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Journal of Combustion
Volume 2013, Article ID 267631, 22 pages
Research Article

Characteristics of Flameless Combustion in 3D Highly Porous Reactors under Diesel Injection Conditions

1Georg Simon Ohm University of Applied Sciences Nuremberg, Department of Mechanical Engineering, Kesslerplatz 12, 90489 Nuremberg, Germany
2Fraunhofer Institute for Building Physics IBP, Department of Energy Systems, Nobelstrasse 12, 70569 Stuttgart, Germany

Received 18 January 2013; Accepted 19 February 2013

Academic Editor: Eliseo Ranzi

Copyright © 2013 M. Weclas and J. Cypris. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The heat release process in a free volume combustion chamber and in porous reactors has been analyzed under Diesel engine-like conditions. The process has been investigated in a wide range of initial pressures and temperatures simulating engine conditions at the moment when fuel injection starts. The resulting pressure history in both porous reactors and in free volumes significantly depends on the initial pressure and temperature. At lower initial temperatures, the process in porous reactors is accelerated. Combustion in a porous reactor is characterized by heat accumulation in the solid phase of the porous structure and results in reduced pressure peaks and lowered combustion temperature. This depends on reactor heat capacity, pore density, specific surface area, pore structure, and heat transport properties. Characteristic modes of a heat release process in a two-dimensional field of initial pressure and temperature have been selected. There are three characteristic regions represented by a single- and multistep oxidation process (with two or three slopes in the reaction curve) and characteristic delay time distribution has been selected in five characteristic ranges. There is a clear qualitative similarity of characteristic modes of the heat release process in a free volume and in porous reactors. A quantitative influence of porous reactor features (heat capacity, pore density, pore structure, specific surface area, and fuel distribution in the reactor volume) has been clearly indicated.