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Experimental investigation and development of an extended two color method (eTCM) with application to internal combustion engines

EXPERIMENTAL INVESTIGATION AND DEVELOPMENT OF AN EXTENDED TWO COLOR METHOD (eTCM) WITH APPLICATION TO INTERNAL COMBUSTION ENGINES by ELENA FLOREA August 2013 Advisor: Dr. Dinu Taraza Major: Mechanical Engineering Degree: Doctor of Philosophy The internal combustion engine is on a continuous path of improvement to reduce exhaust gaseous emissions and improve fuel economy. While recent trends in diesel engine development have lowered the EGR requirements, future regulatory pressure will likely result in a reversed trend in the future. Given this, it is of interest to improve the application range of diagnostic tools such as the two color method (TCM) typically used in evaluating the properties of engine soot, such as temperature and volume fraction. This optical diagnostic method relies on the use of the light emitted by the soot particles along with a soot emissivity model in order to estimate the temperature T and optical thickness KL characterizing the soot cloud of interest. This assumption is reasonable for the “traditional” diesel combustion, where low degrees of premixed combustion result in very low amounts of blue-flame light emission compared to the soot related radiation. However, for LTC (low temperature combustion) combustion modes this assumption is no longer applicable, especially for combustion strategies characterized by very large premixed combustion phases, such as the Partiallypremixed Charge Compression Ignition (PCCI) strategies. 126 The aim is to obtain more information related to the combustion process and specifically on the soot formation and oxidation process. For this reason, the present research can be divided in two major sections. The first section focuses on the development of a combustion optical probe and the optical experimental setup necessary for conducting the experimental work. Information regarding the soot formation and oxidation processes may be inferred from the measured signal. The objective of the second section of the current research is to provide the theoretical background and experimental evidence needed to describe the proposed optical diagnostic tool, the extended two-color method (eTCM). This method attempts to extend the domain of applicability of the classical two color method within the area of strong CO continuum interference as well as providing a method of testing the validity of the conventional two-color method. Further, it provides additional information regarding the strength of the radiation associated with the CO flame continuum. Towards this goal, the work was conducted on a fully accessible optical engine, which allowed the use of multiple synchronous optical measurements targeted towards the evaluation of the proposed optical diagnostic tool. The evidence presented in this work suggests that eTCM is capable of temperature and soot optical thickness factor correction under medium and strong blue-flame interference without significant impact on the temperature estimation uncertainty. Consequently, the currently proposed extended two-color method (eTCM) has the potential for a large-scale impact in the fields of fundamental engine research as well as engine development and calibration.