In the present study, we used a simultaneous PIV-OH PLIF measurement to acquire the strain rate and the chemical intensity and suggested a new combustion phase diagram. This simultaneous measurement was used to analyze the flame structure and to classify the combustion regimes of the opposed impinging jet combustor according to the change of the orifice diameters at the pre-chambers. The shear strain rates were obtained from the velocity measurement by PIV to represent flow characteristics and the OH radical intensities were obtained from OH PLIF to indicate the flame characteristics. When the strain rate and OH intensity at each point of the measurement zones are plotted at the strain rate-chemical intensity diagram, the distribution of each case showed the characteristics of each flame regime. The change of combustor condition made different distribution in the combustion phase diagram. As the orifice diameter of the pre-chamber decreases, well-mixed turbulent flames are produced and the combustion phase is moved from the moderated turbulence regime to the thickened reaction regime.

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