Experimental Investigation And Development Of An Extended Two Color Method (etcm) With Application To Internal Combustion Engines

EXPERIMENTAL INVESTIGATION AND DEVELOPMENT OF ANEXTENDED TWO COLOR METHOD (eTCM) WITH APPLICATION TO INTERNALCOMBUSTION ENGINESbyELENA FLOREAAugust 2013Advisor: Dr. Dinu TarazaMajor: Mechanical EngineeringDegree: Doctor of Philosophy The internal combustion engine is on a continuous path of improvement toreduce exhaust gaseous emissions and improve fuel economy. While recent trends indiesel engine development have lowered the EGR requirements, future regulatorypressure will likely result in a reversed trend in the future.Given this, it is of interest to improve the application range of diagnostic toolssuch as the two color method (TCM) typically used in evaluating the properties ofengine soot, such as temperature and volume fraction. This optical diagnosticmethod relies on the use of the light emitted by the soot particles along with a sootemissivity model in order to estimate the temperature T and optical thickness KLcharacterizing the soot cloud of interest. This assumption is reasonable for the“traditional” diesel combustion, where low degrees of premixed combustion result invery low amounts of blue-flame light emission compared to the soot relatedradiation. However, for LTC (low temperature combustion) combustion modes thisassumption is no longer applicable, especially for combustion strategiescharacterized by very large premixed combustion phases, such as the Partially-premixed Charge Compression Ignition (PCCI) strategies. 126The aim is to obtain more information related to the combustion process andspecifically on the soot formation and oxidation process. For this reason, the presentresearch can be divided in two major sections. The first section focuses on the development of a combustion optical probeand the optical experimental setup necessary for conducting the experimental work.Information regarding the soot formation and oxidation processes may be inferredfrom the measured signal.The objective of the second section of the current research is to provide thetheoretical background and experimental evidence needed to describe the proposedoptical diagnostic tool, the extended two-color method (eTCM). This methodattempts to extend the domain of applicability of the classical two color methodwithin the area of strong CO continuum interference as well as providing a method oftesting the validity of the conventional two-color method. Further, it providesadditional information regarding the strength of the radiation associated with the COflame continuum.Towards this goal, the work was conducted on a fully accessible optical engine, which allowed the use of multiple synchronous optical measurementstargeted towards the evaluation of the proposed optical diagnostic tool.The evidence presented in this work suggests that eTCM is capable oftemperature and soot optical thickness factor correction under medium and strongblue-flame interference without significant impact on the temperature estimationuncertainty.Consequently, the currently proposed extended two-color method (eTCM) has thepotential for a large-scale impact in the fields of fundamental engine research as wellas engine development and calibration.