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In order to simulate and predict the complex mechanism of the high power CO laser excited by transverse dc discharge, a two-dimensional gas flow model has been developed from the authors' one-dimensional model. Based on the control volume method for two-dimensional Cartesian coordinates, the fundamental equations deal with state, continuity, momentum, energy, and reactions. The similar discharge power distribution can be given as the experiment, where the power density is higher around the hollow-cathode array than around the plane anode. Although the speed of the CO gas mixture is in the sub-sonic region, the effect of compression is taken into account. The integration is repeated by SIMPLEST method and the matrices are solved by MICCG method for the pressure equation and by MJLUCR method for the other equations. The computation is carried out by a HITAC S820 supercomputer and a Sun-4 workstation. As a result of the simulation, non-uniform distribution of the gas parameters was made clear.

Telephone +81 471 44 8811, Telefax +81 471 44 8939 ABSTRAO Computer models have been developed for the industrial CO lasers, those are oparated by transverse dc discharge in the temperature region 1 50-200 K. The 1D (dimensional) model has been developed to analyze and predict the output performance characteristics, mainly the laser power. The flow equations are coupled with the kinetic equations of the direct excitation by electron impact in discharge, V-V (vibration to vibration) and V-R/T (vibration to rotation and translation) energy transfer by collision, and spontaneous and stimulated emission. The 2D model to analyze the spatial distribution of the gas temperature and excited molecules is now under development. The flow equations, based on the control volume method for the 2D Cartesian coordinates, are described. The time integration is performed by the SIMPLEST method.

To analyze combustion oscillation in the premixed combustor, a large-eddy simulation program for premixed combustion flow was developed. The subgrid scale (SGS) model of eddy viscosity type for compressible turbulence (Speziale et al., 1988) was adopted to treat the SGS fluxes. The fractal flamelet model, which utilizes the fractal properties of the turbulent premixed flame to obtain the reaction rate, was developed. Premixed combustion without oscillation was analyzed to verify the present method. The computational results showed good accordance with experimental data (Rydén et al., 1993). The combustion oscillation of an “established buzz” type in the premixed combustor (Langhorne, 1988) was also analyzed. The present method succeeded in capturing the oscillation accurately. The detailed mechanism was investigated. The appearance of the non-heat release region, which is generated because the supply of the unburnt gas into the combustion zone stagnates, and its disappearance play an important role.