Implementation of two color method to investigate late cycle soot oxidation process in a CI engine under low load conditions. (25th February 2017)

• Record Type: Journal Article
• Authors: López, J. Javier; Martín, Jaime; García, Antonio; Villalta, David; Warey, Alok
• Is Part Of: Applied thermal engineering. Volume 113(2017:Feb.)
• Page Start: 878
• Page End: 890
• Publication Date: 2017-02-25
• Subjects: Multi-cylinder pyrometer -- Soot oxidation -- Two color method -- Optical thickness -- Mixing capability; Heat engineering -- Periodicals; Heating -- Equipment and supplies -- Periodicals; Periodicals; 621.40205
• DOI: 10.1016/j.applthermaleng.2016.11.095
• Languages: English
• ISSNs: 1359-4311

Abstract

Highlights: High uncertainties in flame transparency are obtained for high load conditions. The half-life time is a good estimator to characterize the soot oxidation process. If injection pressure is reduced, the soot oxidation process is decreased. Lower the ambient density and/or temperature, larger the mixing capability. The soot oxidation process is explained by the mixing process and bulk temperature. Abstract: Soot emissions from diesel engines are an important concern in meeting emissions regulations. Soot emissions are the result of two competing processes: soot formation and soot oxidation. Mechanisms of soot formation are discussed extensively in the literature. Equivalence ratio at lift-off length along with residence time and gas temperature play an important role for soot formation in a diffusion flame. Mixing capability and bulk gas temperature are the most important parameters that influence the in-cylinder soot oxidation process. Normally, research studies of soot formation-oxidation processes have been developed under controlled and not completely representative conditions of engine operation in the field. Therefore, the main objective of this work was to develop a simplified methodology to evaluate in-cylinder soot oxidation under 'real' engine conditions. In particular the impact of mixing process and bulk gas temperature on late cycle soot oxidation was evaluated. The experimental measurements were made in a production light-duty diesel engine varying those parameters that have been demonstrated in the literature as the most relevant in soot formation – oxidation processes; injection pressure, ambient density and intake air temperature. To measure soot, two color method was applied by means of an optoelectronic pyrometer. To evaluate the mixing capability a specific "tracer" Apparent Combustion Time (ACT −1 ) based on the experimental heat release and injection parameters was defined. The relationship between both parameters was used to explain the soot oxidation process.