Atomization of Coal Water Mixtures: Evaluation of Fuel Nozzles and a Cellulose Gum Simulant
An experimental evaluation of four air-assist fuel nozzles has been conducted to determine atomization levels of coal-water mixture (CWM) fuels at operating conditions simulating a high pressure combustor. Two of the nozzles were commercial units marketed for use in atmospheric burners, while two nozzles were specially designed for CWM operation in a high pressure combustor. Sprays from all four injectors were characterized in tests performed over a range of liquid and air flowrates. Most of the tests were performed using a cellulose-gum water solution prepared to match the viscosity and drip characteristics of an available CWM. Atomization data acquired from a limited test series using the CWM were found to be properly represented by the gum solution data. High levels of atomization (SMD ∼ 10 micron) were achieved by two of the nozzles — one commercial unit and one special unit — at an assist airflow level corresponding to a nozzle air-fuel ratio between 0.6–0.8.