Study of Pollutant Formation and Its Control in the Non-Uniform Combustion

点击翻译按钮获取中文摘要

This study aims at the clarification of the non-uniform combustion process in highly-turbulent flowfields for controlling pollutant formation during combustion. The contents of the prsent study are summarized as follows :1.Turbulence in jet diffusion flames was investigated based on observations of instantaneous LLS (laser-light sheet method) images of turbulent eddies. Results show that only larger eddies can be seen mainly on the azimuthal cross-section, and that mixing between fuel and air mainly proceeds by stretching of the interfacial layr during development of vortex rings due to an ejecting flow. Furthermore, the capability of inducing vortices near the zone of a higher density gradient due to baroclinic effect was discussed using a vorticity-transport equation.2.Particle image velocimetry (PIV) for measuring velocity vectors in a turbulent flow was developed based on a two dimensional cross-correlation coefficient between two images with a small time interval. An accuracy of P … More IV was assessed at probable errors using the simulated images. The measured results in jets and jet flames reveal that vortex rings produced associated with the unsteady motion in the shear layr promote the mixing, whereas in the reacting region fluctuating motions are laminarized due to an increase in temperature, causing the complicated pattern of soot layrs in the downstream of flame.3.Production and destruction of nitrogen oxides in the two-stage combustion was investigated based on a detailed chemical kinetics. From the analysis of dilution processes of methane-air fuel-rich burnt gas, it is shown that fast mixing due to strong turbulence causes a considerable NOx reduction, and that a further reduction can be achieved if the temperature decreases with the volume expansion prior to the heat-release due to the dilution. In addition, reaction paths into NOx formation were discussed in the conditions of different presure and air-temperature, and contributions of individual elementary reactions were given by the integration of each NO formation rate. Less