Issues to Overcome Knocking and Pre-ignition in SI Engines

Abstract

Spark ignition engines are widely used for a small generator as well as a passenger vehicle. The exhaust gas emissions no longer have pollution problem by adopting a combination of three-way catalyst and stoichiometric mixture control, but an improvement of thermal efficiency is an urgent task. To achieve this, an increase of compression ratio and down-sizing with a turbo-charger are solutions. However, employing these methods causes abnormal combustion of such as knocking and pre-ignition that will bring about damages to engine components. In this article, why these phenomena occur and how to solve the issues are briefly mentioned with some author's ideas: since autoignition itself does not lead to a heavy knocking, a quick expansion at early expansion stroke and a spatial temperature distribution of mixture inside the cylinder can control the knocking intensity. As pre-ignition at low engine speed is not well analyzed, this phenomenon must be quantitatively examined.