Studies of turbulent oxyacetylene flames used for diamond growth

Turbulence in the flame of an oxyacetylene torch used for diamond growth was studied with mass spectrometry and dark‐field shadowgraphy. H2, CO, N2, and C2H2 were observed in both laminar and turbulent diamond growing flames, while O2, CO2, and H2O were detected in only the turbulent flame. Dark‐field shadowgraphs showed a broken, changing flame front in the turbulent flame, although the boundary layer remained laminar under all flow conditions. The broken flame front suggests that unburned gases are passing through the turbulent flame front to form the detected oxidation products. A model is proposed in which the gas phase environment above the surface in turbulent flame diamond growth oscillates between oxidizing and reducing conditions.