A specially developed macro-cellular SiC non-foam reactor has been used for investigations into Diesel-fuel injection, mixture formation and the heat release process inside a porous structure under piston-engine conditions. The heat release process has been compared to a free Diesel combustion indicating a significant influence of the reactor heat capacity on the thermodynamics of the process. Generally, the low- and high-temperature oxidation processes in a porous reactor are much faster, because of shorter delay time as compared to a free non-premixed combustion. High heat capacity of the porous reactor as compared to the gas heat capacity results in significantly reduced combustion temperature and corresponding combustion pressure peaks. Foam reactors with low and high pore density have also been compared in this investigation. The mixture formation, heat transfer and heat release processes performed in a porous reactor are very complex and depend on a number of different parameters of the combustion reactor in question: reactor structure, its heat capacity, pore size, specific surface area and wall junction geometry. Distribution of characteristic regions plotted in p-T areas indicates qualitative similarity of heat release process as performed under Diesel-like and in porous reactor conditions. (C) 2012 Elsevier Ltd. All rights reserved.