Pressure-atomized Sprays Research Articles

Combustion of drops and sprays of No. 2 diesel oil and its emulsions with water

Experimental results on the combustion of unsupported single drops and pressure-atomized sprays of No. 2D oil and its emulsions with water are presented. The experiments covered the following range of variables: volume fraction of water=0–0.3; surfactant concentration =0–0.05; injection temperature=298–380 K; chamber temperature=400–950 K; chamber pressure=0.44 to 3.92 MPa; chamber inlet oxygen concentration=0.16–0.75; and spray injector nozzles=multihole and pintle. High speed motion photography was used to observe the flames of drops and sprays through quartz-windows. The films were analyzed to study the fragmentation behavior and flame geometry of single drops and the ignition delay and flame length of sprays. The exhaust gases of the test chamber were analyzed to determine the concentrations of CO 2 , O 2 , N 2 , NO, and NO x . The steady temperatures attained in the flames during spray burning were measured also. The results show that unsupported droplets of No. 2D diesel oil-water emulsions undergo disruption during combustion, and the fragmentation increases with water content, surfactant content, injection temperature, chamber oxygen concentration, and chamber temperature, but is not significantly dependent on chamber pressure. Also, the ignition delay increases considerably for volume fractions of water above 0.12. The flame temperature, exhaust emissions of NO and NO x , and oxygen utilization in the combustion chamber are complexly dependent upon the variables examined. These effects can be explained in terms of a physical model where the dominant combustion mode shifts from overall envelope flame to individual drop burning.