylinder fluid dynamics that contribute to the fuel-air mixing, which is one of the most important factors for the control of the fuel burning rate. It significantly affects the ignition delay, magnitude of the premixed burn, and timing of the diffusion burn, and the Emissions of nitric oxide and soot. Detailed simulation of the various features of the in-cylinder fluid motion including heat transfer and combustion processes has now become an achievable goal using Computational Fluid Dynamics (CFD) methodology, an area which is developing for more than a decade. In the present work, computational fluid dynamics investigation on in-cylinder flow for non-reacting as well as firing condition in a DI diesel engine with different types of combustion chamber geometries has been carried out. Validation of simulated results with experimental data available in the literature under motoring condition is presented. In order to verify the reliability of CFD simulation, the values obtained for the simulation are compared with the available experimental results for the engine geometry considered. . The results show good agreement with the experimental results in the literature. In order to verify the reliability of CFD simulation, the values obtained for the simulation are compared with the available experimental results for the engine geometry considered. . The results show good agreement with the experimental results in the literature. Based on the combustion simulation studies carried out in this investigation, it is concluded that to achieve best possible performance and emission characteristics from a DI Diesel engine, the combination of injection timing(start of injection) 20 deg BTDC and 10% EGR concentration is found to be optimum. The multiple injection profile of 40% pilot and 60% main injection is also found to be optimum. The ramp2 injection rate shape is the optimum for a design compared as Ramp1 to boot profile. newline newline newline