A slagging combustor for a coal-fueled gas turbine engine is being developed. The work to date has been accomplished using a bench-scale combustor with one-tenth the heat input required for the full-scale gas turbine unit. The combustor features a fuel-rich slagging primary zone with hot refractory walls. Both single and multiple primary air/fuel injectors have been tested. Aerodynamic jet impaction on a target at one end of the primary zone removes much of the slag. The jet impaction is the result of the single air/fuel injector flow for multiple injectors, the intersection of the multiple jets forms a central jet. There is an additional particulate rejection impact separator between the primary and secondary zones to remove the slag that escapes the primary zone. Secondary air is introduced via multiple jets that rapidly mix with the incoming gas from the particulate removal device, resulting in a minimal formation of thermal NOx and the completion of the combustion process.
Variables that have been evaluated include coal-water mixture properties such as top and mean particle size, viscosity, loading and ash fusion temperature, and primary zone parameters such as volume, cross-sectional area, loading, and equivalence ratio.
Combustor performance was compared with single or multiple fuel injectors, relating the combustor performance to the spray characteristics of the two injector configurations. Modifications of the single injector were evaluated with the goal of attaining at least the same atomization performance as the smaller injectors used in the multiple injector configuration.
Flow visualization, computer modelling, and cold-flow velocity traverses have been employed to aid the development program. The results of the subscale development are being used to design and develop the full-size combustor for integration with the engine.
