EVALUATION OF THE TURBULENCE SCALE IN A FLAME AT THE DIFFUSION COMBUSTION OF DIESEL FUEL

Diffusion combustion generated during combustion both in technological devices and in natural fires is usually implemented during the turbulent flow of combustion products in the flame. Nonstationarity of the process leads to the distortion of the flame shape, which provides surface area extension and combustion rate increase. Turbulence scale and the magnitude of pulsation of the parameters significantly affect the combustion mechanism in turbulent flows. It should be noted that in turbulent conditions the scale of turbulent pulsations and the mixing intensity significantly affect the flame shape, the combustion speed, the thermodynamic parameters of the process, the combustion completeness, and efficiency. The development of the thermography methods gives encouraging results for obtaining reliable temperatures of the flame. Thereby it is possible to visualize the temperature inhomogeneities. Based on the analysis of the flame radiation spectra with the application of high speed infrared cameras, it was found that the temperature in the flame changes repeatedly in time, and there are characteristic frequencies in the range of the temperature changes. These frequencies are caused by the movement of the flame temperature inhomogeneities associated with the structure of the flow. This paper presents results of mathematical modeling of the current in the flame generated during diesel fuel combustion, and experimental estimates of the scale of turbulent eddies in the flame. The results were obtained using the SIMPLEC algorithm and thermography methods. The paper includes the description of the experimental design and data processing. A detailed description of the system of equations used for the mathematical modeling is presented. Comparing the results of numerical simulation and experimental data shows a good correlation of the basic thermodynamic parameters of the flame and the scale of turbulent eddies in it.