Characteristic visualization of the micro/mesoscale liquid ethanol diffusion flame by using deflection tomography

Abstract

The micro/mesoscale combustion system of liquid ethanol and the visualization measurement system of flame were designed and constructed on the basis of the microscale combustion theory of liquid fuels. The characteristics of the micro/mesoscale liquid ethanol diffusion flame were investigated experimentally. The flow fields of flame were visualized and measured using deflection tomography. An image sampling system was proposed for deflection tomography to obtain deflectograms and flame images in one shot. The deflection angles of rays were extracted by the wave-front retrieval of deflectograms, which was suitable for micro/mesoscale combustion. The two-dimensional temperature distributions were reconstructed using the deflection angle revision reconstruction algorithm. The three-dimensional distribution of temperature and structure of flame were obtained using a visualization toolkit equipped with the marching cube and ray casting algorithms. At the same diameter of burner, the height, width and peak temperature of flame did not change significantly as the flow rate of fuel increased in the stable combustion stage. In the oscillation combustion stage, the height and width of flame gradually increased, the peak temperature increased firstly and then decreased, and the oscillation cycle of the flame decreased with the increase in the flow rate of fuel. Under equal flow rate of fuel, the height and width of flame were independent of the diameter of burner in the oscillation combustion stage. At the same time, the distribution of temperature and the oscillation period of flame were closely related to the diameter of burner. The pulsating instability of oscillating flame interacted highly with the heat exchange effect between the flame and the liquid fuel.