Access Type

Open Access Dissertation

Date of Award


Degree Type


Degree Name



Mechanical Engineering

First Advisor

Naeim A. Henein


Diesel engines are known for their superior fuel economy and high power density. However they emit undesirable high levels of nitrogen oxide (NOx) and black particulate smoke (Soot). To reduce these emissions, close loop engine control strategies are required. Therefore, there is a need for an in-cylinder combustion sensor. The ion current sensor has been used for combustion sensing in gasoline engines for which ionization mechanisms have been developed. This is not the case in diesel engines.

In this dissertation, a new mechanism for ionization in diesel engines has been developed and experimentally validated. Moreover, a three dimensional model has been implemented utilizing the new ionization mechanism to get more insight and better understanding of the ion current behavior in complex diesel combustion process. This model has been used to develop a new approach that allows the prediction of the soot content in the engine exhaust based on the ion current signal. Furthermore, a new technique has been applied for the use of the fuel injector as an ion current probe, injection timing sensor, and a diagnostic tool for injection and combustion. Another new technique has been developed to use a fast gas sampling probe as an ion current probe. Such a probe has been used in the dissertation to simultaneously measure the NO content inside the combustion chamber of a heavy duty diesel engine and ion current under different engine operating conditions.

Previous Versions

Aug 10 2011