Ion current sensing for controlled auto ignition in internal combustion engines

Abstract

Envirom-nental pollution is a subject that needs urgent addressing. Since the internal combustion engine has its fair share of accountability on this, research on techniques for increasing engine efficiency and emissions is necessary. Controlled Auto Ignition is a promising combustion mode, which increases fuel efficiency while also reducing NOx emissions to negligible levels. This Thesis concentrates on the implementation of this mode through experimental research, on an engine equipped with a fully variable valvetrain. Investigation of the operational window, emissions, fuel consumption, thermodynamic efficiency is carried out and ways to improve on these are discussed. The governing consideration, however, is the control method for this rather intricate combustion mode. As such, experimental data acquisition and analysis of ion current under the whole operating spectrum, from spark ignition to full autoignition is made. It is found that the expected gains in fuel consumption and emissions are realized. In addition, ion current proves to be a very powerful and cost effective tool for engine monitoring, diagnosis and control. The author concludes that Controlled Auto Ignition is a viable proposition for mass production engine designs and that ion current, although not absolutely vital for engine control, considerably increases engine control thus allowing for greater operating window under autoignition, without compromising reliability or cost