Carbon Deposition on the Venturi of a Gas Turbine Combustor Using Ethanol-Kerosene Blends

This paper reports an investigation of carbon deposition on the venturi component of a gas turbine combustor fueled with ethanol/kerosene fuel blends. China RP-3 kerosene and its ethanol blends(10%, 30%, and 50% ethanol by weight) were used in a gas turbine model combustor. Each combustion test of carbon deposition was conducted at 0.3 MPa for an hour. Measuring carbon deposition became difficult because of the special structure of venturi which is a component of swirl cup air atomization nozzle. An image processing method called planar reconstruction, was developed to evaluate the amount of carbon deposition semi-quantitatively. To study the morphology and structure of the deposition for different test fuels, a Scanning Electron Microscope(SEM) was employed to visualize the detailed structures of carbon deposition. Results show that with the increasing addition of ethanol, the amount of carbon deposition decreases, and the morphology of carbon changes significantly. For pure kerosene case, small spherules and flake graphite were closely interwoven on venturi surface. For other fuel blends, small spherules were not observed, and flake graphite neatly stacked and lined on the venturi surface. These results indicate that the mechanism of carbon deposition can vary significantly, due to the change of fuel’s molecular structures; the current study shows that the morphology and structure of carbon deposition of kerosene were altered remarkably by the ethanol addition.