Influence of Exhaust Gas Recirculation on Ignition and Combustion of Diesel Fuel under Engine Conditions Investigated by Chemical Luminescence

Rieß S, Vogel T, Wensing M (2015)

Publication Type: Conference contribution, Conference Contribution

Publication year: 2015

Event location: Tainan TW

Abstract

In internal combustion engines, exhaust gas recirculation (EGR) is a common means to reduce nitrogen oxide (NOx) emissions. In diesel engines EGR rates up to 50% are used to lower the combustion temperature due to lower oxy-gen content of the ambient gas in the cylinder. As the main mechanism of nitrogen oxide formation (Zeldovich mechanism) is temperature driven, lower NOx emissions can thus be achieved.
In a permanently scavenged high temperature/high pressure injection and combustion vessel (1000 K, 10 MPa) the self-ignition and combustion process of diesel under engine relevant conditions can be investigated using optical measurement techniques under constant and repeatable conditions so that isolated parameter influences on spray and combustion processes can be studied. The test bench can be scavenged either by air, nitrogen or any gas mixture. Thus the influence of different EGR rates on the spray, ignition and combustion process of diesel fuel can be exam-ined. The measurements in the investigation were performed at EGR rates of 0, 10, 20, 30 and 40 percent for differ-ent temperatures of the ambient gas. The visible integral flame signal in the non-premixed diesel flame was recorded with a CCD camera. The chemical luminescence signal of the OH radical in premixed parts of the flame was record-ed simultaneously using an iCCD camera.
During the radical chain reactions of the self-ignition of hydrocarbons the OH radical occurs early in the reaction mechanism and significantly before the occurrence of visible soot radiation. Thus it is an indicator for the ignition delay. As the measurements were performed time resolved in discrete steps the temporal occurrence of OH radical luminescence enables the numerical calculation of the ignition delay for diesel fuel under EGR influence. This anal-ysis quantitatively shows the elongation of the ignition delay for rising EGR rates. Furthermore, a significant change of combustion propagation and reaction rate can be examined spatially and temporally resolved for the premixed and the non-premixed flame by analysis of the intensity images and derived numerical parameters (e.g. penetration, flame lift off). A potential to reduce soot by increased EGR rates is shown and explained by locally reduced reaction rates and therefore increased mixing times.

Authors with CRIS profile

Sebastian Rieß Lehrstuhl für Technische Thermodynamik Thomas Vogel Professur für Fluidsystemtechnik Michael Wensing Professur für Fluidsystemtechnik

How to cite

APA:

Rieß, S., Vogel, T., & Wensing, M. (2015). Influence of Exhaust Gas Recirculation on Ignition and Combustion of Diesel Fuel under Engine Conditions Investigated by Chemical Luminescence. In Proceedings of the 13th International Conference on Liquid Atomization and Spray Systems (ICLASS). Tainan, TW.

MLA:

Rieß, Sebastian, Thomas Vogel, and Michael Wensing. "Influence of Exhaust Gas Recirculation on Ignition and Combustion of Diesel Fuel under Engine Conditions Investigated by Chemical Luminescence." Proceedings of the 13th International Conference on Liquid Atomization and Spray Systems (ICLASS), Tainan 2015.

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