Turbulence Enhancement by Direct Air Injection for a Lean-Burn SI Engine

Authors

Takanori Suzuki, M.Eng.,
SOKEN, Inc., Aichi, Japan;
Dipl.-Ing. Bastian Lehrheuer, Prof. Dr.-Ing. Stefan Pischinger,
Institute for Combustion Engines, RWTH Aachen University, Aachen

Summary

A suitable in-cylinder turbulence contributes to a better combustion process of leanburn SI-engines. This research project focuses on an in-cylinder turbulence enhancement concept close to the spark plug. High-pressure air was injected into the cylinder to generate a consistent turbulence. Turbulence promotes a flame kernel growth after ignition, which leads to faster combustion and higher combustion stability. The turbulence enhancement concept was evaluated under lean-burn conditions. Due to the increased combustion stability, the lean limit was extended by 0.15 point of excess air ratio (1.50 to 1.65) leading to an improvement in ISFC of
1.4% and reduced NOx emissions (790 ppm to 280 ppm).

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