New Generation Multi-hole Fuel Injector for Direct-Injection SI Engines - Optimization of Spray Characteristics by Means of Adapted Injector Layout and Multiple Injection

The paper discusses spray characteristics of fuel injectors with multi-hole nozzle (MHI) for DISI engine applications with homogeneous combustion and optional turbocharger (down-sizing concepts). Depending on the engine's operating mode the predominantly influencing spray parameters change. Although several injection concepts are available for DISI engines multi-hole injectors provide high spray flexibility to meet the requirements. The work presents a methodology called spray targeting for adapting the MHI adequately to the engine and tap its full potential. This requires fundamental knowledge of the influencing parameters on spray formation. A study using a DOE approach is introduced to identify the main influencing parameters on spray characteristics, e.g. nozzle geometry, operating parameters, and injection timing parameters. In particular an injector operation strategy which splits the required fuel quantity per cycle into multiple parts is identified as an adequate measure for effective improvement of spray quality regarding homogeneity and spray geometry. Furthermore it enables controlling of spray parameters and optimization of the mixture to further reduce exhaust emissions (e.g. smoke).