Mixture formation analysis in a direct-injection NG SI engine under different injection timings

摘要

This paper investigates into the mixture formation in a direct injection, turbocharged, spark-ignition, CNG engine. The engine features a pent-roof combustion chamber, a bowl in piston and an outward-opening poppet valve injector, which is located centrally in the chamber dome. In the last few years, many studies have been conducted focusing on direct injection natural gas engines, and the end-of-injection timing has been identified as the main parameter affecting the quality and completeness of the mixture formation process. This paper aims at contributing to the progress of this research field, by means of the presentation and discussion of a large number of experimental and numerical data. The results obtained from the authors' CFD model, which has been developed and validated within the InGAS Collaborative Project of the EC, are in fact introduced and correlated to the outcomes of the experimental activity done by AVL GmbH, Graz, as part of the same research project. This synergy allowed a deep understanding of the mixture formation process, over a wide range of operating conditions.