Development of Numerical Method for the Analysis of Low Emission Combustion using Artificial Turbulence Stimulation

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A new method for the computational analysis of premixed charge compression ignition combustion has been developed. The method employs Very Large Eddy Stimulation (VLES) in conjunction with chemical reactions, solving temporal and spatial fluctuations of velocities and temperatures in a numerical cell size, and simulating the random nature of the appearance of auto-ignition spots. Using a novel idea in the implementation of the simulation, we give statistically reasonable initial condition for a fluctuating turbulent flow field at intake valve closing time. The phase-averaged result of the VLES and the result of the k-epsilon model are well in agreement with respect to mean flow, mean temperature, cylinder-averaged turbulence kinetic energy and pressure during compression. The VLES exhibits the spatially random appearance of auto-ignition sites, which is similar to experimental observations shown in the literature. The analysis shows that the spatially random occurrence of the auto-ignition is due to the local wall heat transfer which changes randomly and generates temperature fluctuations. This study presents a new computational approach to analyze the mechanism of the premixed charge compression ignition combustion.