Investigations on Pre-chamber Ignition Device Using Experimental and Numerical Approaches 2019-01-2163
Nowadays Spark Ignition (SI) engine efficiency is mainly limited by abnormal combustion (knock) and stability issues at high dilution rate (both EGR and air). Increasing the combustion velocity is a relevant way to overcome these limitations. Main strategy to increase the combustion velocity is to enhance the flow motion in the cylinder (tumble motion) in order to increase the turbulence during the combustion. Such approach is mainly performed by working on intake port design which lead to engine volumetric efficiency penalties. Another approach to increase the combustion velocities is to have multiple ignition kernels in the chamber. This can be obtained thanks to Turbulent Jet Ignition (TJI) which uses a pre-chamber to spread the initial flame kernel throughout the combustion chamber. To achieve pre-chamber optimization a deep understanding of the complex phenomena involved in TJI as well as validated numerical tools is required. The present paper aims at providing such understanding using both numerical simulations and experimental investigations. First, dedicated experimental methodology is deployed on an optical engine providing a characterization of the flame jets depending on the pre-chamber geometry. Then, the numerical 3D CFD tool is setup to model these experimental configurations and then used to bring additional information on the breathing mechanisms of the pre-chamber. Finally, experiments are conducted on a single cylinder SI engine, replacing the conventional spark plug by a pre-chamber. The contribution of this ignition device to the improvements of engine efficiency is evaluated.