Open Access Dissertation
Date of Award
Naeim A. Henein
Efforts have been made previously by researchers to quantify the auto-ignition quality of fuels by calculating global activation energy using Arrhenius plots with data measured for the ignition delay period (ID). Large variation in the activation energy of fuels has been observed even for fuels with closer CN values. More recently, the activation energy values obtained by Kook et al in (2005) on an optical engine do not agree with data obtained in an identical metallic engine by Jayakumar using fuels of same CN.
The disparity in their results can be attributed to the differences in ignition delay (ID) and effective temperature definitions used. Most researchers agree upon the start of ID time as the start of injection (SOI). The main point of disagreement has been in defining the end of ID period which is considered to be the start of combustion (SOC). As a result, numerous definitions for the ID period have been used by researchers which lead to variation in calculation of activation energy value. In addition, in heterogeneous combustion equipment to account for changes in charge temperature due to fuel evaporation and piston movement (in engines) an effective temperature value is used. Different definitions for the effective temperature have been reported in the literature. This leads to more variations in the activation energy value calculation. Furthermore, it was observed that engine test conditions and the temperature regime in which the tests are done would also affect the calculation of activation energy value.
This dissertation examines the effects of ignition delay definitions, effective temperatures, engine conditions and temperature regimes on the global activation energy. Moreover, homogeneous charge test data has shown presence of a NTC regime in which the activation energy value can be either positive, negative or zero. However, heterogeneous test data from literature has always shown positive values for activation energy. This dissertation has also explained the reasons behind such a behavior.
Joshi, Umashankar M., "Quantification Of Auto-Ignition In Diesel Engines" (2015). Wayne State University Dissertations. 1341.