Clarification of Mechanism of Unsteady Combustion Phenomena by means of Luminescent Measurement of Chemical Species

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It is very difficult to clarify the mechanism of the unsteady combustion process, because it is proceeding during very short period with simultaneous physical and chemical changes. However, it is capable of modeling on the phenomena, if this mechanism is caught by experiments, and it is expected moreover the development of instruments utilizing the mechanism. From this standpoint, this project was carried out by use of a DI diesel engine with a transparent piston as the representative instrument applying the mechanism. And the objective items were the detection of 2-D statistical spatial distribution of [OH] radical as the representative of chemical species by the method of laser induced fluorescence with the system of Nd : YAG laser and Dye laser, and that of soot relating to [OH] radical owing to the simultaneous application of the elastic scattering method and the laser induced incandescence method with Nd : YAG 1 aser.The following main conlusions are derived from the experiments i … More n these two years :(1) It is possible to catch the 2D spatial distribution of [OH] radical in the flame of unsteady spray by means of the laser induced fluorescence. There was no example of the detection of the radical in this situation.(2) [OH] radical distributes in the wide region of the combustion chamber at the initial stage of combustion, that is, during the period of the pre-mixed burning.(3) [OH] radical shows the high density at the region of soot existence during the period of diffusion burning.(4) The 2D spatial distribution of soot by means of the laser induced incandescence method is corresponding well to that of the elastic scattering method.(5) Soot exists continuously at the envelope of the flame of unsteady spray at the initial stage of combustion.(6) Near the wall of combustion chamber, soot appears always through the combustion period.(7) The re-combustion of soot is active mainly during the period of diffusion burning.(8) There is almost the linear relation between the mean soot diameter and the time passing.It is useful for the construction of model of combustion mechanism of the unsteady spray to apply the experimental results mentioned above as the data base. Less