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CNG is one of the future fuel for a CI engine. Recently, the general tendency is the use of the high pressure injection system over 100 MPa in a CI engine for the near future severe regulation. Combustion phenomenon in a CI engine with such injection system is like a transient gas diffusion flame. The flow in a gas diffusion flame was investigated by the particle image velocimetry on its 2-D images, the relative soot concentration, the temperature and the relative CO2 concentration was detected in the experiments. And the model of transient gas diffusion flame was constructed by use of experimental data.

A transient gas jet and its flame are the most fundamental phenomena of a transient spray and its flame breaking out in a CI engine and an SI engine with the direct injection system. In the case of CNG and LNG engines, the fuel itself is just gaseous state. The 2-LIF technique was applied to the transient gas jet to obtain the mixing process between the surroundings and it, and the simultaneous application of LII and LIS techniques were applied to the transient gas jet flame to obtain the soot formation process.

The development of PM and NOx reduction system with the combination of DOC included DPF and SCR catalyst in addition to the AOC sub-assembly for NH3 slip protection is described. DPF regeneration strategy and manual regeneration functionality are introduced with using ITH, HCI device on the EUI based EGR, VGT 12.3L diesel engine at the CVS full dilution tunnel test bench. With this system, PM and NOx emission regulation for JPNL was satisfied and DPF regeneration process under steady state condition and transient condition (JE05 mode) were successfully fulfilled. Manual regeneration process was also confirmed and HCI control strategy was validated against the heat loss during transient regeneration mode.

The combustion of a diesel spray includes very complex processes, that is, atomization, evaporation, diffusion, turbulent mixing and burning. On the other hand, there are no phenomena of atomization and evaporation in the combustion of a transient gas jet. However, the latter jet can be treated as a fundamental of the former spray. From the standpoint mentioned above, acetylene gas was injected into the ambient during short duration as a transient gas jet and its flow characteristics were investigated by means of photography with a sheet of laser light and LDV to detect the turbulent vortex generated in the boundary layer between it and surroundings, in the experiments presented here. And the experimental results show that the jet itself is divided into four peculiar regions and the modelling of each region is carried out by use of the results to understand the mixture formation process owing to the turbulent diffusive mixing.

A transient gas jet seems to be a model of a diesel spray because it has no vaporization process. Recently, CNG is utilized in a diesel engine. In the case of diesel engine, sprays or jets have the free state in some cases, and they are impinging surely on the piston surface in the other cases. The 2-D image of acetylene gas with tracer particles was taken by high-speed photography. In both jets, the outer shape was measured on the images and the characteristics of the internal flow was obtained by particle image velocimetry. Then, the physical models of these jets were constructed by use of experimental results.