Strut lattice structures of reaction‐bonded silicon infiltrated silicon carbide ceramics (RB‐SiSiC) for air–fuel mixture formation and for nonstationary lean‐burn under pressure applications were fabricated. The lattice design with a high porosity >80% was shaped by indirect three‐dimensional printing. It was shown that pre‐ignition processes in the porous reactor are much faster than in a free combustion, especially at lower temperatures. Interaction of high velocity diesel jets with cylindrical strut ligaments of the SiSiC lattice structure offers a new possibility for quick and efficient fuel distribution (multi‐jet splitting) in space.

Low-and high-temperature oxidation processes, including thermal auto-ignition under diesel-engine-like conditions (non-premixed mixtures), have been investigated. A special combustion chamber, characterized by constant volume and adiabatic conditions, has been used as an engine simulator. The investigated processes are very complex in nature, and depend significantly on the temperature and pressure. There are five characteristic regions of the process characterized by different delay times, reaction rates and number of recognizable oxidation reactions: region 1 corresponds to processes occurring at low initial pressures over a wide range of initial temperatures; region 2 corresponds to low initial temperatures over a wide range of initial pressures; region 3 corresponds to middle pressures and higher temperatures; region 4 corresponds to middle temperatures and higher pressures; and region 5 corresponds to high initial pressures and high temperatures. by analogy to a negative temperature coefficient (as discussed in the literature), a positive pressure coefficient has been introduced here. This indicates that in the selected range of pressures, the delay time of lowtemperature oxidation processes is the shortest, and the rate of these reactions is the highest. Further increases in the pressure behind the positive pressure coefficient range increase the delay time and decrease the reaction rate. The positive pressure coefficient has been observed at lower temperatures (mostly corresponding to cool-flame reactions and transitions to blue flames). Generally, the ignition delay time reduces with increasing chamber temperature and pressure.

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Thermodynamic conditions of the heat release process under Diesel engine-like conditions in a real porous combustion reactor simulated in a special combustion chamber were analyzed. The same analyses were performed for a free volume combustion chamber, that is, no porous reactor is applied. A common rail Diesel injection system was used for simulation of real engine fuel injection process and mixture formation conditions. The results show that thermodynamic of the heat release process depends on reactor heat capacity, pore density, specific surface area, and pore structure, that is, on heat accumulation in solid phase of porous reactor. In real reactor, the gas temperature and porous reactor temperature are not equal influenced by initial pressure and temperature and by reactor parameters. It was found that the temperature of gas trapped in porous reactor volume during the heat release process is less dependent on air-to-fuel-ratio than that observed for free volume combustion chamber, while the maximum combustion temperature in porous reactor is significantly low. As found this temperature depends on reactor heat capacity, mixture formation conditions and on initial pressure. Qualitative behavior of heat release process in porous reactors and in free volume combustion chamber is similar, also the time scale of the process.

In order to realize a homogeneous combustion process it is necessary to decouple this combustion process from fuel injection. This homogeneous combustion process requires the charge to be homogeneous prior to simultaneous volumetric ignition. This kind of ignition is a self-ignition process requiring control of the ignition timing. A late-injection strategy as used in a conventional diesel engine permits control of the ignition timing; however, the time available for mixture formation and the homogenization process is very limited. The present paper deals with a distribution-nozzle concept which combines both strategies: a late-injection strategy for controlling the ignition timing with significantly accelerated fuel distribution in space and corresponding mixture homogenization. The distribution-nozzle concept combines a conventional diesel nozzle with a porous element (ring) positioned in proximity to the nozzle outlet. Because of multi-jet splitting as a result of the diesel-jet interaction with a porous structure, the fuel leaving the porous ring spreads widely in space. Additionally, a very effective fuel vaporization process occurs within the porous structure, supporting quick mixture formation. The paper describes both the fuel distribution in space and its vaporization for different configurations of the distribution elements, the injection pressure, and the porous ring temperature. In comparison with a free diesel injection, the distribution nozzle results in a significantly increased fuel surface area, a reduced jet penetration length, a reduced jet velocity, and very quick fuel vaporization. This process is three dimensional in nature. Depending on the distribution-element structure, the geometry, and its temperature, as well as the injection pressure, the contributions of multi-jet splitting, and fuel vaporization, are different with respect to the surface area, penetration length, and exit velocity, as well as intensity distribution. Generally, at higher injection pressures these parameters are less temperature dependent, except for the fact that the intensity distribution is a function of the fuel vapour's concentration.