Abstract |
The overall combustion process occurring within a liquid spray fueled burner is analyzed in terms of the ongoing dominant subprocesses, with particular emphasis on those subprocesses deemed most critical to pollutant emissions. Liquid fuel evaporation, turbulent mixing, and chemical reaction are each considered separately and are characterized by time scales which typify the importance of each subprocess. An axisymmetric burner consisting of a flame stabilized in the wake of a disc with a liquid fuel spray injected into the wake region from the center of the disc is considered experimentally. The basic flame structure behind the disc is composed of a hollow reaction region (shear layer) along the boundary between the recirculation zone and the free stream. Guided by the model of the flame structure, the developed characteristic times are combined to form burner output correlating parameters. The success of these parameters is demonstrated by the correlation of both carbon monoxide and oxides of nitrogen exhaust emissions from the disc burner for various geometries, a wide range of burner operating conditions, and two non-similar fuels. The developed characteristic time model is extended to a conventional gas turbine combustor, GT-309. The model predicts the effect of changes in both combustor inlet conditions and combustor geometry on exhaust emissions and is used to demonstrate the design of a low NOx burner of the GT-309 class. |